Checking a set of hypotheses

The proposed experiment uses paired samples of old skin and autologous cocultures to study the clearance of persistently damaged fibroblasts while preserving healthy fibroblasts.

Different experimental conditions. Autologous cocultures used irradiated fibroblasts from donors aged 20-46 and non-senescent controls. Older skin was examined separately by histology, rather than through the proposed paired old-skin clearance experiment.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4a; Methods, Autologous co-culture system; Figure 7)

Old skin is hypothesized to contain at least two distinct functional barriers to clearance: CD47-dependent suppression of macrophages through CD47-SIRPα and HLA-E-dependent suppression of cytotoxic cells through HLA-E-NKG2A.

Not verified in the article. The CD47-SIRPα macrophage component was tested. Pereira and colleagues separately tested HLA-E-NKG2A inhibition, but neither study established both functional barriers together in the proposed old-skin system.

Elevated CD47 Expression Impairs Elimination of Photoaged Fibroblasts by Macrophages and Serves as a Potential Biomarker for Photoaging (Results 3.3-3.4; Figures 3-4)

The benefit of selective intervention is hypothesized to depend on matching the target fibroblast's ligand profile to the available effector cells, with the initial ligand profile interacting with effector type to determine clearance.

Not verified in the article. No supplied study tested whether the joint baseline CD47/HLA-E profile interacts with macrophage versus NK availability to predict the benefit of pathway-specific intervention.

The stated scientific rationale includes previously reported roles of CD47 in photoaged fibroblasts and of HLA-E in senescent cells' evasion of natural killer (NK) cell and CD8 responses.

Matches this study. The stated rationale is supported by two separate primary studies: Xu and colleagues reported the photoaging CD47 component, and Pereira and colleagues reported HLA-E-dependent inhibition of NK and CD8 responses.

Elevated CD47 Expression Impairs Elimination of Photoaged Fibroblasts by Macrophages and Serves as a Potential Biomarker for Photoaging (Results 3.2-3.4; Figures 2-4; Pereira et al., Figure 4)

Both CD47 and HLA-E signals must be measured on individual fibroblasts in the paired old-skin samples before intervention.

Not verified in the article. Joint pretreatment measurement of CD47 and HLA-E on individual fibroblasts from paired old-skin samples was not reported.

Autologous cocultures must include separate conditions with added macrophages, added NK cells, and both effector cell types together.

Different experimental conditions. The autologous experiments used NK cells and CD8 T cells. They did not include the required macrophage-only, NK-only, and combined macrophage-NK conditions.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4; Methods, Autologous co-culture system)

Across the effector conditions, the experiment must compare selective intervention in CD47-SIRPα, selective intervention in HLA-E-NKG2A, their combination, and a control.

Not verified in the article. No supplied experiment crossed the three effector compositions with CD47-SIRPα intervention, HLA-E-NKG2A intervention, their combination, and a control.

The intervention result must be confirmed by genetically reducing the corresponding ligand in fibroblasts.

Matches this study. HLA-E knockdown in fibroblasts increased autologous effector degranulation, providing genetic support for that pathway. Xu and colleagues also reduced fibroblast CD47 genetically; these controls were performed in separate studies.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4d; Methods, Transfection of cells with small interfering RNAs)

The experiment must account for baseline effector functionality and NK-cell activating signals.

Not verified in the article. Activating ligands, NKG2D blockade, receptor distributions, and normalized degranulation were examined. Joint accounting for baseline macrophage and NK functionality in the proposed donor-matched experiment was not established.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figures 1, 3 and 4c; Methods, Cytotoxicity assays)

Video tracking must distinguish engulfment of a living target, killing followed by clearance, and mere disappearance of a marker.

Not verified in the article. Live imaging monitored senescent-cell persistence and macrophage interactions, but the complete three-way discrimination of living-target engulfment, killing followed by clearance, and marker loss was not demonstrated for the proposed interventions.

Senescent cells suppress macrophage-mediated corpse removal via upregulation of the CD47-QPCT/L axis (Figure 2; Figure S3; Video 1; Methods, In vitro engulfment assay of senescent cells)

The primary outcome is selective removal of persistently damaged fibroblasts with preservation of healthy fibroblasts.

Different experimental conditions. Senescent and non-senescent fibroblasts were compared using active caspase 3 and effector degranulation. These support preferential cytotoxic responses but do not reproduce direct selective clearance and healthy-cell preservation in the full old-skin experiment.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4b-d; Methods, Cytotoxicity assays)

Secondary outcomes are matrix restoration, free cellular debris, and inflammation assessed after 7-14 days.

Not verified in the article. The combined assessment of matrix restoration, free cellular debris, and inflammation 7-14 days after the specified interventions was not reported.

Assessment of matrix restoration must distinguish newly formed collagen from the original scaffold.

Not verified in the article. No supplied study distinguished newly formed collagen from the original scaffold within the proposed intervention experiment.

The proposed selection scheme fails if the initial ligand profile does not interact with effector type or if healthy and damaged cells are removed equally.

Not verified in the article. The joint decision rule based on ligand-profile-by-effector interaction and differential removal of healthy versus damaged fibroblasts was not tested.

High expression of a single protein is not assumed to be sufficient for choosing an intervention, and the cited rationale does not establish one blockade as universally appropriate for all samples.

Matches this study. CD47 loss restored corpse removal without triggering engulfment of senescent fibroblasts, directly supporting the limitation that a single inhibitory ligand does not by itself establish an effective clearance strategy. No universal blockade-selection rule was validated.

Senescent cells suppress macrophage-mediated corpse removal via upregulation of the CD47-QPCT/L axis (Results, Fibroblast CD47 mediates SCES; Figure S3A; Discussion)

Immune activation may damage tissue, so verification of intervention selectivity is part of the scientific result.

Not verified in the article. A different intervention increased early inflammation and swelling in irradiated rats. This supports the relevance of tissue-injury monitoring, but selective safety of the proposed dual-pathway intervention was not tested.

Targeting the NLRP3 in macrophages contributes to senescence cell clearance in radiation-induced skin injury (Results, Nr-CWS treatment reduces the burden of senescence cells and alleviates RISI; Figure 7)

The pilot study must include 6-8 independent donors.

Different experimental conditions. The autologous system specified five donors aged 20-46, rather than a pilot involving 6-8 independent old-skin donors.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4a; Methods, Autologous co-culture system)

The main study's sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. No supplied study calculated the main sample size for this test using primary-outcome variance and a prespecified minimum useful effect.

The donor is the biological unit, and chips or wells are nested replicates.

Not verified in the article. Distinct donor samples and culture wells were described, but an explicit design treating donors as biological units and chips or wells as nested replicates was not verified.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Figure 4; Methods, Autologous co-culture system and Statistical analysis)

The study must use randomization and blinded analysis.

Not verified in the article. Randomization together with blinded analysis was not documented for a matching experiment in the supplied literature.

Statistical analysis must use a paired model accounting for donor, report confidence intervals, and apply correction for secondary comparisons.

Different experimental conditions. The photoaging study used unpaired t tests, one-way analysis of variance, and correlations, rather than the required paired donor-adjusted model with confidence intervals and correction for secondary comparisons.

Elevated CD47 Expression Impairs Elimination of Photoaged Fibroblasts by Macrophages and Serves as a Potential Biomarker for Photoaging (Methods 2.9, Statistical Analysis)

Neither p16, p21, nor senescence-associated β-galactosidase (SA-β-gal) alone establishes cellular senescence.

Matches this study. Senescence characterization combined growth arrest, p16, persistent DNA-damage foci, and senescence-associated β-galactosidase activity, rather than relying on one of the listed markers alone.

Senescent cells evade immune clearance via HLA-E-mediated NK and CD8+ T cell inhibition (Results, Senescent cells express atypical MHC molecules; Figure 1; Supplementary Figure 1 description)

A result of p>0.05 alone must not be treated as refutation of the hypothesis.

Not verified in the article. The supplied studies did not implement the proposal's explicit rule that p>0.05 alone is insufficient to refute the selection hypothesis.

The proposal is a research hypothesis; the described new experiments have not been performed, and no results from them are claimed.

Not verified in the article. The unperformed status of the new experiments is stated by the proposal. It is not an empirical finding independently verified by the supplied primary studies.

The experimental model uses hematopoietic stem cells (HSCs) from old mice in culture followed by competitive transplantation under an agreed protocol.

Matches this study. Old mouse HSCs were maintained in culture for 16 hours and competitively transplanted with bone marrow competitor cells under a described protocol.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Methods: HSC competitive transplantation; Figure 4a.)

The stated biological premise is that suppression of excessive CDC42 activity improved the characteristics and polarity of old HSCs and the distribution of histone H4 lysine 16 acetylation (H4K16ac), while resistance to repeated stress was not comprehensively examined.

Matches this study. CASIN increased Cdc42, tubulin and H4K16ac polarity and improved regenerative and B-cell output. Serial transplantation examined one form of repeated stress, supporting the premise while leaving broader resistance incompletely characterized.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Results: systemic inhibition of Cdc42 activity; Figures 3-4.)

Temporary correction of CDC42 is hypothesized to establish persistent polarity that protects old HSCs from myeloid skewing during repeated regenerative stress.

Not verified in the article. Early repolarization and improved serial reconstitution were measured separately. Persistent polarity was not established as the mediator of protection against myeloid skewing during repeated regeneration.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Results and Figures 3-4.)

The persistent effect is proposed to arise through reprogramming of the HSC cellular state rather than selection of rare HSCs.

Not verified in the article. Paired daughter-cell experiments support altered division outcomes after CDC42 inhibition, but do not establish that durable population-level benefit arises from reprogramming rather than selection of rare HSCs.

Aging alters the epigenetic asymmetry of HSC division (Results: restoring asymmetry to divisions; Figures 4-5 and S6; Discussion.)

HSCs receive a brief ex vivo correction of CDC42 followed by washout and a subsequent period without exposure.

Matches this study. HSCs received four hours of ex vivo CASIN treatment, were washed and used in subsequent experiments. This procedural component was demonstrated in human HSCs, so it does not establish the complete mouse experiment.

Aging of human hematopoietic stem cells is linked to changes in Cdc42 activity (Methods: CASIN treatment; Xenotransplantation.)

Equal numbers of viable HSCs are compared after the brief correction and washout.

Not verified in the article. A fixed dose of 500 HSCs was transplanted after the treatment procedure, but explicit equalization by viable-cell counts after correction and washout is not documented.

Aging of human hematopoietic stem cells is linked to changes in Cdc42 activity (Methods: CASIN treatment; Xenotransplantation.)

Withdrawal day 0 begins only after cessation of exposure is confirmed by disappearance of the photocurrent or induced protein, or by washout of the substance and restoration of its target's response, as applicable.

Not verified in the article. No supplied study defines withdrawal day 0 through confirmed washout together with restored target responsiveness, or through the alternative exposure-cessation criteria.

HSC polarity and lineage distribution are assessed on days 21-28.

Different experimental conditions. Polarity was evaluated after marrow collection 24 hours after treatment; competitive-transplant blood measurements occurred every eight weeks. This differs from joint assessment of polarity and lineage distribution on days 21-28.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Results: Figure 3; Methods: HSC competitive transplantation.)

Multilineage hematopoiesis and the capacity for secondary recovery are assessed over the longer term.

Matches this study. The study followed multilineage reconstitution for 24 weeks after primary transplantation and evaluated secondary recipients, directly covering long-term hematopoiesis and secondary recovery.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Figure 4b-c; Methods: HSC competitive transplantation.)

The causal test briefly restores CDC42 to its original activity level in old HSCs after the correction course.

Different experimental conditions. The opposing perturbation used Wnt5a to elevate Cdc42 activity in young HSCs. It did not restore the original aged activity transiently in old HSCs after their correction course.

Aging alters the epigenetic asymmetry of HSC division (Introduction; Figures 1-5; Methods: single HSC sorting and culturing.)

The causal test includes a control for the restoration manipulation in untreated cells.

Not verified in the article. A control applying the post-correction CDC42-restoration manipulation to untreated cells is absent from the supplied experiments.

Clones are tracked to distinguish cellular-state reprogramming from selection of rare HSCs.

Different experimental conditions. Individual daughter cells were transplanted into separate recipients to determine division outcomes. This differs from following competing clones through correction and serial regeneration to distinguish reprogramming from selection.

Aging alters the epigenetic asymmetry of HSC division (Figures 4-5; Methods: single daughter cell transplant.)

The primary outcome and success criterion are persistent, more balanced multilineage hematopoiesis and secondary recovery without monoclonal takeover.

Not verified in the article. Improved reconstitution and B-cell output persisted in secondary recipients, but reduced myeloid frequency occurred only in primary recipients at 24 weeks. Absence of monoclonal takeover was not established.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Results: systemic inhibition increases regenerative potential; Figure 4b-c.)

Polarity must predict the effect in an independent experimental series.

Not verified in the article. Modeling linked population polarity frequencies to division symmetry. It did not validate polarity as a predictor of durable multilineage and secondary-recovery benefit in an independent experimental series.

Aging alters the epigenetic asymmetry of HSC division (Results: HSC polarity is strongly associated with the mode of division; Figure 3.)

Rapid loss of polarity, improvement confined to early engraftment, or improvement associated with preferential survival of a single clone would refute the hypothesis.

Not verified in the article. The supplied studies do not implement the complete falsification assessment combining polarity persistence, separation of early and durable benefit, and preferential survival of a single clone.

The experiment includes a baseline old-cell control and a young reference.

Matches this study. Young reference mice and aged control mice were included alongside aged CASIN-treated mice.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Figures 3-4; Methods: mice and CASIN treatment in vivo.)

The experiment includes a vehicle, light, or inducer control, as applicable to the intervention.

Matches this study. Young and aged controls received equivalent cyclodextrin vehicle injections. This matches the vehicle-control component within the systemic-treatment experiment.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Methods: CASIN treatment in vivo.)

Continuous exposure is included as a comparison group.

Not verified in the article. No supplied study compares the proposed brief correction and withdrawal with a continuous-exposure arm over the relevant recovery period.

If combinations are tested, their individual components are tested separately.

Not verified in the article. This requirement is conditional on testing combinations. No relevant combination and corresponding component-control design is established; the condition does not independently imply novelty for the single-agent hypothesis.

Randomization, blinded assessment, and advance selection of the primary functional outcome are mandatory.

Different experimental conditions. The study explicitly states that investigators were not blinded to allocation or outcome assessment. Random selection of mice does not satisfy the required combination of randomization, blinding and a prespecified primary functional outcome.

Aging alters the epigenetic asymmetry of HSC division (Materials and methods: statistical analyses.)

The biological unit is the donor or animal rather than the culture well.

Matches this study. Biological repeats were explicitly defined as experiments on different days starting from different mice, and transplantation outcomes were evaluated in recipient animals rather than treating wells as independent biological replicates.

Aging alters the epigenetic asymmetry of HSC division (Materials and methods: statistical analyses; single daughter cell transplant.)

The proposed human-culture pilot includes at least 6 independent older donors with paired allocation of conditions.

Not verified in the article. The human xenotransplant experiment reports six different donors per cohort, including older donors. The supplied text does not explicitly establish paired allocation of all proposed culture conditions within at least six older donors.

Aging of human hematopoietic stem cells is linked to changes in Cdc42 activity (Methods: primary cells and CASIN treatment; Figure 5 legend.)

The confirmatory sample size is calculated from the pilot variance for 80-90% statistical power, accounting for multiple comparisons.

Not verified in the article. Sample-size estimation software and multiplicity-adjusted tests are described, but a confirmatory calculation using pilot variance and 80-90% power with multiple-comparison adjustment is not verified.

Aging alters the epigenetic asymmetry of HSC division (Materials and methods: statistical analyses.)

Cell death, proliferation, cellular composition, and clonal selection are accounted for separately.

Not verified in the article. Death, division kinetics, lineage output and functional HSC frequency were examined. These measurements do not provide the required separate accounting for clonal selection during durable recovery after correction.

Aging alters the epigenetic asymmetry of HSC division (Figure 1B; Figures 4-5 and S6.)

Work with donor materials and animals requires the necessary approvals.

Matches this study. Approval for human sample collection and investigation and institutional approval for animal experiments are explicitly reported.

Aging of human hematopoietic stem cells is linked to changes in Cdc42 activity (Methods: primary cells; Xenotransplantation.)

The timing of secondary stress and experiment termination is specified in advance.

Not verified in the article. The serial-transplant procedure and follow-up schedule are described, but advance specification of both secondary-stress timing and experiment-termination rules is not established by the supplied text.

Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice (Figure 4; Methods: HSC competitive transplantation.)

The proposal is a research hypothesis rather than demonstrated rejuvenation or a treatment recommendation; its proposed success thresholds are design choices, and the cited literature supports the premises rather than the new prediction.

Not verified in the article. The complete proposal remains an untested research hypothesis in these sources. Its design thresholds and nonclinical status are interpretive constraints, not independently demonstrated biological findings or novelty.

Age-related impairment of immune cell lymphatic exit is hypothesized to be partly caused by loss of a directional CCL21 signal, with signal geometry more important for immune renewal in aged skin than mean CCL21 concentration.

Not verified in the article. The authors propose that lost chemokine gradients contribute to aged-skin dysfunction, but explicitly identify their study as observational. They did not establish that CCL21 geometry outweighs mean concentration.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Discussion: Aging Results in Peri-Lymphatic Accumulation of Inflammatory Cells; study limitations)

The biological premise is reduced CCL21 and impaired dendritic cell migration through lymphatic vessels reported in aged mouse skin; the causal contribution of signal geometry remains unresolved.

Matches this study. Aged mouse skin showed reduced lymphatic CCL21 expression and impaired dendritic-cell trafficking to draining lymph nodes. The observational design leaves the causal contribution of gradient geometry unresolved.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Results: Figures 3A-C and 6A-C; Discussion: limitations)

The experiment uses a skin chip with a separate lymphatic channel and labeled dendritic cells; the species of the experimental donor cells is unspecified.

Different experimental conditions. The experiments used labeled mouse dendritic cells with human lymphatic endothelial monolayers and mouse dermal explants, rather than a skin chip containing a separate lymphatic channel.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions (Methods: Primary lymphatic endothelial cell culture; Live imaging of the DC-LEC co-cultures; Live imaging and analysis of the transmigration events in dermal explants)

The skin chip operates under constant flow.

Not verified in the article. No supplied study documents operation of the proposed skin chip under constant flow; flow-chamber experiments and low-flow endothelial assays do not establish this condition.

The decisive comparison includes a young CCL21 gradient directed toward the lymphatic channel, uniform CCL21, a reversed CCL21 gradient, and a control without supplementation.

Different experimental conditions. The study compared dendritic-cell co-injection with 2.5 µg CCL21 against saline. It did not implement the four specified forward-gradient, uniform, reversed-gradient and unsupplemented conditions.

DC mobilization from the skin requires docking to immobilized CCL21 on lymphatic endothelium and intralymphatic crawling (Results: CCR7 signaling takes part in DC recruitment; Figure 3i)

The comparison is subsequently reproduced using old donor cells; the age of the donor cells used in the initial comparison is unspecified.

Not verified in the article. The supplied literature does not repeat the specified gradient comparison with old donor cells. Studying aged recipient skin does not establish that donor-cell experiment.

The comparison of restored directional and uniform CCL21 signaling must match total CCL21 dose, integrated CCL21 exposure, fluid drainage, and the rate of soluble substance removal.

Not verified in the article. No supplied experiment jointly matches total CCL21 dose, integrated exposure, fluid drainage and soluble-substance removal between directional and uniform signaling.

The actual spatial distribution of the chemokine must be measured in addition to its inlet concentration.

Different experimental conditions. Actual extracellular CCL21 profiles were measured against distance from lymphatic vessels in mouse dermis. This supports spatial measurement, but substitutes native tissue imaging for combined chip-distribution and inlet-concentration measurements.

Shape and Function of Interstitial Chemokine CCL21 Gradients Are Independent of Heparan Sulfates Produced by Lymphatic Endothelium (Methods: Ear Sheet Staining and Image Analyses; Figure 2A-D)

The directional CCL21 gradient is proposed to guide immune cell exit toward the lymphatic vessel through a mechanism requiring CCR7.

Matches this study. Measured interstitial CCL21 gradients accompanied directed wild-type dendritic-cell approach to lymphatic capillaries, whereas Ccr7-deficient cells were randomly distributed. This matches the guidance mechanism as a component, without establishing aged-skin rescue.

Shape and Function of Interstitial Chemokine CCL21 Gradients Are Independent of Heparan Sulfates Produced by Lymphatic Endothelium (Results: Figure 2D-E; Methods: Interstitial Dendritic Cell Migration Assay)

CCR7 must be blocked to test whether it is necessary for directional cell exit.

Different experimental conditions. CCR7 necessity was investigated using genetically deficient dendritic cells. Genetic deficiency differs from the specified receptor-blockade intervention.

DC mobilization from the skin requires docking to immobilized CCL21 on lymphatic endothelium and intralymphatic crawling (Results: Figure 3d-h; Materials and Methods: Transgenic mice)

The primary outcome is the fraction of viable cells that exit directionally into the lymphatic channel within a specified time; the duration is not provided.

Different experimental conditions. The study quantified the percentage of dendritic cells transmigrating endothelial monolayers during 90-minute recordings. It did not measure the specified viable-cell fraction exiting directionally into a lymphatic chip channel.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions (Methods: Live imaging of the DC-LEC co-cultures; Figures 6K and 7M)

Under the matched conditions, the CCL21 gradient toward the lymphatic channel is predicted to produce a greater primary-outcome fraction than uniform CCL21.

Not verified in the article. The supplied studies do not establish superiority of a lymphatic-directed CCL21 gradient over uniform CCL21 for the specified primary outcome under all matched exposure and drainage conditions.

Secondary outcomes include dendritic cell residence time in the dermis, local cytokines, and the function of the remaining fibroblasts.

Not verified in the article. No supplied study measures the specified combination of dermal dendritic-cell residence time, local cytokines and remaining fibroblast function following the proposed gradient intervention.

Equal effectiveness of uniform CCL21 signaling or persistence of directionality during CCR7 blockade would indicate that the proposed gradient mechanism is insufficient.

Not verified in the article. No supplied study applies the proposed insufficiency criteria within the complete experiment. Unchanged migration after CCL21 co-injection does not demonstrate equivalence of uniform and directional signaling under matched conditions.

Preservation of local antigen-presenting capacity after cell exit must be assessed because dendritic cells also protect tissue and increased migration is not necessarily beneficial.

Not verified in the article. The supplied studies do not assess preservation of local antigen-presenting capacity after enhanced cell exit in the proposed intervention.

The reproducibility plan includes a pilot involving 6-8 independent donors.

Not verified in the article. No supplied study describes a pilot of the proposed experiment involving 6-8 independent donors; similarly sized animal groups or replicate counts do not meet this requirement.

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimally useful effect.

Different experimental conditions. Sample sizes were based on prior observations and similar published experiments with significant differences, rather than primary-outcome variance and a prespecified minimally useful effect.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions (Methods: Study design)

The donor is the biological unit, and chips or wells are nested replicates.

Not verified in the article. No supplied experiment documents the proposed donor-level biological units with chip or well measurements explicitly treated as nested replicates.

The study must use randomization and blinded analysis.

Different experimental conditions. The study explicitly states that collection, analysis and quantification were not blinded. The required combination of randomization and blinded analysis is therefore not matched.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions (Methods: Study design)

Statistical analysis must use a paired model accounting for donor, report confidence intervals, and correct secondary comparisons.

Different experimental conditions. The study used unpaired tests, categorical tests and analysis of variance. It did not use the specified paired donor-adjusted model with confidence intervals and correction of secondary comparisons.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions (Methods: Statistics)

p16/p21 or senescence-associated beta-galactosidase (SA-β-gal), assessed separately, do not establish cellular senescence.

Not verified in the article. No supplied study explicitly implements the proposed restriction against establishing senescence from isolated p16/p21 or senescence-associated beta-galactosidase measurements.

New collagen must be distinguished from the original scaffold.

Not verified in the article. No supplied study distinguishes newly synthesized collagen from an original scaffold in the proposed skin-chip experiment.

A result of p>0.05 alone must not be treated as refutation of the hypothesis.

Not verified in the article. No supplied study explicitly adopts the proposed rule that p>0.05 alone cannot refute this hypothesis; reporting a significance threshold does not establish that rule.

The proposal is a research hypothesis: the described new experiments have not been performed, and no experimental results are claimed.

Not verified in the article. The submission identifies the complete experiment as an unperformed proposal. That status is supplied context, not an empirical result verified by a literature study.

The hypothesis concerns collagen preservation as a separately reproducible component of retinoid action in aged dermis.

Different experimental conditions. The study examined cytokine-induced degradation in human skin from donors of varied ages, rather than separately reproducing retinoid-associated collagen preservation in aged dermis.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and methods: skin explant preparation; Table 1; Introduction)

Experimental models must have an accumulated pro-MMP1 reserve that is measured before the intervention comparison.

Not verified in the article. Native tissue and cultured samples were characterized, but an accumulated pro-MMP1 reserve was not quantified before comparing interventions.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Results: MMP profiling; Figure 7)

MMP3 can participate in tissue procollagenase activation in a context-dependent manner and is also involved in skin repair.

Matches this study. The article explicitly describes MMP3-mediated collagenase activation and participation in wound repair, with context-dependent effects. These premises include cited background; its own experiments concern murine MMP13.

Matrix Metalloproteinase-3 is Key Effector of TNF-α-Induced Collagen Degradation in Skin (Introduction; Discussion)

The intervention must briefly restrict specifically the MMP3-dependent activation step of accumulated pro-MMP1.

Different experimental conditions. UK370106 inhibited MMP3 in extracted-proteinase assays. This differs from briefly restricting activation of a measured accumulated pro-MMP1 pool in living aged dermis.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Type I collagenolytic activity assay; Figure 5B-D)

Compare MMP3 suppression by CRISPR interference, MMP1 suppression by CRISPR interference, and a control group.

Different experimental conditions. The genetic comparison used MMP3-knockout and MMP3-overexpressing mice with their wild-type controls. It lacked the specified MMP3-CRISPRi versus MMP1-CRISPRi comparison.

Matrix Metalloproteinase-3 is Key Effector of TNF-α-Induced Collagen Degradation in Skin (Materials and Methods 4.1-4.2; Tables 2-3)

Brief restriction of MMP3-dependent activation is predicted to prevent abrupt collagen-network degradation more effectively than an equivalent reduction in MMP1 transcription.

Not verified in the article. Selective MMP3 inhibition reduced collagenolysis, but superiority over an equivalent reduction in MMP1 transcription was not tested.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Results: Type I collagenolysis; Figure 5)

The proposed causal mechanism is that restricting activation of accumulated pro-MMP1 interrupts the MMP3-pro-MMP1 loop and prevents a proteolytic surge in aged dermis.

Not verified in the article. The results support an MMP3-MMP1 collagenolytic pathway, but do not establish a reserve-driven proteolytic surge or interruption of the proposed loop in aged dermis.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Discussion; Figures 5 and 7)

Quantify the MMP1 proenzyme, intermediate forms, and active enzyme separately.

Not verified in the article. Western blots distinguished latent and active MMP1 forms. Separate quantitative resolution of proenzyme, activation intermediates, and fully active MMP1 was not achieved.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Results: Effect of TNF-α on MMP-1; Figure 7B; Discussion)

Test causality by restoring active MMP1 during MMP3 restriction; this restoration is predicted to abolish the protective effect.

Not verified in the article. Active recombinant MMP1 served in enzyme assays and inhibitor-specificity checks, not as a rescue during MMP3 restriction in skin.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Figure 5D-F)

The proposed loop fails to explain the result if MMP3 reduction does not change MMP1 activation or if the effect persists after MMP1 restoration.

Not verified in the article. No supplied study applied both proposed falsification criteria by measuring MMP1 activation after MMP3 reduction and testing whether protection persisted after MMP1 restoration.

After intervention withdrawal, assess collagen-network degradation, mechanical properties, and repair.

Not verified in the article. No supplied experiment jointly assessed degradation, mechanical properties, and repair after withdrawal of the proposed intervention.

Account for MMP3's own substrates when interpreting the intervention effects.

Matches this study. The interpretation explicitly considers MMP3 substrates beyond collagenases, including cytokines and growth factors. This is qualitative consideration, not experimental isolation of their contributions.

Matrix Metalloproteinase-3 is Key Effector of TNF-α-Induced Collagen Degradation in Skin (Introduction; Discussion)

A benefit is unacceptable if it is accompanied by a persistent wound-healing defect.

Not verified in the article. MMP3 knockdown delayed wound closure, supporting the relevance of healing assessment. Persistent impairment after withdrawal and the specified benefit-rejection criterion were not tested.

MMP-3 plays a major role in calcium pantothenate-promoted wound healing after fractional ablative laser treatment (Results; Figures 2 and 4)

The functional objective is to preserve aging skin strength, renewal, and recovery after injury.

Not verified in the article. The supplied studies do not jointly demonstrate preservation of strength, renewal, and injury recovery in aging skin.

Use paired models from multiple independent donors, treating the donor as the biological unit and wells as technical replicates.

Matches this study. Explants from each independent donor were distributed across treatments; donor-level samples were pooled or aggregated, and paired analyses treated donors as biological units.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Skin explant preparation; Statistical analyses; Figures 1-3)

Use randomization and blinded assessment.

Matches this study. Explants were randomly allocated, and histological scoring and apoptosis assessment included blinded investigators.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Skin explant allocation; Histology; Figure 4B)

Calculate sample size from pilot variability.

Not verified in the article. The supplied methods do not report calculating sample size from pilot variability.

Prespecify the primary functional outcome and account for multiple comparisons.

Not verified in the article. Bonferroni adjustment addressed multiple comparisons, but the proposed primary functional outcome in aging skin was not prespecified and tested.

Matrix Metalloproteinase-3 is Key Effector of TNF-α-Induced Collagen Degradation in Skin (Statistics 4.4; Introduction)

Control for viability, cellular composition, and intervention specificity.

Not verified in the article. Viability, morphology, apoptosis, and inhibitor specificity were examined, but comprehensive cellular-composition controls for the proposed genetic interventions were absent.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Results: LDH, morphology and apoptosis; Figures 3-5)

In reconstructed models, distinguish old and new collagen fractions using sequential stable-isotope labeling.

Not verified in the article. Sequential stable-isotope labeling of old and new collagen in reconstructed models was not reported.

In native explants, label only newly synthesized collagen and account for the unlabeled pool by mass balance.

Different experimental conditions. Native explant turnover was assessed through hydroxyproline and collagen cleavage or synthesis markers, rather than new-synthesis isotope labeling with unlabeled-pool mass balance.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Type I collagen degradation and biosynthesis; Figure 2)

Account for precursor enrichment and label recycling in isotope-based measurements.

Not verified in the article. No supplied study reports the required corrections for precursor enrichment and isotope-label recycling.

Use second-harmonic generation to characterize collagen organization while retaining separate measurements of mass, mechanics, and wound healing.

Not verified in the article. Second-harmonic generation combined with separate measurements of collagen mass, mechanics, and wound healing was not reported.

Verify MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. MMP1-neutralizing antibody established the enzyme's contribution to collagenolytic activity, but an independent genetic MMP1 intervention was absent.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Type I collagenolytic activity assay; Figure 5B)

For active-MMP1 restoration experiments, use genetic suppression or wash out the inhibitor beforehand.

Not verified in the article. No active-MMP1 rescue experiment used genetic suppression or prior inhibitor washout as specified.

Include catalytically inactive protein as a control in the active-MMP1 restoration experiment.

Not verified in the article. A catalytically inactive protein control for active-MMP1 restoration was not reported.

When testing effects after withdrawal, rule out residual drug persistence.

Not verified in the article. No supplied withdrawal experiment excluded residual drug persistence.

An increase in collagen can support an interpretation of rejuvenation only if collagen organization and function also improve.

Not verified in the article. No supplied study applied the combined collagen-quantity, organization, and functional-improvement criterion to establish rejuvenation.

