Scientists have discovered the reason why specialized pigment-producing cells, melanocytes, stop producing hair color. Although, the scientists note that genetics, chronic stress or serious illness can still be contributing factors for gray hairs.
As people age, melanocyte stem cells (McSCs) get trapped in the follicle bulge and are stopped from developing into melanocytes.
Earlier research by the NYU Grossman School of Medicine showed that WNT signaling, a transduction pathway where proteins pass signals through cell surface receptors into cells, was needed to stimulate the McSCs to mature and produce pigment. The new peer-reviewed study, published in the journal Nature, is a continuation of that research.
How and what did the researchers discover?
The researchers came to this understanding by putting mice through a forced aging process. The aged mice had 35% more hair follicle bulges clogged with McSCs.
The mice’s cells failed to continue the regeneration or maturation of pigment.
The researchers found that McSCs can switch between a stem cell state and a transit-amplifying state. A transit-amplifying state is a state whereby the stem cell has not fully developed into melanocyte cells.
The transit-amplifying state is a crucial stage for McSC health and its continued production of hair color. However, as the researchers discovered, trans-amplifying cells can only develop in specific locations not including the follicle bulges they become stuck in.
"It is the loss of chameleon-like function in melanocyte stem cells that may be responsible for graying and loss of hair color," says dermatologist Mayumi Ito, from New York University.
This information means that McSCs behave in a unique way, unlike other cells. The mobility and flexibility of the cells are essential for the continued production of melanin color pigmentation.
"These results identify a new model whereby dedifferentiation is integral to homeostatic stem cell maintenance and suggest that modulating McSC mobility may represent a new approach for the prevention of hair graying," the researchers wrote.
Hair can keep growing once it loses color as the hair follicle stem cells don’t require transformation into follicle cells.
What could this discovery lead to?
"Our study adds to our basic understanding of how melanocyte stem cells work to color hair," says dermatologist Qi Sun from New York University. "The new-found 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."