Cellular senescence

The Hayflick limit deliberates that the average cell will divide around 50 times before reaching a stage known as senescence. As the cell divides, the telomeres on the end of a linear chromosome get shorter. The telomeres will eventually no longer be present on the chromosome. This end stage is the concept that links the deterioration of telomeres to aging.
Top: Primary mouse embryonic fibroblast cells (MEFs) before senescence. Spindle-shaped.
Bottom: MEFs became senescent after passages. Cells grow larger, flatten shape and expressed senescence-associated β-galactosidase (SABG, blue areas), a marker of cellular senescence.

Cellular senescence is a phenomenon characterized by the cessation of cell division.[1][2][3] In their experiments during the early 1960s, Leonard Hayflick and Paul Moorhead found that normal human fetal fibroblasts in culture reach a maximum of approximately 50 cell population doublings before becoming senescent.[4][5][6] This process is known as "replicative senescence", or the Hayflick limit. Hayflick's discovery of mortal cells paved the path for the discovery and understanding of cellular aging molecular pathways.[7] Cellular senescence can be initiated by a wide variety of stress inducing factors. These stress factors include both environmental and internal damaging events, abnormal cellular growth, oxidative stress, autophagy factors, among many other things.[8]

The physiological importance for cell senescence has been attributed to prevention of carcinogenesis, and more recently, aging, development, and tissue repair.[9] Senescent cells contribute to the aging phenotype, including frailty syndrome, sarcopenia, and aging-associated diseases.[10] Senescent astrocytes and microglia contribute to neurodegeneration.[11][12]

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  7. ^ Shay JW, Wright WE (October 2000). "Hayflick, his limit, and cellular ageing". Nature Reviews. Molecular Cell Biology. 1 (1): 72–76. doi:10.1038/35036093. PMID 11413492. S2CID 6821048.
  8. ^ Kuilman T, Michaloglou C, Mooi WJ, Peeper DS (November 2010). "The essence of senescence". Genes & Development. 24 (22): 2463–2479. doi:10.1101/gad.1971610. PMC 2975923. PMID 21078816.
  9. ^ van Deursen JM (May 2014). "The role of senescent cells in ageing". Nature. 509 (7501): 439–446. Bibcode:2014Natur.509..439V. doi:10.1038/nature13193. PMC 4214092. PMID 24848057.
  10. ^ Cite error: The named reference pmid32752135 was invoked but never defined (see the help page).
  11. ^ Rivera-Torres J, San José E (2019). "Src Tyrosine Kinase Inhibitors: New Perspectives on Their Immune, Antiviral, and Senotherapeutic Potential". Frontiers in Pharmacology. 10: 1011. doi:10.3389/fphar.2019.01011. PMC 6759511. PMID 31619990.
  12. ^ Shafqat, Areez; Khan, Saifullah; Omer, Mohamed H.; Niaz, Mahnoor; Albalkhi, Ibrahem; AlKattan, Khaled; Yaqinuddin, Ahmed; Tchkonia, Tamara; Kirkland, James L.; Hashmi, Shahrukh K. (2023). "Cellular senescence in brain aging and cognitive decline". Frontiers in Aging Neuroscience. 15. doi:10.3389/fnagi.2023.1281581. ISSN 1663-4365. PMC 10702235. PMID 38076538.