SenNet proposes the “senotype,” a description of a senescent cell along five coordinates
SenNet proposes the “senotype,” a description of a senescent cell along five coordinates
On July 29, the SenNet consortium published a perspective on “senotypes” in Nature Aging. The authors propose describing a senescent cell not by a single protein marker, but by a set of features that explains what happened to the cell and what it does within the tissue.
A senescent cell stops dividing but remains alive. It changes the substances it secretes and affects the behavior of neighboring cells. In one tissue, this process may contribute to healing. In another, it may sustain chronic inflammation. The senescence marker proteins p16 or p21 therefore provide only part of the answer: the same signal can occur in cells from different tissues, following different types of damage, and at different stages.
In the SenNet perspective, Marissa Schafer and colleagues call this description a “senotype.” A senotype asks five questions about a cell: what type of cell it is and where it is located; what caused it to stop dividing; how long ago this occurred; what changes are visible in its molecules and structure; and what function it performs within the tissue. The authors associate the senotype with a combination of persistent cell cycle arrest, altered secretion, damage to cellular components, and disrupted internal homeostasis.
A single marker does not identify the cell. In a Petri dish, a researcher can induce senescence with a specific treatment and follow the course of the experiment. In human tissue, other information matters more: where the cell is located, which cells surround it, and which process it is associated with. A shared set of coordinates makes it possible to compare these two types of observation and determine where the broad label “senescent” encompasses distinct cellular states.
Senotherapy needs an address, not a general marker. Selecting a target requires researchers to distinguish between cells that show the same signal but have different histories and functions. SenNet is compiling atlases of senescent cells across different tissues and stages of life. The Mayo Clinic describes this work as a series of maps of these cells. The proposed framework gives laboratories a shared method for naming the relevant cell type, confirming its features, and only then searching for an intervention: either a senolytic that removes the cells or a senomorphic that changes their behavior.