Cellular Senescence of “Undead” Cells

This student blog post is written by Aaron M and is about zombie cells. Have you ever heard of these so-called zombie cells that are not functional cells but not dead cells? No? Find out all about them below! Take it away, Aaron!

Throughout this class we have obviously talked a lot about the function and structure of eukaryotic cells, but what I found the most interesting is when things go wrong, and how the human body fixes it. In particular, I am interested in what happens to ensure damaged cells do not have harmful effects on the organism, such as cancers. In this course we talked extensively about programmed cell death, aka cellular apoptosis, but this is not the only way the body protects itself against damaged cells.

When cells are damaged there are two measures of protection the body can take, either cellular apoptosis or cellular senescence. Cellular senescence, the transformation from a damaged cell to a senescent cell or more commonly known as a “zombie cell,” is the shut down of cellular processes rather than complete cell death. (Nelson and Faquin, 2023) Cellular senescence is characterised by inhibition of cell division in selected damaged cells to prevent cells from becoming cancerous or continuing to spread when cancerous. (Nelson and Faquin, 2023) This process was first discovered by two scientists, Leonard Hayflick and Paul Moorhead in 1961, and was originally though to be positive function of the body. (Wong, 2024) Initially zombie cells were only shown to turn off the spread of damaged cell, but later it was found that these cells send off inflammatory signals, which has dangerous effects to the body when in large amounts. (Caldwell, n.d.)

Figure: Image showing the difference between a regularly functioning Eukaryotic cell and a forming Senescent cell, showing how damage can create a cell that secretes harmful signals. Image by the National Institute on Aging (n.d.).

The toxic signals released from zombie cells are known to increase fragility, decrease cognitive function and weaken the immune system. (Wong, 2024) Damage from senescent cells comes with increased age, as children are often protected from zombie cell accumulation. (Jacobbi and Satake, 2024) There are many studies that have found the accumulation of senescent cells in the system has a hand in cause a multitude of diseases, such as Alzheimer’s, type two diabetes, osteoporosis, etc. (Wong, 2024)

There have been many drug studies trying to find a treatment for senescent cell build up, this type of experiment drugs is called senolytics. (Scudellari, 2017) Many of these studies have been proved successful, unfortunately only on mice, there has yet to be a successful senolytic for humans. (Scudellari, 2017) Unfortunately for us humans as well, many scientists have hypothesized that even if we were able to have senolytic drugs work for us, they would have to be annual treatments to keep up with the aging process. (Scudellari, 2017) There is also a bed side to these drugs, as zombie cells can also be helpful to the body by blocking cancerous cells from reproducing, in fact some cancer treatment specifically target damaged cells and send them int senescence. (Nelson and Faquin, 2023)

In conclusion, these “undead” cells are a strange phenomenon in eukaryotic cells that can be both positive and negative to the organism. I would love to continue to see research on this topic come out, hopefully yielding a more positive outcome for the future of senolytics.

Work Cited:

Caldwell, A. (n.d.). “What Are Zombie Cells?” Mayo Clinic, Mayo Foundation for Medical Education and Research. Available: https://mayomagazine.mayoclinic.org/2026/02/zombie-cells/

Huang, W., Hickson, L.J., Eirin, A., Kirkland, J.L., & Lerman, L.O. (2022). Cellular senescence: The good, the bad and the unknown. Nature Reviews Nephrology, 18(10): 611–627. https://doi.org/10.1038/s41581-022-00601-z

Jacobbi, V., Satake, A.L. (2024). “Health and Zombie Cells in Aging — Mayo Clinic News Network.” Mayo Clinic, Mayo Foundation for Medical Education and Research. Available: https://newsnetwork.mayoclinic.org/discussion/health-and-zombie-cells-in-aging/

NIA (2021). “Does Cellular Senescence Hold Secrets for Healthier Aging?” National Institute on Aging. Available: www.nia.nih.gov/news/does-cellular-senescence-hold-secrets-healthier-aging.

Nelson, B., & Faquin, W. (2023). Understanding the ‘zombie cells’ that won’t die. Cancer Cytopathology, 131(10): 601–602. https://doi.org/10.1002/cncy.22765.

Scudellari, M. (2017) To Stay Young, Kill Zombie Cells. Nature, 550: 448–450. https://www.nature.com/articles/550448a

Wong, C. (2024). How to Kill the ‘Zombie’ Cells That Make You Age. Nature News. Available: https://www-nature-com.library.smu.ca/articles/d41586-024-01370-4