English: Figure 1. - The hallmarks, causes and effects of cellular senescence. (a) The key features of a senescent cell, which include an enlarged and irregular/flattened shape, DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS) and foci, altered gene expression and cell cycle arrest, mitochondrial dysfunction and release of reactive oxygen species (ROS), protein modifications, lipofuscin granules, expression of SA-β-galactosidase and release of SASP factors. (b) Cellular senescence can occur in response to cellular or DNA damage, oncogene, mitogen and cytokine signalling, telomere attrition/shortening, ionizing radiation and anti-cancer drugs. (c) Cellular senescence plays a dual role during development and throughout tissue repair and regeneration, where it can promote the clearance of cell debris, reduces fibrosis, elicits epigenetic alterations and acts as a potent barrier against tumorigenesis, while also leading to senescence spread, DNA damage, further tissue injury, and ultimately leading to age-associated tissue deterioration and pathologies. Created with Biorender.com.