Types of cell senescence

1. Quiescence

Quiescence (G₀) is a reversible cell cycle exit state that cells enter in response to growth factor withdrawal or contact inhibition, retaining the capacity to re-enter the cell cycle upon mitogenic stimulation. Senescence, by contrast, is a deeply entrenched, generally irreversible cell cycle arrest accompanied by extensive phenotypic changes including chromatin remodeling, metabolic reprogramming, and the senescence-associated secretory phenotype (SASP). Senescence functions as an evolutionary failsafe to permanently incapacitate cells carrying high oncogenic risk—such as those with activated oncogenes (oncogene-induced senescence, OIS) or critically short telomeres (replicative senescence)—by rendering mitosis physically impossible [1–3].

Fujimaki and Yao (2020) have