Cells age via far more routes than previously known

A comprehensive review catalogued all known triggers of cellular senescence, the process by which a cell permanently exits the cell cycle. The study covers not only classic triggers such as DNA damage and telomere shortening, but also lesser-known routes including cell-cell fusion, signals from already-senescent cells that push neighbours into the same state, and developmental cues.

Why this matters

Senescent cells secrete a cocktail of pro-inflammatory molecules known as the SASP (senescence-associated secretory phenotype). This mixture damages surrounding tissue and accelerates ageing processes elsewhere in the body. But which specific SASP composition a cell produces turns out to depend heavily on how it became senescent. A cell driven into senescence by DNA damage secretes different molecules than one triggered by oncogene activation (the accidental switching-on of growth-promoting genes).

This has direct consequences for therapeutic research. Drugs that clear senescent cells or suppress their secretion are under development for a wide range of diseases, from arthritis to Alzheimer’s, heart disease to cancer. If the senescent cells in each of those conditions carry a different profile, broadly targeted therapies may be less effective than commonly assumed.

No universal molecular marker

That senescent cells lack a uniform molecular profile has been known for some time, but this review makes the scale of that variation concrete. No single marker reliably identifies all senescent cells across all tissues. Researchers must combine multiple markers, calibrated to the tissue type and the trigger that caused senescence in the first place.

For those following ageing science, this review offers a more nuanced framework: senescence is less an on/off switch than a spectrum of states.

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