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Cellular Senescence: Difference between revisions
→Types and Classifications of Senescent Cells
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* '''Oncogene Activation''': Oncogenes are genes that, when activated or overexpressed, can drive cells into uncontrolled growth and potentially lead to tumor formation. In certain scenarios, the activation or aberrant expression of these genes can be recognized by the cell as a precancerous signal. To counteract the risk of malignancy, the cell initiates a senescent program, effectively halting its own proliferation and thus reducing the risk of tumor development. | * '''Oncogene Activation''': Oncogenes are genes that, when activated or overexpressed, can drive cells into uncontrolled growth and potentially lead to tumor formation. In certain scenarios, the activation or aberrant expression of these genes can be recognized by the cell as a precancerous signal. To counteract the risk of malignancy, the cell initiates a senescent program, effectively halting its own proliferation and thus reducing the risk of tumor development. | ||
* Additionally, other lesser-known factors like epigenetic changes, mitochondrial dysfunction, and chronic inflammation have also been implicated in driving cells toward senescence. As research advances, our understanding of these causative factors and their interplay will pave the way for more effective therapeutic interventions targeting cellular senescence. | * Additionally, other lesser-known factors like epigenetic changes, mitochondrial dysfunction, and chronic inflammation have also been implicated in driving cells toward senescence. As research advances, our understanding of these causative factors and their interplay will pave the way for more effective therapeutic interventions targeting cellular senescence. | ||
== Mechanisms of Senescent Cell Clearance == | |||
Senescent cells are cleared from the body primarily through the immune system, specifically by specialized immune cells that recognize and eliminate these non-dividing, functionally altered cells. Here's a detailed look at the mechanisms: | |||
# '''Macrophages''': One of the primary cells responsible for clearing senescent cells are macrophages. These immune cells "eat" or phagocytose senescent cells, breaking them down and eliminating them from the tissue. | |||
# '''Natural Killer (NK) Cells''': NK cells are another type of immune cell that can recognize and kill senescent cells. They often target cells that exhibit stress signals on their surface without displaying the normal "self" markers. | |||
# '''T Cells''': Some types of T cells, especially CD4+ helper T cells and CD8+ cytotoxic T cells, can recognize and help eliminate senescent cells. | |||
# '''Senescence-Associated Secretory Phenotype (SASP)''': While the SASP is known for its pro-inflammatory properties, certain components of the SASP can attract immune cells to the location of the senescent cells, aiding in their clearance. | |||
# '''Apoptosis''': In some circumstances, senescent cells can undergo programmed cell death, or apoptosis. While this isn't the immune system clearing them, it's a way for the body to rid itself of these cells. | |||
In healthy young organisms, the immune system efficiently clears senescent cells, ensuring they don't accumulate in tissues. However, as organisms age and the immune system's function declines (a phenomenon known as immunosenescence), the removal of senescent cells becomes less efficient. This reduced clearance, combined with an increased rate of cells entering senescence, can result in the accumulation of senescent cells in tissues, contributing to aging and age-related diseases. | |||
== Types and Classifications of Senescent Cells == | == Types and Classifications of Senescent Cells == | ||