The proposed effect remains a research hypothesis rather than an established effect or a recommendation for use; the supporting observations do not establish the hypothesis.

Not verified in the article. The complete proposed intervention remains untested in the supplied literature; its research-only status is an interpretive condition, not an experimentally demonstrated treatment effect.

Conclusions from cellular and animal models require verification in human skin.

Not verified in the article. Human skin explants provide evidence for part of the pathway, but the complete proposed test has not been verified in human skin.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and methods; Figures 1-8)

The hypothesis concerns collagen preservation as a separately reproducible component of retinoid action in aging skin, with preservation of dermal strength, renewal and recovery after injury as the functional goal.

Not verified in the article. The study addresses collagen fragmentation and fibroblast mechanics in skin aging, but does not isolate collagen preservation as a component of retinoid action or test the specified functional goals together.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Introduction; Results, Figures 1-4; Discussion)

Age-related collagen stiffness and fragmentation must be treated as distinct characteristics, and their effects must be tested by varying them independently while maintaining identical cellular composition.

Different experimental conditions. The study manipulates substrate stiffness and collagen architecture in mouse muscle progenitors. Crosslinking, fibril size and alignment replace the proposed independent manipulation of age-related stiffness and fragmentation in skin.

Matrix stiffness and architecture drive fibro-adipogenic progenitors’ activation into myofibroblasts (Results, Figures 1-6; Methods, Collagen gel fabrication)

In an already stiff, crosslinked matrix, prolonged protection against MMP1-mediated collagen degradation is hypothesized to preserve stiff collagen excessively, sustain pathological mechanical stimulation, enhance the contractile phenotype and initiate a self-sustaining contracture.

Different experimental conditions. Human dermal fibroblast constructs show sustained activation governed by mechanical loading and matrix feedback. The initiating intervention is static stretch, with no test of prolonged MMP1 protection in an already stiff, crosslinked matrix or irreversible contracture.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Results, Figures 1-5; Discussion and Conclusions)

Brief protection against MMP1 in a less crosslinked collagen network is predicted not to induce the same contractile effect.

Different experimental conditions. The short-duration comparison uses 1 h of stretching versus 24 h. It does not test brief MMP1 protection in a less crosslinked collagen network.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Results, Figures 1, 4 and 5)

The experiment must compare temporary and prolonged MMP1 repression using CRISPR interference (MMP1-CRISPRi).

Different experimental conditions. The study uses MMI270, recombinant MMP-1 and dominant-negative c-Jun. These interventions do not reproduce temporary versus prolonged MMP1-CRISPRi.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, Figures 2 and 3; Experimental procedures, Cell culture and Transfection)

After withdrawal of the intervention, residual contracture, alpha-smooth muscle actin (αSMA), active transforming growth factor beta (TGF-beta), relaxation and the wound response must be measured.

Different experimental conditions. Contractile force, relaxation and αSMA are assessed after mechanical unloading. Withdrawal of MMP1 repression, active TGF-beta, wound responses and residual irreversible contracture are not jointly assessed.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Results, Figures 1, 2 and 5; Materials and Methods, Immunofluorescence and Cell Imaging)

Cells must be transferred to a soft control matrix to test whether the phenotype depends on the surrounding matrix.

Not verified in the article. Transfer to softer substrates is described through earlier literature. The study's own experiment unloads existing constructs rather than transferring treated cells to a soft control matrix.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Introduction, discussion of mechanical memory; Materials and Methods)

Contractility that is independent of initial matrix stiffness or is fully explained by toxicity would refute the hypothesis.

Not verified in the article. No supplied study applies initial-stiffness independence or toxicity as a falsification criterion for the proposed MMP1-protection experiment.

An increase in strength accompanied by irreversible contracture must be interpreted as a negative anti-aging outcome.

Not verified in the article. Excessive graft contraction is discussed as harmful, but increased strength accompanied by irreversible contracture is not evaluated as an anti-aging outcome.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Introduction; Discussion and Conclusions)

The study must use paired models from multiple independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. The study uses commercial adult human dermal fibroblasts and independent construct replicates. Paired models from multiple independent donors with donor-level biological replication are not established.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Materials and Methods, Cell Culture and 3D Tissue Construction; Statistical Methods and Image Analysis)

The study must use randomization and blinded assessment.

Not verified in the article. Animals were randomly selected from cages, but this does not establish randomized allocation to experimental conditions together with blinded assessment.

Matrix stiffness and architecture drive fibro-adipogenic progenitors’ activation into myofibroblasts (Methods, Animal handling; Imaging and analysis)

Sample size must be calculated from pilot variability.

Different experimental conditions. Sample sizes were based on preliminary power analyses in previous studies. Calculation from pilot variability for the proposed experiment is not documented.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Materials and Methods, Statistical Methods and Image Analysis)

The primary functional outcome must be selected in advance, and multiple comparisons must be accounted for.

Not verified in the article. Holm-Sidak multiple-comparison tests are reported, but advance selection of a primary functional outcome is not documented; the combined requirement is incomplete.

Cell–matrix feedback controls stretch-induced cellular memory and fibroblast activation (Materials and Methods, Statistical Methods and Image Analysis)

Cell viability, cellular composition and intervention specificity must be monitored.

Not verified in the article. Joint monitoring of viability, cellular composition and specificity of the proposed MMP1 intervention is not reported.

In reconstructed models, old and new collagen fractions must be distinguished by sequential stable isotope labeling.

Not verified in the article. None of the supplied experiments distinguishes old and new collagen using sequential stable isotope labeling in reconstructed models.

In native explants, only newly synthesized collagen must be labeled, and the unlabeled pool must be accounted for by mass balance.

Not verified in the article. Labeling newly synthesized collagen in native explants with mass-balance accounting for the unlabeled pool is not reported.

Isotope measurements must account for precursor enrichment and label recycling.

Not verified in the article. The supplied studies do not report collagen isotope measurements accounting for precursor enrichment and label recycling.

Second-harmonic generation (SHG) must be used to characterize collagen organization, with separate measurements of collagen mass, mechanics and healing.

Not verified in the article. Second-harmonic generation images collagen distribution and remodeling, but the same experiment does not combine it with separate collagen-mass, mechanics and healing measurements.

Matrix stiffness and architecture drive fibro-adipogenic progenitors’ activation into myofibroblasts (Results, Figures 4 and 6; Methods, Imaging and analysis)

MMP1 must be evaluated with a specific activity assay and an independent genetic intervention.

Not verified in the article. Collagen cleavage, MMP inhibition and recombinant MMP-1 provide functional evidence, while genetic perturbation targets c-Jun. The required specific MMP1 activity assay plus independent genetic intervention on MMP1 is not established.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, Figures 2 and 3; Experimental procedures, Cell culture)

For restoration of active MMP1, the proposed procedure specifies genetic suppression or prior inhibitor washout, without specifying the target of that genetic suppression.

Different experimental conditions. Secreted MMP-1 is activated using trypsin after washing, and latrunculin-A withdrawal restores cell spreading. Neither procedure reproduces the specified active-MMP1 restoration; the hypothesis leaves the genetic-suppression target unspecified.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Experimental procedures, Cell culture; Results, Figure 4)

A catalytically inactive protein must be included as a control for restoration of active MMP1.

Not verified in the article. A catalytically inactive protein control for restoration of active MMP1 is absent from the supplied experiments.

Assessment after withdrawal must establish that the drug does not persist.

Not verified in the article. Extensive washing after latrunculin-A withdrawal is described, but residual drug is not measured or otherwise explicitly excluded, and MMP1 suppression is not the withdrawn intervention.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, restoration of cell shape/mechanical tension; Figure 4)

An increase in collagen alone does not establish rejuvenation unless collagen organization and function also improve.

Not verified in the article. The supplied studies do not apply the proposed rejuvenation criterion requiring improved collagen organization and function in addition to increased collagen amount.

The proposed effect must be treated as a research hypothesis rather than an established effect or a recommendation for use; the cited evidence supports the starting observations but does not demonstrate the hypothesis.

Not verified in the article. This is a requirement governing interpretation of the proposed experiment. The supplied empirical findings support components but do not establish the complete effect or a recommendation for its use.

Conclusions from cellular and animal models require validation in human skin.

Not verified in the article. Human fibrotic skin specimens support observational comparisons, while causal interventions use mouse cells and mice. Validation of the proposed MMP1-protection experiment in human skin is absent.

Mechanical stiffness promotes skin fibrosis through Piezo1-mediated arginine and proline metabolism (Results, Figures 3-5; Methods, Patient samples and Animal models of fibrosis)

The proposed mechanism applies to a subset of aged human dermal fibroblasts.

Different experimental conditions. The mitochondrial RNA/MAVS mechanism was tested in embryonic lung fibroblasts, including MRC5 and IMR90, rather than a defined subset of aged human dermal fibroblasts.

Mitochondrial RNA cytosolic leakage drives the SASP (Results, Figs. 1-4; Methods, Cell culture and treatments.)

Suppression of the cyclic GMP-AMP synthase (cGAS)-STING pathway is hypothesized to be insufficient because cytosolic mitochondrial RNA maintains a MAVS-dependent senescence-associated secretory phenotype (SASP) and damage to neighboring cells after STING suppression.

Not verified in the article. Mitochondrial RNA-driven SASP and combined STING/MAVS inhibition were studied, but persistent mitochondrial RNA-dependent paracrine damage after STING suppression was not demonstrated. Combined inhibition produced no additive SASP suppression in the tested model.

Mitochondrial RNA cytosolic leakage drives the SASP (Results, MAVS aggregation contributes to the SASP; Supplementary Fig. 8a,b.)

The cited biological rationale concerns mitochondrial RNA and MAVS as contributors to SASP, as well as mitochondrial double-stranded RNA, PNPT1 and inflammation in senescent cells; whether this pathway determines resistance of aged human dermis to STING intervention remains unestablished.

Matches this study. The study provides the stated biological rationale through mitochondrial double-stranded RNA accumulation, reduced PNPT1, MAVS activation and SASP attenuation. Its experiments do not establish resistance of aged human dermis to STING intervention.

Release of mitochondrial dsRNA into the cytosol is a key driver of the inflammatory phenotype of senescent cells (Results, Fig. 1f-h and Fig. 3; Discussion, Fig. 6.)

The experiment must compare primary fibroblasts from young and aged photoprotected human skin.

Not verified in the article. Dermal fibroblasts from different donor ages were compared, including young and old donors in three-dimensional cultures, but photoprotected sampling was not documented.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods, 2.1 Cell Culture and 2.4 3D Cell Culture and Treatment Protocol.)

Senescence induced by ultraviolet A radiation (UVA) must be reproduced separately.

Different experimental conditions. Senescence was induced by X-rays, replicative exhaustion or chemotherapy. A separate UVA-induced senescence arm was not performed.

Mitochondrial RNA cytosolic leakage drives the SASP (Methods, Cell culture and treatments.)

Each donor must contribute to four experimental groups: control, STING suppression, MAVS suppression and combined STING and MAVS suppression.

Different experimental conditions. Control, MAVS knockdown, STING inhibition with SN-011 and combined treatment were compared in irradiated IMR90 cells. The four-arm design was not implemented within each young and aged skin donor.

Mitochondrial RNA cytosolic leakage drives the SASP (Results, Supplementary Fig. 8a,b; Methods, STING inhibition and siRNA gene knockdown.)

After removal of the reagents, the secretome must be transferred to untreated recipient fibroblasts in a three-dimensional dermal equivalent.

Different experimental conditions. Conditioned-medium transfer used monolayer recipients stimulated with TGF-β1. Three-dimensional dermal cultures were separate experiments, without the proposed transfer after STING/MAVS reagent removal.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods, 2.3 Co-Culture and 2.4 3D Cell Culture and Treatment Protocol; Fig. 7.)

Recipient cultures must be observed for 14-21 days after secretome transfer.

Different experimental conditions. Conditioned-medium recipients were assessed after 96 hours, while separate dermal equivalents were maintained for 28 days. Neither implements 14-21 days after the proposed secretome transfer.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods, 2.3 Co-Culture and 2.4 3D Cell Culture and Treatment Protocol.)

Suppression of each target must be validated using two independent reagents and rescue with a suppression-resistant construct.

Not verified in the article. MAVS knockdown was validated using a pooled siRNA preparation, and STING was inhibited with SN-011. Independent validation with two reagents per target plus suppression-resistant rescue was not reported.

Mitochondrial RNA cytosolic leakage drives the SASP (Fig. 4c; Supplementary Fig. 8; Methods, siRNA gene knockdown.)

The purity of the cytosolic fraction must be checked, and mitochondrial RNA and mitochondrial DNA must be assessed separately.

Matches this study. Cytosolic fraction purity was checked by immunoblotting, including absence of mitochondrial AIF, and mitochondrial RNA and DNA were measured separately. These methodological components were implemented outside the proposed donor experiment.

Release of mitochondrial dsRNA into the cytosol is a key driver of the inflammatory phenotype of senescent cells (Results, Fig. 1d and Supplementary Figs. 1j, 3d,e; Methods, Separation of cytoplasmic and mitochondrial fractions and Mitochondrial DNA content.)

The secretome must be normalized to viable donor cells so that donor-cell death does not mimic a reduction in SASP.

Not verified in the article. Secreted cytokines were reported per medium volume and confluent well, and viability was assessed separately for mitofusin drugs. Normalization of transferred secretome to viable donor-cell counts was not documented.

Release of mitochondrial dsRNA into the cytosol is a key driver of the inflammatory phenotype of senescent cells (Fig. 2g; Methods, Conditioned medium analysis and Cell viability assay.)

Combined STING and MAVS suppression is predicted to reduce paracrine harm more than either suppression alone while preserving cell-cycle arrest.

Different experimental conditions. MAVS knockdown reduced SASP expression without changing proliferation-related gene expression, but combined STING/MAVS treatment lacked additive SASP suppression. Recipient damage and durable arrest under dual treatment were not tested.

Mitochondrial RNA cytosolic leakage drives the SASP (Fig. 4g; Results, MAVS aggregation contributes to the SASP; Supplementary Fig. 8b.)

The primary outcome is new type I collagen formation by recipient cells, and newly formed collagen must be distinguished from the original scaffold.

Different experimental conditions. Collagen expression and recipient collagen I protein were measured, and separate dermal models used inert polystyrene scaffolds. Newly synthesized recipient collagen I was not the primary endpoint of a dual STING/MAVS secretome-transfer experiment.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Results, 3.1 and 3.3; Figs. 2, 4 and 7; Methods, 2.4.)

Secondary outcomes include interleukin-6 (IL-6), interleukin-8 (IL-8) and MAVS aggregates.

Matches this study. IL-6, IL-8 and MAVS aggregates were assessed as mechanistic outcomes. Their measurement does not establish the proposed donor-specific dual-blockade result.

Mitochondrial RNA cytosolic leakage drives the SASP (Fig. 4a,b; Fig. 5e,f; Supplementary Figs. 3e and 9.)

Secondary outcomes also include persistent suppression of the 5-ethynyl-2′-deoxyuridine (EdU) readout after washout, p16/p21 and DNA damage.

Not verified in the article. The study assessed p16/p21, proliferation markers and DNA damage in different experiments, but persistent suppression of EdU incorporation after intervention washout was not verified.

Mitochondrial RNA cytosolic leakage drives the SASP (Fig. 3d,e; Fig. 6b-d; Methods, Cell culture and treatments.)

A STING×MAVS interaction is expected predominantly in samples with high mitochondrial RNA levels.

Not verified in the article. The combined treatment experiment did not establish a STING×MAVS interaction stratified by mitochondrial RNA abundance or a preferential effect in mitochondrial-RNA-high samples.

Mitochondrial RNA cytosolic leakage drives the SASP (Results, Supplementary Fig. 8a,b.)

The additional RNA mechanism in this model must be rejected if validated MAVS suppression provides no improvement beyond STING suppression and the confidence interval excludes a prespecified useful effect.

Not verified in the article. Reported non-additivity was not evaluated using the proposed collagen endpoint and a confidence interval excluding a prespecified useful incremental MAVS effect.

Mitochondrial RNA cytosolic leakage drives the SASP (Results, Supplementary Fig. 8b.)

A result of p>0.05 alone must not be treated as refutation.

Not verified in the article. The supplied studies do not document the proposed decision rule separating p>0.05 from refutation based on exclusion of a useful effect.

The intended benefit is limitation of secretory harm; genome restoration and demonstrated rejuvenation are outside the stated claim.

Matches this study. The study explicitly frames SASP suppression with preservation of growth arrest as an anti-inflammatory strategy. This supports the limited therapeutic rationale, without demonstrating genome restoration or rejuvenation.

Mitochondrial RNA cytosolic leakage drives the SASP (Introduction; Results, Figs. 3h,i and 4g; Discussion.)

A separate functional control is required because dual blockade of nucleic acid sensing may weaken protective responses.

Not verified in the article. No supplied study reports a separate functional test of protective responses under the proposed combined STING/MAVS blockade in aged dermal fibroblasts.

A pilot study must include 6-8 independent donors.

Not verified in the article. A pilot of the proposed experiment involving 6-8 independent skin donors is not reported.

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimally useful effect.

Not verified in the article. No supplied study calculates the proposed main-study sample size from recipient collagen I variance and a prespecified minimally useful effect.

The donor is the biological unit, and chips or wells are nested replicates.

Not verified in the article. The proposed analysis treating independent skin donors as biological units and chips or wells as nested replicates is not documented.

The study must use randomization and blinded analysis.

Different experimental conditions. Random allocation and blinded analysis were explicitly used in mouse experiments targeting BAX/BAK. These controls were not demonstrated for the proposed human dermal STING/MAVS experiment.

Apoptotic stress causes mtDNA release during senescence and drives the SASP (Methods, Mouse models and treatments.)

Statistical analysis must use a paired model accounting for donor, report confidence intervals and correct for secondary comparisons.

Not verified in the article. Paired patient-level comparisons were used for adipose explants, and multiple-comparison procedures were described. The complete donor-adjusted paired model with confidence intervals and secondary-outcome correction for this dermal experiment was not reported.

cGAS–STING drives ageing-related inflammation and neurodegeneration (Extended Data Fig. 3; Methods, Statistics and reproducibility.)

Neither p16/p21 nor senescence-associated β-galactosidase (SA-β-gal), considered alone, establishes senescence.

Matches this study. Senescence was assessed using p16/p21, senescence-associated β-galactosidase and absence of proliferation markers, with additional damage measurements. This implements a multi-marker assessment rather than reliance on a single marker.

Apoptotic stress causes mtDNA release during senescence and drives the SASP (Methods, Cell culture and treatments; Fig. 3e-m.)

This is a research hypothesis: the proposed new experiments have not been performed, and no experimental results are claimed.

Not verified in the article. The unperformed status of the proposed experiments is the submitter's declaration. The supplied publications report other completed experiments and provide no results for this complete proposal.

The hypothesis concerns collagen preservation as a separately reproducible component of retinoid action, with the aim of preserving the strength, renewal and recovery after injury of aging skin.

Not verified in the article. No supplied study isolates collagen preservation as a reproducible component of retinoid action and tests the specified skin-function objectives.

Senescent fibroblasts can secrete matrix metalloproteinases, and a mechanically damaged collagen network can itself alter neighboring cell function.

Not verified in the article. Senescent adult dermal fibroblasts showed increased MMP1 expression and protein abundance, but this study did not test damaged collagen acting on neighboring cells. The combined requirement is only partially supported.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Results 3.2, Figure 3; Discussion)

Matrix metalloproteinase-1 (MMP1) in the senescent secretome is hypothesized to damage the collagen matrix and thereby transmit part of the secretome's harmful effect to neighboring cells.

Different experimental conditions. Senescent fibroblasts altered young fibroblast gene expression partly through secreted complement factor D. MMP1 induction in recipient cells differs from demonstrating secretome-derived MMP1 damage transmitted through collagen.

Senescent dermal fibroblasts negatively influence fibroblast extracellular matrix-related gene expression partly via secretion of complement factor D (Results 3.1-3.3, Figures 1-3)

Selective protection of the collagen network before secretome exposure is predicted to preserve nonsenescent fibroblast function by preventing the matrix-mediated component of harm while leaving the secretome unchanged.

Not verified in the article. Preservation of nonsenescent fibroblast function by selectively protecting collagen before exposure to an unchanged senescent secretome was not demonstrated.

Identical collagen networks with and without selective collagen protection must be exposed to the same secretome.

Not verified in the article. The supplied experiments do not compare identical selectively protected and unprotected collagen networks exposed to the same senescent secretome.

The experiment must additionally include immunodepletion of MMP1 from the secretome and restoration of active MMP1 in a comparable amount.

Not verified in the article. MMP1 immunodepletion from the senescent secretome followed by comparable active-MMP1 add-back was not reported.

After secretome exposure and washing, the networks must be seeded with fresh nonsenescent cells.

Different experimental conditions. Fresh control lung fibroblasts were seeded onto washed, decellularized fibroblast-deposited matrix. This substitutes a lung-derived matrix-deposition model for collagen networks exposed to senescent secretome.

Regulation of Cellular Senescence Is Independent from Profibrotic Fibroblast-Deposited ECM (Methods 2.2 and 2.4)

The experiment must measure the function of the newly seeded cells, residual cytokines and network mechanics.

Not verified in the article. Reseeded-cell proliferation, gene expression and cytokine secretion were measured, but residual cytokines after washing and network mechanics were not established together with these outcomes.

Regulation of Cellular Senescence Is Independent from Profibrotic Fibroblast-Deposited ECM (Methods 2.4-2.8; Results 3.2-3.5)

Persistence of dysfunction despite prevention of collagen fragmentation would indicate that a matrix intermediary does not explain the proposed component of the harmful effect.

Not verified in the article. No supplied experiment tests whether dysfunction persists when collagen fragmentation from the senescent secretome has been selectively prevented.

Transmission of dysfunction exclusively through soluble factors would indicate that a matrix intermediary does not explain the proposed component of the harmful effect.

Not verified in the article. Transwell coculture supports transmission by secreted factors, but it does not establish exclusive soluble-factor transmission or exclude an additional collagen-mediated component.

Senescent dermal fibroblasts negatively influence fibroblast extracellular matrix-related gene expression partly via secretion of complement factor D (Methods 2.2; Results 3.1-3.3)

The study must use paired models from several independent donors, with the donor as the biological unit and wells as technical replicates.

Not verified in the article. Multiple donor-derived lines and matched senescent/nonsenescent lines were used, but the complete donor-level paired protection experiment is absent; the paracrine Figure 7 experiment reports n = 1.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods 2.1, 2.2 and 2.7; Figures 3 and 7)

The study must use randomization and blinded assessment.

Not verified in the article. Senescence-staining images were randomized and counted blindly. Random allocation of the proposed experimental conditions and blinded functional assessment were not documented.

The expression of fibrosis-related genes is elevated in doxorubicin-induced senescent human dermal fibroblasts, but their secretome does not trigger a paracrine fibrotic response in non-senescent cells (Methods, SA-β-gal staining and BrdU incorporation)

Sample size must be calculated from pilot variability.

Not verified in the article. A sample-size calculation based on pilot variability for the proposed test was not reported.

A primary functional outcome must be selected in advance, and multiple comparisons must be accounted for.

Not verified in the article. The lung-matrix study used multiple-comparison adjustment, but a prespecified primary functional outcome for the proposed collagen-protection experiment is absent.

Regulation of Cellular Senescence Is Independent from Profibrotic Fibroblast-Deposited ECM (Methods 2.8)

Cell viability, cellular composition and intervention specificity must be controlled.

Not verified in the article. Complement factor D cytotoxicity and knockdown specificity received checks, including a second small interfering RNA. Viability, cellular composition and specificity of selective collagen protection were not jointly controlled.

Senescent dermal fibroblasts negatively influence fibroblast extracellular matrix-related gene expression partly via secretion of complement factor D (Methods 2.1-2.2; Results 3.3)

In reconstructed models, old and new collagen fractions must be distinguished by sequential stable isotope labeling.

Not verified in the article. Sequential stable-isotope labeling to distinguish old and new collagen in reconstructed models was not reported.

In native explants, only new synthesis must be labeled, and the unlabeled pool must be accounted for by mass balance.

Not verified in the article. Native-explant labeling restricted to newly synthesized collagen, with mass-balance accounting for the unlabeled pool, was not reported.

Interpretation of isotope labeling must account for precursor enrichment and label recycling.

Not verified in the article. Accounting for precursor enrichment and isotope-label recycling was not documented.

Second-harmonic generation (SHG) must be used to characterize collagen organization, while collagen mass, mechanics and healing must be measured separately.

Not verified in the article. Second-harmonic microscopy and mechanical measurements were included, but the required combination with independent collagen-mass and healing measurements in the proposed test was not performed.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Experimental procedures, second harmonic generation microscopy and atomic force microscopy; Figures 1-4)

MMP1 must be examined using a specific activity assay and an independent genetic intervention.

Different experimental conditions. Collagen cleavage, recombinant MMP1 and an MMP inhibitor were examined, while the genetic intervention targeted c-Jun. This differs from independently manipulating MMP1 itself alongside a specific activity assay.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, Figures 2-3; Experimental procedures)

Restoration of active MMP1 must use genetic suppression or prior washout of the inhibitor.

Not verified in the article. Active-MMP1 restoration using genetic suppression or prior inhibitor washout was not reported.

A catalytically inactive protein must be added as a control for restoration of active MMP1.

Not verified in the article. A catalytically inactive MMP1 protein control for the active-protein add-back experiment was not reported.

The effect must be tested after treatment withdrawal, and persistence of the drug must be ruled out.

Different experimental conditions. Latrunculin-A withdrawal and extensive washing restored cell spreading and reduced MMP1. This tests reversal of cytoskeletal disruption, rather than persistence of collagen-protection benefits with residual drug excluded.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, Figure 4)

An increase in collagen alone must not be interpreted as rejuvenation unless collagen organization and function also improve.

Not verified in the article. The supplied studies do not apply the specified joint collagen-quantity, organization and functional criterion to establish rejuvenation by the proposed intervention.

The proposed effect must be treated as a research hypothesis rather than an established effect or a recommendation for use; the cited evidence supports the starting observations but does not establish the hypothesis.

Not verified in the article. The complete proposed effect remains a research hypothesis within the supplied evidence; no primary study establishes it or supports a recommendation for its use.

Conclusions obtained from cellular and animal models require validation in human skin.

Matches this study. The authors explicitly state that their cultured-cell findings have limited applicability to human skin and require translation to in vivo tissue. This matches the validation caveat, not completed validation of the proposed intervention.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Discussion, limitations of in vitro models)

The hypothesis concerns collagen preservation as a separable component of retinoid effects and tests whether collagen protection can be separated from the senolytic action of the candidate MMP1 inhibitor IP10-3.

Not verified in the article. Neither supplied study tests retinoids or separates IP10-3-mediated collagen protection from its senolytic action.

The starting observation is that IP10-3 has been reported to affect MMP1-associated measures and apoptosis in cells rendered senescent by ultraviolet A irradiation.

Not verified in the article. The cited IP10-3 article is mentioned in the hypothesis bibliography, but its results are absent from the supplied scientific sources.

Direct collagen protection and removal of senescent cells are hypothesized to make distinct contributions, with selective extracellular MMP1 suppression reproducing collagen fiber protection independently of senescent cell removal and without obligatory fibroblast death.

Different experimental conditions. The abstract reports collagen protection through interventions involving plasmin and prostaglandin E2. It does not establish selective extracellular MMP1 suppression or independence from fibroblast death and senescent-cell removal.

Plasmin Derived from Senescent Fibroblasts Is Induced by Prostaglandin E2 and Increases the Degradation of Collagen (Abstract)

The experiment must compare IP10-3, genetic reduction of MMP1, and independent removal of an equal number of senescent cells.

Different experimental conditions. The reported interventions include tranexamic acid and NS398, rather than the required comparison of IP10-3, genetic MMP1 reduction, and matched senescent-cell removal.

Plasmin Derived from Senescent Fibroblasts Is Induced by Prostaglandin E2 and Increases the Degradation of Collagen (Abstract)

Direct inhibition of MMP1 by the candidate must be tested in a cell-free fibrillar matrix, including assessment of fibril protection.

Different experimental conditions. Collagen degradation was studied in a three-dimensional matrix containing senescent fibroblasts. This does not reproduce the cell-free fibrillar assay of direct IP10-3 inhibition.

Plasmin Derived from Senescent Fibroblasts Is Induced by Prostaglandin E2 and Increases the Degradation of Collagen (Abstract)

Initial and final cellularity must be normalized in the skin experiments.

Not verified in the article. Seeding densities and gene-expression normalization are described, but normalization of both initial and final skin cellularity is not established.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods, sections 2.1, 2.4 and 2.5)

Apoptosis, collagen flux, and tissue mechanics must be measured after cell restoration.

Not verified in the article. Neither supplied study reports cell restoration followed by measurements of apoptosis, collagen flux, and tissue mechanics.

The direct anticollagenase mechanism is not demonstrated if the candidate fails to protect cell-free fibrils and its tissue effect is fully explained by a reduction in the number of source cells.

Not verified in the article. Neither study combines a cell-free fibril test with quantitative attribution of the tissue effect to loss of source cells.

The functional objective is to preserve aging skin strength, renewal, and recovery after injury.

Different experimental conditions. The study measures fibroblast migration and molecular features of matrix production, rather than preservation of skin strength, renewal, and recovery after injury.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods, section 2.8; Results, section 3.3; Figure 6h)

The study must use paired models from several independent donors, randomization, and blinded assessment.

Not verified in the article. Several donor-derived lines and matched senescent and nonsenescent lines are described, but randomization and blinded assessment are not documented.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods, sections 2.1 and 2.2; Figure 2 legend)

The donor must be treated as the biological unit, and wells must be treated as technical replicates.

Not verified in the article. The analysis uses independent cell lines and repeated samples, but the required donor-as-biological-unit and wells-as-technical-replicates hierarchy is not explicitly established.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods, sections 2.2 and 2.7; Results, opening paragraphs)

Sample size must be calculated from pilot variability.

Not verified in the article. A sample-size calculation based on pilot variability is absent from the supplied material.

The primary functional outcome must be selected in advance, and multiple comparisons must be accounted for.

Not verified in the article. Bonferroni and false-discovery-rate corrections are reported, but a prespecified primary functional outcome is not documented.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods, section 2.7)

Viability, cellular composition, and intervention specificity must be controlled.

Not verified in the article. The supplied studies do not establish the combined viability, cellular-composition, and intervention-specificity controls required for the proposed IP10-3 experiment.

Old and new collagen fractions must be distinguished by sequential stable isotope labeling in reconstructed models.

Not verified in the article. Sequential stable isotope labeling of old and new collagen fractions in reconstructed models is not reported.

In native explants, only newly synthesized collagen must be labeled, and the unlabeled pool must be accounted for by mass balance.

Not verified in the article. Native-explant labeling of new collagen with mass-balance accounting for the unlabeled pool is not reported.

Isotopic enrichment of the precursor and label recycling must be accounted for.

Not verified in the article. Accounting for precursor isotopic enrichment and label recycling is not reported.

Second harmonic generation must characterize collagen organization, while collagen mass, mechanics, and wound healing must be measured separately.

Not verified in the article. Neither supplied study documents second harmonic generation together with separate measurements of collagen mass, tissue mechanics, and wound healing.

MMP1 involvement must be assessed with a specific activity assay and an independent genetic intervention.

Different experimental conditions. MMP1 transcript and protein abundance are measured. The authors distinguish these from activity, and the required specific activity assay plus independent genetic intervention is absent.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Results, section 3.2; Figure 3; Discussion)

The experiment restoring active MMP1 must use genetic suppression or preliminary inhibitor washout.

Not verified in the article. Active MMP1 restoration following genetic suppression or inhibitor washout is not reported.

Catalytically inactive MMP1 protein must be included as a control for restoration of active MMP1.

Not verified in the article. A catalytically inactive MMP1 protein control for active-enzyme restoration is not reported.

