Cellular Senescence

Cells can enter senescence in response to telomere changes, DNA damage, oncogenic signals, stress, and other triggers. The response can help limit the replication of a damaged cell and can participate in tissue remodelling. Senescence is therefore not simply a harmful switch; its significance depends on timing, cell type, tissue, and whether senescent cells persist.

Some senescent cells release a mixture of signalling molecules known collectively as a senescence-associated secretory phenotype. The composition varies and can influence neighbouring cells and immune activity. There is no single universal marker that identifies every senescent cell, so laboratory research often combines several features rather than relying on one signal.

Cellular senescence is included in the hallmarks-of-aging framework and is studied alongside autophagy, mitochondrial function, and genomic stability. A blood biomarker or biological-age estimate does not directly count all senescent cells in the body. Clinical claims about changing senescence require evaluation at the level of a defined intervention and outcome.

Senescence also differs from quiescence, a generally reversible pause in cell division, and from apoptosis, a regulated process of cell death. These states can share some markers while having different consequences. Precise experiments use combinations of behaviour, molecular signals, and tissue context to distinguish them rather than one universal label.