Skin Pressing: An Easy and Reliable Method to Induce Acute Hair Greying in Mice and Useful for Studying Canities.

Grey hair is a hallmark of aging, and its restoration is a major concern. Using aged mice for studying hair greying has disadvantages, such as individual variability and time requirements. In this study, we developed a simple method to induce acute and less variable hair greying in mice. After induction of the hair cycle anagen in black mice, the dorsal skin was pinched and pressed from both sides using a pair of C-shaped neodymium magnets cushioned with a thin silicone rubber. This pressure was maintained for 8 h. Grey hair was consistently observed on the skin just below the area where the skin press was applied and sporadically inside, but not outside, the area in all treated mice. No obvious differences were observed in hair characteristics (length, thickness, shape, and hair-type ratio) between the induced grey hair and normal black hair, except for a slight delay in hair emergence. The sporadic greying pattern resembled that of age-related hair depigmentation. The grey pattern was stable through three consecutive hair cycles, and melanocyte stem cells were observed in the bulge area of the grey hair, suggesting that the skin press method offers a reliable model for studying the mechanisms and treatment of canities.