The effect must be tested after treatment withdrawal, and residual presence of the drug must be excluded.

Not verified in the article. Post-withdrawal testing with exclusion of residual IP10-3 is not reported.

An increase in collagen alone cannot establish rejuvenation; improved organization and function are required for that interpretation.

Not verified in the article. The authors caution that expression measurements cannot establish matrix production and degradation, but they do not test rejuvenation through combined improvements in collagen quantity, organization, and function.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Discussion, limitations)

The proposed mechanism must be treated as a research hypothesis rather than an established effect or a recommendation for use; the starting observations do not establish the hypothesis.

Not verified in the article. Neither supplied study discusses the proposed IP10-3 separation experiment as a research hypothesis; this qualification belongs to the submitted proposal.

Conclusions obtained from cell and animal models require verification in human skin.

Matches this study. The authors explicitly state that all tested conditions were in vitro and that relevance to human skin depends on translation to in vivo tissue. This matches the need for human-skin verification, not completion of that verification.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Discussion, limitations of in vitro models)

The proposed age-related defect in intercellular support reflects reduced usefulness of individual fibroblast migrasomes due to cargo quality, independently of particle number and uptake efficiency.

Different experimental conditions. Senescence-associated cargo and transmission of senescence were demonstrated in mesenchymal stem cells and fibroblasts. Reduced support of old keratinocytes per internalized fibroblast migrasome was not tested.

Migrasomes trigger innate immune activation and mediate transmission of senescence signals across human cells (Results, Figures 2-5; Methods, Cell culture and treatment)

At the same number of internalized particles, migrasomes from old fibroblasts are predicted to restore keratinocyte barrier function and motility less effectively than migrasomes from young fibroblasts.

Not verified in the article. Young migrasomes improved HaCaT migration and mouse wound closure, but old migrasomes were not compared at matched uptake and barrier recovery was not measured.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figures 4-6)

Simply increasing the production of migrasomes by old fibroblasts is proposed to be insufficient to compensate for the support defect.

Not verified in the article. No supplied study increased migrasome production by old fibroblasts and tested whether that intervention compensated for deficient keratinocyte support.

The stated experimental background is that migrasomes from young fibroblasts improved signs of keratinocyte aging and wound healing in experimental models.

Matches this study. Young primary fibroblast migrasomes reduced senescence-associated markers and improved function in peroxide-treated HaCaT cells and promoted wound healing in naturally aged mice.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figures 4-7)

The experiment must use migrasomes isolated from young and old primary fibroblasts and test them in primary old keratinocytes in organotypic skin.

Different experimental conditions. Treatment used young oral-mucosal primary fibroblast migrasomes, peroxide-treated HaCaT cells and aged mice. Old primary fibroblast preparations and old primary keratinocytes in organotypic skin were absent.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Methods, Cell culture; Mouse skin wound model and treatments; Results, Figures 3-6)

The purity, size and number of isolated migrasomes must be measured.

Not verified in the article. Electron microscopy and marker analysis characterized preparations, and protein concentration was measured. Counts on producing cells do not establish particle numbers in isolated young and old preparations.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Methods, Isolation of migrasomes from cultured cells; Figures 3-4)

Young and old fibroblast migrasomes must be compared at equal particle numbers, equal protein mass and equal numbers of actually internalized migrasomes to distinguish the contributions of quantity, composition and uptake efficiency.

Not verified in the article. Dosing used protein concentration and imaging demonstrated uptake, but the three required young-versus-old normalization comparisons were not performed.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figure 4D-I; Methods, Isolation of migrasomes from cultured cells)

Control fractions must include particle-free medium, small extracellular vesicles and disrupted migrasomes.

Not verified in the article. Exosomes were isolated for characterization and cargo comparison, but the complete functional control set of particle-free medium, small vesicles and disrupted migrasomes was not tested.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Methods 2.7-2.9; Results 3.3, Figure 3; Figure 8m)

After a candidate cargo component is identified, its depletion and restoration must be tested to assess causality.

Not verified in the article. CXCL12 knockdown reduced migrasome effects on fibroblast proliferation, migration and endothelial tube formation. Cargo restoration and the age-dependent organotypic keratinocyte test were absent.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Methods 2.29; Results 3.8, Figure 8b-l)

TSPAN4 must not be treated as the sole evidence of preparation purity.

Matches this study. Preparation characterization combined morphology with multiple enriched markers and assessment of cellular and small-vesicle markers, extending beyond TSPAN4 alone.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Results 3.3, Figure 3b-c)

The primary outcome must be barrier recovery after identical microinjury.

Different experimental conditions. The study measured full-thickness wound closure and histology in mice, rather than functional barrier recovery after identical microinjury in organotypic skin.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Methods, Mouse skin wound model and treatments; Figure 6)

Secondary outcomes must include directed migration, resistance to repeated stress and signs of senescence after washout.

Not verified in the article. Scratch and transwell migration assays and senescence markers were reported. Resistance to repeated stress and persistence of senescence changes after migrasome washout were not assessed.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figures 4-5)

If young and old migrasomes are equally effective after uptake is matched, the result must favor an explanation based on delivery or quantity over the cargo-quality hypothesis.

Not verified in the article. No supplied study evaluated young-versus-old efficacy after uptake matching or applied the specified interpretation of equal efficacy.

The interpretation must allow for heterogeneous cargo within migrasomes.

Matches this study. The study explicitly describes heterogeneous migrasome contents and detects mitochondria, endogenous retroviral components and inflammatory cytokines.

Migrasomes trigger innate immune activation and mediate transmission of senescence signals across human cells (Results, Figures 2-4; Discussion)

Improvement in HaCaT cells must not be accepted as sufficient evidence for aged human epidermis.

Different experimental conditions. Functional keratinocyte experiments used HaCaT cells, supplemented by mouse experiments. These results do not supply the required validation in aged human epidermis.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Methods, Cell culture; Results, Figures 4-7; Discussion)

The pilot study must include 6-8 independent donors.

Different experimental conditions. Primary young fibroblasts came from five healthy young volunteers; a pilot involving 6-8 independent donors for the proposed comparison was not reported.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Methods, Cell culture)

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Different experimental conditions. Sample sizes were based on similar studies, explicitly without statistical predetermination, rather than primary-outcome variance and a prespecified minimum useful effect.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Methods 2.30, Statistical Analysis)

The donor must be the biological unit, with chips or wells treated as nested replicates.

Not verified in the article. No supplied study implements the proposed donor-level biological unit with chips or wells modeled as nested replicates.

The study must use randomization and blinded analysis.

Matches this study. Rat allocation was randomized and migrasomes were counted by two blinded observers. These practices are reported, although not within the proposed aged organotypic experiment or for every outcome.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Methods 2.6; Figure 2e)

The statistical analysis must use a paired model accounting for donor, report confidence intervals and correct for secondary comparisons.

Different experimental conditions. The study reports unpaired tests and analysis of variance, with a statement about 95% confidence intervals. It does not implement the required paired donor-adjusted model and secondary-outcome correction.

Single-Cell Analysis Reveals Fibroblast-Derived Migrasomes as CXCL12 Carriers Promoting Skin Wound Repair (Methods 2.30; Figure 7e-h)

p16/p21 or senescence-associated beta-galactosidase (SA-β-gal), considered separately, must not be treated as proof of senescence.

Matches this study. Senescence assessment combined p16/p21, senescence-associated beta-galactosidase, proliferation and other functional or inflammatory measures. This matches the multi-measure requirement, without establishing durable reversal after washout.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figures 4-5 and 7)

New collagen must be distinguished from the original scaffold.

Not verified in the article. Masson's staining assessed collagen in healing mouse skin. No assay distinguished newly synthesized collagen from an original organotypic scaffold.

Young fibroblast-derived migrasomes alleviate keratinocyte senescence and enhance wound healing in aged skin (Results, Figure 6F)

A result of p>0.05 alone must not be considered a refutation of the hypothesis.

Not verified in the article. No supplied study specifies the proposed refutation rule or distinguishes uptake-matched equivalence from a merely nonsignificant difference in this test.

The hypothesis concerns collagen preservation as a separately reproducible component of retinoid action, with the aim of preserving the strength, renewal and recovery after injury of aging skin.

Different experimental conditions. The study concerns UV-associated collagen damage and decorin protection, but does not isolate a component of retinoid action or test the specified aging-skin functional outcomes.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Introduction; Results, Figures 1, 4 and 5; Materials and Methods)

Develop a specific reversible ligand that locally shields the collagen cleavage site from matrix metalloproteinase-1 (MMP1).

Not verified in the article. Decorin binding and protection against collagen cleavage are demonstrated, but development of a specific ligand with verified reversible binding at the cleavage site is not reported.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figure 4; Discussion)

The proposed protection must result from reversible shielding of the cleavage site, without crosslinking collagen fibrils or directly inhibiting MMP1 activity on other substrates.

Not verified in the article. Decorin-mediated protection supports a component of shielding, but binding reversibility, exclusion of fibril crosslinking and preserved MMP1 activity on other substrates are not jointly verified.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 4 and 5; Materials and Methods, collagen cleavage assay)

Before the comparative experiment, verify ligand binding, the reversibility of binding and the absence of direct MMP1 inhibition on other substrates.

Not verified in the article. Electron microscopy supports collagen association, but the required preliminary verification of reversibility and lack of direct inhibition on other substrates is absent.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figure 4; Materials and Methods)

Compare temporary shielding, persistently chemically modified collagen and direct MMP1 blockade at the same initial degree of protection.

Different experimental conditions. The experiments use mutant collagen resistant to cleavage and enzyme inhibitors, rather than the specified three-arm comparison including temporary shielding and chemical stabilization at equal initial protection.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figures 5, 6 and 7)

Measure collagen turnover and functional recovery after ligand removal; temporary shielding is predicted to provide better recovery after withdrawal than permanent chemical stabilization of the matrix.

Not verified in the article. Elastase digestion removes decorin protection, but this is not ligand withdrawal followed by measurement of collagen turnover and superior functional recovery relative to permanent stabilization.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figure 5; Materials and Methods, collagen cleavage assay)

If a specific reversible ligand cannot be obtained, the approach remains untested.

Not verified in the article. The supplied studies do not establish the required specific reversible ligand, so the proposed approach remains untested under this condition.

Protection attributable to crosslinking, toxicity or general enzyme inactivation rejects the proposed mechanism.

Not verified in the article. No supplied study tests the proposed shielding mechanism with the combined exclusion of crosslinking, toxicity and general enzyme inactivation.

Experimental resistance of collagen to collagenases does not establish preservation of physiological collagen turnover.

Not verified in the article. Failure of keratinocytes to migrate on resistant collagen supports the functional caution, but physiological collagen turnover itself was not measured.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figure 6; Discussion)

Use paired models from several independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. Duplicate conditions and repeated experiments with different donors are described, but donor-level biological-unit analysis for the proposed paired comparison is not established; several figures summarize wells.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Colloidal Gold Migration Assay; Figures 6 and 7)

Use randomization and blinded assessment.

Not verified in the article. Randomized treatment allocation and blinded assessment are not documented; random selection of microscopy fields does not establish these safeguards.

Calculate sample size from pilot variability, prespecify the primary functional outcome and account for multiple comparisons.

Not verified in the article. The supplied studies do not document the required combination of pilot-based sample sizing, a prespecified primary functional outcome and multiplicity adjustment.

Control for viability, cellular composition and intervention specificity.

Not verified in the article. Protein synthesis, inhibitor stereoisomers, antibodies and gelatin controls address some alternative explanations, but the complete viability, cellular-composition and specificity controls for the ligand experiment are absent.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figures 5-7; Table I)

In reconstructed models, distinguish old and new collagen fractions using sequential stable isotope labeling.

Not verified in the article. Sequential stable isotope labeling of old and new collagen in reconstructed models is not reported.

In native explants, label only newly synthesized collagen and account for the unlabeled pool by mass balance.

Not verified in the article. Labeling only new collagen synthesis in native explants with mass-balance accounting of the unlabeled pool is not reported.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. The required collagen isotope analysis accounting for precursor enrichment and label recycling is absent.

Use second-harmonic generation (SHG) to characterize collagen organization, while separately measuring collagen mass, mechanical properties and healing.

Not verified in the article. Electron microscopy and collagen-fragment analysis are provided, but second-harmonic generation together with separate collagen mass, mechanical and healing outcomes is absent.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 4 and 5; Materials and Methods, Electron Microscopy)

Test MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. Antibody blockade supports MMP1 specificity, but collagen mutation is not a genetic intervention on MMP1, and the thiopeptolide assay uses a gelatinase catalytic domain.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Thiopeptolide Assay; Results, Figures 6 and 7; Table II)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout.

Not verified in the article. Growth-factor induction of MMP1 in HaCaT cells is described, but active-MMP1 restoration after genetic suppression or inhibitor washout is not tested.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figure 4; Materials and Methods, Colony Dispersion Migration Assay)

Include catalytically inactive MMP1 protein as a control in the active MMP1 restoration experiment.

Not verified in the article. No supplied study includes catalytically inactive MMP1 protein as a control in the specified restoration experiment.

When testing effects after withdrawal, exclude persistence of the administered agent.

Not verified in the article. The study measures persistence of inhibitor activity during culture, but does not exclude residual agent after withdrawal in a recovery experiment.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Table II; Materials and Methods, Thiopeptolide Assay)

An increase in collagen amount alone does not establish rejuvenation; interpretation must also consider improvement in organization and function.

Not verified in the article. Structural stability and fibroblast responses are examined, but rejuvenation assessed jointly through collagen amount, organization and function is not established.

Development of collagenase-resistant collagen and its interaction with adult human dermal fibroblasts (Abstract; Conclusion; cell-adhesion and cytoskeleton section snippets)

The proposed effect remains a research hypothesis rather than an established effect or a recommendation for use; the supporting observations do not prove the hypothesis.

Not verified in the article. The supplied observations support components, while the proposed comparative benefit remains an untested hypothesis and provides no established recommendation for use.

Conclusions from cellular and animal models require validation in human skin.

Not verified in the article. Human skin observations concern UV-induced decorin degradation and collagen association; the proposed reversible-ligand intervention and recovery advantage are not validated in human skin.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 1, 4 and 5; Materials and Methods, human tissue procurement)

The experimental model consists of old laboratory mice maintained on a standardized diet and with their baseline microbiota characterized.

Matches this study. Parker and colleagues used 18- and 24-month-old laboratory mice on standard chow and characterized fecal microbiota before antibiotic treatment and transfer.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Methods: Experimental model details, Mice; Microbiota transfer; Results, Fig. 5.)

A limited course of microbiota transfer is proposed to switch the old intestinal ecosystem into a stable functional state that persists without repeated administrations.

Not verified in the article. Three daily transfers produced lasting compositional, metagenomic and host-transcriptional changes through day 56. A stable state conferring the proposed barrier benefit was not demonstrated.

Establishment and resilience of transplanted gut microbiota in aged mice (Results: Establishment of transplanted gut microbiota; Long-term effects; Figs. 2-3; Methods: Fecal microbiota transplantation.)

The experiment must compare limited transfer of young microbiota, limited transfer of old microbiota, and a procedural control.

Not verified in the article. The closest finite-course study compared young heterologous and old autologous transfers with spontaneous recovery and untreated controls. A matched sham-transfer procedure was not documented, and donor age was confounded with vendor and autologous status.

Establishment and resilience of transplanted gut microbiota in aged mice (Fig. 2A; Methods: Antibiotic treatment; Fecal microbiota transplantation.)

Mice must be observed for 21-56 days after the last administration, with cells and metabolites tracked during this period.

Not verified in the article. Transfers occurred on days 2-4 and follow-up extended to day 56, approximately 52 days after the last transfer. Microbial composition, metagenomic pathways and colon transcription were assessed, but the required combined cellular and metabolite tracking was not reported.

Establishment and resilience of transplanted gut microbiota in aged mice (Figs. 2-3; Methods: Fecal microbiota transplantation; RNA-seq of colon samples.)

After the observation period, intestinal barrier function must be tested following a moderate, reversible dietary challenge.

Different experimental conditions. The challenge was seven days of 3% dextran sulfate sodium beginning on day 26, producing acute colitis. This differs scientifically from a moderate, reversible dietary challenge followed by barrier testing.

Establishment and resilience of transplanted gut microbiota in aged mice (Results: The resilience of transplanted gut microbiota against colon inflammation; Fig. 4; Methods: DSS-induced colon inflammation.)

The proposed mechanism is a persistent ecological change induced by microbiota transfer that supports intestinal barrier function.

Not verified in the article. Microbiota replacement accompanied improved barrier-related biomarkers, supporting a microbial contribution. Persistent ecological maintenance of barrier function after cessation was left for future investigation.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Results: Heterochronic FMT reverses age-associated breakdown of epithelial barrier integrity; Figs. 4-6; Discussion: Signature microbes.)

The causal test must determine both whether donor organisms persist and whether their continued presence is required for the effect.

Not verified in the article. Donor-like community persistence was followed, but continued donor-organism necessity was not experimentally tested. Community resemblance does not establish strain-level persistence or its causal necessity.

Establishment and resilience of transplanted gut microbiota in aged mice (Figs. 2-4; Discussion; Limitations of the study.)

Persistence of donor microbes would support an ecological mechanism and would not establish a cell-autonomous mechanism; conclusions must distinguish the cell/host-cell and cell/ecosystem levels described by the author.

Not verified in the article. Stebegg and colleagues showed microbiota-responsive recovery of aged gut germinal centres and argued against an irreversible cell-intrinsic defect. They did not test the proposed donor-persistence-based distinction for lasting barrier restoration.

Heterochronic faecal transplantation boosts gut germinal centres in aged mice (Results: Heterochronic faecal transplantation boosts the GC in PPs; Fig. 6; Discussion.)

All preparatory interventions and housing conditions must be identical across the comparison groups.

Different experimental conditions. Transfer groups received antibiotics and donor-soiled cages with renewed bedding, whereas PBS-only controls lacked antibiotics and antibiotic-only controls returned to their home cages. Preparation and microbial housing exposure were therefore not identical across all comparisons.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Methods: Microbiota transfer; Fig. 1.)

The stated primary outcome and success criterion are improved intestinal barrier resilience and metabolic profile after administrations have stopped.

Not verified in the article. Barrier-related biomarkers and metabolic pathways changed, but donor bedding was replenished every three days and tissues were collected 18 days post-transfer. Post-cessation barrier resilience was not established; fecal metabolite profiles also lacked significant pairwise group differences after correction.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Methods: Microbiota transfer; Results, Figs. 4 and 7; Heterochronic FMT alters lipid and vitamin metabolism.)

The beneficial effect must recur with independent donor communities.

Not verified in the article. Pooled donor material and multiple recipient mice were used. Replication of the specified barrier and metabolic benefit across independently constituted donor communities was not demonstrated.

Establishment and resilience of transplanted gut microbiota in aged mice (Methods: Fecal microbiota transplantation; Figs. 2-4.)

The hypothesis is refuted if the benefit requires continuous administrations or is attributable to the preparatory procedure.

Not verified in the article. Antibiotic-only recovery provides a preparation-related comparison, but finite versus continuous transfer was not tested for the proposed benefit. Reduced resilience after chemical colitis does not refute the complete dietary-challenge hypothesis.

Establishment and resilience of transplanted gut microbiota in aged mice (Fig. 2; Discussion; Fig. 4.)

The stated literature premise is that microbiota transfer from young mice changed some age-associated behavioral, immune, and barrier measures in old recipients; this premise establishes neither clinical efficacy nor the necessity of young donors.

Matches this study. Young-to-old transfer improved intestinal permeability, inflammatory measures and selected behavioral outcomes. These mouse results support the premise while leaving clinical efficacy and the necessity of young donors unestablished.

Abnormalities in microbiota/butyrate/FFAR3 signaling in aging gut impair brain function (Results: Transplanting old microbiota transfers aged phenotypes; Fig. 2J-R.)

The proposal is a research hypothesis rather than established rejuvenation or a treatment recommendation, and its scope excludes home or clinical microbiota transfers.

Not verified in the article. This defines the proposal's research-only scope and interpretive limits. The supplied studies do not constitute a completed test of this proposal or a clinical treatment recommendation.

Under the stated series standard, withdrawal day 0 begins only after cessation of the intervention has been confirmed through disappearance of photocurrent or induced protein, or through washout of a substance and recovery of its target response; the text does not specify which of these criteria applies to microbiota transfer.

Not verified in the article. No applicable withdrawal verification based on photocurrent, induced protein, substance washout or target recovery is specified for this microbiota experiment. Its absence cannot be converted into a definite additional transfer-specific condition.

The series standard requires a baseline old control, a young reference, and a continuous-exposure comparison group.

Not verified in the article. Young references and old controls were included. A concurrent comparison of limited versus continuous exposure under the proposed follow-up and challenge conditions was absent.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Fig. 1; Methods: Experimental model details and Microbiota transfer.)

The series standard requires vehicle/light/inducer controls and, for combinations, separate-component groups; the text does not specify which of these conditional controls applies to this transfer experiment.

Not verified in the article. PBS gavage and antibiotic-only controls were present, with fewer control groups available for 24-month-old mice. The proposal leaves light, inducer and separate-component controls conditional; they should not be imposed as additional interventions.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Methods: Microbiota transfer; Fig. 1.)

Randomization, blinded assessment, and advance selection of the primary functional outcome are mandatory.

Not verified in the article. Random reassignment to cages was described. The complete requirement for randomized treatment allocation, blinded assessment and advance selection of the specified primary functional outcome was not verified.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain (Methods: Microbiota transfer; Brain Iba-1 cell staining and counts; Statistical analysis.)

The biological unit must be the donor or the animal rather than the culture well.

Matches this study. Recipient mice were biological replicates, and individual endpoint profiles represented individual animals. This satisfies the animal-unit requirement, independently of the separate question of donor-community replication.

Establishment and resilience of transplanted gut microbiota in aged mice (Figs. 2-3; Quantification and statistical analysis.)

The series standard specifies that a human-culture pilot must include at least 6 independent older donors with paired allocation of conditions; the text does not establish a human-culture pilot as an additional model for this mouse experiment.

Not verified in the article. A paired pilot using at least 6 independent older human donors was not reported. This is a conditional series standard, not an established additional model or independent novelty claim for the mouse proposal.

The confirmatory sample size must be calculated from the pilot variance to provide 80-90% power while accounting for multiple comparisons.

Not verified in the article. The supplied studies do not document the specified pilot-variance-based confirmatory sample-size calculation targeting 80-90% power with multiplicity accounted for. Multiple-testing correction alone does not meet this requirement.

Any proposed success thresholds must be treated as design criteria rather than literature results.

Not verified in the article. The proposal's success criteria remain prospective design criteria. No supplied experiment establishes them as observed results of the complete proposed test.

Cell death, proliferation, cellular composition, and clonal selection must be accounted for separately.

Not verified in the article. Lineage tracing, mitotic activity and stem/Paneth-cell counts address some cellular alternatives. Separate accounting for cell death and clonal selection throughout the specified withdrawal-and-dietary-challenge experiment was not performed.

Microbiota from young mice restore the function of aged ISCs (Results: A young microbiota enhances the function of aged ISCs; Fig. 3; Figs. S1F-K; Methods: Lineage tracing.)

Work involving donor materials and animals requires the necessary approvals.

Matches this study. The study explicitly reports institutional animal care and use committee approval for its animal experiments.

Establishment and resilience of transplanted gut microbiota in aged mice (STAR Methods: Experimental model and subject details, Animals.)

The timing of the secondary challenge and termination of the experiment must be specified in advance.

Different experimental conditions. The study specified transfer, chemical-challenge and endpoint schedules, including follow-up to day 74 after colitis. The scheduled secondary challenge was chemically induced inflammation rather than the proposed dietary challenge.

Establishment and resilience of transplanted gut microbiota in aged mice (Figs. 2A and 4A; Methods: DSS-induced colon inflammation.)

The hypothesis applies to aged skin with repeated erythrocyte extravasation and demonstrated heme/iron loading; it is not a general theory of healthy skin aging.

Different experimental conditions. The study examined myeloid ferroportin deletion in mice, including young animals, rather than aged skin selected for repeated erythrocyte extravasation and demonstrated heme loading.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Methods, Animals; Results, Figures 1-4)

Morphological verification of hemosiderin and microhemorrhages is required as the first step to establish the relevance of the model.

Not verified in the article. Perls staining demonstrated iron accumulation in wound macrophages, but preliminary morphological confirmation of both hemosiderin and microhemorrhages was not established.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figure 4B)

The stated biological rationale is the association between macrophage iron overload and impaired healing of venous ulcers in humans and mice.

Not verified in the article. The article cites Sindrilaru and colleagues' 2011 human and mouse study as supporting this rationale. That primary article's methods and results are not supplied, so the precise venous-ulcer rationale is supported only indirectly here.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Introduction; Discussion; Reference 17)

Repeated heme input maintains iron-loaded macrophages and reprograms them to damage fibroblasts, causing the defect to recur after temporary suppression of inflammation.

Different experimental conditions. Ferroportin deletion caused macrophage iron retention and impaired stromal proliferation, attributed to stromal iron deprivation. Increased inflammatory polarization was not observed, and recurrence after repeated heme input and inflammatory suppression was not tested.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figures 4-6; Discussion)

Eliminating microhemorrhages and the incoming heme flux is proposed as necessary for durable recovery of aged dermis and should produce more sustained recovery than an equivalent brief reduction in tumor necrosis factor (TNF).

Not verified in the article. No supplied experiment compares elimination of microhemorrhages or incoming heme with an equivalent brief TNF reduction for durable recovery of aged dermis.

The decisive experiment is to be performed in a vascular-dermal chip.

Different experimental conditions. The relevant wound-repair experiments used mice rather than a vascular-dermal chip.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Methods, Animals; Results, Figure 4)

Single and repeated standardized heme inputs must be compared at the same total heme dose.

Not verified in the article. No supplied study compares single and repeated standardized heme inputs at an equal cumulative heme dose.

After initial damage, the experiment must compare stopping heme input with continuing it during temporary TNF neutralization.

Not verified in the article. Stopping versus continuing heme input after initial damage during temporary TNF neutralization was not tested.

The experiment must include macrophages with normal iron removal and macrophages with impaired iron removal.

Matches this study. Control mice were compared with mice lacking myeloid ferroportin, directly providing macrophages with normal versus impaired iron export. This component was tested in a mouse model, outside the proposed aged-skin chip experiment.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Methods, Animals; Results, Figures 4-6)

Heme, labile iron, ferritin and macrophage number must be measured separately.

Not verified in the article. Ferritin, macrophage abundance and histological iron deposition were assessed, but separate measurements of heme and labile iron completing the required panel are not documented.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figures 3-5)

Transfer of purified macrophage secretome must be used to distinguish direct heme toxicity from immune mediation.

Not verified in the article. No supplied experiment transfers purified macrophage secretome to distinguish immune-mediated injury from direct heme toxicity.

Oxygenation must be matched between experimental conditions to distinguish the proposed effect from ischemia.

Not verified in the article. The authors argue against defective oxygenation from normal adult hemoglobin levels, but this does not document experimentally matched oxygenation across the proposed heme conditions.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Discussion, paragraph addressing vascularization and adult hemoglobin levels)

The primary outcome is preservation of new collagen after withdrawal of the anti-inflammatory intervention, with more durable preservation predicted when heme input is stopped.

Different experimental conditions. The study measured wound closure, fibroplasia and collagen I staining during repair. It did not measure preservation of new collagen after anti-inflammatory withdrawal or compare durability after stopping heme.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figures 4 and 6)

New collagen must be distinguished from the original scaffold.

Not verified in the article. Collagen I immunostaining does not establish the required distinction between newly synthesized collagen and the original scaffold.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figure 6)

Secondary outcomes are a renewed rise in TNF, persistent fibroblast dysfunction and oxidative damage.

Not verified in the article. Inflammatory mediators and stromal proliferation were assessed, but the combined secondary outcomes of renewed TNF elevation, persistent fibroblast dysfunction and oxidative damage after the proposed intervention are unverified.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figures 5-6 and discussion of Supplementary Figure S5)

The proposed persistence mechanism is not supported if repeated heme input does not cause recurrence of the defect at a comparable load or if the effect is entirely independent of macrophages.

Not verified in the article. The supplied studies do not test recurrence under comparable repeated heme loading or complete macrophage independence as falsification conditions for this persistence mechanism.

A pilot study must include 6-8 independent donors.

Not verified in the article. A pilot involving 6-8 independent donors for the proposed chip experiment is not documented.

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. No supplied methods document the required sample-size calculation using new-collagen outcome variance and a prespecified minimum useful effect.

The donor is the biological unit, and chips or wells are nested replicates.

Different experimental conditions. The reported observations concern mice, wounds and microscopic fields rather than independent human donors with nested chips or wells.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Results, Figures 4 and 6)

The study must use randomization and blinded analysis.

Not verified in the article. The supplied article texts do not verify both randomized allocation and blinded analysis for the proposed experiment.

Statistical analysis must use a paired model accounting for donor, report confidence intervals and apply correction for secondary comparisons.

Different experimental conditions. The study reports unpaired Mann-Whitney or Student tests and one-way analysis of variance, with means and standard errors. The specified paired donor model, confidence intervals and secondary-comparison correction are not documented.

Macrophage ferroportin is essential for stromal cell proliferation in wound healing (Methods, Statistical analysis)

p16, p21 or senescence-associated beta-galactosidase (SA-β-gal), assessed individually, must not be treated as proof of cellular senescence.

Not verified in the article. The supplied studies do not document the specified safeguard against establishing senescence from p16, p21 or SA-β-gal individually.

A result of p>0.05 alone must not be considered a refutation of the hypothesis.

Not verified in the article. Neither supplied primary study tests this hypothesis using the explicit rule that p>0.05 alone cannot constitute refutation.

The proposal is a research hypothesis: the described new experiments have not been performed, and no experimental results are claimed.

Not verified in the article. The submission explicitly presents an unperformed research proposal. This is its declared status, rather than a finding independently verified by a supplied publication.

The proposed benefit of targeting LINE-1 depends on cytosolic LINE-1 complementary DNA (cDNA) content and senescence duration rather than the overall p16 level.

Not verified in the article. Late senescent fibroblasts responded to inhibitors, but baseline cytosolic cDNA and senescence duration were not tested as response predictors against overall p16.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Results, EN inhibitors impact senescence-associated inflammatory markers; Fig. 6)

A late LINE-1-dependent interferon response is proposed to link cytosolic LINE-1 cDNA and senescence duration to the sensitivity of aged dermis to reverse-transcription suppression.

Not verified in the article. The late LINE-1/interferon mechanism is discussed and inflammatory suppression is measured, but its connection to aged dermal treatment sensitivity is untested.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Introduction; Results, Fig. 6; Discussion)

The scientific premise is a reported association of LINE-1 with the interferon response of senescent cells and age-related inflammation, while the predictive value of this axis for functional dermal recovery remains unestablished.

Matches this study. The article documents the stated literature premise and experimentally supports inflammatory suppression in senescent fibroblasts; prediction of functional dermal recovery remains outside its experiments.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Introduction, discussion of De Cecco et al. and Simon et al.; Fig. 6)

The experiment must compare a time course after identical sublethal ultraviolet A (UVA) damage with fibroblasts from elderly donors.

Different experimental conditions. The model used replicatively senescent embryonic lung LF1 fibroblasts, rather than a matched sublethal UVA time course compared with elderly-donor fibroblasts.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Methods, Cell culture and Senescent cell culture and RT-qPCR; Fig. 6a)

Cultures must be stratified by LINE-1 cDNA content before intervention.

Not verified in the article. No supplied study stratified intervention cultures by pretreatment LINE-1 cDNA content.

The decisive intervention groups must compare genetic LINE-1 suppression, a research reverse-transcriptase inhibitor, and a control.

Different experimental conditions. The senescence experiments compared endonuclease inhibitors, lamivudine, and untreated controls; genetic LINE-1 suppression was absent from this comparison.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Results, Fig. 6b-c; Methods, Senescent cell culture and RT-qPCR)

Following the interventions, the secretome must be tested in a skin model using untreated recipients.

