WASHINGTON (Reuters) – Marie Antoinette’s hair turned white at night, according to folklore, before being executed by the guillotine in 1793 during the French Revolution. The unfortunate queen embodied an extreme example of the phenomenon of stress-induced hair aging.
FILE PHOTO: A woman dressed as Marie Antoinette from the video game “Assassin’s Creed: Unity” promotes the game at the Ubisoft booth at the Electronic Entertainment Expo 2014, known as E3, in Los Angeles, California, June 10, 2014. REUTERS / Kevork Djanseziano
The biological mechanism behind that aging had long remained a mystery. But investigators said Wednesday that they have discovered how it happens: it is driven by the body’s response to “fight or flee” to danger.
The researchers used experiments with mice to observe how stress affects the stem cells in the hair follicles that are responsible for producing melanocytes, the pigment-producing cells that give hair color: black, brown, blond, red or at some point intermediate. People generally have about 100,000 hair follicles in the scalp.
Initially, the researchers suspected that a stress-induced immune attack might be targeting melanocyte stem cells, but that hypothesis did not work. They then explored whether the hormone cortisol, elevated under stress, could be the culprit, but it was also a dead end.
Instead, they discovered that the sympathetic nervous system of the body, which governs the response of mammals to “fight or flee” to danger, played a central role. It comprises a network of nerves that go everywhere, including the skin, in which they are like ribbons that wrap each hair follicle and are very close to the melanocyte stem cells.
When the mice were subjected to short-term pain or placed under stressful laboratory conditions, these nerves released the chemical norepinephrine, which was then absorbed by the stem cells in the hair follicle that serve as a finite deposit of melanocytes.
“Normally, when the hair regenerates, some of these stem cells become pigment producing cells that dye the hair. But when exposed to the sympathetic nerve norepinephrine, all stem cells are activated and become pigment producing cells, “said Ya-Chieh Hsu, associate professor of stem cells and regenerative biology at Harvard University and a stem cell. from Harvard, principal investigator of the institute.
“That means there are none left. In just a few days, the deposit of pigment regenerating stem cells is depleted. And once they disappear, the pigment can no longer be regenerated, “added Hsu, lead author of the research published in the journal Nature.
Hair aging is one of the many ways that stress wreaks havoc on the body. The findings could guide the development of stress-related aging treatments, or potentially other changes related to tissue stress, although this could take years, he said.
Stress is not the only reason why hair can turn gray. The natural aging process is the main cause. Genetic mutations and, in some cases, immune attacks can also contribute to hair loss of color.
“Melanocyte stem cells are also lost during aging,” said Hsu. “An interesting hypothesis could be that stress is an accelerated aging process. But we still don’t know if that’s true. We are interested in finding the link. ”
Will Dunham Report; Edited by Sandra Maler