- Hair follicles contain several different types of cells, including melanocyte stem cells that generate cells that produce the pigment melanin responsible for hair color.
- A new study in mice shows that these melanocyte stem cells migrate between two sites in the hair follicle during each cycle of hair growth and shedding— from a site where they produce the pigment for hair color to another where they produce stem cells.
- The study found that aging results in a greater portion of these melanocyte stem cells getting stuck at the site where they produce stem cells, which leaves a smaller portion of stem cells to generate melanin-producing cells, resulting in the graying of hair.
- These results provide insight into the mechanisms underlying the graying of hair and could help devise treatments for the treatment of hair graying.
Hair follicles, the structures that produce hair, undergo several cycles of growth over an individual’s lifetime. The increase in the number of follicle growth cycles with aging is associated with deficits in
Melanocyte stem cells are found in two distinct locations at the base of each hair follicle. In one of the locations—called the bulge— these McSCs undergo self-renewal to maintain a population of immature stem cells. In the other location—called the hair germ area—McSCs can differentiate to form melanocytes that produce melanin pigment for hair.
In other words, during each growth cycle, the McSCs can differentiate into a pigment-producing partially differentiated state and then revert back to an undifferentiated state.
The study also showed that the migration of the cells between these regions is disrupted with repeated hair follicle growth cycles. This results in fewer stem cells that can develop into pigment-producing melanocytes, thus leading to hair…
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