For a long time, anecdotes have connected stressful experiences with the phenomenon of hair graying. Now, for the first time, Harvard University scientists have discovered exactly how the process plays out: 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, published in Nature, advances scientists' knowledge of how stress can impact the body.
Everyone - Anecdote - Share - Body - Skin
"Everyone has an anecdote to share about how stress affects their body, particularly in their skin and hair -- the only tissues we can see from the outside," said senior author Ya-Chieh Hsu, the Alvin and Esta Star Associate Professor of Stem Cell and Regenerative Biology at Harvard. "We wanted to understand if this connection is true, and if so, how stress leads to changes in diverse tissues. Hair pigmentation is such an accessible and tractable system to start with -- and besides, we were genuinely curious to see if stress indeed leads to hair graying. "
Because stress affects the whole body, 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, researchers turned to the hormone cortisol. But once more, it was a dead end.
Stress - Levels - Hormone - Cortisol - Body
"Stress always elevates levels of the hormone cortisol in the body, so we thought that cortisol might play a role," Hsu said. "But surprisingly, when we removed the adrenal gland from the mice so that they couldn't produce cortisol-like hormones, their hair still turned gray under stress."
After systematically eliminating different possibilities, researchers honed in on the sympathetic nerve system, which is responsible for the body's fight-or-flight response.
Nerves - Hair - Follicle - Skin
Sympathetic nerves branch out into each hair follicle on the skin. The...
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