A senescent cell is one that has entered a permanent state of cell cycle arrest in response to damage (telomere shortening, DNA damage, oncogene activation, or oxidative stress). Unlike apoptotic cells that die cleanly, senescent cells persist and actively harm neighboring tissue by secreting the Senescence-Associated Secretory Phenotype (SASP) — a complex mixture of inflammatory cytokines, proteases, and growth factors.

No. Senescent cells serve beneficial purposes in wound healing, embryonic development, and cancer suppression. The problem is their accumulation with aging — too many senescent cells overwhelm beneficial functions and drive pathology through chronic SASP.

Can senescent cells become normal again (reverse senescence)?

In most cases, replicative and stress-induced senescence is irreversible. Some forms (particularly OIS) can be reversed under specific conditions. Senolytics eliminate rather than reverse senescent cells.

Do cancer treatments cause senescent cells?