New research shows that stem cells, which can move between hair follicle compartments of growth, end up getting stuck as one ages. This, in turn, makes them lose their ability to mature and maintain their hair color.
Hair Maturity and Color
According to Science Daily, the study focused on melanocyte stem cells (McSCs), which can be found in both mice and humans. The color of hair is controlled by multiplying but non-functional McSCs pools inside hair follicles that obtain signals to turn into mature cells. These mature cells make the pigments of protein that are responsible for hair color.
Findings reveal that McSCs were quite plastic, which meant that they moved back and forth in the maturity spectrum during typical hair growth. As they move, they end up transiting between compartments of hair follicles that are growing. Neuroscience News adds that it is within these hair follicle compartments that the MsSCs get exposed to varying levels of protein signals that influence maturity.
More specifically, the scientists observed that McSCs transform between the transit-amplifying stage, which is their next maturation stage, and their most primitive state.
Stem Cells Get Stuck With Age, Lead to Gray Hair
They further discovered that a growing number of McSCs end up getting stuck inside the compartment known as the hair follicle bulge due to aging, shedding, and regrowth of hair. They stay in this compartment and do not mature and reach the transit-amplifying stage. They also do not reach the germ compartment, where they were originally located and where they would have been prodded by WNT proteins to regenerate cells for pigmentation.
The study was led by researchers from the NYU Grossman School of Medicine and was published in Nature. Qi Sun, Ph.D., a postdoctoral fellow from NYU Langone Health, says that their study supplements current understanding of the role McSCs play with regards to hair color.
Such findings show the possibility that such fixed-position McSCs could also be found in humans. If this is so, it could pave the way for preventing or reversing gray hair. More specifically, these stuck stem cells could be assisted so that they might move again across compartments.
While McSCs have plasticity, this is not the case for other stem cells that self-regenerate. This could be an explanation as to why hair growth continues despite pigmentation failures.
In their experiments among mice with physically aged hair due to forced regrowth or plucking, the quantity of hair follicles with McSCs inside the bulge went up by 15%. This was in comparison to the state before the hair was plucked to almost half after aging was forced. Such cells did not have the capacity to regenerate. They could also not mature into melanocytes that produced pigments.
While prior research showed that WNT signaling was necessary for McSCs to become mature and pigment-producing, the stuck stem cells had halted regeneration due to their lack of WNT signaling exposure. This also ceased their capacity to produce pigment in newer follicles. In contrast, the moving McSCs retained their regenerative and pigment-producing capacities.
Mayumi Ito, Ph.D., the study's senior investigator and a professor from the Department of Cell Biology and the Ronald O. Perelman Department of Dermatology at NYU Langone Health, says that such findings suggest that the reversible differentiation and motility of the McSCs are key to maintaining hair color and health.
The team plans to look into how the motility of McSCs could be restored or how they could be physically transferred to the germ compartment. It is within such a compartment that the cells can become pigment-producing.
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