If only our stem cells didn’t get stuck in place after a while, maybe we wouldn’t have gray hair. Thanks to a new study published in the journal Nature and led by researchers from New York University’s Grossman School of Medicine, the team has revealed how stuck melanocyte stem cells (McSCs) can’t make the protein needed to pigment hair, potentially explaining gray hair.
Using mice as research subjects, the team found that McSCs travel between compartments of developing hair follicles in a healthy situation. These differing compartments allow the McSCs to mature and pick up the protein that regenerates into pigment cells, continually coloring hair as it grows. These McSCs shift back and forth between maturity levels over time as they move between the compartments, a unique aspect of McSCs.
However, in some cases, the McSCs get stuck in the hair follicle bulge compartment and become unable to move back to the germ compartment, where WNT proteins encourage the cells to regenerate into pigment cells. Getting stuck means no pigment cells, which leads to gray hair.
“It is the loss of chameleon-like function in melanocyte stem cells that may be responsible for graying and loss of hair color,” said Mayumi Ito, study senior investigator and professor in the Ronald O. Perelman Department of Dermatology and Department of Cell Biology at NYU Langone Health, in a news release. “These findings suggest that melanocyte stem cell motility and reversible differentiation are key to keeping hair healthy and colored.”
“Our study adds to our basic understanding of how melanocyte stem cells work to color hair,” added Qi Sun, a postdoctoral fellow at NYU Langone Health. “The newfound mechanisms raise the possibility that the same fixed positioning of melanocyte stem cells may exist in humans. If so, it presents a potential pathway for reversing or preventing the graying of human hair by helping jammed cells to move again between developing hair follicle compartments.”
The McSCs focus on pigment-making and are different from cells responsible for hair growth, Sun explained, so hair can continue growing even without pigment. The NYU study showed that as the hair regrowth process aged, the number of McSCs lodged in the follicle bulge continued to increase. At some points, this non-pigment-producing follicle bulge contained roughly 50 percent of all McSCs.
The McSCs that remained mobile retained their ability to produce pigment, but with the ever-shifting requirements of McSCs breaking down over time, the rise of gray hair coincided with aging. While stress has also been associated with graying hair, unrelated Harvard research suggests that stress simply increases the hair regrowth pattern, speeding up the aging process for hair follicles.
“For unknown reasons, the melanocyte stem cell system fails earlier than other adult stem cell populations, which leads to hair graying in most humans and mice,” according to the NYU study.
The next step for the NYU team involves investigating how to get McSCs moving again once they become stuck. Because once they move, they create pigment, which could potentially mean the end of gray hair.