There could be some truth in the anecdotal belief that stress can turn your hair grey. The appearance of grey hairs after periods of stress or skin damage could be the result of depletion of stem cells from the base of the hair follicle, according to a new study in mice.
The study, reported in Nature Medicine , may also point to new methods of treatment for skin pigmentation disorders such as vitiligo or piebaldism.
Hair and skin are both pigmented by melanin, produced by cells called melanocytes,which in turn are produced by melanocyte stem cells that live in a region at the very base of the hair follicle called the bulge.
Dr Mayumo Ito and colleagues from New York Universityfound that when the skin is damaged or irradiated, these melanocyte stem cells help to repair skin damage by leaving the bulge and travelling to the skin to replenish the store of melanocytes in the outer layer of the skin.
However in the process, they leave the bulge without its own supply of melanocyte stem cells.
The discovery that the stem cells migrate without replicating is a surprise, says Associate Professor Rick Sturm, principle research fellow at the Institute of Molecular Biosciences at the University of Queensland.
"Normally stem cells only stay where they're supposed to be, in the bulge region, the cells divide and the daughter cells go into the hair follicle to create the hair pigment," says Sturm, who was not involved in the study.
However in the case of a skin injury or UV exposure, as occurred in this mouse experiment, the stem cells appear to migrate out without replicating. "When that happens, if you lose the stem cells from the bulge region, you lose the capacity to make melanin... so they get this small number of hair follicles around the injury which become white," explains Sturm.
The discovery could lead to treatments for conditions such as vitiligo -- depigmentation of the skin -- and to prevent hyperpigmentation, which is too much pigment in the skin. "If we can know more about how melanocytes migrate from hair follicle area to the epidermis, we may get the ability to promote this process for the treatment of hypopigmentation disorders," says Ito.
"Our results suggest that melanocyte migration from the hair follicle to the epidermis may partly contribute to skin pigmentation, thus inhibition of this migration process may be a novel approach to prevent UV induced hyperpigmentation, or post-inflammatory hyperpigmentation commonly seen after surgery."
Via Dr. Stefan Gruenwald