Senescent cells are those that have entered a state of permanent cell cycle arrest. This means that, despite being alive and metabolically active, they can no longer divide and reproduce. Cellular senescence is a natural response to various forms of stress, such as DNA damage, oxidative stress, and telomere shortening, and it plays a crucial role in aging, tissue repair, and the prevention of tumorigenesis.
Cells that commonly undergo senescence include:
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Somatic cells: Most normal and differentiated cells can undergo senescence in response to stress, including human fibroblasts and epithelial cells.
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Stem Cells: Certain types of stem cells can also enter senescence, impacting tissue regeneration and repair.
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Immune cells: T cells and other immune cells can become senescent, especially as an organism ages or in chronic inflammatory conditions.
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Cancer cells: While often seen as proliferative, some cancer cells can enter a senescent state in response to therapies or genetic alterations.
Senescent cells can secrete various pro-inflammatory cytokines, growth factors, and proteases, contributing to what is known as the senescence-associated secretory phenotype (SASP). This can affect the surrounding tissue environment and has implications for various age-related diseases.