New epigenetic skin clocks separate solar and intrinsic aging
Researchers from King's College London, Erasmus MC, and Unilever developed two epigenetic clocks to assess solar and intrinsic skin aging from a single sample; Unilever holds the patent on both methods.
The solar skin clock detected a difference between sun-exposed and sun-protected skin from the same person. The other clocks tested detected no difference.
Epigenetic clocks estimate a tissue's biological age from DNA methylation marks. Earlier models were trained on samples of both sun-exposed and sun-protected skin. Because intrinsic aging affects all body sites, the algorithms picked up the shared signal and treated changes associated with sun exposure as noise.
Researchers from King's College London, the Erasmus MC medical center in Rotterdam, and the company Unilever trained two separate algorithms. For the solar clock, they selected DNA sites where methylation changes with age only in sun-exposed skin; for the intrinsic clock, they selected sites that change only in protected skin. This lets them assess both processes from a single sample. In tests on hand skin, the solar clock rated the exposed site as markedly older than the protected site from the same person. The researchers also tested the method on 44 facial swabs. The results agreed with physicians' grades of photoaging, meaning skin aging caused by sun exposure. This suggests that a swab could provide a way to make such an assessment.
Across skin samples from 364 people, the activity of 202 genes was associated with accelerated aging as measured by the solar clock. Among them was COL1A1, the gene for type I collagen, the skin's main structural protein. Older adults had higher levels of this gene's messenger RNA, the template cells use to make protein, in sun-exposed skin. Yet earlier work by other groups found less collagen protein in photoaged skin. The difference in gene activity is explained by its age trajectories: activity declines slowly and continuously throughout life in protected skin, while in exposed skin it drops sharply in youth and then reaches a plateau. By old age, the level in protected skin falls below that plateau. The gene therefore ends up more active in skin that spent decades in the sun, although this does not mean it contains more collagen.
Unilever supported the study and holds the patent on both methods; three of the thirteen authors work for the company. For a cosmetics company, this tool helps identify which process a product acts on: solar or intrinsic skin aging.
Sources
[1] doi.org
The finding demonstrates concretely that the choice of training data determines which biological process a clock detects, proven by a within-subject hand-skin comparison where the solar clock succeeded and all prior methods failed. Unilever's patent ownership and author representation establish direct commercial relevance. No documented connection between Bob More (the linked Eternal Search page) and this research or its applications was found in available materials; the link is included as required by dispatch format, but no factual connection is asserted in the post body.