Cellular aging

The progressive loss of organ function over time is commonly called aging. Aging is a natural process directly related to the increased risk of pathologies development such as cancer, diabetes, cardiovascular diseases, and neurodegenerative diseases.

But why do we age?

Cells (the smallest unit of an organism) experience aging linked to the number of divisions they have undergone which leads to a progressive decline in tissue function. Many genetic and environmental factors are implied in this decline of function, for instance, short telomeres (nucleotides that protect chromosomal DNA) cause cell senescence (loss of cells power to divide and grow)- limit of Hayflick.

In addition, molecular compounds such as DNA, RNA, proteins, lipids, and organelles are susceptible to damage that will trigger DNA repair machinery, apoptosis ( programmed cell death), or cell senescence.

There are many sources of the damages such as hypoxia (oxygen deficiency) and ischemia (reduced blood supply), toxins, infectious agents, immunologic reactions (like autoimmune reactions), genetic abnormalities, nutritional imbalance (protein-calorie insufficiency), physical agents (trauma), oxidative stress that refers to cellular abnormalities that are induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS) and inflammation.

Epidemiologic studies showed that physical activity and calorie restriction slow aging, on the other hand, stresses accelerate the aging process.

It's important to refer that the precise mechanisms behind aging are not completely defined.

References

• Mohamad Kamal, N. S., Safuan, S., Shamsuddin, S., & Foroozandeh, P. (2020). Aging of the cells: Insight into cellular senescence and detection Methods. European Journal of cell biology, 99(6), 151108. https://doi.org/10.1016/j.ejcb.2020.151108

• Liu, J., Wang, L., Wang, Z., & Liu, J.-P. (2019). Roles of Telomere Biology in Cell Senescence, Replicative and Chronological Ageing. Cells, 8(1), 54. doi:10.3390/cells8010054

• DiLoreto, R., & Murphy, C. T. (2015). The cell biology of aging. Molecular biology of the cell, 26(25), 4524–4531. https://doi.org/10.1091/mbc.E14-06-1084

• Kumar, V., Abbas, A. K., & Aster, J. C. (2015). Robbins and Cotran pathologic basis of disease (Ninth edition.). Philadelphia, PA: Elsevier/Saunders.

• https://www.cellsignal.com/science-resources/overview-of-cellular-senescence

• https://www.quora.com/How-does-the-Hayflick-limit-link-to-cancer-and-do-different-cells-have-different-limits