Difference between Quiescent cells and Senescent cells

8 Difference between Quiescent cells and Senescent cells 

Quiescent cells and senescent cells are two distinct states of cellular inactivity, each with unique characteristics and implications. Quiescent cells are cells that exist in a reversible state of cell cycle arrest, primarily due to lack of nutrition and growth factors. Senescent cells are cells that exist in an irreversible state of cell cycle arrest due to ageing and serious DNA damages.

Quiescent cells	Senescent cells
Definition: Cells in a reversible state of inactivity, capable of re-entering the cell cycle when stimulated with nutrients or growth factors	Cells that exist in irreversible state of stable cell cycle arrest, cannot re-enter the cell cycle even when stimulated with nutrients.
Stress tolerance: Capable of withstanding cellular stress and surviving harsh conditions	Reduced capability to cope with stress, more susceptible to DNA damage and oxidative stress
Dividing potential: Retain ability to re-enter the cell cycle and proliferate	Lose the ability to divide and replicate
Causes: Lack of nutrients and growth factors leading to temporary halt in cell division	Telomere shortening, severe DNA damage, or oncogene activation due to ageing
Cell Structure: Reduced metabolic activity, smaller cell size, low levels of RNA and protein synthesis	Enlarged and flattened morphology, altered chromatin structure, increased senescence-associated beta-galactosidase activity, heterochromatin foci
Upregulated genes: Id genes, HES -1 in neural stem cells, SOX2 and PAX6, stress response genes	P53, P21, senescence-associated secretory phenotype (SASP)genes like IL-6, IL-8, Oxidative Stress Response Genes
Significance: Important for tissue regeneration and repair	Contribute to aging and age-related diseases

Examples of Quiescent cells:

1. Hematopoietic Stem Cells: These cells reside in the bone marrow and can enter quiescence to maintain a reserve population for blood cell production.

2. Muscle Stem Cells (Satellite Cells): These cells are found in skeletal muscle and can become quiescent until muscle injury occurs, then they can proliferate and differentiate to repair the tissue.

3. Neural Stem Cells: Located in specific regions of the brain, these cells can remain quiescent until needed for neurogenesis or repair.

4. Lymphocytes: Certain immune cells like memory cells can enter a quiescent state after activation, remaining ready to respond to future infections.

Senescent Cells:

1.  Senescent Fibroblasts: These cells can accumulate in tissues due to stress or damage, contributing to aging and fibrosis.

2.  Senescent Endothelial Cells: These cells line blood vessels and can enter senescence in response to oxidative stress, contributing to vascular aging and dysfunction.

3. Senescent Adipocytes: Fat cells can become senescent with age or obesity, contributing to metabolic dysfunction and inflammation.

4.  Senescent Chondrocytes: Found in cartilage, these cells can accumulate senescence markers in osteoarthritis, leading to joint degradation.

Reference:

Terzi MY, Izmirli M, Gogebakan B. The cell fate: senescence or quiescence. Mol Biol Rep. 2016 Nov;43(11):1213-1220. doi: 10.1007/s11033-016-4065-0. Epub 2016