concept

Cellular senescence

A state in which a cell permanently stops dividing yet remains alive and metabolically active, triggered by DNA damage, oxidative stress, or critical telomere erosion. The arrested cell switches on cell-cycle inhibitors such as p16 and p21, and protects itself from programmed death through a family of survival proteins. Initially this is an anti-cancer barrier: a cell at risk of turning malignant is better off not dividing. But with age these cells accumulate and secrete a mixture of inflammatory cytokines and matrix-degrading enzymes that damages the healthy tissue around them and pushes neighbouring cells into the same state. What began as a protective mechanism becomes one of the principal drivers of age-related systemic decline.