Different experimental conditions. Conditioned media underwent proteomic profiling after acute LINE-1 overexpression; secretomes were not transferred to untreated recipients in a skin model.

Acute LINE-1 overexpression rewires the transcriptome, proteome and secretome of primary human fibroblasts (Fig. 2a; Methods, Transfections and sample collections for ‘omics’ analyses)

The primary outcome is a reduction in the secretome's ability to suppress new collagen in untreated recipients.

Different experimental conditions. The available abstract reports collagen-synthesis inhibition by directly applied interferons, not reversal of secretome-mediated collagen suppression after LINE-1 inhibition.

Selective inhibition of human diploid fibroblast collagen synthesis by interferons. (Abstract)

Late foci or cultures with high LINE-1 levels are predicted to show a greater primary-outcome response than early damaged cells or cultures with low LINE-1 levels, which should respond substantially less.

Not verified in the article. Treatment of late senescent cultures does not establish greater collagen recovery than in early damaged or LINE-1-low cultures; that comparison was absent.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Fig. 6a-c)

Baseline LINE-1 cDNA must predict the response, and the interaction between baseline LINE-1 and response must be tested.

Not verified in the article. No supplied study tested baseline LINE-1 cDNA as a treatment-response predictor or the specified interaction.

Genetic LINE-1 suppression is predicted to reproduce the drug effect.

Not verified in the article. The supplied experiments do not show genetic LINE-1 suppression reproducing the drug effect on recipient collagen synthesis.

LINE-1 RNA, ORF1p protein, and LINE-1 cDNA must be measured separately, and genomic contamination must be excluded.

Not verified in the article. ORF1 protein and cytoplasmic DNA/RNA hybrids were assessed, but separate LINE-1 RNA, sequence-specific cytosolic cDNA, and genomic-contamination controls are not established as the required combined assay.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Supplementary Fig. 8 description; Methods, Immunofluorescence staining and imaging)

The drug must also be tested when LINE-1 is already suppressed; persistence of the drug effect under this condition would indicate another mechanism.

Not verified in the article. No supplied experiment tested persistence of the drug effect after prior genetic LINE-1 suppression.

Mitochondrial toxicity, the number of living cells, and the baseline level of damage must be controlled.

Not verified in the article. HeLa assays included general viability and DNA-damage measurements, but the full combination of mitochondrial toxicity, living-cell counts, and baseline damage controls was not established for the proposed dermal experiment.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Fig. 4a; Fig. 5; Methods, HeLa dual-luciferase L1 retrotransposition assay)

Secondary outcomes must include type I interferon (IFN-I), interferon genes, the epidermal barrier, and persistence of the effect after washout.

Not verified in the article. Interferon expression and interferon-response genes were measured, but epidermal barrier function and persistence after washout were not reported.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Fig. 6b-c)

The claimed selectivity is not supported if baseline cDNA fails to predict response, genetic suppression fails to reproduce the drug effect, or the effect is equal in groups with high and low LINE-1 levels.

Not verified in the article. The specified selectivity criteria were not evaluated together, including prediction by baseline cDNA, genetic reproduction of drug effects, and high-versus-low comparisons.

The drug is an experimental tool; clinical benefit and long-term safety remain unknown.

Not verified in the article. The inhibitors are presented as research tools and starting points for therapeutic development, but the proposed dermal intervention has no clinical-benefit or long-term-safety evaluation.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Discussion, concluding paragraphs)

A reduction in interferon must not be interpreted as removal of damaged cells.

Not verified in the article. Reduced inflammatory gene expression is reported, but damaged-cell removal was not independently measured to verify the specified distinction.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Fig. 6; Methods, Senescent cell culture and RT-qPCR)

The reproducibility plan requires a pilot study involving 6-8 independent donors.

Different experimental conditions. The six initial replicates per group were independently transfected IMR-90 cultures, not a pilot involving 6-8 independent donors.

Acute LINE-1 overexpression rewires the transcriptome, proteome and secretome of primary human fibroblasts (Fig. 2a; Methods, Transfections and sample collections for ‘omics’ analyses)

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimally useful effect.

Not verified in the article. No supplied study calculated the proposed main sample size from recipient-collagen outcome variance and a prespecified minimally useful effect.

The donor must be treated as the biological unit, with chips or wells treated as nested replicates.

Different experimental conditions. Independent transfections constituted replicates; the proposed donor-level design with nested chips or wells was not used.

Acute LINE-1 overexpression rewires the transcriptome, proteome and secretome of primary human fibroblasts (Methods, Transfections and sample collections for ‘omics’ analyses)

The study must use randomization and blinded analysis.

Not verified in the article. The supplied texts do not establish both randomization and blinded analysis for a matching experiment.

Statistical analysis must use a paired model accounting for donor, confidence intervals, and correction for secondary comparisons.

Different experimental conditions. Proteomic analyses used paired t-tests and multiple-testing correction, but not the required donor-adjusted paired model with confidence intervals and correction of the specified secondary outcomes.

Acute LINE-1 overexpression rewires the transcriptome, proteome and secretome of primary human fibroblasts (Methods, DIA-MS Data Processing and Statistical Analysis)

p16, p21, or senescence-associated beta-galactosidase (SA-β-gal), considered individually, must not be treated as proof of senescence.

Matches this study. Senescence was verified with multiple measures, including growth arrest, morphology, beta-galactosidase activity, inflammatory and senescence markers, and DNA-damage foci.

Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease (Results, EN inhibitors impact senescence-associated inflammatory markers; Supplementary Fig. 8 description)

New collagen must be distinguished from the pre-existing scaffold.

Not verified in the article. No supplied skin-model experiment distinguished newly produced recipient collagen from a pre-existing scaffold.

A result of p > 0.05 alone must not be considered a refutation of the hypothesis.

Not verified in the article. The proposed rule against treating p > 0.05 alone as refutation is not documented as an analysis condition for this complete test.

The proposal is a research hypothesis; the described new experiments have not been performed, and no results are claimed.

Not verified in the article. This describes the proposal's status rather than a published experimental finding; no supplied study reports completion of the proposed experiment.

The proposed experiment uses identical old fibroblasts across conditions to test a limit on functional recovery imposed by the extracellular matrix.

Different experimental conditions. The dermal fibroblasts came from women aged 18-23 years and underwent acute glyoxal treatment; identical old fibroblasts were not tested across the proposed matrix conditions.

Glycation by glyoxal leads to profound changes in the behavior of dermal fibroblasts (Research design and methods: Cell culture)

Restoring cathepsin D (CTSD) activity is hypothesized to reduce intracellular advanced glycation end products (AGE) through CTSD-related degradation and improve fibroblast function only up to a limit imposed by the glycated extracellular matrix.

Different experimental conditions. CTSD overexpression restored proliferation and migration in an endothelial cell line. Intracellular AGE clearance was discussed through earlier literature, while a glycated-matrix ceiling in old fibroblasts was not tested.

Advanced Glycation End Products Inhibit the Proliferation of Human Umbilical Vein Endothelial Cells by Inhibiting Cathepsin D (Results 2.4-2.6; Discussion; Figures 4-6)

Extracellular glycation adducts and crosslinks are hypothesized to impose a residual limit on functional recovery; CTSD-related AGE degradation reported in photoaged dermal fibroblasts does not establish cleavage of mature extracellular glycation crosslinks.

Not verified in the article. Specific collagen modifications altered reconstructed-skin responses, but their residual effect after CTSD-mediated intracellular recovery and cleavage of mature extracellular crosslinks were not examined.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Results: Patterns of gene expression; Discussion; Figure 3)

The decisive experiment uses a factorial design with four combinations: ordinary collagen with maintained CTSD activity, ordinary collagen with restored CTSD activity, glycated collagen with maintained CTSD activity, and glycated collagen with restored CTSD activity.

Not verified in the article. No supplied study combines both collagen conditions with both maintained and restored CTSD activity in the specified four-group factorial experiment.

The matrices used in the experiment must be verified as cleaned.

Not verified in the article. Extensive dialysis is described, but independent verification that the matrices were cleaned is not reported.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Materials and Methods: Preparation of collagen modified by AGEs)

After intracellular function has been restored, some cells must be transferred to a normal matrix.

Not verified in the article. Transfer to normal matrix after restoration of intracellular function is absent from the supplied experiments.

With matched reductions in intracellular AGE, fibroblasts on highly crosslinked collagen are predicted to remain less functional than fibroblasts on ordinary collagen.

Not verified in the article. No study compares functional recovery on ordinary and highly crosslinked collagen after matching the reduction in intracellular AGE.

Intracellular AGE and specific extracellular glycation adducts and crosslinks must be quantified separately, using measurements beyond total fluorescence alone.

Not verified in the article. Chromatography and mass spectrometry quantified specific collagen-linked adducts and pentosidine, but paired, separate quantification of intracellular AGE was absent.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Materials and Methods: Quantification of collagen-linked AGEs; Table 1)

Matrix stiffness must be controlled in the causal assessment.

Not verified in the article. Stiffness was measured in acellular gels. This does not establish control of stiffness in the proposed causal assessment; the authors explicitly did not measure stiffness in cell-seeded matrices.

Fibroblast viability and phenotypic changes within glycated stiffened three-dimensional collagen matrices (Methods: Gel mechanical measurements; Figure 3; Discussion)

Cell adhesion must be controlled in the causal assessment.

Different experimental conditions. The preview reports inhibition of focal-adhesion signaling in a fibroblast-activation model. This differs from controlling cell adhesion during CTSD restoration in old fibroblasts, and full methods are unavailable.

Targeting extracellular matrix glycation to attenuate fibroblast activation (Abstract; Statement of significance)

Signaling through the receptor for advanced glycation end products (RAGE) must be controlled in the causal assessment.

Different experimental conditions. RAGE-neutralizing antibodies were reported in immortalized fibroblasts undergoing a cancer-associated phenotype transition, rather than in the specified old-fibroblast recovery experiment.

Targeting extracellular matrix glycation to attenuate fibroblast activation (Abstract; Section snippets: Human fibroblast cell culture)

Catalytically inactive CTSD must be used to test whether proteolysis is necessary for the effect.

Different experimental conditions. The catalytically inactive D295N CTSD control was used, but in endothelial cells exposed to AGE-modified albumin. Catalytic activity was required for proliferation rescue, whereas migration rescue also occurred with D295N.

Advanced Glycation End Products Inhibit the Proliferation of Human Umbilical Vein Endothelial Cells by Inhibiting Cathepsin D (Results 2.4-2.6; Methods 4.3; Figures 4-6)

The primary outcome is new collagen per unit of live cells.

Different experimental conditions. Collagen secretion, maturation and deposition were assessed using protein-normalized immunoblots and microscopy, rather than newly produced collagen per live cell.

Glycation by glyoxal leads to profound changes in the behavior of dermal fibroblasts (Methods: Extracellular matrix and supernatant protein extraction; Results; Figure 3)

New collagen must be distinguished from the original scaffold.

Different experimental conditions. Human procollagen I staining distinguished a biosynthetic marker within a bovine-collagen model, but did not quantify newly produced collagen separately from the original scaffold as proposed.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Materials and Methods: Histology and immunohistochemistry; Figures 1-2)

Lysosomal flux is a secondary outcome.

Different experimental conditions. Autophagic flux was assessed with chloroquine and LC3/p62 measurements in endothelial cells, rather than as a secondary outcome in old fibroblasts on the two matrices.

Advanced Glycation End Products Inhibit the Proliferation of Human Umbilical Vein Endothelial Cells by Inhibiting Cathepsin D (Results 2.3-2.4; Figures 3-4)

Cell traction is a secondary outcome.

Different experimental conditions. Cell traction was inferred from collagen elastic modulus near glyoxal-treated young fibroblasts, rather than measured during the specified CTSD-restoration experiment.

Glycation by glyoxal leads to profound changes in the behavior of dermal fibroblasts (Methods: Atomic force microscopy; Results; Figure 2D-E)

The response to a standard regenerative stimulus is a secondary outcome.

Not verified in the article. No supplied experiment tests the response to a standard regenerative stimulus after CTSD-mediated recovery under the specified matrix conditions.

Tissue mechanics is a secondary outcome.

Different experimental conditions. Acellular collagen-gel mechanics were measured, rather than tissue mechanics following intracellular recovery in the proposed fibroblast model.

Fibroblast viability and phenotypic changes within glycated stiffened three-dimensional collagen matrices (Methods: Gel mechanical measurements; Figure 3; Table 1)

Equally complete functional recovery on ordinary and glycated matrices after intracellular AGE reduction would indicate that the proposed extracellular limit is absent in this model.

Not verified in the article. Equally complete recovery on both matrices after intracellular AGE reduction was neither demonstrated nor tested as the proposed falsification criterion.

The reproducibility plan includes a pilot study with 6-8 independent donors.

Different experimental conditions. The dermal-fibroblast study used three donors, rather than a pilot with 6-8 independent donors.

Glycation by glyoxal leads to profound changes in the behavior of dermal fibroblasts (Methods: Cell culture; Figures 1-4)

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. A sample-size calculation based on primary-outcome variance and a prespecified minimum useful effect is not reported for the proposed experiment.

The donor is the biological unit, and chips or wells are nested replicates.

Not verified in the article. Donors and replicate wells are described, but a consistent inferential hierarchy treating donors as biological units and wells as nested replicates is not established.

Glycation by glyoxal leads to profound changes in the behavior of dermal fibroblasts (Figure 2 legend; Statistical analysis)

The experiment must use randomization.

Not verified in the article. Random allocation to experimental conditions is not documented. Random selection of cells or imaging fields in some articles does not establish treatment randomization.

The analysis must be blinded.

Not verified in the article. Blinded analysis is not documented in the supplied descriptions of the relevant experiments.

Statistical analysis must use a paired model accounting for donor.

Not verified in the article. A mixed linear model was used for viability, but the text does not specify the required paired model accounting for donor.

Fibroblast viability and phenotypic changes within glycated stiffened three-dimensional collagen matrices (Methods: Statistical analyses)

The analysis must report confidence intervals.

Not verified in the article. Confidence intervals for the proposed recovery comparison are absent; the relevant articles primarily report means with standard deviations or standard errors.

Secondary comparisons must be corrected for multiplicity.

Different experimental conditions. Bonferroni post hoc correction was used in the endothelial study, but a corrected set of the proposed secondary comparisons in old fibroblasts was not tested.

Advanced Glycation End Products Inhibit the Proliferation of Human Umbilical Vein Endothelial Cells by Inhibiting Cathepsin D (Methods 4.12: Statistical Analysis)

p16/p21 or senescence-associated β-galactosidase (SA-β-gal), considered separately, do not establish cellular senescence.

Not verified in the article. The supplied experiments do not document the proposed safeguard against establishing senescence from isolated p16/p21 or SA-β-gal measurements.

A result of p>0.05 alone must not be treated as falsification of the hypothesis.

Not verified in the article. No supplied study implements the proposed falsification rule distinguishing equally complete recovery from a nonsignificant comparison alone.

Laboratory-glycated collagen incompletely reproduces aged dermis, which limits interpretation of the model.

Matches this study. The authors explicitly limit extrapolation to aged human skin because some collagen modifications are supraphysiological and reconstructed skin lacks vessels and inflammatory cells.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Discussion: paragraph beginning “A word of caution”)

The result is intended to guide selection of the compartment for intervention, but would not justify clinical use of CTSD activators.

Not verified in the article. Selection between intracellular and extracellular intervention based on this complete experiment is not reported, and the supplied studies do not establish clinical use of CTSD activators.

This is a research hypothesis: the proposed new experiments have not been performed, and no results from them are claimed.

Not verified in the article. The proposal declares that its experiments remain unperformed. No supplied study reports completion of this exact test; this is a statement of proposal status rather than an experimental result.

The hypothesis concerns repair of voids in aged dermis and treats collagen preservation as a separately reproducible component of retinoid action.

Different experimental conditions. The study examines collagen homeostasis after fibroblast-specific MMP14 deletion in mice, rather than void repair in aged dermis or an independently reproduced collagen-preserving component of retinoid action.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Results: Generation of mice with fibroblast-specific depletion; Discussion)

Matrix metalloproteinase 14 (MMP14) supports fibroblast invasion into collagen, whereas matrix metalloproteinase 1 (MMP1) participates in degradation of the extracellular network.

Not verified in the article. The experiments establish MMP14-dependent pericellular collagenolysis and survival, including rescue by membrane-tethered MMP1 catalytic-domain chimeras. The specified division between fibroblast invasion and extracellular MMP1-mediated degradation is not directly tested; invasion studies are cited as prior work.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Introduction; Results: Structure/function analysis; Discussion)

Formation of a new collagen network requires a fibroblast invasion zone that is temporarily free from blockade, so even selective protection against MMP1 must preserve spatial routes for cell access.

Not verified in the article. Proteolytic relief of matrix confinement supports fibroblast survival, but a temporarily blockade-free invasion zone during new-network formation under selective MMP1 protection is not tested.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results: Type I collagenolysis and the induction of fibroblast shape change-dependent apoptosis; Figure 3)

Combining protection of load-bearing collagen fibers with accessible channels into defects is proposed to permit cell penetration and improve incorporation of new collagen into the old network.

Different experimental conditions. Fibroblasts enter scaffold micropores and deposit collagen, providing a close component. The scaffold combines collagen and polycaprolactone, without selective protection of old load-bearing fibers or measurement of new-to-old network integration.

Microporous Dermal-Mimetic Electrospun Scaffolds Pre-Seeded with Fibroblasts Promote Tissue Regeneration in Full-Thickness Skin Wounds (Results: Infiltrating fibroblasts deposit ECM into scaffold micropores; Figures 4-6)

The main experiment must create local defects in reconstructed dermis.

Different experimental conditions. Local full-thickness defects were created in rat back skin and implanted with scaffolds. These are native animal wounds, not local defects in reconstructed aged dermis.

Microporous Dermal-Mimetic Electrospun Scaffolds Pre-Seeded with Fibroblasts Promote Tissue Regeneration in Full-Thickness Skin Wounds (Materials and Methods: Scaffold implantation into full-thickness skin defects; Figure 7)

The experiment must compare uniform MMP1 blockade with patterned protection that leaves entrances into the defects.

Not verified in the article. None of the supplied studies compares uniform MMP1 blockade with patterned protection preserving entrances into defects.

The reconstructed dermis conditions must have equal porosity and matrix mass, and the comparison of collagen integration must also maintain equal MMP1 activity.

Different experimental conditions. Native and reduced collagen gels had similar measured pore sizes, but differed in crosslinking and were used to assess survival. This does not reproduce the integration comparison at equal porosity, matrix mass, and MMP1 activity.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results: Type I collagenolysis and the induction of fibroblast shape change-dependent apoptosis; Figure 3C-D)

MMP14 must be separately disabled to test the role of cell invasion.

Different experimental conditions. MMP14 was independently deleted, including acute deletion in cultured fibroblasts. The tested endpoint was survival and morphology, not the contribution of invasion to patterned-protection-mediated collagen integration.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figures 2-3 and S3; Materials and methods: Lentiviral transduction)

Labeling must track cell movement and incorporation of new collagen into the edges of the old collagen network.

Different experimental conditions. Nanocrystal-labeled fibroblasts were localized within pores, while collagen deposition was assessed by staining and immunoblotting. New collagen incorporation into old-network edges was not traced by labeling.

Microporous Dermal-Mimetic Electrospun Scaffolds Pre-Seeded with Fibroblasts Promote Tissue Regeneration in Full-Thickness Skin Wounds (Materials and Methods: Fibroblast-mediated ECM deposition into scaffold pores; Figures 5-6)

Patterned protection is predicted to improve collagen integration, and this improvement must depend on cell penetration; failure to improve integration under the matched conditions or independence from cell penetration falsifies the spatial hypothesis.

Not verified in the article. No supplied experiment tests whether patterned protection improves collagen integration specifically through cell penetration under the required matched conditions.

The functional objective is preservation of aging skin strength, renewal, and recovery after injury.

Different experimental conditions. Skin mechanics and wound closure were examined in mouse MMP14 mutants, with increased stiffness and comparable wound closure. Preservation of strength, renewal, and recovery in aging skin was not tested as the proposed intervention's objective.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Figure 4; Results: Comparable collagen synthesis in bleomycin-induced fibrosis and in wound repair)

The study must use paired models from several independent donors, randomization, and blinded assessment.

Not verified in the article. Different treatments were compared within individual rats, but paired reconstructed models from independent donors, treatment randomization, and blinded assessment are not documented together.

Microporous Dermal-Mimetic Electrospun Scaffolds Pre-Seeded with Fibroblasts Promote Tissue Regeneration in Full-Thickness Skin Wounds (Materials and Methods: Scaffold implantation into full-thickness skin defects; Figure 7)

The donor must be the biological unit, and wells must be treated as technical replicates.

Not verified in the article. The required donor-based biological unit with wells explicitly treated as technical replicates is not documented for the proposed experiment.

Sample size must be calculated from pilot variability, the primary functional outcome must be selected in advance, and multiple comparisons must be accounted for.

Not verified in the article. Multiple comparisons were addressed with Dunnett or Tukey procedures, but pilot-based sample-size calculation and advance selection of the proposed primary functional outcome are not documented.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Materials and methods: Statistical analysis)

The study must control cell viability, cellular composition, and intervention specificity.

Matches this study. The study measures viability, separates papillary and reticular fibroblast populations, and checks intervention specificity using other metalloproteinase knockouts, acute deletion, and rescue constructs. These controls match this component within a different experimental system.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figures 1-3, S3 and S7; Materials and methods: Isolation and culture of mouse dermal fibroblasts)

Old and new collagen fractions in reconstructed models must be distinguished by sequential stable isotope labeling.

Not verified in the article. Sequential stable isotope labeling of old and new collagen fractions in reconstructed models is absent from the supplied experiments.

In native explants, only newly synthesized collagen must be labeled, and the unlabeled pool must be accounted for by mass balance.

Not verified in the article. Skin explants received fluorescently labeled fibroblasts for survival assessment; new collagen labeling with mass-balance accounting of the unlabeled pool was not performed.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figure 4D-E; Materials and methods: Skin explant culture)

Labeling analyses must account for precursor enrichment and label recycling.

Not verified in the article. The supplied studies do not report collagen-labeling analyses accounting for precursor enrichment and label recycling.

Second harmonic generation (SHG) must characterize collagen organization, while collagen mass, mechanics, and healing must be measured separately.

Not verified in the article. Second harmonic generation, hydroxyproline-based collagen quantification, and matrix microrheology cover several measurement components. Separate healing assessment within the specified integration experiment is absent.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figures S4, 4C and 6A; Materials and methods: Dermal collagen content)

MMP1 must be assessed with a specific activity assay and an independent genetic intervention.

Not verified in the article. MMP1 catalytic-domain chimeras and collagen-cleavage staining were used, but endogenous MMP1-specific activity assessment combined with independent MMP1 genetic perturbation was not reported.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figure S7; Materials and methods: Lentiviral transduction)

For restoration of active MMP1, the proposed procedure must use genetic suppression or prior inhibitor washout.

Not verified in the article. Restoration of active MMP1 using the specified genetic-suppression or prior inhibitor-washout procedure is not reported.

A catalytically inactive protein must be included as a control for restoration of active MMP1.

Different experimental conditions. The catalytically inactive control is MMP14 E240A in an MMP14 rescue experiment, rather than an inactive protein control for restoration of active MMP1.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figure 3A-B; Results: Structure/function analysis)

The effect must be tested after treatment withdrawal, and residual persistence of the drug must be excluded.

Not verified in the article. Fibrosis resolution was followed after bleomycin treatment, but withdrawal of the proposed protective intervention and exclusion of residual drug were not tested.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Results: Comparable collagen synthesis in bleomycin-induced fibrosis and in wound repair; Supplementary Figure S6)

An increase in collagen can support an interpretation of rejuvenation only if collagen organization and function also improve.

Not verified in the article. Increased collagen accompanies a fibrosis-like phenotype and increased stiffness, illustrating why collagen quantity alone is insufficient. The specified joint organization-and-function criterion for rejuvenation was not tested.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Figures 2-4; Discussion)

The proposed effect remains a research hypothesis rather than an established effect or a recommendation for use, and the supporting observations do not establish the proposed hypothesis.

Not verified in the article. The complete proposed effect remains untested in these sources. Its research-only status is consistent with this evidence gap, but is not an experimentally matched result.

Conclusions obtained in cellular and animal models require validation in human skin.

Not verified in the article. No supplied study validates the complete proposed intervention and mechanism in human skin; references to human fibroblast work do not supply that validation.

The hypothesis concerns a subset of aged fibroblasts and proposes collagen preservation as a distinct, reproducible component of retinoid action.

Different experimental conditions. Experiments used fibroblasts from healthy adults with mean age 35 ± 5 years and latrunculin A. They did not test collagen preservation as a component of retinoid action in aged fibroblasts.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts (Methods 2.2; Results 3.1-3.4)

Ultraviolet exposure can suppress TGF-beta type II receptor/Smad signaling, and damage to mechanical support can impair collagen turnover; these observations motivate the proposed mechanism.

Matches this study. The article explicitly describes both motivating observations, citing prior studies of ultraviolet-associated receptor loss and matrix fragmentation. These passages provide background rather than a combined experimental test.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts (Introduction; Discussion, paragraphs on collagen fragmentation and ultraviolet-irradiated human skin)

Protecting collagen is proposed to restore mechanical support and receptor sensitivity to physiological TGF-beta without increasing its concentration, thereby enabling secondary collagen formation without enhanced stimulation of synthesis.

Different experimental conditions. Mechanical restraint restored receptor and matrix-component expression, and receptor replacement restored signaling. The intervention was matrix constraint rather than collagen protection; unchanged ligand transcripts do not establish unchanged physiological ligand concentration.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Results, Figures 3-5; Supporting information, Figure S2)

Compare MMP1 repression by CRISPR interference (MMP1-CRISPRi) with a control in both intact and fragmented matrices while maintaining a fixed external TGF-beta concentration.

Different experimental conditions. The study compared constrained and unconstrained collagen lattices and used TGF-beta1 at 5 ng/mL in specified assays. It did not compare MMP1-CRISPRi with control in intact and fragmented matrices.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Figures 1-4; Experimental procedures, Human dermal fibroblasts culture in 3D collagen lattices)

Measure TGF-beta type II receptor, Smad phosphorylation, collagen synthesis, and collagen integration into the matrix.

Not verified in the article. Receptor abundance, Smad3 phosphorylation and type I procollagen expression were measured. Integration of newly synthesized collagen into the matrix was not established.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Figures 2-5; Experimental procedures, Western blots)

Suppress the receptor after mechanical support has been restored and determine whether secondary collagen formation disappears.

Different experimental conditions. Receptor knockdown was introduced in the latrunculin-withdrawal experiment and blocked recovery of Smad3 phosphorylation. It was not initiated after verified support restoration, and disappearance of secondary collagen formation was not measured in that knockdown arm.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts (Results 3.3-3.4; Figures 3 and 4B)

Failure to restore sensitivity or persistence of matrix gain when the receptor is switched off would mean that the proposed pathway does not explain the effect.

Not verified in the article. The receptor-knockdown experiment assessed signaling recovery. It did not test whether matrix gain persisted with the receptor suppressed after collagen-mediated support restoration.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts (Results 3.4; Figure 4B)

An increase in fibrosis markers and contracture would refute the usefulness of the intervention.

Not verified in the article. Neither supplied study tested increased fibrosis markers together with contracture as a criterion rejecting the proposed intervention's usefulness.

The functional objective is to preserve aging skin strength, renewal, and recovery after injury.

Not verified in the article. Skin fragility and impaired wound healing motivate the work, and cellular mechanical properties were measured. Preservation of aging skin strength, renewal and injury recovery was not tested.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Discussion, proposed dermal-aging model; Figures 1 and 5)

Use paired models from multiple independent donors, with randomization and blinded assessment.

Not verified in the article. Multiple human donors and paired statistical tests are documented. Paired donor models with randomization and blinded assessment for the proposed experiment are not documented.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Experimental procedures, Procurement of human skin samples; Statistical analysis)

Treat the donor as the biological unit and wells as technical replicates.

Not verified in the article. The supplied methods do not explicitly establish donors as biological units and wells as technical replicates throughout the relevant intervention experiments.

Calculate sample size from pilot variability, prespecify the primary functional outcome, and account for multiple comparisons.

Not verified in the article. Tukey adjustment addresses multiple pairwise comparisons. Pilot-based sample-size calculation and a prespecified primary functional outcome are not reported.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Experimental procedures, Statistical analysis)

Control for viability, cellular composition, and intervention specificity.

Not verified in the article. Viable-cell recovery, ligand-binding specificity and antibody specificity were checked. The combined controls for viability, cellular composition and specificity of the proposed collagen-preservation intervention were not performed.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Experimental procedures, Cell culture and Western blots; Figure 3D; Figure S3)

Distinguish old and new collagen fractions using sequential stable-isotope labeling in reconstructed models.

Not verified in the article. Neither article used sequential stable-isotope labeling to distinguish old and new collagen in reconstructed models.

In native explants, label only newly synthesized material and account for the unlabeled pool by mass balance.

Not verified in the article. Neither article reports labeling only new synthesis in native explants while accounting for the unlabeled pool by mass balance.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. Precursor enrichment and label recycling were not addressed for collagen isotope tracing in either supplied study.

Use second-harmonic generation (SHG) to characterize organization, alongside separate measurements of mass, mechanics, and healing.

Not verified in the article. Atomic force microscopy measured cellular mechanical properties. The required combination of second-harmonic imaging with separate collagen mass, mechanics and healing measurements is absent.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Figures 1 and 5; Experimental procedures, Atomic force microscopy)

Verify MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. Neither supplied study combined a specific MMP1 activity assay with an independent genetic intervention targeting MMP1.

For restoration of active MMP1, use genetic suppression or prior inhibitor washout, as proposed without further specification of the genetic suppression target.

Not verified in the article. Restoration of active MMP1 under genetic suppression or after inhibitor washout was not tested. The hypothesis leaves the genetic-suppression target unspecified.

Include a catalytically inactive protein as a control for restoration of active MMP1.

Not verified in the article. Neither article included a catalytically inactive protein control for restoration of active MMP1.

Test the effect after treatment withdrawal and rule out persistence of the drug.

Different experimental conditions. Latrunculin withdrawal, extensive washing and recovery were tested. This concerns withdrawal of a cytoskeletal disruptor, rather than durability after the proposed protective treatment, and residual drug was not analytically excluded.

Actin cytoskeleton assembly regulates collagen production via TGF-β type II receptor in human skin fibroblasts (Results 3.3-3.4; Figures 3 and 4B)

An increase in collagen alone is insufficient to establish rejuvenation; organization and function must also improve.

Not verified in the article. Neither study demonstrated rejuvenation using the required joint improvement in collagen amount, organization and tissue function.

Treat the proposed effect as a research hypothesis rather than an established effect or recommendation for use; the supporting observations do not establish the hypothesis.

Not verified in the article. The supplied studies establish related mechanisms but do not establish or recommend this proposed intervention. Its research-hypothesis status remains appropriate.

Conclusions obtained from cellular and animal models require validation in human skin.

Not verified in the article. Young and aged human skin provided observational evidence of receptor and matrix-expression differences. The complete collagen-preservation intervention was not validated in human skin.

Reduction of fibroblast size/mechanical force down-regulates TGF-β type II receptor: implications for human skin aging (Results, Figure 6; Experimental procedures, Procurement of human skin samples)

A high extracellular NAD-hydrolase load imposed by macrophages is hypothesized to limit the ability of an administered NAD precursor to restore metabolism in neighboring fibroblasts through extracellular CD38 catalytic activity.

Different experimental conditions. Macrophages blocked NMN-induced NAD elevation in mouse decidual stromal cells; recombinant CD38 reproduced the effect and ectoenzyme inhibition reversed it. These are uterine stromal cells, with NAD abundance rather than the proposed dermal fibroblast metabolic restoration as the endpoint.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Results, Figure 6i-k; Methods, Cell isolation and culture)

The response is hypothesized to depend on CD38 activity per cell and the availability of the specific precursor, with the number of CD38-positive cells alone being insufficient to determine the response.

