A recent paper indicated that with increasing age, some stem cells are unable to mature and retain hair color because they become caught in the growth stages of hair follicles.
Gray Hair
The published study focused on studying the growth of melanocyte stem cells in the skin tissue of the mice. Melanocyte stem cells (McSCs) are found in humans too. Researchers from New York University published their findings in the journal ‘Nature.’
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What are melanocyte stem cells?
McScs are constantly growing groups of cells within hair follicles that develop into fully developed cells that generate protein pigments. The color of the hair is determined by the signal reception by these cells to develop into mature cells that produce protein pigments responsible for the color of the hair.
How do they mature?
Melanocyte stem cells oscillate along the maturity axis when they travel between compartments of the growing hair follicle, where they get exposed to varying quantities of maturation-influencing protein signals. Depending on where they are, they switch between their primitive stem cell and transit-amplifying states.
How did the scientists study the cells?
The researchers employed new 3D-intravital-imaging and scRNA-seq methods to follow these stem cells as they developed, matured, and moved within each hair follicle in near real-time.
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What did this study reveal?
For this study, the scientists aged mice’s hair by plucking and regrowing them. The current research in mice with hair that has physically aged found that the number of hair follicles with McSCs trapped in the follicle bulge compartment rose from 15% before plucking to almost 50% after physically aging. These McSCs could not regenerate or mature into melanocytes that could produce hair pigment. This lack of maturation primarily happened due to a lack of WNT signaling. Whereas, throughout the two-year research period, additional McSCs that continued to migrate between the follicle bulge and hair germ retained their capacity to regenerate, develop into melanocytes, and create pigment.
Researchers at NYU discovered that the other self-regenerating stem cells lack this McSC adaptability, such as those found in the hair follicle. According to them, this lack of adaptability explains why hair may continue to grow even in the presence of pigmentation failure.
Learning through previous research
Previously, the same researchers at this university demonstrated that WNT signaling played an essential role in encouraging McSCs to develop and create the pigment. They also showed that McSCs in the hair follicle bulge received exposure to WNT signaling many billions of times less than in the hair germ compartment.
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The next step for the team
According to one of the researchers, the team intends to look at ways either restore McSC motility or physically transport them back to their germ compartment, where they can manufacture pigment.
What did one of the researchers say about these results?
A Professor of Dermatology and Cell Biology at NYU Langone Health, Mayumi Ito, Ph.D., and one of the senior researchers in this study, believes that graying and hair color loss may be caused by the loss of chameleon-like activity in melanocyte stem cells. According to Ito, these findings imply that motility and reversible maturation of melanocyte stem cells are critical for maintaining healthy and colorful hair.
How can these findings help scientists in the future?
This study points towards a possible explanation for the role of McSCs in producing hair color.
Further studies in humans replicating similar results will enhance understanding of these pathways and their signaling mechanisms. Those findings will provide evidence to develop methods to revert hair graying and impair the growth of tumors like melanoma.
Further information about funding sources and the team members involved in this study is available on the provided link.
References
Dedifferentiation maintains melanocyte stem cells in a dynamic niche
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