A recent study has uncovered a potential reason behind graying hair: stem cells that get stuck in place and lose their ability to produce pigment. Published in the journal Nature by researchers from New York University’s Grossman School of Medicine, the study sheds light on how melanocyte stem cells (McSCs) contribute to hair color and why their dysfunction leads to gray hair.
The research primarily focused on McSCs, which play a pivotal role in producing pigment. Under normal circumstances, these stem cells move between different compartments within hair follicles. These compartments provide environments that allow McSCs to mature, acquire the proteins necessary to regenerate into pigment cells, and maintain hair color. What makes McSCs unique is their ability to shift between states of maturity as they travel between these compartments.
However, the study revealed that some McSCs get stuck in the hair follicle bulge compartment, preventing them from returning to the germ compartment. In the germ compartment, WNT proteins drive the regeneration of pigment cells. When McSCs remain immobile in the bulge, they lose their capacity to produce pigment, resulting in 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, the study’s senior investigator and a professor in the Ronald O. Perelman Department of Dermatology and Department of Cell Biology at NYU Langone Health. “These findings suggest that melanocyte stem cell motility and reversible differentiation are key to keeping hair healthy and colored.”
The implications of the research suggest that if McSCs can continue moving freely or can be encouraged to move when stuck, it may be possible to maintain natural hair color indefinitely.
“Our study adds to our basic understanding of how melanocyte stem cells work to color hair,” explained Qi Sun, a postdoctoral fellow at NYU Langone Health and one of the study’s authors. “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 study also highlighted the difference between McSCs and the cells responsible for hair growth. According to Sun, even when pigment production ceases, hair growth can continue, albeit without color. As hair follicles age and undergo cycles of regrowth, an increasing number of McSCs become lodged in the follicle bulge, unable to regenerate pigment cells. Eventually, these stuck McSCs can account for approximately half of all the McSCs in a follicle bulge.
The research found that mobile McSCs retained their pigment-producing ability. However, over time, the requirements for McSC functionality become more challenging to meet, contributing to the appearance of gray hair as individuals age.
While stress is commonly linked to gray hair, separate research from Harvard indicates that stress accelerates hair follicle aging by increasing the regrowth cycle. This faster cycling ultimately speeds up the breakdown of McSC functionality, leading to earlier graying.
“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,” the NYU study stated.
The next phase of the research aims to determine how to restore mobility to McSCs once they become stuck. If successful, this could pave the way for treatments that reverse or prevent gray hair by ensuring McSCs remain functional and capable of producing pigment.
As Ito remarked, “These findings suggest a promising avenue for interventions that could one day prevent or even reverse the graying process, bringing hope to those seeking to maintain their natural hair color throughout life.”