Not verified in the article. Age-dependent macrophage activity, catalytic dependence, and precursor specificity were examined, but fibroblast responses were not jointly tested against per-cell catalytic activity and CD38-positive cell counts.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figures 1i-k, 5c-f and 7f-h; Extended Data Figure 7m-n)

The proposed biological context is that the senescent secretome can increase CD38 in macrophages and be accompanied by a decrease in tissue NAD.

Matches this study. Conditioned medium from senescent pre-adipocytes increased macrophage CD38 expression and activity; its administration increased CD38 activity and reduced NAD in mouse adipose tissue.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Accumulation of CD38 in vivo can be induced by SASP; Figure 4a-b; Extended Data Figure 4a-b)

The investigation concerns human dermis, where the cellular source of the proposed activity and the actual metabolic flux must be established.

Different experimental conditions. The study concerns placental and uterine tissues, with human placental observations and mouse mechanistic experiments. It does not establish cellular sources and metabolic flux in human dermis.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Results, Figures 1-6; Methods, Human sample collection and Cell isolation and culture)

The decisive experiment must co-culture primary fibroblasts and macrophages from old donors.

Different experimental conditions. Co-cultures used mouse decidualized endometrial stromal cells and macrophages derived from 6-8-week-old mice. They were not primary human dermal fibroblasts and macrophages both obtained from old donors.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Methods, Cell isolation and culture; Results, Figure 6)

Several chemically defined NAD precursors must be compared, preserving their identities as distinct substrates rather than assuming substrate equivalence.

Matches this study. NMN, nicotinamide riboside, and nicotinic acid were compared as distinct precursors, demonstrating different CD38 dependence. This component was tested in macrophage–AML12 co-cultures rather than the proposed dermal system.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figure 7f-h; Extended Data Figure 7m-n)

The precursor comparison must include conditions with intact CD38, selective reduction of CD38 only in macrophages, and restoration of either active or catalytically inactive CD38 after reduction.

Different experimental conditions. Active and inactive CD38 constructs were tested in 293T cells, while separate experiments used CD38-knockout macrophages. No macrophage-specific reduction followed by active or inactive CD38 rescue was performed in the required co-culture.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figure 6a-f; Extended Data Figure 7m; Methods, 293T and AML 12 Cell Lines)

An isotope-labeled precursor must be used, and incorporation of its label into intracellular fibroblast NAD must be the primary outcome.

Not verified in the article. None of the supplied studies measures isotope-labeled precursor incorporation into fibroblast NAD. Isotopic internal standards in placental metabolomics quantify abundance rather than metabolic label flux.

Metabolites must be measured separately in the fibroblast and macrophage populations.

Different experimental conditions. Macrophage metabolites, extracellular NMN, and recipient AML12 metabolites were measured in distinct experiments. The required separate fibroblast and macrophage measurements in the proposed donor co-cultures are absent.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figure 7a-k; Methods, BMDMs and co-culture experiments)

A macrophage-free control must be included to distinguish poor precursor import from extracellular degradation.

Different experimental conditions. AML12 cells cultured alone provided a macrophage-free control for NMN responses and direct treatment effects. The analogous control with old-donor fibroblasts and isotope tracing was not performed.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figure 7f; Extended Data Figure 7l)

Cell numbers and inflammatory exposure must be equalized across the experimental comparisons.

Not verified in the article. Fixed macrophage seeding and comparable inflammatory-marker responses between genotypes provide partial controls. Equal cell numbers and inflammatory exposure across all arms of the proposed dermal rescue experiment are not established.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Methods, BMDMs; Extended Data Figure 2i-j)

Energy reserve, new collagen, DNA damage, and an increase in the senescence-associated secretory phenotype must be assessed as secondary outcomes, recognizing that this secretory phenotype may itself depend on NAD.

Not verified in the article. Placental senescence, secretory signatures, and DNA-damage markers were assessed, but the complete secondary-outcome set, including fibroblast energy reserve and new collagen, was not examined.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Results, Figures 5-7; Supplementary Figures 4 and 11)

New collagen must be distinguished from the pre-existing scaffold.

Not verified in the article. The supplied studies do not distinguish newly synthesized collagen from a pre-existing scaffold in this experiment.

If catalytic inactivation of CD38 changes neither label flux nor the functional response, the extracellular hydrolase is not the leading limitation for the selected precursor.

Not verified in the article. Catalytically inactive CD38 was tested for effects on NAD abundance in other models, but the joint label-flux and functional-response criterion was not tested.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Results, Figures 5 and 6)

An increase in NAD without tissue improvement, or with an increase in the senescence-associated secretory phenotype, must not count as successful restoration.

Not verified in the article. NAD elevation accompanied by macrophage inflammation supports separating biochemical from functional benefit. The specified tissue-restoration criterion, including senescence-associated secretion, was not implemented.

Dihydronicotinamide Riboside Is a Potent NAD+ Precursor Promoting a Pro-Inflammatory Phenotype in Macrophages (Results, Figures 1-5; Discussion)

A pilot study must include 6-8 independent donors.

Not verified in the article. No pilot involving 6-8 independent old human donors in the required co-culture system is reported.

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. No main-study sample-size calculation based on fibroblast label-incorporation variance and a prespecified minimum useful effect is reported.

The donor must be treated as the biological unit, with chips or wells treated as nested replicates.

Not verified in the article. The required hierarchy of independent human donors and nested chips or wells is not documented for the proposed experiment.

The study must use randomization and blinded analysis.

Not verified in the article. Randomization is mentioned for offspring dietary experiments, but randomization together with blinded analysis is not documented for the required old-donor co-culture test.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Methods, Drug treatment, Offspring Studies)

Statistical analysis must use a paired model accounting for donor, report confidence intervals, and correct secondary comparisons.

Different experimental conditions. Co-culture comparisons used unpaired two-sided t-tests and mean ± SEM. They do not implement the specified paired donor-adjusted analysis with confidence intervals and corrected secondary comparisons.

CD38 ecto-enzyme in immune cells is induced during aging regulating NAD+ and NMN levels (Methods, Statistical Analysis; Figure 7 legend)

Neither p16/p21 nor senescence-associated beta-galactosidase alone must be treated as proof of senescence.

Matches this study. Placental senescence was assessed using p16/p21, beta-galactosidase, Ki67, γ-H2AX, lamin B1, and BrdU incorporation, providing corroboration beyond either isolated marker class. This matches the evidential principle in a different tissue.

CD38-activated macrophages drive age-related placental senescence by depleting NAD+ in decidual stromal cells (Results, Age-related NAD⁺ decline is localized to the decidual basalis and junctional zones; Supplementary Figure 4e-q)

A result of p > 0.05 alone must not be treated as refutation of the hypothesis.

Not verified in the article. No supplied study implements the proposed refutation rule for this hypothesis; labeling a comparison nonsignificant does not establish that rule.

The work is a research hypothesis: the proposed new experiments have not been performed, and no experimental results are claimed.

Not verified in the article. The unperformed status belongs to the submitted proposal and is preserved here. The supplied empirical articles do not verify the proposal's execution history or provide results from its complete test.

Matrix metalloproteinase-1 (MMP1) fragments dermal collagen, and the resulting damage to structural support impairs fibroblast function.

Matches this study. Purified human MMP1 fragmented collagen lattices, in which dermal fibroblasts increased several metalloproteinases and reduced type I procollagen expression. This directly supports impaired fibroblast matrix homeostasis following collagen fragmentation.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Results describing Figure 2a-e; discussion of collagen homeostasis.)

Collagen preservation is hypothesized to reproduce a beneficial component of retinoid action only above a threshold of residual collagen network connectivity sufficient for force transmission; MMP1 blockade alone is insufficient once the network has disintegrated into isolated fragments.

Not verified in the article. The discussion connects fragmentation with mechanical support, but no experiment establishes a connectivity threshold for retinoid-related benefit or failure of MMP1 blockade below that threshold.

Create aged three-dimensional models with a gradient of prior collagen fragmentation while keeping collagen mass equal.

Different experimental conditions. The study compares intact and MMP1-fragmented lattices modeling protected and photodamaged dermis. It does not establish aged models with a graded fragmentation series and equal measured collagen mass.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Results describing the intact and fragmented three-dimensional collagen lattices; Figure 2a.)

Remove the enzyme used for prior fragmentation before administering the experimental interventions.

Not verified in the article. Removal of the fragmentation enzyme before the proposed interventions is not documented; the citation to an earlier protocol cannot establish this condition.

Compare selective MMP1 blockade, tretinoin, their combination, and vehicle.

Different experimental conditions. The experimental comparison is intact versus fragmented collagen, rather than the specified four treatment groups involving selective MMP1 blockade, tretinoin, their combination, and vehicle.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Figure 2 and accompanying experimental description.)

Map collagen fiber connectivity before intervention.

Not verified in the article. Atomic force microscopy documents fibril morphology, but pretreatment mapping of network connectivity is not reported.

After intervention, measure load transfer, new matrix, and microwound repair.

Different experimental conditions. The study measures metalloproteinase and procollagen expression. It does not perform the specified combined assessment of load transfer, new matrix formation, and microwound repair after treatment.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Figure 2b-e.)

Initial fiber connectivity must predict the functional response beyond total collagen mass and viability; failure to do so rejects the threshold hypothesis.

Not verified in the article. No analysis tests whether initial connectivity predicts functional treatment response after accounting for collagen mass and viability.

Determine the connectivity threshold using training donors and test it in independent donors.

Not verified in the article. The study reports no connectivity threshold derived in training donors and tested in independent donors.

Retention of collagen fragments without restoration of force transmission constitutes a negative result.

Not verified in the article. Fragment retention is not evaluated against restored force transmission as a prespecified negative-result criterion.

The intended benefit is preservation of aging skin function, specifically strength, renewal, and recovery after injury.

Not verified in the article. The study addresses collagen homeostasis in photodamage, but does not test preservation of aging skin strength, renewal, and injury recovery as functional benefits.

Use paired models from multiple independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. Subject-matched human skin samples and repeated lattice experiments are reported, but paired donor-derived models with donors as biological units and wells as technical replicates are not established.

Use randomization and blinded assessment.

Not verified in the article. Random allocation and blinded outcome assessment are not documented in the supplied article.

Calculate sample size from pilot variability.

Not verified in the article. Reported experiment counts do not establish a sample-size calculation based on pilot variability.

Prespecify the primary functional outcome and account for multiple comparisons.

Not verified in the article. The article does not document a prespecified primary functional outcome or adjustment for multiple comparisons.

Control viability, cellular composition, and intervention specificity.

Not verified in the article. Dermal isolation and fibroblast culture do not establish the complete requested controls for viability, cellular composition, and treatment specificity.

In reconstructed models, distinguish old and new collagen fractions using sequential stable isotope labeling.

Not verified in the article. Sequential stable isotope labeling to distinguish old and new collagen in reconstructed models is not reported.

In native explants, label only newly synthesized material and account for the unlabeled pool by mass balance.

Not verified in the article. The study does not report selective labeling of new synthesis in native explants with mass-balance accounting of the unlabeled pool.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. No isotope-labeling analysis accounts for precursor enrichment and label recycling.

Use second-harmonic generation (SHG) to characterize organization, while separately measuring mass, mechanics, and healing.

Different experimental conditions. Fibril organization is examined by atomic force microscopy. The specified second-harmonic generation assessment alongside separate mass, mechanics, and healing measurements is absent.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Figure 2a and its legend.)

Verify MMP1 using a specific activity assay and an independent genetic intervention.

Different experimental conditions. The study uses collagen-substrate in situ zymography and purified MMP1 exposure. It does not combine an MMP1-specific activity assay with an independent genetic intervention.

Elevated Matrix Metalloproteinases and Collagen Fragmentation in Photodamaged Human Skin: Impact of Altered Extracellular Matrix Microenvironment on Dermal Fibroblast Function (Figure 1e; Figure 2 experimental description.)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout.

Not verified in the article. Restoration of active MMP1 under genetic suppression or after inhibitor washout is not tested.

Include catalytically inactive MMP1 protein as a control for restoration of active MMP1.

Not verified in the article. A catalytically inactive MMP1 protein control for active-MMP1 restoration is not reported.

Test the effect after treatment withdrawal and exclude residual drug retention.

Not verified in the article. Persistence of effects after treatment withdrawal and exclusion of residual drug retention are not investigated.

An increase in collagen alone does not establish rejuvenation; improvement in organization and function is required.

Not verified in the article. The study does not evaluate a rejuvenation criterion requiring collagen gain together with improved organization and function.

Treat the proposed effect as a research hypothesis rather than an established effect or a recommendation for use; the supporting observations do not prove the hypothesis.

Not verified in the article. The article supplies supporting observations but does not formulate or test this proposed threshold-dependent intervention; it therefore establishes neither its efficacy nor a recommendation for use.

Conclusions from cellular and animal models require validation in human skin.

Not verified in the article. Human skin observations support the fragmentation-related component, but they do not validate the proposed threshold-dependent treatment effect in human skin.

The experimental models are keratinocytes from elderly human donors and organotypic epidermis.

Different experimental conditions. The senescence study used monolayers of neonatal foreskin keratinocytes from one donor, aged through culture, rather than elderly-donor cells and organotypic epidermis.

Bioelectric characterization of senescing human keratinocytes (STAR Methods: Experimental model and study participant details; Cell culture; Limitations of the study.)

Differences in chloride gradients between aged donor cells are hypothesized to explain opposite responses to an anion opsin, with benefit restricted to samples in which light actually normalizes the plasma membrane potential (Vm).

Not verified in the article. No supplied study links elderly-donor chloride-gradient differences to opposite anion-opsin responses and benefit restricted to light-normalized Vm.

The chloride potential relative to Vm determines the direction of the anion-opsin response, which can be depolarizing under the corresponding chloride gradient; applicability of this mechanism to aging epidermis requires measurement.

Different experimental conditions. GtACR2-induced axonal excitation and its reduction by KCC2 support the chloride-dependent mechanism in neurons. Its application to aging epidermis was not tested.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Results: GtACR2-mediated antidromic spikes are reduced by KCC2; Figures 1-2; Discussion.)

The two principal experimental variables are the optical tool, GtACR2 or the light-controlled potassium channel BLINK2, and the baseline chloride potential relative to Vm.

Different experimental conditions. The study compared GtACR2 constructs and manipulated KCC2 in neurons. It did not compare GtACR2 with BLINK2 across baseline chloride potentials in the proposed epidermal models.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Results: Figures 1-4; Methods: Calcium phosphate transfection of cultured neurons.)

The chloride potential must be measured using gramicidin-perforated patch-clamp, preserving intracellular chloride rather than replacing it with the pipette solution.

Different experimental conditions. Gramicidin-perforated recordings preserving intracellular chloride were performed in rat hippocampal neurons, using GABA reversal measurements and eNpHR3.0 loading. The method is established, but the proposed epidermal measurement is absent.

Chloride dynamics alter the input-output properties of neurons (Results: Experimental characterisation of neuronal chloride extrusion; Figure 1; Methods: Experimental procedures.)

The direction of the Vm shift must be predicted before the functional experiment.

Not verified in the article. No supplied experiment prospectively predicts each epidermal sample's light-induced Vm direction before testing its barrier function.

Barrier function after stimulation must be compared under conditions of equal viability.

Different experimental conditions. Calcein staining and recovery after inhibitor washout addressed cell damage during migration assays. They do not establish equal-viability comparisons of epidermal permeability after optical stimulation.

TRPV3-ANO1 interaction positively regulates wound healing in keratinocytes (Results: Effects of an ANO1 inhibitor or low chloride medium on NHEK cell migration/proliferation; Figures 5-6.)

A subgroup must undergo a reversible alteration of chloride transport with a separate control for that intervention.

Different experimental conditions. Controlled ANO1 inhibition and low-chloride exposure were reversed by washout or medium replacement. These tested keratinocyte migration and proliferation, not a subgroup within the proposed aged-epidermis optogenetic experiment.

TRPV3-ANO1 interaction positively regulates wound healing in keratinocytes (Results: Figures 5-6; Methods: Culture insert assay.)

The primary success criterion is a prospectively predicted improvement in permeability of at least 20%, occurring exclusively in the group with confirmed normalization of Vm.

Not verified in the article. No supplied study tests the prospective permeability improvement threshold of at least 20% exclusively in samples with confirmed Vm normalization.

BLINK2 must provide an independent check of the proposed effect.

Not verified in the article. No supplied source reports BLINK2 as an independent confirmation of the proposed epidermal effect.

The hypothesis is falsified if the measured chloride gradient fails to explain the sign of the photocurrent or if the functional outcome is unrelated to the achieved Vm.

Not verified in the article. No study applies both proposed falsification tests linking measured chloride gradient to photocurrent sign and achieved Vm to epidermal function.

The intervention must not aim to maximize chloride accumulation, and disruption of cell volume excludes a stimulation regime from being considered beneficial.

Not verified in the article. No supplied epidermal optogenetic study excludes stimulation regimes by a cell-volume criterion while explicitly avoiding chloride-maximization as its objective.

The experiment requires a calibrated plate-based light stimulator of the PixCells/LITOS class and separate electrophysiology and microscopy equipment.

Different experimental conditions. The study used calibrated microscope illumination and fiber-based delivery with electrophysiology and microscopy, rather than a PixCells/LITOS-class plate stimulation setup.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Methods: In vitro illumination and drug application; In vivo electrophysiology.)

The first validation stage is planned for 6-9 months, conditional on the availability of the team and models; this period concerns an initial preclinical answer rather than development of a therapy.

Not verified in the article. The conditional 6-9-month initial preclinical schedule belongs to the proposal; no supplied study documents that proposed stage.

The proposed intervention is a preclinical hypothesis rather than an established rejuvenation method, and its numerical thresholds are prospective decision criteria rather than published experimental results.

Not verified in the article. The proposed intervention and its numerical decision threshold are not reported experimental results or an established rejuvenation method in the supplied literature.

Experiments with human cells must include at least six independent donors in the studied age group, with donors serving as independent biological units; wells and individual cells cannot substitute for donors.

Different experimental conditions. The keratinocytes originated from one neonatal donor. Multiple culture replicates therefore cannot satisfy the requirement for at least six independent elderly donors.

Bioelectric characterization of senescing human keratinocytes (STAR Methods: Experimental model and study participant details; Quantification and statistical analysis.)

A young reference group must be studied using the same protocol.

Different experimental conditions. Comparisons involved different culture durations of neonatal cells, rather than young and elderly donor groups studied under the proposed common protocol.

Bioelectric characterization of senescing human keratinocytes (Results: Figures 1-4; STAR Methods: Cell culture.)

The findings must receive independent confirmation.

Not verified in the article. Independent confirmation of the complete elderly-donor epidermal optogenetic effect is not documented in the supplied studies.

The confirmatory sample size must be calculated from pilot variance before the main experiment.

Different experimental conditions. The GtACR2 study explicitly states that sample sizes were not statistically predetermined. It therefore does not supply the required pilot-variance-based confirmatory design.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Methods: Data analysis and statistical methods.)

Experimental conditions must be randomized, and analysis must be blinded.

Different experimental conditions. The keratinocyte study explicitly reports that neither blinding nor randomization was applied.

Bioelectric characterization of senescing human keratinocytes (STAR Methods: Quantification and statistical analysis.)

The primary outcome must be selected in advance, donor and cohort effects must be accounted for, and 95% confidence intervals must be reported.

Different experimental conditions. The study reports culture-replicate comparisons, significance tests, and error summaries. It does not implement the proposed prespecified permeability endpoint, donor/cohort adjustment, and 95% confidence-interval framework.

Bioelectric characterization of senescing human keratinocytes (STAR Methods: Quantification and statistical analysis; Figures 1-7.)

A confidence interval compatible with both benefit and absence of an effect must be interpreted as uncertainty rather than falsification.

Not verified in the article. No supplied study applies the proposed rule that an interval spanning benefit and no effect leaves this epidermal hypothesis uncertain.

Optogenetic controls must include the active tool in darkness, light without the tool, and the corresponding inactive tool under illumination.

Not verified in the article. Dark-expression and illuminated non-opsin controls were included in neuronal experiments. The complete required set, including the corresponding inactive tool under light in the epidermal test, is unverified.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Results: Figures 5 and 7; Methods: Optogenetic silencing during novel environment exploration.)

Tool localization and the required current or signal must be confirmed before calibrating the illumination spectrum, power at the sample, temperature, and phototoxicity.

Not verified in the article. Localization, photocurrents, wavelength, and light power were characterized. The full specified sequence, including temperature and phototoxicity calibration in the proposed epidermal models, is not documented.

High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins (Results: Figures 1-4; Methods: In vitro illumination and drug application.)

The stimulation dose must be determined in a pilot experiment and then fixed.

Not verified in the article. No supplied study documents a pilot-selected and subsequently fixed optical dose for the proposed epidermal confirmation experiment.

The optical signal used to assess plasma membrane potential must be confirmed by perforated patch-clamp; a mitochondrial dye cannot substitute for this verification.

Different experimental conditions. The study assessed Vm using BeRST and VoltageFluor fluorescence-lifetime imaging, without the required perforated-patch confirmation of the optical signal.

Bioelectric characterization of senescing human keratinocytes (STAR Methods: Bioelectric imaging of resting voltage potential; Spatial autocorrelation imaging and analysis.)

Assessment of aging-related effects must measure tissue function, viability, persistent DNA damage, and behavior after withdrawal of the intervention.

Different experimental conditions. The study assessed cell counts, senescence markers, cytokines, and bioelectric behavior after two days of treatment withdrawal. It lacks the combined tissue-function, viability, and persistent-DNA-damage assessment required here.

Bioelectric characterization of senescing human keratinocytes (Results: Bioelectric modulation of keratinocytes alters senescence-associated phenotypes; Figures 5-7.)

Faster cell division, a reduction in a single marker, or a change in dye color alone must not be treated as evidence of rejuvenation.

Not verified in the article. The supplied studies do not apply the proposal's complete rejuvenation-evidence standard to the GtACR2/BLINK2 epidermal test; marker or proliferation findings cannot establish that test.

The primary experiment uses oocytes from mice of reproductive age and naturally aged mice to investigate reproductive aging.

Different experimental conditions. The study uses fetal and adult mouse oocytes to investigate cohesion maintenance, rather than the specified reproductive-aging comparison with naturally aged mice.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Results and Discussion; Figures 3 and 4.)

Restoring NAD+ in an aged oocyte is hypothesized to improve the probability of chromosomally normal offspring mainly while a sufficient reserve of functional sister-chromatid cohesion remains; this reserve acts as a causal modifier that limits the functional response to metabolic intervention.

Not verified in the article. No supplied experiment tests cohesion reserve as a causal modifier of NAD+-dependent production of chromosomally normal offspring.

With substantial loss of sister-chromatid cohesion, NAD+ restoration may improve energetic status, maturation and survival while leaving the principal cause of chromosome segregation errors unresolved, allowing energetic improvement to diverge from segregation improvement.

Not verified in the article. The proposed divergence between metabolic improvement and segregation rescue under substantial cohesion loss is untested.

Compare NAD+ repletion with a control at both preserved and experimentally weakened cohesion reserve while controlling baseline age.

Not verified in the article. The supplied literature contains no age-controlled comparison crossing NAD+ treatment with preserved and weakened cohesion.

Induce additional partial cohesion loss in young oocytes to test the causal role of cohesion reserve independently of other age-related changes.

Different experimental conditions. Engineered Rec8 cleavage tests cohesion establishment and maintenance; it does not implement partial cohesion loss in young oocytes to test NAD+ responsiveness.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (A Functional Cohesion Rescue Assay in Meiosis I Oocytes; Figure 1.)

Experimental weakening must preserve some cohesion rather than destroy it completely, because total destruction would make functional recovery intrinsically impossible.

Different experimental conditions. The cleavage assay converts all bivalents to chromatids in susceptible oocytes, unlike the required weakening that retains functional cohesion.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figure 1C; A Functional Cohesion Rescue Assay in Meiosis I Oocytes.)

Compare the responses at different cohesion reserves only after confirming comparable NAD+ restoration.

Not verified in the article. Comparable NAD+ restoration across cohesion-reserve groups is not demonstrated.

Quantify NAD+ levels and mitochondrial function.

Not verified in the article. The supplied scientific text provides no quantitative NAD+ and mitochondrial-function measurements for the proposed experiment.

Quantitatively assess the meiotic spindle and chromosome positioning.

Not verified in the article. Chromosomes are imaged and classified, but the required quantitative assessment of both spindle structure and chromosome positioning is not established.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figures 1, 3 and 4.)

Quantify distances between sister kinetochores and assess REC8 and Sgo2 quantitatively.

Not verified in the article. Rec8-Myc localization and fluorescence are examined, but sister-kinetochore distances and quantitative Sgo2 assessment are not supplied.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figures 3C-D and 4B.)

Quantify chromosome segregation errors.

Not verified in the article. Scoring bivalents versus chromatids after cleavage measures functional cohesion, not the specified frequency of chromosome segregation errors.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figures 1C and 4F.)

Use matched parallel cohorts for destructive measurements, and use validated nondestructive predictors where available; destructive measurements cannot establish the baseline state of the same oocyte subsequently followed for outcomes.

Not verified in the article. Imaging followed by genotyping is described, but the specified baseline design using matched parallel cohorts and validated nondestructive predictors is not documented.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figures 3 and 4; live-cell imaging and subsequent single-cell genotyping.)

Analyze chromosome segregation with blinding.

Not verified in the article. Blinded chromosome-segregation analysis is not verified in the supplied text.

The primary outcomes are euploid embryos per initial cohort and healthy offspring per initial reproductive attempt.

Not verified in the article. Fertility checks address effects of genetic induction, but neither euploid embryos per initial cohort nor healthy offspring per initial reproductive attempt is reported as specified.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Timely Controlled Rec8 Activation in Fetal and Adult Arrested Oocytes.)

Count every initial follicle, including follicles that die or fail to mature, because selecting better-surviving oocytes could create a false appearance of aneuploidy correction.

Not verified in the article. Complete initial-follicle accounting, including deaths and maturation failures, is not documented.

Measure maturation and fertilization as intermediate outcomes.

Not verified in the article. The article discusses maturation and fertility after induction, but does not establish the required paired maturation and fertilization outcomes under NAD+ treatment.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Timely Controlled Rec8 Activation in Fetal and Adult Arrested Oocytes.)

An increase in mature oocytes without a corresponding increase in euploid embryos per initial follicle would support the proposed cohesion-dependent boundary of NAD+ benefit; improvement confined to maturation would not establish harm from the intervention.

Not verified in the article. No supplied experiment compares increased maturation with euploid embryo yield per initial follicle under NAD+ repletion.

Equal restoration of chromosome segregation accuracy by NAD+ at low and preserved cohesion reserve would refute the hypothesis.

Not verified in the article. Equal NAD+-dependent segregation rescue at low and preserved cohesion has not been tested in the supplied literature.

Restoration of functional cohesion itself by NAD+ would refute the hypothesis.

Not verified in the article. The functional assay tests newly expressed Rec8, not whether NAD+ restores cohesion; its negative rescue result cannot settle this proposed refutation.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figure 4; Conclusions.)

The benefit of NAD+ must not automatically be attributed solely to SIRT2, because the cited intervention study does not establish a universal requirement for SIRT2.

Not verified in the article. The cited NAD+ intervention study and its SIRT2 experiments are absent from the supplied scientific texts, so universal necessity cannot be assessed.

Improvement in an individual energetic marker is insufficient to establish improved oocyte quality.

Not verified in the article. No supplied experiment links an energetic marker to the specified comprehensive measures of oocyte quality.

Prior NAD+ repletion experiments improved reproductive outcomes in aged mice and provide the experimental basis for the proposed metabolic intervention.

Not verified in the article. The aged-mouse NAD+ fertility study is cited in the hypothesis but its scientific text is not supplied; the other NAD+-related entry contains only a cookie notice.

The stated biological rationale links age-related meiotic segregation errors to preceding depletion of cohesin and Sgo2 and identifies weakened centromeric cohesion as a supported causal contributor to age-related oocyte aneuploidy.

Not verified in the article. The article summarizes age-related cohesion weakening and cites the relevant studies, but their causal and temporal experiments are not supplied. The separate Lister entry contains only a cookie notice.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Results and Discussion, opening paragraphs; references 20 and 21.)

In mouse oocytes arrested for months, cohesion established by REC8-cohesin during fetal development was maintained without detectable substantial turnover; this observation concerns that specific state and leaves the possibility of cohesion repair open.

Matches this study. Fetal Rec8 activation establishes functional cohesion, whereas activation in arrested adult oocytes yields no detectable rescue after 2 or 4 months despite synthesis. The result is bounded by the assay and does not test every possible repair intervention.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figures 3 and 4, especially Figure 4C-F; Conclusions.)

Human oocytes also show age-associated weakening of chromosome cohesion, but the proposed interaction between cohesion reserve and NAD+ was not tested in the cited human evidence.

Not verified in the article. Human age-related cohesion weakening appears as cited background; the specified human primary study and any NAD+-cohesion interaction experiment are absent.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Results and Discussion, opening paragraphs; reference 18.)

The cited evidence leaves both the absolute irreversibility of cohesion loss and the effectiveness of NAD+ under cohesion deficiency unresolved.

Matches this study. The study supports restricted renewal under its tested conditions. Its interpretation of irreplaceable loss does not experimentally exclude every repair mechanism, and NAD+ efficacy under cohesion deficiency remains untested.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Figure 4; Conclusions, discussion of assay sensitivity and cohesion maintenance.)

The hypothesis concerns reproductive aging; mouse findings do not establish a recommendation for human infertility treatment or demonstrate lifespan extension.

Matches this study. The evidence concerns mouse oocyte cohesion and its relevance to reproductive aging; it provides neither a human infertility treatment test nor a lifespan-extension experiment.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice (Summary; Conclusions.)

The stated scientific premise is that OSK improved regeneration and some measures of vision in mouse models through a TET1/2-dependent effect; this premise does not establish autonomous recovery lasting multiple weeks after OSK withdrawal.

Matches this study. Lu and colleagues demonstrated TET1/2-dependent regeneration and visual improvement during OSK expression. These experiments do not establish multiweek functional persistence after withdrawal.

Reprogramming to recover youthful epigenetic information and restore vision (Results, Regeneration requires DNA demethylation; Restoration of vision in old mice; Figure 4f; Extended Data Figures 6 and 10m.)

The hypothesis proposes that TET-dependent remodeling is necessary to initiate recovery of the aged retina, but that restored retinal neuron function subsequently persists after a short OSK course without continued OSK or TET activity.

Not verified in the article. Concurrent TET knockdown establishes a requirement during treatment, but neither TET-independent maintenance nor persistence after OSK withdrawal was tested.

Reprogramming to recover youthful epigenetic information and restore vision (Results, Restoration of vision in old mice; Figure 4f; Extended Data Figure 10m.)

The main experimental model consists of old mice with a locally inducible system for OSK exposure.

Matches this study. The aging experiments used local retinal delivery of tetracycline-regulated OSK vectors, including mice treated at 11 months and assessed at 12 months.

Reprogramming to recover youthful epigenetic information and restore vision (Results, Restoration of vision in old mice; Methods, AAV2 intravitreal injection and In vivo doxycycline induction or suppression; Figure 4.)

Switch-off of the inducible system must first be verified in ganglion cell cultures.

Different experimental conditions. Switch-off was demonstrated in mouse retinal wholemounts after doxycycline administration, rather than first validated in ganglion cell cultures.

Reprogramming to recover youthful epigenetic information and restore vision (Extended Data Figure 2a; Methods, Human neuron differentiation and regeneration assay.)

A limited OSK course must be followed by confirmed disappearance of the factors and observation for 4-8 weeks without induction.

Different experimental conditions. Aged mice were assessed after four weeks of OSK expression. This substitutes an on-treatment endpoint for 4-8 weeks of observation after confirmed factor disappearance.

