Definition
Programmed cell death: a regulated process by which cells dismantle themselves without provoking inflammation.
Apoptosis is a controlled form of cell death in which the cell shrinks, condenses its chromatin, fragments its DNA and breaks into membrane-bound apoptotic bodies that neighbouring cells engulf, avoiding the inflammation caused by necrosis. Two main pathways converge on executioner caspases: the extrinsic pathway, triggered by death receptors such as Fas, and the intrinsic pathway, controlled by BCL-2 family proteins at the mitochondria, which release cytochrome c. The tumour suppressor p53 can promote apoptosis after DNA damage. Researchers measure apoptosis with annexin V staining, caspase activity assays and TUNEL labelling. Senolytic approaches, including FOXO4-DRI, aim to restore apoptosis selectively in senescent cells.