Senescent refers to a state in which cells lose the ability to proliferate or divide, typically after a certain number of divisions or in response to stress factors. This process is known as cellular senescence and is characterized by irreversible growth arrest, changes in cell morphology, and the secretion of pro-inflammatory cytokines, growth factors, and proteases, collectively known as the senescence-associated secretory phenotype (SASP).
Cells that can undergo senescence include:
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Somatic cells: Most differentiated somatic cells can enter senescence, such as fibroblasts, epidermal cells, and endothelial cells, often due to factors like telomere shortening or oxidative stress.
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Stem cells: Even some stem cells can undergo senescence, which can impact tissue regeneration and repair.
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Immune cells: Certain immune cells, including T cells and macrophages, can also become senescent, particularly in the context of chronic inflammation or aging.
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Cancer cells: While cancer cells often evade senescence to continue proliferating, certain treatments (like chemotherapy and radiation) can induce senescence in these cells.
Overall, cellular senescence plays a role in both aging and various diseases, including cancer, by contributing to tissue homeostasis and the aging process.