Reprogramming to recover youthful epigenetic information and restore vision (Results, Restoration of vision in old mice; Figure 4a-b; Extended Data Figure 9e-h.)

Withdrawal day 0 must begin only after confirmed cessation of exposure; the stated general verification criteria are disappearance of the photocurrent or induced protein, or washout of the substance together with recovery of its target's response.

Not verified in the article. Regulated suppression was characterized, but no withdrawal follow-up began at a day 0 defined by verified cessation of exposure.

Reprogramming to recover youthful epigenetic information and restore vision (Extended Data Figure 2a; Methods, In vivo doxycycline induction or suppression.)

The experiment must compare visual function, electrophysiology, and neuronal preservation.

Matches this study. The aged-mouse experiments compared visual acuity, retinal electrical responses, ganglion cell density and axon density. These outcomes were measured during treatment.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 4b; Extended Data Figure 9e-h; Methods, Optomotor response and Pattern electroretinogram.)

After the main observation period, the compared groups must receive the same moderate ex vivo challenge, with repeated severe eye injury excluded from this challenge.

Not verified in the article. No supplied study applied the same moderate ex vivo challenge after the proposed aged-retina withdrawal observation period.

Separate experimental branches must reversibly interfere with TET1/2 either only during initiation of recovery or after completion of the OSK course to distinguish initiation from maintenance requirements.

Different experimental conditions. The study used concurrent Tet1/Tet2 knockdown and Tet2 conditional deletion. It did not use reversible, separately timed initiation-only and post-course perturbations.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 2f; Figure 4f; Extended Data Figures 6 and 10m.)

The causal experiment must control for damage caused by the TET1/2 intervention itself.

Not verified in the article. Scrambled-RNA controls and Tet2 deletion comparisons address parts of intervention specificity and survival. They do not establish damage controls for both proposed reversible TET1/2 timing branches in old mice.

Reprogramming to recover youthful epigenetic information and restore vision (Extended Data Figure 6b-j; Figure 4f; Extended Data Figure 10m.)

The experiment must verify preservation of cellular identity.

Not verified in the article. Retinal markers, architecture and proliferation assays support preserved identity during OSK expression. Identity preservation after withdrawal combined with early or late TET interference was not verified.

Reprogramming to recover youthful epigenetic information and restore vision (Results, Reset of ageing signatures, not identity; Extended Data Figures 2, 3 and 9.)

The primary success criterion is preservation of a functional advantage for at least 28 days after withdrawal, with late withdrawal of TET activity compatible with its preservation and early withdrawal incompatible with it.

Not verified in the article. No supplied experiment demonstrated a functional advantage for at least 28 days after verified withdrawal together with the predicted early-versus-late TET dependence.

The hypothesis is falsified if improvement disappears when OSK is switched off, if only a molecular signature remains, or if TET activity is continuously required; continuous TET dependence specifically rejects the proposed one-time establishment of the restored state.

Not verified in the article. Blocking OSK expression or knocking down TET during treatment prevented benefits, but these comparisons did not test loss of an already restored state after withdrawal or continuous TET dependence.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 1d-e; Figure 4f; Extended Data Figure 10m.)

The experimental design must include a baseline old control and a young reference.

Matches this study. Young reference mice and untreated or non-induced old control groups were included in the aging comparisons.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 4b-d; Extended Data Figure 9g-j.)

The experimental design must include a carrier/light/inducer control, as specified in the general series standard.

Matches this study. Non-induced vector controls and doxycycline-dependent expression controls cover the relevant carrier and induction-control components of this OSK system.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 4 legends; Extended Data Figure 2a-b; Methods, In vivo doxycycline induction or suppression.)

A continuous-exposure group must serve as a comparator for the limited course followed by withdrawal.

Not verified in the article. Continuous-expression experiments were reported, but no continuous-exposure group was compared with a limited course followed by verified withdrawal in the proposed aged-retina test.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 4; Extended Data Figure 2c-i.)

For combinations, the design must include the individual components as separate comparison conditions.

Different experimental conditions. Individual Oct4, Sox2 and Klf4 and an Oct4-Sox2 combination were tested in optic nerve injury experiments, rather than in the aged-retina withdrawal and maintenance experiment.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 1d; Extended Data Figure 3e; Figure 4.)

Randomization, blinded assessment, and advance selection of the primary functional outcome are mandatory.

Not verified in the article. Blinded functional and histological assessments are described. Random allocation and advance designation of the proposed primary functional outcome are not verified.

Reprogramming to recover youthful epigenetic information and restore vision (Methods, Optomotor response; Quantification of optic nerve axons; Quantification of retinal ganglion cells; Statistical analysis.)

The donor or animal must be treated as the biological unit, rather than an individual culture well.

Not verified in the article. Several aged-retina sample sizes are reported as eyes or retinas. Animal-level independence and handling of paired eyes are not sufficiently specified to verify the required biological-unit rule throughout.

Reprogramming to recover youthful epigenetic information and restore vision (Figure 4b,f; Extended Data Figure 9; Methods, Human neuron differentiation and regeneration assay.)

The general series standard specifies a human culture pilot with at least 6 independent elderly donors and paired allocation of conditions.

Different experimental conditions. The human OSK experiments used differentiated SH-SY5Y neuroblastoma cells, rather than paired cultures from at least 6 independent elderly donors.

Reprogramming to recover youthful epigenetic information and restore vision (Methods, Human neuron differentiation and regeneration assay; Extended Data Figure 8.)

The confirmatory sample size must be calculated from the pilot variance for 80-90% statistical power, accounting for multiple comparisons.

Not verified in the article. Multiple-comparison procedures are reported, but a confirmatory sample-size calculation using pilot variance and 80-90% power is not documented.

Reprogramming to recover youthful epigenetic information and restore vision (Methods, Statistical analysis and figure preparation; figure legends.)

Cell death, proliferation, cellular composition, and clonal selection must each be accounted for separately.

Not verified in the article. Survival, proliferation and selected cellular proportions were assessed. Separate accounting for all four requirements, particularly clonal selection during the proposed withdrawal experiment, is absent.

Reprogramming to recover youthful epigenetic information and restore vision (Extended Data Figures 3, 4i-k, 8 and 9; Methods, RGC survival and Cell cycle analysis.)

The timing of the secondary challenge and termination of the experiment must be specified in advance.

Not verified in the article. No supplied study documents advance specification of both the proposed secondary ex vivo challenge and termination of the withdrawal experiment.

Work involving donor materials and animals requires the necessary approvals.

Not verified in the article. Institutional animal approvals are explicitly reported. Approval coverage for the complete proposed design, including its elderly-donor culture pilot, is absent because that pilot was not performed.

Reprogramming to recover youthful epigenetic information and restore vision (Methods, Mouse lines; Surgery; Human neuron differentiation and regeneration assay.)

The proposal must be treated as a research hypothesis, with success thresholds designated as planned criteria rather than literature results; it does not establish rejuvenation or constitute a treatment recommendation.

Not verified in the article. The supplied studies do not establish the proposed success thresholds. The complete proposal therefore retains its stated status as a research hypothesis rather than an established rejuvenation result or treatment recommendation.

The experimental model consists of monocyte-derived macrophages from six elderly donors and six young donors, with sequential supplies of labeled apoptotic cells.

Different experimental conditions. Human monocyte-derived macrophages received sequential labeled apoptotic cells, but the continual-efferocytosis experiment used five healthy donors without specified elderly and young groups.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figure 3A; Experimental Section, Primary Human PBMC Isolation and MoDM Culture)

Brief Rac1 activation separated by recovery periods is hypothesized to restore sequential efferocytosis in aged macrophages and thereby improve their ability to clear dead cells.

Different experimental conditions. Maresin conjugates enhanced continual efferocytosis and modulated Rac1 activity, but programmed Rac1 pulses with recovery were not tested for restoration in aged macrophages.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Results 2.4 and 2.8; Figures 3A-B and 5C-G)

The proposed restoration of clearance is expected to reduce inflammation after senolytic removal of aged cells.

Different experimental conditions. Restoring efferocytosis through MerTK-related interventions reduced inflammation in aged mice after liver ischemia-reperfusion, rather than after senolytic treatment.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury (Results, Restoration of MerTK-mediated efferocytosis; Figures 6-7)

The stated rationale is Rac1 involvement in efferocytosis and the availability of optogenetic tools for Rho GTPases; restoration of the age-related defect by the selected activation regimen remains unproven.

Not verified in the article. Rac1 involvement is experimentally supported, but the supplied articles do not verify the optogenetic-tool component or age-defect restoration by the selected regimen.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Results 2.8; Figure 5)

The cited experimental method for optogenetic control of Rho GTPases in macrophages and the 2024 work on efferocyte-derived MCTRs, Rac1 and sequential efferocytosis serve as supporting rationale rather than confirmation of the proposed hypothesis.

Not verified in the article. The 2024 maresin-conjugate study supplies relevant mechanistic rationale. The cited macrophage optogenetics method is not supplied as an article, so both cited foundations cannot be fully checked.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Results 2.4 and 2.8; Figures 3 and 5)

Photoactivatable Rac1 must be used to compare pulsed activation with prolonged activation, with donor age as the other main experimental variable.

Different experimental conditions. The study compares mediator pretreatment and interjacent treatment and uses pharmacological Rac1 inhibition, rather than photoactivatable Rac1 with pulsed versus prolonged activation across donor ages.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figures 3A-B and 5D-G)

Rac1 activity must be measured quantitatively.

Matches this study. Active Rac1 was measured quantitatively over time using a G-LISA activation assay in human monocyte-derived macrophages.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figure 5D; Experimental Section, Macrophage Rac1/RhoA Activity G-LISA Assays)

Two differently labeled batches of apoptotic cells must be supplied sequentially.

Matches this study. Macrophages received pHrodo Red-labeled apoptotic cells, a wash and two-hour rest, then CypHer5E-labeled apoptotic cells.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figure 3A-B; Experimental Section, In Vitro Macrophage Continual Efferocytosis Assays)

The assay must distinguish cellular ingestion from adhesion of apoptotic cells to the macrophage surface.

Matches this study. The study distinguishes bound from ingested apoptotic cells using pH-sensitive fluorescence, microscopy and a cytochalasin D ingestion control.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figure 1B-E; Results 2.8; Figure S5D-E descriptions)

The primary success criterion is an increase of at least 30% in the proportion of aged macrophages that completely ingest both batches, with neither impaired intracellular degradation nor increased inflammatory secretion; the reference for this increase and whether it is relative or absolute are unspecified.

Not verified in the article. No supplied study tests the combined 30% elderly-macrophage success criterion with preserved degradation and unchanged inflammatory secretion; the proposal also leaves the percentage reference undefined.

After the second batch, intracellular degradation, IL-1β and IL-6, and the effect of the medium on a skin equivalent must be assessed.

Different experimental conditions. IL-1β and IL-6 were measured in mouse serum after liver injury, rather than after a second apoptotic-cell batch with intracellular degradation and skin-equivalent testing.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury (Figures 5D,G, 6F and 7F; Materials and Methods, ELISA)

Improvement confined to the first ingestion, substrate accumulation without digestion, or increased ingestion of living cells would each fail to demonstrate restoration of clearance function.

Not verified in the article. Successive uptake is measured, but the combined failure criteria covering first-only improvement, undigested accumulation and living-cell ingestion are not evaluated.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figure 3; Experimental Section, In Vitro Macrophage Continual Efferocytosis Assays)

The proposed equipment includes a calibrated plate-format light stimulator of the PixCells/LITOS class and separate electrophysiology and microscopy equipment.

Not verified in the article. The specified calibrated plate light stimulator with separate electrophysiology and microscopy equipment is not documented in the supplied studies.

The first testing stage is planned for 6-9 months, assuming the team and models are available; this period concerns the first preclinical answer rather than development of a therapy.

Not verified in the article. The conditional 6-9-month preclinical schedule belongs to the proposal and is not established by these studies.

The proposal must be treated as a preclinical hypothesis rather than an established rejuvenation method, and its numerical thresholds are planned decision criteria rather than published experimental results.

Not verified in the article. The proposed optical regimen and its numerical decision thresholds remain prospective; the supplied studies do not establish it as a rejuvenation method.

The general human-cell validation standard requires at least six independent donors in the age group under study, a young reference group tested with the same protocol, and independent confirmation.

Not verified in the article. Some assays use six human donors, but six elderly donors, a young reference under the same protocol and independent confirmation of this intervention are not documented.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figures 3A and 5D; Experimental Section, Human MoDM Culture)

Donors must be treated as independent biological units; wells and individual cells cannot substitute for donors.

Matches this study. Human donor counts are identified as biological replicate counts, rather than substituting wells or individual cells for donors.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Figures 3A and 5D; Experimental Section, Statistical Testing)

The confirmatory sample size must be calculated from pilot variance before the main experiment.

Different experimental conditions. Animal group sizes were based on prior or pilot variability, but a prospective confirmatory human-donor sample-size calculation from pilot variance is not reported.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Experimental Section, Statistical Testing)

Experimental conditions must be randomized and analysis must be blinded.

Not verified in the article. Random allocation is stated for animals, but randomized human-cell conditions together with blinded analysis of the proposed experiment are not verified.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Experimental Section, Animal Experiments)

The primary outcome must be selected in advance, donor and cohort effects must be accounted for, and 95% confidence intervals must be reported.

Not verified in the article. The study describes means, standard deviations and significance tests, but does not document the required prespecification, donor/cohort adjustment and 95% confidence intervals for the proposed primary outcome.

Efferocyte-Derived MCTRs Metabolically Prime Macrophages for Continual Efferocytosis via Rac1-Mediated Activation of Glycolysis (Experimental Section, Statistical Testing)

A confidence interval compatible with both benefit and no effect must be interpreted as uncertainty rather than refutation.

Not verified in the article. The specified interpretation of confidence intervals spanning benefit and no effect is not documented as a decision rule for the proposed test.

Optogenetic controls must include the active tool in darkness, illumination without the tool, and the corresponding inactive tool under illumination.

Not verified in the article. The supplied studies do not include the required active-tool dark, light-only and illuminated inactive-tool controls.

Tool localization and the required current or signal must be confirmed before calibrating the illumination spectrum, power at the sample, temperature and phototoxicity.

Not verified in the article. Verification of optogenetic localization and signal followed by spectrum, sample power, temperature and phototoxicity calibration is not reported.

The dose must be determined in a pilot study and then fixed.

Not verified in the article. Pilot selection followed by fixation of the optical intervention dose is not documented.

Under the submitted general validation standard, Vm denotes plasma membrane potential, and its optical measurement must be confirmed by perforated patch-clamp recording; a mitochondrial dye cannot substitute for this confirmation.

Not verified in the article. The supplied studies do not confirm optical plasma membrane potential measurements using perforated patch-clamp recording.

The submitted general standard for aging studies requires measurement of tissue function, viability, persistent DNA damage and behavior after intervention withdrawal.

Not verified in the article. Liver injury and DNA-related staining were assessed, but the required combined evaluation of tissue function, viability, persistent DNA damage and post-withdrawal behavior was not performed.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury (Figures 5-7; Materials and Methods, Mouse Liver IRI Model)

Accelerated cell division, reduction of a single marker or a change in dye color alone must not be interpreted as rejuvenation.

Not verified in the article. The specified rule excluding division, a single marker or dye-color change as sufficient evidence of rejuvenation is not evaluated as part of this proposed test.

The hypothesis concerns collagen preservation as a distinct, reproducible component of retinoid action, with the goal of preserving aging skin strength, renewal, and recovery after injury.

Different experimental conditions. The study tests α-ionone in ultraviolet B-exposed Hs68 fibroblasts, substituting a different compound and cellular model for the proposed investigation of retinoid action and aging skin function.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.2-2.5; Methods 4.2-4.4)

Collagen fragments suppress hyaluronan synthase 2 (HAS2) and hyaluronan secretion in skin fibroblasts through integrin signaling.

Not verified in the article. The discussion attributes the collagen fragment-integrin-HAS2 mechanism to earlier research. The supplied experiments do not test this pathway, and the cited primary article is supplied only as a reference.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Discussion 3, final paragraph; reference 35)

Part of the improvement in viscoelasticity following protection of collagen from matrix metalloproteinase-1 (MMP1) is hypothesized to result from restoration of the endogenous hyaluronan environment rather than increased collagen mass.

Not verified in the article. Changes in procollagen secretion, MMP1 expression and hyaluronan are reported, but causal mediation of improved viscoelasticity by endogenous hyaluronan at fixed collagen mass is untested.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.2, 2.4 and 2.5; Figures 2, 4 and 5)

Compare CRISPR interference targeting MMP1 (MMP1-CRISPRi) with a control under both preserved and suppressed HAS2 conditions.

Different experimental conditions. The intervention is α-ionone treatment around ultraviolet exposure. There is no factorial comparison of MMP1-targeted CRISPR interference with control under preserved and suppressed HAS2.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Methods 4.3-4.5)

Measure hyaluronan mass and molecular size, hydration, and stress relaxation.

Not verified in the article. Hyaluronan in culture supernatants was quantified by an immunoassay, providing partial outcome coverage. Hyaluronan molecular size, hydration and stress relaxation were not measured.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.5; Figure 5; Methods 4.4)

Perform the hyaluronan, hydration, and stress-relaxation comparisons at equal collagen content.

Not verified in the article. The supplied study does not establish equal collagen content for comparisons of hyaluronan, hydration and stress relaxation.

Add purified collagen fragments back to test whether the HAS2-dependent component of the effect is lost.

Not verified in the article. No experiment adds purified collagen fragments back to test loss of a HAS2-dependent functional benefit.

The proposed hyaluronan-mediated mechanism is not supported if the functional benefit is independent of HAS2.

Not verified in the article. Functional dependence on HAS2 was not tested, so the proposed falsification criterion cannot be evaluated.

The proposed mechanism is not supported if the functional benefit is explained solely by changes in water in the medium.

Not verified in the article. The supplied experiments do not distinguish a hyaluronan-mediated mechanical benefit from an effect attributable solely to water changes in the medium.

Restoration of hyaluronan is insufficient to support the hypothesis unless mechanics also improve.

Not verified in the article. Increased hyaluronan secretion is reported, but accompanying improvement in mechanics is not demonstrated.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.5; Figure 5; Conclusions 5)

Use paired models from multiple independent donors, treating the donor as the biological unit and wells as technical replicates.

Different experimental conditions. The study uses Hs68 cells and repeated experiments, rather than paired models from multiple independent donors with donor-level biological replication.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Methods 4.2, 4.5 and 4.6; figure legends)

Use randomization and blinded assessment.

Not verified in the article. Randomization and blinded assessment are not documented in the supplied study.

Calculate sample size using pilot variability.

Not verified in the article. A sample-size calculation based on pilot variability is not reported.

Prespecify the primary functional outcome and account for multiple comparisons.

Not verified in the article. The statistical section describes Student's t tests. It does not document a prespecified primary functional outcome or adjustment for multiple comparisons.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Methods 4.7)

Control for viability, cellular composition, and intervention specificity.

Not verified in the article. A tetrazolium-based viability assay covers one component, but the required controls for cellular composition and intervention specificity are not established.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.1; Figure 1; Methods 4.3)

Distinguish old and new fractions through sequential stable-isotope labeling in reconstructed models.

Not verified in the article. Sequential stable-isotope labeling of old and new fractions in reconstructed models is absent.

In native explants, label only newly synthesized material and account for the unlabeled pool through mass balance.

Not verified in the article. Native explants with selective labeling of new synthesis and mass-balance accounting for the unlabeled pool were not studied.

Account for precursor enrichment and label recycling in the labeling analyses.

Not verified in the article. The study contains no labeling analysis accounting for precursor enrichment and label recycling.

Use second-harmonic generation (SHG) to characterize organization while retaining separate measurements of mass, mechanics, and healing.

Not verified in the article. Second-harmonic generation combined with separate measurements of mass, mechanics and healing is not reported.

Verify MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. MMP1 messenger RNA expression was measured, but neither a specific MMP1 activity assay nor an independent genetic intervention verifies its causal role.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.4; Figure 4C; Methods 4.5)

For restoration with active MMP1, use genetic suppression or preliminary inhibitor washout.

Not verified in the article. Active MMP1 restoration following genetic suppression or inhibitor washout is not tested.

Include catalytically inactive protein as a control for restoration with active MMP1.

Not verified in the article. There is no catalytically inactive protein control for an active MMP1 restoration experiment.

Test whether the effect persists after treatment withdrawal and exclude residual drug persistence.

Not verified in the article. α-Ionone was present during post-irradiation incubation. Washing before irradiation does not establish persistence after withdrawal or exclude residual drug effects.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Methods 4.3 and 4.4)

An increase in collagen alone does not establish rejuvenation; improved organization and function are also required.

Not verified in the article. The collagen-related outcome is procollagen I C-terminal peptide in supernatants. Improved collagen organization and tissue function are not demonstrated alongside it.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Results 2.2; Figure 2; Conclusions 5)

Treat the proposed effect as a research hypothesis rather than an established effect or a recommendation for use; the supporting observations do not establish the hypothesis.

Not verified in the article. The proposed MMP1-HAS2 mechanical mechanism remains a research hypothesis in this comparison. The supplied observations do not establish it or justify a recommendation for use.

Findings from cellular and animal models require validation in human skin.

Not verified in the article. The experiments use human fibroblasts, not intact human skin. The conclusion makes tissue-level applicability conditional and calls for additional research, so human-skin validation remains outstanding.

α-Ionone Protects Against UVB-Induced Photoaging in Human Dermal Fibroblasts (Methods 4.2; Conclusions 5)

The models are primary old and young dermal fibroblasts and a separate model of stress-induced senescence; the old fibroblasts have elevated lysosomal pH.

Different experimental conditions. Dermal fibroblasts at early and late passages showed different lysosomal pH, and ultraviolet-induced stress was examined separately. The main comparison used replicative senescence, rather than the specified old and young age-group design.

Extracellular Vesicles Derived from Senescent Fibroblasts Attenuate the Dermal Effect on Keratinocyte Differentiation (Results 2.1 and 2.4; Methods 4.1; Figure 4; Supplementary Figure S2)

Optical activation of Lyso-pHoenix is used to restore lysosomal acidity in old fibroblasts to the young range.

Different experimental conditions. Lyso-pHoenix acidified lysosomes in bafilomycin-treated HEK 293 cells. Restoration to a young reference range in old dermal fibroblasts was not tested.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Results, Light-driven acidification of lysosomes; Figure 6)

The proposed causal chain is that restoring lysosomal acidity restores degradation of damaged proteins and thereby reduces the senescence-inducing effect of conditioned medium and secondary senescence in neighboring cells.

Different experimental conditions. The summary reports restored acidification and autophagic flux with suppression of senescence-associated secretory factors through organelle-contact restoration. It does not verify damaged-protein degradation as the mediator or conditioned-medium induction of secondary senescence, and the intervention differs.

Mitochondria-lysosome coupling contributes to lysosome acidification and aging (Highlights and Summary)

Lyso-pHoenix can acidify lysosomes, but whether pH correction alone is sufficient to restore age-impaired proteostasis remains unestablished and is the question being tested.

Not verified in the article. The acidification capability is demonstrated, but lysosomal catabolism is proposed as a future application. Sufficiency for restoring age-impaired proteostasis is not experimentally established.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Figure 6; Discussion, proposed applications of lyso-pHoenix)

The experiment varies Lyso-pHoenix activation and tests it with both preserved and suppressed lysosomal proteolytic activity.

Different experimental conditions. Protein degradation and flux were measured with and without ammonium chloride and leupeptin in palbociclib-treated melanoma cells. This is not a factorial comparison of Lyso-pHoenix activation and proteolytic competence.

The lysosomal proteome of senescent cells contributes to the senescence secretome (Results 2.2; Figure 2; Methods 4.2 and 4.4)

Lysosomal localization of the optogenetic tool and the required current or signal must be confirmed before subsequent optical calibration.

Not verified in the article. Lysosomal localization and a light-dependent acidification signal were demonstrated in HeLa and HEK 293 cells, respectively. Their verification before subsequent optical calibration in the proposed fibroblast experiment is not documented.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Figure 6b-d; Online Methods, Light delivery and live-cell imaging)

Lysosomal pH must be measured ratiometrically.

Matches this study. Lysosomal pH was calculated from the FITC-dextran emission ratio at 530 and 610 nm using a calibration curve. This matches the measurement requirement as a component.

Autophagy Impairment Induces Premature Senescence in Primary Human Fibroblasts (Materials and Methods, Measurement of lysosomal pH; Figure 3C)

The experiment must compare degradation of a labeled long-lived substrate, autophagic flux, and protein aggregates; LC3 accumulation must not serve as the sole measure.

Not verified in the article. Radiolabeled long-lived protein degradation and multiple autophagic-flux assays were combined. The required joint assessment with protein aggregates under Lyso-pHoenix activation in old fibroblasts is absent.

The lysosomal proteome of senescent cells contributes to the senescence secretome (Figure 2; Methods 4.2-4.4)

Lysosomal integrity must be assessed, including whether the intervention damages the lysosomal membrane.

Different experimental conditions. Galectin-1 puncta assessed lysosomal membrane damage at baseline and after a lysosome-permeabilizing agent. These experiments do not assess membrane integrity during Lyso-pHoenix-mediated acidification.

TFEB-dependent lysosome biogenesis is required for senescence (Results; Figure EV2A-F)

Conditioned medium must be tested on untreated cells to assess its senescence-inducing effect.

Different experimental conditions. Isolated fibroblast-derived extracellular vesicles were applied to keratinocytes, mainly assessing differentiation and inflammatory responses. Whole conditioned medium after optical acidification was not tested for secondary senescence.

Extracellular Vesicles Derived from Senescent Fibroblasts Attenuate the Dermal Effect on Keratinocyte Differentiation (Results 2.5; Methods 4.11; Figure 5; Supplementary Figure S6C)

The primary success criterion is an increase of at least 25% in the degradation rate of damaged protein substrate together with a reduction in the senescence-inducing effect of the medium and preserved lysosomal integrity; the comparator for the percentage increase is unspecified.

Not verified in the article. No supplied study tests the combined criterion of at least 25% faster damaged-protein degradation, reduced medium-induced senescence, and intact lysosomes. The proposal leaves the percentage comparator unspecified.

Normalization of acidity without restoration of degradation, or damage to the lysosomal membrane, is the proposed refutation criterion and would indicate that pH is not a sufficient target.

Not verified in the article. No supplied study applies the proposed refutation rule after Lyso-pHoenix normalization of lysosomal pH in old fibroblasts.

The experiment requires a light source with confirmed spectral overlap for Lyso-pHoenix, pH microscopy, and flux measurement; compatibility of an RGB matrix must be checked.

Not verified in the article. The study specifies effective illumination wavelengths and fluorescence imaging equipment. The combined setup with autophagic-flux measurement and a compatibility check for an RGB matrix is not documented.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Online Methods, Light delivery and live-cell imaging)

The first testing stage is planned for 6-9 months, assuming that the team and models are available; this is the timeframe for an initial preclinical answer rather than development of a therapy.

Not verified in the article. The supplied studies do not document the proposed 6-9-month first testing stage conditional on available personnel and models. This is a planning condition.

The proposal is preclinical, and its numerical thresholds are planned decision criteria rather than results of published experiments or evidence of an established rejuvenation method.

Not verified in the article. The preclinical status and prospective decision thresholds characterize this proposal. No supplied experiment validates those thresholds or establishes the proposed intervention as rejuvenation.

If human cells are used, the studied age group must include at least six independent donors, with donors as the independent biological units rather than wells or individual cells.

Different experimental conditions. The fibroblast study used strains from two young donors aged 6 and 11 years, rather than at least six independent donors in the studied age group.

Autophagy Impairment Induces Premature Senescence in Primary Human Fibroblasts (Materials and Methods, Cell cultures)

Work with human cells requires a young reference tested under the same protocol and independent confirmation of the findings.

Not verified in the article. Early-passage comparators and repeated experiments were included, but the specified young age-group reference and independent confirmation of the Lyso-pHoenix test are not documented.

Extracellular Vesicles Derived from Senescent Fibroblasts Attenuate the Dermal Effect on Keratinocyte Differentiation (Methods 4.1; Figures 1 and 4)

The confirmatory sample size must be calculated from pilot variance before the main experiment.

Different experimental conditions. Sample sizes were explicitly not predetermined statistically and were chosen to resemble previous publications. This differs from a confirmatory calculation based on pilot variance.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Online Methods, Data collection and analysis)

Experimental conditions must be randomized, analysis must be blinded, and the primary outcome must be selected in advance.

Different experimental conditions. Wells and recording order were randomized, but collection and analysis were explicitly unblinded. The proposed prespecified degradation outcome was absent.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Online Methods, Data collection and analysis)

The analysis must account for donor or cohort effects and report 95% confidence intervals.

Not verified in the article. No supplied study reports the required donor- or cohort-adjusted analysis with 95% confidence intervals for the proposed optical-acidification experiment.

A confidence interval compatible with both benefit and no effect must be interpreted as uncertainty rather than refutation.

Not verified in the article. The supplied studies do not apply the specified uncertainty rule to confidence intervals for the proposed primary outcome.

Optogenetic controls must include the active tool in darkness, illumination without the tool, and the corresponding inactive tool under illumination.

Not verified in the article. Dark intervals and illuminated CD63-pHluorin controls were used. The lysosomal experiment does not document all three required controls, including the corresponding inactive Lyso-pHoenix tool under illumination.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Figure 6d; Online Methods, Cloning strategy and virus production)

Optical calibration must cover the spectrum, power at the sample, temperature, and phototoxicity.

Not verified in the article. Wavelengths, intensities measured above the objective, and recording temperature were described. Full calibration at the sample, including illumination-induced heating and phototoxicity, is not verified.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Online Methods, Light delivery and live-cell imaging; Electrophysiology)

The intervention dose must be determined in a pilot experiment and then fixed.

Not verified in the article. No supplied study documents pilot selection followed by fixation of the intervention dose for the proposed fibroblast test.

The general verification standard defines Vm as plasma membrane potential and requires confirmation of its optical signal by perforated patch-clamp; a mitochondrial dye is insufficient for this purpose.

Different experimental conditions. The study used whole-cell neuronal recordings to assess photocurrents and synaptic transmission. It did not use perforated patch-clamp to validate an optical plasma-membrane-potential signal.

Optogenetic Acidification of Synaptic Vesicles and Lysosomes (Figure 1c; Online Methods, Electrophysiology)

The general aging-assessment standard requires measurement of tissue function, viability, persistent DNA damage, and behavior after withdrawal of the intervention.

Not verified in the article. Cell survival, DNA-damage foci, and cell-cycle arrest were examined after different interventions. The full combination with tissue function, persistent damage, and post-withdrawal behavior under optical acidification is absent.

TFEB-dependent lysosome biogenesis is required for senescence (Figure EV2; Figure 3; Appendix Figure S2 as described in Results)

Faster cell division, reduction of a single marker, or a change in dye color alone is insufficient to establish rejuvenation.

Not verified in the article. Reduced senescence markers coexisted with persistent DNA-damage foci and cell-cycle arrest, supporting caution about marker-only conclusions. The complete stated rejuvenation standard was not tested.

TFEB-dependent lysosome biogenesis is required for senescence (Results, TFEB/TFE3 depletion; Figure 3D-G; Appendix Figure S2B-C)

The hypothesis proposes collagen preservation as a distinct, reproducible component of retinoid action.

Not verified in the article. No supplied primary study isolates collagen preservation as a reproducible component of retinoid action.

The proposed mechanism concerns old nonsenescent dermal fibroblasts in dermis with a low proportion of senescent cells.

Different experimental conditions. Old-donor fibroblasts with a minority of senescence-marker-positive cells were studied in monolayer culture, rather than within dermis with a verified low senescent-cell proportion.

Maintenance of Chronological Aging Features in Culture of Normal Human Dermal Fibroblasts from Old Donors (Methods 2.1; Results 3.1; Figure 1)

Age-related changes in fibroblasts are considered only partially overlapping with experimentally induced senescence, and mechanical support is considered a determinant of fibroblast function.

