In a recent study from Harvard, scientists discovered that stress activates nerves that are part of the fight-or-flight response, which in turn cause permanent damage to pigment-regenerating stem cells in hair follicles.
The study is published in Nature. One authoris Ya-Chieh Hsu.
In the study, the team examined if the connection between stress and grey hair is true, and if so, how stress leads to changes in diverse tissues.
Because stress affects the whole body, the researchers first had to narrow down which body system was responsible for connecting stress to hair color.
The team first hypothesized that stress causes an immune attack on pigment-producing cells. However, when mice lacking immune cells still showed hair graying.
After systematically eliminating different possibilities, the researchers honed in on the sympathetic nerve system, which is responsible for the body’s fight-or-flight response.
Sympathetic nerves branch out into each hair follicle on the skin.
The researchers found that stress causes these nerves to release the chemical norepinephrine, which gets taken up by nearby pigment-regenerating stem cells.
In the hair follicle, certain stem cells act as a reservoir of pigment-producing cells. When hair regenerates, some of the stem cells convert into pigment-producing cells that color the hair.
The researchers found that the norepinephrine from sympathetic nerves causes the stem cells to activate excessively. The stem cells all convert into pigment-producing cells, prematurely depleting the reservoir.
The finding underscores the negative side effects of an otherwise protective evolutionary response.
To connect stress with hair graying, the researchers started with a whole-body response and progressively zoomed into individual organ systems, cell-to-cell interaction and, eventually, all the way down to molecular dynamics.
The process required a variety of research tools along the way, including methods to manipulate organs, nerves, and cell receptors.
The team says with this study, they now know that neurons can control stem cells and their function, and can explain how they interact at the cellular and molecular level to link stress with hair graying.
If you care about hair health, please read studies about a new way to activate stem cells to make hair grow and findings of this treatment could help regrow your hair.
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