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Wang, X., Ramos, R., Phan, A.Q. et al. Signalling by senescent melanocytes hyperactivates hair growth. Nature 618, 808–817 (2023). https://doi.org/10.1038/s41586-023-06172-8
Stem cells are cells that eventually can develop into blood, muscle, brain, and bone cells. Niche signals are signals that regulate stem cells and tell them whether to stay in their dormant phase—meaning remaining as unspecialized stem cells—or transform into a specific type of cell for replacing (“regeneration”) old cells that have died or been injured. When these niche signals are unbalanced, it disrupts this transformation of stem cells into specialized cells.
Research has found that senescent melanocytes incite stem cells to leave their dormant phase and transform into a specialized cell. Breaking this down, “senescent” means the process of growing old, indicating that a cell ages and stops dividing into new cells, yet is not dead. “Melanocytes,” on the other hand, are cells found in the eyes and in the skin that create melanin, which is what leads to pigmentation in the body. Together, senescent melanocytes are melanocytes which have aged and are no longer undergoing cellular division.
The way that this process works is actually contrary to the previously accepted notions about senescent melanocytes. Before, the accumulation of senescent cells was considered to prevent the regeneration of cells because it causes stem cells to become senescent, ultimately preventing them from dividing and becoming specialized cells. However, this study demonstrates that senescent cells are able to interact with adjacent senescent cells, a method that incites them into regeneration.
Scientists discovered all this when the experiment was done on mice and they noticed that the subject mice had hyperactive amounts of hair growth. Essentially, when senescent cells are activating each other to become specialized cells like hair cells, there is an increase in hair growth because of an increase in hair cells and amount of division of the hair cells. Senescent melanocytes create multiple signaling molecules, with the main one being osteopontin, a protein found in the human bones. In research trials done with mice, injection with osteopontin led to rapid hair growth, while its removal hindered excessive hair growth. In humans, osteopontin is generally overexpressed, leading to the growth of even more hair cells. Thus, it is important that it be regulated.
Right now, scientists are diving deeper into the topic of senescent melanocytes by investigating its potential for regenerative diseases, which necessitates the regeneration of old cells that died or were injured from illness. Some examples of these kinds of diseases being researched right now are Alzheimer’s, diabetes, vision disorders, cancer, and more. In each of these diseases, it is crucial that new cells are produced to replace the cells that are dying and through senescent melanocytes, it is possible that regeneration can happen at greater rates. However, more research still needs to be done regarding how to effectively implement this and how effective exactly treatment would be.
Works Cited:
Eckes, Beate, and Sabine A Emming. “Tissue Fibrosis: A Pathomechanistically Unresolved Challenge and Scary Clinical Problem.” Wiley Online Library, onlinelibrary.wiley.com/doi/10.1111/exd.13165. Accessed 25 June 2023.
“FDA Warns about Stem Cell Therapies.” U.S. Food and Drug Administration, 2019, www.fda.gov/consumers/consumer-updates/fda-warns-about-stem-cell-therapies#:~:text=Sometimes%20called%20the%20body%27s%20“master,all%20of%20the%20body%27s%20organs.
“NCI Dictionary of Cancer Terms.” National Cancer Institute, www.cancer.gov/publications/dictionaries/cancer-terms/def/melanocyte#:~:text=(meh%2DLAN%2Doh%2D,contains%20the%20pigment%20called%20melanin. Accessed 25 June 2023.
“NCI Dictionary of Cancer Terms.” National Cancer Institute, www.cancer.gov/publications/dictionaries/cancer-terms/def/senescence#:~:text=(seh%2DNEH%2Dsents),in%20tissues%20throughout%20the%20body. Accessed 25 June 2023.
“Osteopontin.” Osteopontin - an Overview | ScienceDirect Topics, 2008, www.sciencedirect.com/topics/medicine-and-dentistry/osteopontin#:~:text=Osteopontin%20(OPN)%20is%20one%20of,a%20humoral%20factor%2C%20or%20cytokine.
“What Is Regenerative Medicine?: Goals and Applications: ISCRM.” Institute for Stem Cell & Regenerative Medicine, 14 Feb. 2022, iscrm.uw.edu/what-is-regenerative-medicine/.
“What Is Regenerative Medicine?” Regenerative Medicine at the McGowan Institute, 27 May 2022, mirm-pitt.net/about-us/what-is-regenerative-medicine/#:~:text=Regenerative%20medicine%20seeks%20to%20replace,primarily%20on%20treating%20the%20symptoms.
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