Matches this study. The study explicitly describes mechanical regulation of fibroblasts and experimentally distinguishes donor-age effects from induced senescence. Mechanical regulation is background in this study, not its tested intervention.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Introduction; Results 3.1-3.3; Figures 2-7)

Protection against matrix metalloproteinase-1 (MMP1) is predicted to preserve collagen support and thereby restore some functions of old nonsenescent fibroblasts without removing cells, establishing a mechanism independent of senolysis.

Different experimental conditions. MMP inhibition prevented collagen fragmentation, and latrunculin-A withdrawal restored cellular mechanics. These experiments used adult fibroblasts averaging 31 ± 4 years and did not establish MMP1-mediated rescue of old nonsenescent cells independently of senolysis.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results; Figures 2 and 4; Experimental procedures, Cell culture)

Compare old donor cells with experimentally induced senescent cells on identical matrices.

Matches this study. Old-donor and irradiation-induced senescent fibroblasts were compared using the same Alvetex scaffold platform and culture protocol.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods 2.4; Results 3.2; Figure 4)

Assess senescence comprehensively in old donor cells, and do not classify senescence using a single marker.

Matches this study. Old-donor cultures were assessed using senescence-associated β-galactosidase, DNA-damage-associated 53BP1 staining, P16 transcripts and P16/P21 proteins, rather than a single marker.

Maintenance of Chronological Aging Features in Culture of Normal Human Dermal Fibroblasts from Old Donors (Methods 2.2-2.4; Results 3.1; Figure 1)

Apply CRISPR interference targeting MMP1 (MMP1-CRISPRi) while keeping cell numbers unchanged.

Not verified in the article. No supplied study applies MMP1-targeted CRISPR interference while maintaining unchanged cell numbers.

Track individual cells and measure synthesis, force and migration.

Not verified in the article. Collagen expression and migration were assessed, but the combined measurement of synthesis, force and migration with longitudinal individual-cell tracking is absent.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods 2.6 and 2.8; Figure 6; Discussion)

Use individual cell tracking to exclude selective survival of a young subpopulation as the explanation for improvement.

Not verified in the article. No supplied experiment uses individual-cell tracking to exclude selective survival of a young subpopulation.

Improvement occurring only after senescent cell death or removal would fail to support a mechanism independent of senolysis.

Not verified in the article. No supplied experiment tests whether functional improvement depends on senescent-cell death or removal.

The functional goal is to preserve aging skin strength, renewal and recovery after injury.

Not verified in the article. The study links collagen mechanics to skin integrity and discusses wound healing, but does not demonstrate preservation of aging skin strength, renewal and injury recovery together.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Introduction; Figures 1-4; Discussion)

Use paired models from several independent donors.

Matches this study. Multiple independent donor lines were studied with paired senescent and nonsenescent conditions derived from the same lines.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods 2.1-2.5; Figures 2 and 3)

Use randomization and blinded assessment.

Not verified in the article. Randomization together with blinded assessment is not documented in the supplied methods.

Treat the donor as the biological unit and wells as technical replicates.

Matches this study. Independent donor-derived fibroblast cultures are identified as biological replicates, and repeated well measurements are distinguished as technical replicates.

Maintenance of Chronological Aging Features in Culture of Normal Human Dermal Fibroblasts from Old Donors (Methods 2.1 and 2.8; Figures 4 and 5 legends)

Calculate sample size using variability estimated in a pilot study.

Not verified in the article. No supplied study documents sample-size calculation based on pilot variability.

Prespecify the primary functional outcome and account for multiple comparisons.

Not verified in the article. Bonferroni and false-discovery-rate corrections were used, but prespecification of a primary functional outcome is not documented.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Methods 2.7)

Monitor viability, cellular composition and intervention specificity.

Not verified in the article. The combined monitoring of viability, cellular composition and specificity during the proposed MMP1 intervention is absent.

In reconstructed models, distinguish old and new collagen fractions using sequential stable isotope labeling.

Not verified in the article. Sequential stable-isotope labeling to distinguish old and new collagen fractions in reconstructed models is absent.

In native explants, label only newly synthesized material and account for the unlabeled pool using mass balance.

Not verified in the article. No supplied experiment labels new synthesis in native explants while accounting for the unlabeled pool by mass balance.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. Accounting for precursor enrichment and isotope-label recycling is not documented.

Use second harmonic generation (SHG) to characterize collagen organization while separately measuring collagen mass, mechanics and healing.

Not verified in the article. Second harmonic generation microscopy and mechanical measurements are described, but the required combined assessment of organization, collagen mass, mechanics and healing is absent.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Experimental procedures, microscopy methods; Figures 1-4)

Verify the involvement of MMP1 using a specific activity assay and an independent genetic intervention.

Different experimental conditions. Collagen cleavage, recombinant MMP-1 and an MMP inhibitor were combined with dominant-negative c-Jun, rather than a specific MMP1 activity assay paired with independent genetic targeting of MMP1.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Figures 2 and 3; Experimental procedures)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout.

Different experimental conditions. Activated recombinant MMP-1 served as a positive control, and secreted enzyme was activated with trypsin. These procedures do not constitute active-MMP1 restoration after genetic suppression or inhibitor washout.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Figure 2C; Experimental procedures, Cell culture)

Include catalytically inactive MMP1 protein as a control for restoration of active MMP1.

Not verified in the article. A catalytically inactive MMP1 protein control for active-enzyme restoration is absent.

Test whether the effect persists after treatment withdrawal and exclude residual drug retention.

Different experimental conditions. Latrunculin-A withdrawal tested recovery from cytoskeletal disruption, rather than persistence after withdrawal of a collagen-protective treatment; residual drug retention was not measured.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, restoration of cell shape/mechanical tension; Figure 4)

An increase in collagen alone does not establish rejuvenation; improved collagen organization and function are also required.

Not verified in the article. Collagen organization and cellular mechanics were assessed, but rejuvenation was not established using the required joint criteria of increased collagen, improved organization and improved function.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Figures 2 and 4; Discussion)

Treat the proposed effect as a research hypothesis rather than an established effect or a recommendation for use; supporting observations do not prove the hypothesis.

Not verified in the article. The complete proposed intervention remains a research hypothesis in this comparison; the supplied component studies do not establish its efficacy or justify recommending its use.

Conclusions obtained in cellular and animal models require verification in human skin.

Matches this study. The authors explicitly state that their in vitro findings require translation to human skin in vivo and cannot establish how aged and senescent cells behave there.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Discussion, limitations)

The motivating cell-free observation is that decorin and other small proteoglycans can protect collagen fibrils from cleavage by collagenases.

Matches this study. The article preview explicitly reports that recombinant decorin, fibromodulin, and lumican reduced collagenase cleavage of cell-free type I and II collagen fibrils. The supplied material is a preview rather than the complete article.

SLRP interaction can protect collagen fibrils from cleavage by collagenases (Abstract; Results and Discussion snippets)

Restore physiological decorin coverage of collagen fibrils to reproduce the collagen-preserving component of retinoid action.

Not verified in the article. Decorin supplementation protected collagen lattices, but physiological coverage restoration and reproduction of retinoid-associated collagen preservation were not tested.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 4-5; Discussion)

Decorin must protect collagen by binding to it and shielding the fibrillar substrate from collagenase cleavage, while leaving the amount of matrix metalloproteinase-1 (MMP1) unchanged and preserving its access to other substrates.

Not verified in the article. Binding and protection were demonstrated with a fixed added MMP-1 concentration. Preserved access to other substrates and unchanged enzyme abundance during the skin intervention were not established.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figure 4; Methods, Cleavage of Type I Collagen Lattices by Purified MMP-1)

First compare purified decorin with a variant that has impaired collagen binding on cell-free collagen fibrils under conditions with equal MMP1.

Different experimental conditions. Purified mouse decorin core protein and binding-impaired mutants were compared for collagen binding and fibrillogenesis, rather than protection of fibrils from equal MMP1 exposure.

The Concave Face of Decorin Mediates Reversible Dimerization and Collagen Binding (Experimental Procedures, Collagen Fibrillogenesis Assay and Solid-phase Binding Assay; Figure 6; Table 2)

After the cell-free experiment, transfer the intervention to aged three-dimensional skin.

Different experimental conditions. The study combined acute ultraviolet exposure of adult human skin with cell-free collagen lattices. It did not transfer decorin restoration into aged three-dimensional skin.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Methods, UV Irradiation and Human Tissue Procurement; Electron Microscopy; Figures 1, 4-5)

In aged three-dimensional skin, control for decorin signaling effects, synthesis, and total MMP1 activity.

Not verified in the article. No supplied study controls decorin signaling, collagen synthesis, and total MMP1 activity together during decorin restoration in aged three-dimensional skin.

Measure collagen fiber lifespan, mechanical properties, and healing.

Different experimental conditions. Skin tensile properties were measured after decorin gene disruption in mice. Fiber lifespan and healing were not jointly assessed under the proposed restoration intervention.

Targeted Disruption of Decorin Leads to Abnormal Collagen Fibril Morphology and Skin Fragility (Methods, Biomechanical Test of Skin Tensile Strength; Results, Figure 4)

Substrate shielding is supported only if protection requires collagen binding and cannot be explained by reduced MMP1 or altered synthesis; failure of either requirement means that substrate shielding has not been demonstrated.

Not verified in the article. Cell-free protection excludes new collagen synthesis in that assay, and elastase digestion removes protection. However, the required binding-impaired comparison and exclusion of alternative mechanisms in aged skin are absent.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 4-5)

Excessive decorin coverage that impedes renewal constitutes a lack of useful benefit.

Not verified in the article. The supplied studies do not test excessive decorin coverage against a renewal-based criterion of useful benefit.

The functional objective is to preserve the strength, renewal, and recovery after injury of aging skin.

Different experimental conditions. Decorin deficiency impaired mouse skin strength, supporting a functional role. Preservation of strength, renewal, and injury recovery in aging skin after restoration was not tested.

Targeted Disruption of Decorin Leads to Abnormal Collagen Fibril Morphology and Skin Fragility (Results, Figure 4; Conclusions)

Use paired models from multiple independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. The study included multiple human participants and paired statistical comparisons, but it does not document the specified paired donor-derived aged-skin models with wells treated as technical replicates.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Methods, UV Irradiation and Human Tissue Procurement; Statistical Analysis)

Use randomization and blinded assessment.

Not verified in the article. Randomization and blinded assessment are not documented for the proposed decorin-restoration experiment.

Calculate the sample size from pilot variability, prespecify the primary functional outcome, and account for multiple comparisons.

Not verified in the article. The supplied studies do not document the required combination of pilot-based sample-size calculation, a prespecified primary functional outcome, and multiple-comparison adjustment.

Control viability, cellular composition, and intervention specificity.

Not verified in the article. Joint control of viability, cellular composition, and intervention specificity is not verified in the required aged-skin restoration model.

In reconstructed models, distinguish old and new fractions using sequential stable-isotope labeling.

Not verified in the article. Sequential stable-isotope labeling of old and new collagen fractions in reconstructed models is absent from the supplied experiments.

In native explants, label only new synthesis and account for the unlabeled pool using mass balance.

Not verified in the article. The supplied studies do not label new synthesis in native explants while accounting for the unlabeled collagen pool by mass balance.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. Accounting for precursor enrichment and label recycling in the specified collagen-labeling experiment is not reported.

Use second-harmonic generation (SHG) to characterize organization, while measuring mass, mechanics, and healing separately.

Not verified in the article. No supplied experiment combines second-harmonic generation with separate measurements of collagen mass, mechanics, and healing under the proposed intervention.

Assess MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. Purified MMP-1-mediated collagen cleavage was assayed, but the required accompanying independent genetic intervention was absent.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Methods, Cleavage of Type I Collagen Lattices by Purified MMP-1; Figures 4-5)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout, as specified without further clarification of the genetic suppression target.

Not verified in the article. Restoration of active MMP1 using genetic suppression or prior inhibitor washout is not reported. The proposed genetic suppression target remains unspecified.

Include a catalytically inactive protein as a control in the active-MMP1 restoration experiment.

Not verified in the article. A catalytically inactive protein control in the specified active-MMP1 restoration experiment is absent.

Test whether the effect persists after treatment withdrawal and exclude persistence of the administered agent.

Not verified in the article. Persistence of the protective effect after withdrawal, with exclusion of residual administered agent, was not tested in the supplied studies.

An increase in collagen alone does not establish rejuvenation unless organization and function also improve.

Not verified in the article. The proposed rejuvenation criterion requiring improved collagen organization and function alongside collagen accumulation was not evaluated.

Treat the proposed effect as a research hypothesis requiring experimental verification, with the cited observations supporting its premises rather than establishing the hypothesis.

Not verified in the article. The supplied observations support premises of the proposal; no supplied study experimentally verifies the complete proposed hypothesis.

Findings from cellular and animal models require validation in human skin.

Not verified in the article. Human skin observations establish decorin localization and ultraviolet-associated degradation, but they do not validate the proposed restorative intervention and functional outcomes in human skin.

Solar Ultraviolet Irradiation Induces Decorin Degradation in Human Skin Likely via Neutrophil Elastase (Results, Figures 1 and 4; Methods, Human Tissue Procurement)

The cited biological rationale includes the observation that expression of catalytically active MMP1 in dermal fibroblasts induces collagen fragmentation and functional alterations resembling aged human skin.

Not verified in the article. The cited active-MMP1 fibroblast study is named in the hypothesis, but its experimental text is absent from the supplied literature. The specified aging-like phenotype cannot be independently verified here.

The cited biological rationale also includes the requirement for collagenase-1 activity in keratinocyte migration on a type I collagen matrix.

Not verified in the article. The cited keratinocyte-migration study is not supplied as experimental source text, so the requirement for collagenase-1 activity on type I collagen cannot be verified from these materials.

Collagen preservation is proposed as a separately reproducible component of retinoid action that supports microvascular stability in aged dermis.

Not verified in the article. The supplied studies do not isolate collagen preservation as a reproducible component of retinoid action supporting aged dermal microvessels.

The motivating observation is that increased structural support in aged human skin was accompanied by changes in fibroblasts, endothelial cells and keratinocytes; the causal role of protection against MMP1 in vascular stability remains unestablished.

Not verified in the article. The motivating aged-human-skin study is named in the hypothesis, but its methods and results are not supplied for verification of the three cellular responses or the vascular causal inference.

Preserving a continuous collagen network is predicted to provide load-bearing dermal support and reduce mechanical collapse of already formed microvessels under load, even without stimulating angiogenesis.

Different experimental conditions. Collagen architecture and fibril stiffness affected capillary morphology and leakage through perivascular cells and NOTCH3. This tested fibrotic matrix signaling, rather than preservation of a continuous dermal network against compression-induced collapse independently of angiogenesis.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Results, Figures 1-5; Discussion)

The experiment must use perfused organotypic skin in which identical microvessels are formed first, followed by reproduction of aged, fragmented dermis.

Different experimental conditions. Human vascular cells were seeded into preassembled rat-tail collagen I matrices with different architectures. The model was a vascular chip, and matrix differences preceded vessel formation rather than following formation of identical vessels in organotypic skin.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Materials and Methods, Collagen preparation and Cell seeding; Figure 1)

MMP1 must be selectively limited after identical microvessels have been formed and aged, fragmented dermis has been reproduced.

Different experimental conditions. A neutralizing MMP1 antibody prevented matrix degradation before rat endothelial cells were added. Selective limitation after vessel formation and subsequent reproduction of aged dermis was not tested.

Vascular tube formation on matrix metalloproteinase-1-damaged collagen (Materials and Methods, Preparation and degradation of polymerised collagen lattices; Results, Figure 3)

Microvascular patency, leakage and recovery of perfusion after compression must be measured.

Not verified in the article. Dextran leakage through perfused vascular lumens was measured, but compression-dependent patency and recovery of perfusion were not assessed.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Figure 3; Materials and Methods, Dextran assay for barrier function measurement)

Vascular cells and growth factors must be kept equal across experimental comparisons.

Matches this study. Within matrix comparisons using the same cellular configuration, the study used the same vascular cell sources, seeding protocol and supplemented endothelial medium. This matches the input-control component in a different experimental system.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Materials and Methods, Collagen preparation, Cell culture and Cell seeding)

Collagen types I and IV must be assessed separately.

Different experimental conditions. The study characterized collagen I and examined basement-membrane laminin. Laminin measurement does not reproduce separate assessment of collagens I and IV.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Figures 1 and 3; Materials and Methods, Cell staining and imaging)

Improvement attributable only to increased vessel numbers, direct effects on the endothelium or changes in the basement membrane does not establish the proposed mechanism of load-bearing dermal support.

Not verified in the article. Endothelial-only controls, sprout measurements and laminin staining addressed related alternatives, but did not isolate load-bearing protection from vessel-number, endothelial and basement-membrane effects during compression.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Results, Figures 2, 3 and 5)

The broader functional objective is to preserve the strength, renewal and recovery after injury of aging skin.

Not verified in the article. Preservation of aging skin strength, renewal and recovery after injury was not tested as the proposed functional objective.

Paired models from several independent donors must be used, with the donor treated as the biological unit and wells treated as technical replicates.

Matches this study. Skin from six donors supplied paired treatment conditions, with multiple explants pooled within donors and donor-level statistical comparisons. This matches the donor-based replication principle, but in a different explant experiment.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and Methods, Preparation and allocation of skin explants and Statistical analyses; Figures 1-4)

The experiments must use randomization and blinded assessment.

Matches this study. Explants were randomly allocated to treatment groups, and histological scoring and apoptosis image assessment were blinded.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and Methods, Allocation to treatment groups and Histology; Figure 4 legend)

Sample size must be calculated from pilot variability.

Not verified in the article. No supplied study reports a sample-size calculation based on pilot variability for the proposed test.

The primary functional outcome must be selected in advance, and multiple comparisons must be accounted for.

Not verified in the article. Tukey post hoc comparisons were used, but prospective selection of the proposed primary functional outcome is not documented.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Materials and Methods, Statistical analysis)

Viability, cellular composition and intervention specificity must be controlled.

Not verified in the article. Viability, apoptosis and enzyme specificity were examined. The combined requirement to control viability, cellular composition and specificity in the proposed vascular experiment remains unverified.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Results, Figures 3-7; Materials and Methods, Collagenolytic activity assay)

In reconstructed models, old and new collagen fractions must be distinguished by sequential stable isotope labeling.

Not verified in the article. Sequential stable isotope labeling of old and new collagen in reconstructed models is absent from the supplied studies.

In native explants, only newly synthesized collagen must be labeled, and the unlabeled pool must be accounted for by mass balance.

Different experimental conditions. Native skin explants were assessed using hydroxyproline, collagen degradation products and procollagen propeptides. This substitutes biochemical markers for labeling new collagen and accounting for the unlabeled pool by mass balance.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and Methods, Collagen degradation and Type I collagen degradation and biosynthesis; Figures 1 and 2)

Precursor enrichment and label recycling must be accounted for when interpreting isotope labeling.

Not verified in the article. Accounting for precursor enrichment and isotope-label recycling is not reported.

Second harmonic generation must be used to characterize collagen organization, with separate measurements of collagen mass, mechanics and healing.

Not verified in the article. Second harmonic generation characterized collagen architecture, and indentation measured bulk and fibril mechanics. Separate collagen-mass and healing measurements completing this requirement were not reported.

Perivascular cells function as key mediators of mechanical and structural changes in vascular capillaries (Figure 1; Materials and Methods, Atomic force microscopy)

The involvement of MMP1 must be tested using both a specific activity assay and an independent genetic intervention.

Not verified in the article. A collagenolytic activity assay with MMP1-neutralizing antibody established an MMP1-dependent component. An independent genetic MMP1 intervention was not performed.

Tumor necrosis factor-α-accelerated degradation of type I collagen in human skin is associated with elevated matrix metalloproteinase (MMP)-1 and MMP-3 ex vivo (Materials and Methods, Type I collagenolytic activity assay; Figure 5)

For restoration with active MMP1, genetic suppression or prior inhibitor washout must be used.

Not verified in the article. No supplied experiment restores active MMP1 after genetic suppression or inhibitor washout. Washing collagen after enzyme digestion in the tube-formation study is a different procedure.

A catalytically inactive protein must be included as a control for restoration with active MMP1.

Not verified in the article. A catalytically inactive MMP1 protein control for the restoration experiment is absent.

The effect must be assessed after treatment withdrawal, and residual drug persistence must be excluded.

Not verified in the article. Persistence of the protective effect after treatment withdrawal, with residual drug excluded, was not tested.

An increase in collagen alone does not establish rejuvenation unless collagen organization and function also improve.

Not verified in the article. No supplied study establishes rejuvenation through the required combined improvement in collagen organization and skin function.

The proposed effect must remain a research hypothesis rather than an established effect or recommendation for use, and findings from cellular and animal models require validation in human skin.

Not verified in the article. Human explant data support collagen degradation mechanisms, but the complete vascular protection test has not been validated in human skin and remains a research hypothesis.

The hypothesis examines collagen preservation as a separate, reproducible component of retinoid action in aging skin, with the aim of preserving skin strength, renewal, and recovery after injury.

Not verified in the article. The supplied studies do not isolate collagen preservation as a component of retinoid action or test preservation of strength, renewal, and repair in aged skin.

The proposed mechanism relies on the experimental finding that matrix metalloproteinase-1 (MMP1) activity is required for keratinocyte migration on type I collagen.

Matches this study. Human keratinocyte migration on native type I collagen required MMP1 activity, supported by inhibitory antibodies, collagenase-resistant collagen, and complementary inhibition experiments.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figures 4-7)

MMP1 must first be restricted equally in aged skin, after which a standardized microwound must be created.

Different experimental conditions. The study used cultured human keratinocytes and wounded neonatal human skin grafts, rather than equally pretreated aged skin receiving standardized microwounds.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Cell Culture and In Situ Hybridization; Figure 1)

After microwounding, randomize the models to continued MMP1 restriction, withdrawal of the intervention until wound closure, or a control group whose treatment is unspecified.

Not verified in the article. No supplied experiment randomized previously restricted, microwounded models among continuation, withdrawal until closure, and control groups.

Temporary withdrawal of the collagen-preserving intervention during re-epithelialization is hypothesized to restore MMP1 activity and keratinocyte migration, eliminate delayed healing, and retain part of the dermal structural support preserved by prior MMP1 blockade.

Not verified in the article. The experiments establish a migration requirement for MMP1, but do not test withdrawal-mediated recovery of healing together with retention of previously preserved dermal support.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figures 4-7)

Map MMP1 activity at the wound edge and outside it.

Different experimental conditions. The spatial measurement localized MMP1 messenger RNA at the migrating wound edge and its absence in intact epidermis, rather than mapping enzyme activity.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, In Situ Hybridization; Figure 1)

Measure keratinocyte migration speed, the amount of old collagen lost, and late mechanical properties.

Not verified in the article. Migration was quantified through track area and colony expansion over time; old collagen loss and late mechanical properties were not measured.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, migration assays; Figures 4-7)

Safe temporal separation requires both healing and preserved late function; failure of withdrawal to restore migration or rapid loss of the entire structural benefit would refute it.

Not verified in the article. No supplied experiment jointly tests healing recovery and retained late function after withdrawal or applies the proposed rejection criteria.

Use paired models from several independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. Experiments included duplicate conditions and keratinocytes from different donors, but a paired aged-skin design with donor-level biological inference is not established; some results summarize wells.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Colloidal Gold Migration Assay; Figures 5-7)

Assess experimental outcomes under blinded conditions.

Not verified in the article. Blinded outcome assessment is not documented in the supplied experimental methods.

Calculate sample size from pilot variability, prespecify the primary functional outcome, and account for multiple comparisons.

Not verified in the article. Pilot-based sample-size calculation, a prespecified primary functional outcome, and adjustment for multiple comparisons are not documented.

Monitor viability, cellular composition, and intervention specificity.

Not verified in the article. Specificity controls and unchanged total secreted protein synthesis provide partial support, but the complete monitoring of viability and cellular composition is not established.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figures 5-7; Table I)

In reconstructed models, distinguish old and new collagen fractions using sequential stable-isotope labeling.

Not verified in the article. Sequential stable-isotope labeling of old and new collagen in reconstructed models is absent from the supplied experiments.

In native explants, label only newly synthesized collagen and account for the unlabeled pool by mass balance.

Not verified in the article. The supplied studies do not combine labeling of newly synthesized collagen in native explants with mass-balance accounting of the unlabeled pool.

Account for precursor enrichment and label recycling when interpreting isotope-labeling measurements.

Not verified in the article. Accounting for precursor enrichment and label recycling in collagen turnover measurements is not documented.

Use second-harmonic generation (SHG) to characterize collagen organization, while retaining separate measurements of collagen mass, mechanical properties, and healing.

Not verified in the article. No supplied experiment combines second-harmonic generation with separate measurements of collagen mass, mechanics, and healing.

Test MMP1 using a specific activity assay and an independent genetic intervention.

Different experimental conditions. Specific antibodies and mutant collagen support MMP1 involvement, but the genetic alteration targets collagen, and the inhibitor-persistence assay uses the 92-kD gelatinase catalytic domain rather than a specific MMP1 assay.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Thiopeptolide Assay; Table II; Figures 6-7)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout; the target of genetic suppression and its relationship to restoration are unspecified.

Different experimental conditions. Epidermal growth factor induced MMP1 production and migration in HaCaT cells; restoration through genetic suppression or prior inhibitor washout was not tested.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, induction of collagenase-1 in HaCaT keratinocytes; Figure 4)

Include catalytically inactive MMP1 protein as a control for restoration of active MMP1.

Not verified in the article. The weakly inhibitory stereoisomer SC44201 served as a comparator, but catalytically inactive MMP1 protein was not used as a restoration control.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Migration of Primary Human Keratinocytes; Figure 5)

Test the effect after withdrawal and rule out persistence of the drug.

Different experimental conditions. The assay demonstrated sustained inhibitor activity during culture, rather than recovery after withdrawal and exclusion of residual drug.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Thiopeptolide Assay; Table II)

An increase in collagen qualifies as rejuvenation only if collagen organization and skin function also improve.

Not verified in the article. The supplied studies do not evaluate rejuvenation through concurrent improvements in collagen quantity, organization, and skin function.

The proposed effect remains a research hypothesis rather than an established effect or a recommendation for use, and the cited evidence supports the starting observations rather than proving the hypothesis.

Not verified in the article. The supplied evidence supports a starting mechanism, while the proposed withdrawal benefit remains untested and provides no established recommendation for use.

Conclusions from cellular and animal models require validation in human skin.

Different experimental conditions. Human cells and neonatal human skin grafted onto mice were studied, but the full withdrawal intervention was not validated in aged human skin.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Cell Culture and In Situ Hybridization; Figure 1)

The supplied supporting literature identifies expression of catalytically active MMP1 in dermal fibroblasts as inducing collagen fragmentation and functional alterations resembling aged human skin.

Not verified in the article. The hypothesis cites the fibroblast study, but its article text is absent from the supplied literature; its methods and reported aging-like functional changes cannot be verified here.

The experiment uses layered skin equivalents containing dermal collagen I and basal collagen IV to compare lipid-adduct damage in the deep dermal matrix and the basement membrane.

Different experimental conditions. Keratinocytes were cultured on modified collagen IV separately from skin equivalents containing modified dermal collagen I. These systems do not provide the proposed comparison of independently modified compartments within the same layered model.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.6, 2.11, 3.7-3.8; Figures 7-8)

At the same total carbonyl burden, lipid adducts localized in basement-membrane collagen IV are hypothesized to impair epidermal differentiation and function more strongly than comparable damage localized in deep dermal collagen I.

Not verified in the article. Collagen modification and epidermal responses were demonstrated, but greater functional damage from collagen IV than collagen I at equal carbonyl burden was not tested. Stronger carbonyl staining of collagen IV does not establish this functional comparison.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 3.1, 3.7-3.8; Figures 1, 7-8)

The total level of 4-hydroxynonenal (4-HNE) is hypothesized to conceal functionally different forms of aging because the location of lipid adducts determines their effects.

Not verified in the article. The supplied studies do not demonstrate different aging-related functions at equal total 4-HNE levels through experimentally controlled redistribution of lipid adducts.

The decisive experiment compares four groups: unmodified layers, modified dermal collagen I only, modified basal collagen IV only, and both layers modified.

Different experimental conditions. Skin equivalents compared native dermal collagen with collagen modified by HNE or oxidized phospholipids. The four groups independently varying modification of collagen I and collagen IV were absent.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.11, 3.8; Figure 8)

Free aldehydes must be removed before cells are introduced into the modified skin equivalents.

Not verified in the article. Coated culture surfaces were washed before cell seeding, providing a relevant methodological component. The skin-equivalent protocol does not document free-aldehyde removal before fibroblasts were introduced, so that condition cannot be transferred from the separate coating experiments.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.6 and 2.11)

Adducts must be measured by mass spectrometry, and their burden must be matched between the modification conditions being compared.

Not verified in the article. Mass spectrometry identified collagen adducts, and carbonyl assays compared modifications. Mass-spectrometric quantification and matching of adduct burdens between the proposed collagen I and collagen IV compartments were not documented.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.4-2.5, 3.1; Figure 1C-F)

The thickness, porosity, and modulus of each layer must be controlled, with mechanics matched for the comparison of modification locations.

Not verified in the article. The authors identify collagen elasticity and stability as subjects for future investigation. Controlling each layer's thickness, porosity and modulus while matching mechanics across modification locations was not reported.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Section 4.4)

After a defect has formed, only the damaged layer must be replaced with a normal layer as a test of causality.

Not verified in the article. Neither supplied full article reports replacing only the damaged layer after a defect develops to test restoration of epidermal function.

A separate free-aldehyde control must distinguish direct aldehyde toxicity from signaling by the modified, fixed matrix.

Different experimental conditions. A transwell experiment tested fibroblast responses with or without direct contact with modified collagen. This is a relevant contact control, but it substitutes a different comparison for the proposed separate free-aldehyde exposure control in skin equivalents.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.6, 3.4; Figure 4C)

The primary outcome is the permeability of the mature epidermal barrier, with basement-membrane modification predicted to cause greater barrier impairment than dermal collagen I modification.

Different experimental conditions. The study assessed differentiation, parakeratosis and epidermal thickness after five days at the air-liquid interface. It did not measure mature barrier permeability or compare that outcome between collagen IV and collagen I modification.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.9, 2.11, 3.8; Figure 8)

Secondary outcomes are basal integrin distribution, epidermal differentiation, intercellular lipids, and DNA damage, assessed at equal viability.

Not verified in the article. Epidermal differentiation and a DNA-damage marker were assessed, while integrin gene expression was examined in fibroblasts. The complete panel of basal integrin distribution, intercellular lipids and the other outcomes at equal viability was not verified.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 3.3, 3.8, 4.2.2; Figures 8C, 8J-K; Supplementary Figure 2B)

The hypothesis of preferential basement-membrane damage is rejected if modification location does not affect the barrier after adduct burden and mechanics have been matched; a result of p > 0.05 alone does not constitute refutation.

Not verified in the article. The location-dependent barrier test with matched burden and mechanics was not performed, and the proposed rejection criterion distinguishing absence of an effect from p > 0.05 was not applied.

The reproducibility plan includes a pilot study with 6-8 independent donors.

Different experimental conditions. Skin equivalents were studied in three independent experiments using three fibroblast-keratinocyte donor combinations, each in duplicate. This is not the specified pilot design with 6-8 independent donor biological units.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Sections 2.1 and 2.14; Figure 8A)

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. Neither full article reports the specified main-study sample-size calculation using mature barrier-permeability variance and a prespecified minimum useful effect.

The donor is the biological unit, while chips or wells are nested replicates.

Not verified in the article. Donor combinations and duplicate skin equivalents were described, but the analysis did not explicitly establish the donor as the biological unit with chip or well measurements treated as nested replicates.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Section 2.14)

The experiment must use randomization and blinded analysis.

Not verified in the article. Randomization and blinded analysis for the proposed comparison are not documented in the supplied studies.

