Hair growth is maintained by stem cells laying in the hair follicle. Stem cells that are responsible for hair pigmentation are able to move between growth compartments during the lifecycle of hair; however, if they are stuck on the way, which has a more frequent incidence at older age, a grey strand of hair will be grown.
The study, that was led by the researchers of NYU Grossman School of Medicine, and published in the reputable Nature journal, focuses on so called melanocyte stem cells, or McSCs, which are present in the hair follicles, and when exposed to stimuli from the body, they begin to produce the pigment responsible for hair color.
McSCs are quite plastic regarding their state of differentiation. Depending on the stimuli they receive, and their position inside the hair follicle, they act as stem cells to a higher extent, or to a lesser extent, thus their ‘stemness’ is not constant.
Naturally, hair has a life cycle of 4 phases: growth phase, transitional phase, when hair growth slowly terminates, telogen or resting phase, and exogen phase, when hair strands fall out. After the cycle, hair follicles are able to produce new hair strands, and the cycle starts again.
During the investigation, it was observed that after the repeated cycles, more and more McSCs are stuck in the bulge compartment under the sebaceous gland, thus they can’t reach the germ compartment, where McSCs could transform into melanocytes to fulfill their task of pigment production.
The revealed mechanism was seen only for the pigment producing stem cells, while other kinds of stem cells, which are responsible for hair growth, were functioning independently – and this is the reason why grey hair grows.
The principal investigator of the study said that the discovery can lead to the development of a strategy to slow down, or even to reverse hair greying. To reach this goal, the aging of McSCs has to be slowed down, because if the aging is faster, stem cells are more prone to get stuck.
Read the full study here: Dedifferentiation maintains melanocyte stem cells in a dynamic niche
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