Senescent cells, which have entered a state of permanent cell cycle arrest due to stressors such as DNA damage and telomere shortening, include various types of somatic cells, certain stem cells, immune cells, and even some cancer cells, and they secrete pro-inflammatory cytokines and growth factors that contribute to the senescence-associated secretory phenotype (SASP), impacting the tissue environment and playing a significant role in aging and age-related diseases.
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:
1. **Somatic cells**: Most normal and differentiated cells can undergo senescence in response to stress, including human fibroblasts and epithelial cells.
2. **Stem Cells**: Certain types of stem cells can also enter senescence, impacting tissue regeneration and repair.
3. **Immune cells**: T cells and other immune cells can become senescent, especially as an organism ages or in chronic inflammatory conditions.
4. **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.
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