Statistical analysis must use a paired model accounting for donor, report confidence intervals, and apply correction for secondary comparisons.

Different experimental conditions. The study used analysis of variance and t-tests, with multiple-comparison procedures for gene-expression analyses. It did not report the specified paired donor-adjusted model and confidence intervals for the proposed primary and secondary outcomes.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Section 2.14; Figure 8)

p16/p21 or senescence-associated beta-galactosidase (SA-β-gal), considered separately, do not establish cellular senescence.

Matches this study. The article explicitly calls for integrating multiple senescence markers and assesses several complementary markers. This supports the methodological principle that an isolated p16/p21 or beta-galactosidase measurement is insufficient, without validating the proposed location comparison.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Section 1; Sections 3.8 and 4.2.1; Figure 8E-K)

New collagen must be distinguished from the original scaffold.

Not verified in the article. Procollagen I staining provides a related measure of collagen synthesis in glycated skin equivalents. It does not establish the proposed distinction between newly produced collagen and the original lipid-modified scaffold throughout the experiment.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Materials and Methods, Histology and immunohistochemistry; Results, Figures 1-2)

The basement membrane is multicomponent, and collagen IV represents only one of its components, which limits the model's representation of basement-membrane damage.

Not verified in the article. The article discusses collagen IV and laminin 5 in the dermal-epidermal junction, supporting its multicomponent nature. It does not evaluate the stated limitation of representing basement-membrane lipid damage through selectively modified collagen IV.

Biological Effects Induced by Specific Advanced Glycation End Products in the Reconstructed Skin Model of Aging (Introduction; Discussion, laminin 5 and basement-membrane structure)

The model does not establish that adducts can be safely removed from a patient's skin.

Not verified in the article. The supplied studies provide no clinical test of safe adduct removal from patients' skin. The proposal's limitation is therefore appropriate, but it is not an experimentally matched condition or evidence of novelty.

The proposal remains a research hypothesis: the described new experiments have not been performed, and no experimental results are claimed.

Not verified in the article. The submitted proposal states that its experiments remain unperformed. The supplied literature contains completed component studies, but no completed version of this full proposed test; the proposal's status is not itself scientific novelty.

The hypothesis attributes reduced collagen production during aging to both changes intrinsic to fibroblasts and defective mechanical stimulation.

Matches this study. The introduction explicitly attributes fibroblast aging to intrinsic cellular changes and altered mechanical interaction with the matrix. This matches the stated rationale as background, not an experimental demonstration of the complete hypothesis.

Age, gender and UV-exposition related effects on gene expression in in vivo aged short term cultivated human dermal fibroblasts (Introduction, Homeostasis of dermal extracellular matrix; In vivo interaction of dermal fibroblasts with extracellular matrix)

With an equally preserved matrix network, young and old fibroblasts are expected to show similar protection of existing collagen but different increases in new matrix, because cellular age autonomously limits secondary restoration and thereby limits replacement of the full retinoid response with matrix protection alone.

Not verified in the article. Lower collagen production in adult fibroblasts independent of senescence supports a component. Equal protection of existing collagen, matched matrix networks, and a limit on substituting protection for the retinoid response were not tested.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Results 3.1-3.3; Figures 2, 4, 6; Discussion)

The experiment must use a crossed design in which standardized young-like and damaged matrices are each seeded with young and old nonsenescent fibroblasts.

Different experimental conditions. Fibroblasts from different donor-age groups were grown on porous polystyrene scaffolds with transforming growth factor beta-1 and ascorbic acid. This differs from crossing both ages with standardized young-like and damaged collagen matrices.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods 2.4; Results 3.2; Figure 4)

Cellular age must be defined by donor age, and culture passage number must not substitute for donor age.

Matches this study. Age groups were defined by donor age, and experimentally induced senescence was examined separately. Passage number did not define the age groups.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods 2.1, 2.4; Figure 4)

Compare CRISPR interference targeting matrix metalloproteinase-1 (MMP1-CRISPRi) with a retinoid under conditions of equal residual MMP1 enzyme activity.

Not verified in the article. None of the supplied studies compared MMP1-targeted CRISPR interference with a retinoid at matched residual enzyme activity.

Measure the old and new matrix fractions, mechanical properties, and changes in cellular composition.

Different experimental conditions. The study measured cellular mechanical properties, collagen fragmentation, and fibril organization. It did not separately quantify old and newly synthesized matrix or changes in cellular composition.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results; Figures 1, 2, 4; Experimental procedures, Atomic force microscopy)

Reject the proposed autonomous cellular-age limit if cellular age ceases to affect restoration after the matrix network and MMP1 have been matched.

Not verified in the article. The absence of consistent donor-age transcriptional differences concerns cultured fibroblasts without matched matrix protection or MMP1 activity. It therefore does not implement the proposed rejection test.

Age, gender and UV-exposition related effects on gene expression in in vivo aged short term cultivated human dermal fibroblasts (Results, Analysis of age related differential gene expression; Discussion)

The functional objective is to preserve aging skin strength, renewal, and recovery after injury.

Not verified in the article. Cell migration was measured and implications for wound healing were discussed, but preservation of aging skin strength, renewal, and recovery after injury was not demonstrated.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods 2.8; Results 3.3; Figure 6h; Discussion)

Use paired models from several independent donors, treating the donor as the biological unit and wells as technical replicates.

Not verified in the article. Independent donor-derived lines and repeated measurements were used. The specified paired matrix-intervention models, with donors as biological units and wells explicitly treated as technical replicates, were not established.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods 2.1, 2.2, 2.7; Figures 2-4)

Use randomization and blinded assessment.

Not verified in the article. Randomization and blinded assessment for the proposed experiment are not documented in the supplied studies.

Calculate sample size from pilot variability, prespecify the primary functional outcome, and account for multiple comparisons.

Not verified in the article. Multiple-testing adjustments were applied, but a sample-size calculation from pilot variability and a prespecified primary functional outcome were not reported.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Materials and Methods 2.7, Data Analysis)

Monitor viability and cellular composition, and verify intervention specificity.

Not verified in the article. The combined controls for viability, cellular composition, and specificity of the proposed MMP1 and retinoid interventions are not documented.

In reconstructed models, distinguish old and new fractions using sequential stable-isotope labeling.

Not verified in the article. Sequential stable-isotope labeling of old and new matrix in reconstructed models was not reported.

In native explants, label only new synthesis and account for the unlabeled pool by mass balance.

Not verified in the article. New-synthesis labeling combined with mass-balance accounting of the unlabeled pool in native explants was not reported.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. No supplied study reported the required matrix-labeling analysis accounting for precursor enrichment and label recycling.

Use second-harmonic generation (SHG) to characterize organization while retaining separate measurements of mass, mechanics, and healing.

Not verified in the article. Second-harmonic generation microscopy was described, alongside mechanical and structural measurements. The complete combination with separate matrix mass and healing measurements was not reported.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Experimental procedures, CellTracker, Phalloidin staining, Immunohistology, and second harmonic generation microscopy; Figures 1-4)

Verify MMP1 using a specific activity assay and an independent genetic perturbation.

Different experimental conditions. Collagen cleavage, recombinant MMP-1, an MMP inhibitor, and dominant-negative c-Jun were used. These differ from an MMP1-specific activity assay combined with an independent genetic perturbation of MMP1.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Figures 2-3; Experimental procedures, Cell culture; Transfection and Western blotting)

For restoration of active MMP1, use genetic suppression or prior inhibitor washout.

Not verified in the article. Recombinant active MMP-1 served as a positive control, and secreted enzyme was activated with trypsin. Neither procedure establishes active-MMP1 restoration after genetic suppression or inhibitor washout.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Figure 2; Experimental procedures, Cell culture)

Include catalytically inactive protein as a control in the active-MMP1 restoration experiment.

Not verified in the article. A catalytically inactive MMP1 protein control for the restoration experiment was not reported.

Test whether the effect persists after treatment withdrawal and rule out persistence of the drug.

Different experimental conditions. Latrunculin-A withdrawal and washing tested reversal of cytoskeletal disruption. This differs from persistence of matrix protection after retinoid or MMP1-directed treatment withdrawal, and residual drug was not analytically excluded.

Age-associated reduction of cellular spreading/mechanical force up-regulates matrix metalloproteinase-1 expression and collagen fibril fragmentation via c-Jun/AP-1 in human dermal fibroblasts (Results, Restoration of lost cell shape/mechanical tension; Figure 4)

An increase in collagen alone is insufficient to establish rejuvenation; improved organization and function are also required.

Not verified in the article. No supplied study evaluated the proposed rejuvenation criterion requiring increased collagen together with improved organization and function.

Treat the proposed effect as a research hypothesis rather than an established effect or a recommendation for use; the cited evidence supports starting observations but does not establish the hypothesis.

Not verified in the article. The complete proposed effect remains untested in these articles. Their component findings provide a rationale but do not establish the hypothesis or a recommendation for use.

Findings from cellular and animal models require validation in human skin.

Matches this study. The authors explicitly state that relevance to human skin depends on translation to in vivo tissue. This matches the requirement for validation, while providing no completed human-skin validation of the proposed test.

Cell Senescence-Independent Changes of Human Skin Fibroblasts with Age (Discussion, limitations of in vitro models)

Test the hypothesis in aged three-dimensional skin models.

Different experimental conditions. The study used early postnatal mouse skin, neonatal mouse fibroblasts in collagen hydrogels, and young mouse skin explants rather than aged three-dimensional skin models.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figures 1, 2 and 4; Materials and methods, Isolation and culture of mouse dermal fibroblasts)

Selective restriction of soluble MMP1 is proposed to preserve load-bearing collagen fibers and retain an anti-aging effect while MMP14 remains intact, with less impairment of cell migration than broad suppression of collagenases.

Different experimental conditions. Selective MMP1-blocking antibodies and a broad metalloproteinase inhibitor both suppressed human keratinocyte migration on collagen. This tested a different cellular setting without verified preservation of MMP14, matched bulk degradation, or anti-aging and load-bearing outcomes.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Migration of Primary Keratinocytes on Type I Collagen Is Blocked by Collagenase Antibodies; Figure 7)

The proposed functional separation relies on retaining MMP14-dependent pericellular dermal remodeling and maintenance of cells within collagen while restricting MMP1.

Not verified in the article. MMP14-dependent pericellular remodeling and fibroblast survival were demonstrated, but their retention during selective suppression of soluble MMP1 was not tested.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figures 2, 3 and 5-7)

Collagen preservation is proposed as a distinct, reproducible component of retinoid action.

Not verified in the article. No supplied study experimentally isolated collagen preservation as a reproducible component of retinoid action.

Compare five groups: MMP1 suppression by CRISPR interference, MMP14 suppression by CRISPR interference, dual suppression of MMP1 and MMP14, tretinoin treatment, and a control group.

Different experimental conditions. The experiments compared Mmp14 knockout, acute Cre-mediated deletion, re-expression constructs, and inhibitors. They did not implement the five specified CRISPR-interference, dual-suppression, tretinoin, and control groups.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figure 3 and Figure S3; Materials and methods, Lentiviral transduction)

Compare functional effects at equal reductions in bulk collagen degradation.

Not verified in the article. No supplied study matched the interventions for equal reductions in bulk collagen degradation before comparing functional outcomes.

Assess pericellular cell movement, apoptosis, healing, and resistance to tearing.

Not verified in the article. Skin tensile failure and wound closure were assessed, but pericellular migration and apoptosis were not assessed together with these outcomes in the proposed experiment.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Results, Figure 4; Comparable collagen synthesis in bleomycin-induced fibrosis and in wound repair; Supplementary Figure S7)

Restore MMP14 in the dual-suppression group to test the proposed separation of functions.

Different experimental conditions. Re-expression of MMP14 rescued Mmp14-null fibroblast survival, but the cells were not subjected to dual MMP1/MMP14 suppression.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Structure/function analysis of Mmp14-dependent prosurvival activity; Figure 3 and Figure S3)

Equally strong inhibition of migration by selective MMP1 reduction despite preserved MMP14 would invalidate the proposed functional separation.

Different experimental conditions. MMP1 antibodies and broad inhibition produced near-complete migration blockade in keratinocytes, but preserved MMP14 and equal bulk collagen degradation were not established. This does not execute the proposed falsification test.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Results, Figure 7)

An increase in collagen mass accompanied by fibroblast death is not considered beneficial.

Not verified in the article. The study demonstrates fibroblast death when Mmp14-dependent remodeling is lost and collagen becomes abundant during development. It does not evaluate an intervention-induced collagen gain against the specified benefit criterion.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figures 1 and 4; Discussion)

The functional objective is to preserve aging skin strength, renewal, and recovery after injury; increased collagen alone does not establish rejuvenation unless collagen organization and skin function also improve.

Not verified in the article. MMP14 deletion increased collagen, stiffness, and tensile strength while impairing fibrosis resolution. The study did not establish rejuvenation through preservation of aging-skin strength, renewal, organization, and injury recovery.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin (Results, Figures 2-4; Discussion; Supplementary Figures S6 and S7)

Use paired models from several independent donors, with randomization and blinded assessment.

Not verified in the article. Migration experiments were repeated with cells from different donors and duplicate conditions, but paired aged skin models, randomized allocation, and blinded assessment were not documented.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Colloidal Gold Migration Assay)

Treat the donor as the biological unit and wells as technical replicates.

Not verified in the article. Different donors, duplicate samples, and triplicate wells are described, but the donor is not explicitly established as the biological unit for the required analysis.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Colloidal Gold Migration Assay; Figures 4-7)

Calculate sample size from pilot variability, prespecify the primary functional outcome, and account for multiple comparisons.

Not verified in the article. The analysis included correction for multiple comparisons, but pilot-based sample-size calculation and prespecification of a primary functional outcome were not documented.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Materials and methods, Statistical analysis)

Monitor viability, cellular composition, and intervention specificity.

Different experimental conditions. Apoptosis assays, fibroblast subtype sorting, other protease knockouts, and construct validation addressed survival, cell identity, and specificity for Mmp14 experiments. These controls were not applied to the proposed aged-skin MMP1/tretinoin comparison.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figures 1-3; Figures S3 and S7; Materials and methods)

Distinguish old and new collagen fractions by sequential stable-isotope labeling in reconstructed models.

Not verified in the article. Sequential stable-isotope labeling of old and new collagen fractions in reconstructed skin was not reported.

In native explants, label only newly synthesized collagen and account for the unlabeled pool using mass balance.

Not verified in the article. Labeling newly synthesized collagen in native explants with mass-balance accounting for the unlabeled pool was not reported.

Account for precursor enrichment and label recycling when interpreting isotope labeling.

Not verified in the article. No supplied experiment incorporated the specified accounting for precursor enrichment and recycling of stable-isotope labels.

Use second-harmonic generation to characterize collagen organization while separately measuring collagen mass, mechanical properties, and healing.

Not verified in the article. Second-harmonic imaging, hydroxyproline measurements, and hydrogel microrheology were performed, but the complete combination with skin mechanics and healing under the proposed aged-skin conditions was absent.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Figure S4; Figures 4 and 6; Materials and methods, Dermal collagen content and optical tweezer-based active microrheology)

Verify MMP1 using a specific activity assay and an independent genetic intervention.

Not verified in the article. MMP1-blocking antibody activity was checked against purified collagenase, but an independent genetic intervention targeting MMP1 was absent. The retracted fibroblast-silencing paper cannot supply reliable confirmation.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Colony Dispersion Migration Assay; Results, Figure 7)

For restoration of active MMP1, use genetic suppression or wash out the inhibitor beforehand.

Different experimental conditions. The genetic rescue restored MMP14 in Mmp14-null cells and tested MMP14/MMP1 chimeras; it did not restore active soluble MMP1 after its suppression or inhibitor washout.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figure 3; Materials and methods, Lentiviral transduction)

Include catalytically inactive MMP1 protein as a control for restoration of active MMP1.

Different experimental conditions. The catalytic-dead control was MMP14 E240A, whereas the required control is catalytically inactive MMP1 during restoration of active MMP1.

Mmp14-dependent remodeling of the pericellular–dermal collagen interface governs fibroblast survival (Results, Figure 3 and Figure S3)

Test whether the effect persists after treatment withdrawal and rule out residual drug retention.

Not verified in the article. No supplied study tested persistence of the proposed collagen-preserving effect after treatment withdrawal while excluding residual drug retention.

Treat the proposed effect as a research hypothesis rather than an established effect or a recommendation for use; the supporting observations do not establish the hypothesis.

Not verified in the article. The complete selective-MMP1 anti-aging proposition was not evaluated in the supplied primary studies and therefore retains its stated research-hypothesis status.

Validate conclusions from cellular and animal models in human skin.

Not verified in the article. Human keratinocytes and wounded neonatal human skin grafts were examined, but they did not validate the proposed MMP1/MMP14 functional separation and anti-aging effect in human skin.

The Activity of Collagenase-1 Is Required for Keratinocyte Migration on a Type I Collagen Matrix (Materials and Methods, Cell Culture and In Situ Hybridization; Figure 1)

The hypothesis concerns senescent fibroblasts in the dermal extracellular matrix and proposes that their ferroptotic removal may promote renewed dermal aging through lipid-damaged matrix.

Different experimental conditions. Dermal fibroblasts and reconstructed skin were studied using chemically lipid-modified collagen; senescent-cell removal by ferroptosis was not performed.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.3, 2.6, 2.11; Results 3.3-3.8)

At an equal number of removed damaged fibroblasts, ferroptosis is proposed to leave a more harmful extracellular trace than apoptosis because lipid aldehydes modify collagen, allowing the altered matrix to impair subsequently introduced healthy fibroblasts.

Different experimental conditions. Collagen adduction and subsequent fibroblast dysfunction were demonstrated after direct lipid treatment, without comparing apoptosis and ferroptosis at equal cell removal.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Results 3.1-3.4; Figures 1-4)

The stated scientific rationale connects separately reported NCOA4-dependent ferroptosis of senescent fibroblasts in a diabetic wound and cellular consequences of lipid modification of dermal matrix; their sequential causal connection remains unestablished.

Not verified in the article. Wei and colleagues demonstrated NCOA4-dependent ferroptosis susceptibility in high-glucose-treated mouse fibroblasts. Jelleschitz and colleagues separately demonstrated effects of modified dermal collagen. Their sequential connection was not tested, and selective senescent-cell clearance as the cause of improved wound healing remains uncertain.

Defective NCOA4-dependent ferroptosis in senescent fibroblasts retards diabetic wound healing (Results, Figures 4-6; Discussion)

Comparable fractions of senescent fibroblasts must be removed by apoptosis or ferroptosis in identical three-dimensional matrices.

Not verified in the article. No supplied study compares removal of comparable senescent-fibroblast fractions by apoptosis and ferroptosis in identical three-dimensional matrices.

After cell removal, reagents, cellular debris and soluble secretome must be cleared using equivalent cleaning conditions before identical healthy fibroblasts are seeded as a second wave.

Different experimental conditions. Modified collagen coatings were washed before fibroblast seeding, but there was no preceding cell-removal stage requiring clearance of debris, senolytics and secretome.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.6; Results 3.2-3.4)

The experiment must include a group with extracellular aldehyde trapping during cell death to test whether limiting extracellular aldehydes reduces the adverse effect.

Different experimental conditions. Carnosine was added to HNE-modified type II collagen before osteoarthritic chondrocyte seeding. This differs in cell type, timing and matrix from extracellular aldehyde trapping during senescent-fibroblast death.

Perturbation of adhesion molecule-mediated chondrocyte-matrix interactions by 4-hydroxynonenal binding: implication in osteoarthritis pathogenesis (Results, carnosine intervention; Figure 6)

Because an aldehyde trap may alter cell death itself, comparisons involving aldehyde trapping are interpretable only when the numbers of removed cells are comparable.

Not verified in the article. Comparable numbers of removed senescent cells with and without extracellular aldehyde trapping were not established in the supplied studies.

The type of cell death must be confirmed using independent rescue controls.

Different experimental conditions. Ferrostatin-1 and α-tocopherol suppressed erastin-associated death in mouse fibroblast models. Independent rescue validation of both death modes in the proposed dermal-matrix experiment was not performed.

Lipid peroxidation and the subsequent cell death transmitting from ferroptotic cells to neighboring cells (Results; Figure 1K-M; Supplementary Figure S3E-G)

The experiment must verify the absence of residual senolytic activity after cleaning.

Different experimental conditions. Drug-exposed cell-free dishes controlled for residual erastin after medium replacement. This is a carryover control for medium-transfer and coculture experiments, not validation of cleaned post-senolysis dermal matrix.

Lipid peroxidation and the subsequent cell death transmitting from ferroptotic cells to neighboring cells (Results; Figures 3A-E and 5H-I)

Collagen adducts must be measured to assess collagen modification.

Matches this study. Biochemical assays and mass spectrometry measured collagen modification and identified lipid-derived adducts, satisfying this measurement component in a chemically modified matrix model.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.4-2.5; Results 3.1; Figure 1)

Purified matrix and conditioned medium must be transferred separately to distinguish a persistent matrix-associated trace from a soluble trace.

Different experimental conditions. A transwell experiment tested dependence on direct contact with modified collagen. It did not separately transfer purified post-death matrix and conditioned medium from matched cell-removal groups.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.6; Results 3.4; Figure 4C)

The primary outcome is new collagen formation by second-wave fibroblasts, compared between matrices previously exposed to apoptotic or ferroptotic cell removal and the group with extracellular aldehyde trapping.

Different experimental conditions. Collagen gene expression was assessed in fibroblasts on modified collagen. New collagen formation by second-wave cells was not measured across apoptosis, ferroptosis and extracellular-trapping groups.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.10; Results 3.4; Figure 4)

Newly formed collagen must be distinguished from the original scaffold.

Not verified in the article. The supplied studies do not establish the required measurement separating newly deposited second-wave collagen from the original scaffold.

Persistent cell-cycle arrest in second-wave fibroblasts must be assessed as a secondary outcome.

Different experimental conditions. Reduced proliferation and early senescence-associated expression were observed, but the fibroblast phenotype was described as transient. Persistent arrest of second-wave fibroblasts after senolysis was not established.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Results 3.3-3.4; Discussion 4.2.1; Figures 3-4)

Inflammation must be assessed as a secondary outcome.

Matches this study. Inflammatory gene expression and cytokine responses were measured after exposure to lipid-modified collagen, matching the inflammation-assessment component outside the proposed death-mode comparison.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Results 3.4-3.5; Figures 4-5)

Adducts of 4-hydroxynonenal (4-HNE) must be assessed as a secondary outcome.

Matches this study. HNE adducts were identified by mass spectrometry and immunostaining, including collagen-associated adducts; their formation after ferroptotic senolysis was not tested.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Results 3.1-3.2; Figures 1F and 2A,C)

Matrix mechanical integrity must be assessed as a secondary outcome.

Not verified in the article. Matrix mechanical integrity was not assessed in the required experiment. The dermal collagen study explicitly identifies elasticity and stability as subjects for future investigation.

The predicted result is stronger impairment of new-cell function by ferroptosis-exposed matrix, with reduced harm when extracellular aldehydes are limited.

Not verified in the article. No supplied study reports greater harm from cleaned ferroptosis-exposed matrix than apoptosis-exposed matrix together with rescue by extracellular aldehyde trapping during death.

Equal support of new cells by the matrices after equivalent cleaning, or failure of adduct suppression to rescue cell function, would indicate that matrix-mediated transmission of harm does not explain the difference between removal methods.

Not verified in the article. The specified tests of equivalent matrix support and functional rescue despite adduct suppression were not performed under the proposed comparative conditions.

A pilot experiment must include 6-8 independent donors.

Different experimental conditions. The fibroblast expression experiments used four donors, and skin equivalents used three donor combinations; these are not a pilot with 6-8 independent donors.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.1 and 2.14; Figure 4)

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimum useful effect.

Not verified in the article. No supplied study describes the specified sample-size calculation using variance of second-wave collagen formation and a prespecified minimum useful effect.

The donor must be treated as the biological unit, with chips or wells treated as nested replicates.

Not verified in the article. Multiple donors and replicate cultures are described, but analysis treating donors as biological units and wells as nested replicates is not verified.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.14; Figure 4)

The study must use randomization and blinded analysis.

Not verified in the article. Some supplied studies report animal randomization or blinded histological analysis, but the required combination is not documented for the proposed matrix-transfer experiment.

Statistical analysis must use a paired model accounting for donor, report confidence intervals and correct secondary comparisons.

Different experimental conditions. The study reports ANOVA, unpaired tests and multiple-comparison procedures, rather than the specified paired donor-adjusted model with confidence intervals and correction of secondary comparisons.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Methods 2.14)

Senescence must not be considered established by p16/p21 or senescence-associated β-galactosidase (SA-β-gal) alone.

Matches this study. The study uses multiple senescence-associated measurements, including proliferation, lamin B1, cell-cycle regulators and DNA-damage markers. This matches the multi-marker principle, while persistent second-wave senescence remains unverified.

Modification of the dermal matrix by senescence associated lipids and its functional consequence (Introduction; Results 3.3-3.4 and 3.8; Discussion 4.2.1)

A result of p > 0.05 alone must not be treated as falsification of the hypothesis.

Not verified in the article. The supplied studies do not implement the proposed falsification rule that distinguishes p > 0.05 from evidence against the complete matrix-mediated mechanism.

The proposal is a research hypothesis whose described new experiments have not been conducted and for which no experimental results are claimed.

Not verified in the article. The unperformed status is declared in the proposal and cannot be independently established from these articles; no supplied study reports completion of the specified experiment.

The hypothesis concerns impaired lymphatic drainage in aged skin, with aged mouse skin providing the stated observation of impaired lymphatic function and collagen accumulation near lymphatic channels; this observation alone does not establish mechanical causality.

Matches this study. Aged mouse skin showed impaired lymphatic pumping and perilymphatic collagen accumulation; the authors explicitly describe their study as observational.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Results, Figures 3 and 5G-H; Discussion, limitations)

Aged perilymphatic collagen is proposed to mechanically restrict vessel deformation and fluid entry, leaving drainage poor even after lymphatic endothelial cells are restored and limiting the benefit of restoring signaling through vascular endothelial growth factor receptor 3 (VEGFR3).

Not verified in the article. Reduced VEGFR3 signaling and collagen accumulation were observed, but mechanical restriction of deformation and fluid entry after endothelial restoration was not tested.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Results, Figures 4 and 5G-H; Discussion, limitations)

The decisive experiment must use a lymphatic chip with either a normal or a compacted perivascular collagen sheath.

Different experimental conditions. The study used cells on fibronectin-coated substrates of different stiffness and a fibrin-gel sprouting assay, rather than a lymphatic chip with alternative collagen sheaths.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program (Methods, In vitro matrix stiffness analysis and LEC sprouting assay; Figures 2 and 5)

The normal and compacted sheath conditions must have the same total collagen content.

Not verified in the article. Neither supplied study compares normal and compacted collagen sheaths with equal total collagen content.

The experiment must compare restoration of VEGFR3 signaling alone, local mechanical normalization of the sheath alone, their combination, and a control under the normal and compacted sheath conditions.

Different experimental conditions. The intervention compared Gata2 deletion and control cells with or without VEGF-C; it did not combine VEGFR3 restoration with local sheath normalization under both sheath conditions.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program (Results, GATA2 controls LEC responsiveness to VEGF-C; Figure 5e-h)

Local mechanical normalization of the sheath is predicted to provide an additional drainage benefit beyond that produced by restoring VEGFR3 signaling alone.

Not verified in the article. No supplied experiment measures an additional drainage benefit from sheath normalization beyond VEGFR3 restoration alone.

Hydraulic measurements must be performed separately from measurements of endothelial permeability.

Not verified in the article. Pumping and lectin leakage were assessed separately, but this does not establish separate hydraulic and endothelial-permeability measurements in the proposed chip experiment.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Methods, Lymphatic Function Analysis; Figure 3)

The pressure gradient, osmolarity, and cell number must be matched across the compared conditions.

Not verified in the article. Matching pressure gradient, osmolarity, and cell number across the proposed intervention groups is not documented.

Local modification of the sheath must be checked for preservation of endothelial contacts and absence of an artificial leak.

Not verified in the article. Age-related leakage and junctional changes were examined, but preservation of contacts and exclusion of artificial leakage after sheath modification were not tested.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Figures 3H-I and 6D-F)

The primary outcome must be functional transport of fluid and a macromolecular tracer into the lymphatic channel.

Different experimental conditions. The study measured indocyanine-green pumping and pooling and macromolecular lectin extravasation in mice, rather than primary fluid and tracer transport into an engineered lymphatic channel.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Methods, Lymphatic Function Analysis; Figure 3D-I)

Secondary outcomes must include vessel wall deformation, interstitial pressure, inflammation, and the epidermal barrier.

Not verified in the article. Vessel morphology, pumping, and inflammation were assessed, but the specified secondary-outcome set including wall deformation, interstitial pressure, and epidermal barrier function was not measured.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Figures 2, 3 and 5)

Complete normalization of transport by VEGFR3 restoration regardless of sheath condition would fail to support the proposed mechanical limitation.

Not verified in the article. Neither study tests whether VEGFR3 restoration completely normalizes transport independently of sheath condition.

An effect of sheath modification attributable entirely to barrier rupture would fail to support the proposed mechanical limitation.

Not verified in the article. Neither study tests whether an apparent benefit of sheath modification is explained entirely by barrier rupture.

Improved drainage must not be interpreted as elimination of all causes of aging.

Not verified in the article. The specific interpretive condition separating drainage improvement from elimination of all aging causes is not evaluated in a drainage-restoration experiment.

Sheath geometry must be verified in human tissue before the conclusion is transferred to humans.

Not verified in the article. Human dermal lymphatic endothelial cells were cultured, but perilymphatic sheath geometry was not verified in human tissue.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program (Methods, Cell culture and in vitro gene deletion using 4-OHT)

The reproducibility plan must include a pilot study with 6-8 independent donors.

Not verified in the article. Neither article describes a pilot of the proposed experiment involving 6-8 independent donors.

The main study sample size must be calculated from the variance of the primary outcome and a prespecified minimally useful effect.

Not verified in the article. A main-study sample-size calculation based on primary transport-outcome variance and a prespecified minimally useful effect is not reported.

The donor must be the biological unit, with chips or wells treated as nested replicates.

Not verified in the article. Neither study documents the required donor-level design with chips or wells treated as nested replicates.

The experiment must use randomization and blinded analysis.

Different experimental conditions. The matrix-stiffness study explicitly states that experiments were not randomized and analyses were not blinded; the aging study reports some blinded image assessments but does not establish both requirements.

Matrix stiffness controls lymphatic vessel formation through regulation of a GATA2-dependent transcriptional program (Methods, Statistics)

Statistical analysis must use a paired model accounting for the donor, report confidence intervals, and apply correction for secondary comparisons.

Different experimental conditions. The aging study used unpaired Student’s t-tests or Mann-Whitney tests and reported mean ± standard deviation, rather than the specified paired donor-adjusted analysis with confidence intervals and secondary-comparison correction.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Methods, Statistical Analysis; figure legends)

Neither p16/p21 nor senescence-associated β-galactosidase (SA-β-gal), assessed separately, is sufficient to establish cellular senescence.

Not verified in the article. The study assessed macroH2A1 as a senescence marker, but did not evaluate the specified insufficiency of p16/p21 or SA-β-gal alone.

Structural and Functional Changes in Aged Skin Lymphatic Vessels (Results, Figure 4H-K)

New collagen must be distinguished from the original scaffold.

Not verified in the article. Neither study distinguishes newly produced collagen from a pre-existing collagen scaffold in the proposed chip.

A result of p > 0.05 alone must not be treated as refutation of the hypothesis.

Not verified in the article. The studies specify significance thresholds but do not document the proposed rule that p > 0.05 alone cannot refute this mechanical hypothesis.

The proposed work remains a research hypothesis: the described new experiments have not been performed, and no results are claimed.

Not verified in the article. The unperformed status is stated in the submitted proposal; neither supplied primary article reports results from its proposed experiment.