December 2, 2023

Despite the growing popularity of gray hair in recent years, it’s still a very visible sign of aging that some people prefer not to publicize. Despite much research into the mechanisms that lead to the depletion of melanin-producing stem cells (and thus the pigmented pigment protein), it’s still a bit of a, er, gray area.

A breakthrough may be on the horizon, as researchers led by a team at NYU Grossman School of Medicine studied these melanocyte stem cells (McSCs), which humans also possess, in mice. They found that the movement of these cells along the hair follicle is key to their transformation and, in turn, their pigmentation. Over time, the system breaks down and they get “stuck” at a point, unable to evolve the cell types that can be induced to produce color.

“Loss of chameleon-like function in melanocyte stem cells may be responsible for hair graying and discoloration,” said study senior investigator Mayumi Ito, Ronald O. Perelman Professor in the Department of Dermatology and Department of Cytology at NYU Langone Biology of Health Center.

As they age and move between the different compartments of the developing hair follicle, McSCs display extreme plasticity, which exposes McSCs to varying levels of protein signals that affect maturation.

But as hair ages, falls out, and regrows, MCSC numbers swell and they get “stuck” in a compartment called the follicular bulge, which prevents them from returning to their original location — the germ compartment — and the WNT protein Help them develop into pigment cells.

Pink (left) hair dye stem cells need to be in the hair germ chamber to be activated (right) to develop into pigment.  Sun, Q., Lee, W., Hu, H. et al. (CC by 4.0)
Pink (left) hair dye stem cells need to be in the hair germ chamber to be activated (right) to develop into pigment. Sun, Q., Lee, W., Hu, H. et al. (CC 4.0)

“Our study advances our fundamental understanding of how melanocyte stem cells color hair,” said Qi Sun, Ph.D., the study’s principal investigator and a postdoctoral fellow at NYU Langone Health. “The newly discovered mechanism raises the possibility that the same fixed localization of melanocyte stem cells may exist in humans. If so, it provides a mechanism for reversing or Preventing hair graying in humans offers a potential avenue.”

Earlier, the researchers contacted WNT signal and Stimulation of mature McSCs to produce pigments. Stem cells “stuck” in the follicle’s bulge compartment, located just above the germ compartment, were shown to be trillions of times less exposed to WNT signaling.

To demonstrate the hair growth-shedding-regrowth cycle, the researchers plucked and forced hair regrowth in mice. They found that with the forced aging cycle, the McSCs populating the follicle bulge increased from 15 percent to nearly 50 percent. The cells then fail to regenerate or mature into pigment producers. Meanwhile, the cells moving between the compartments continued to mature and produce pigment during the two-year study period.

While the discovery in the mouse model isn’t yet a quick fix for age-related graying, it does pave the way for studying the movement of McSCs to stop or even reverse the process.

“These findings suggest that motility and reversible differentiation of melanocyte stem cells are key to maintaining healthy and colored hair,” said Ito, a professor in the Department of Cell Biology at NYU Langone.

The researchers now aim to test how best to move the McSCs back into their bacterial compartments so they can produce pigments again.

The study was published in the journal nature.

source: NYU Grossman School of Medicine