How does stress make mouse hair gray? Affects stem cells in hair follicles

BEIJING, Feb. 18 (Xinhua) — For centuries, even thousands of years, talk of fear or other stress turning hair white has been circulating among the public. However, it was not until a recent study of mice that first-hand concrete evidence of the phenomenon was provided. The study may also provide a biological explanation for the occurrence of this phenomenon.

How does stress make mouse hair gray? Affects stem cells in hair follicles

Henriette Campan, a teacher and close-knit maid to Queen Marie Antoinette of France, once wrote that the 35-year-old queen was in great pain during the French Revolution of 1791, and that her hair was “in the dark of the night of June 20th, when the royal family tried to flee France and failed.” become white, like a seventy-year-old. The story of early whitening of hair is not just about members of the royal family, but a 2013 study found that nearly 200 such cases have been recorded in the medical literature since 1800.

This phenomenon of “one night white head” is medically known as “canitis subita”, ancient and modern both in China and abroad have been recorded. However, these stories can be heard as legends, even if they contain credible witness statements. Some researchers offer more common explanations: for example, this person may have a rare autoimmune disease that causes sudden hair loss, a condition known as “hidden spotting” that affects only their last remaining colored hair. If this selective hair loss occurs, the person ends up with only gray hair, or just regrows gray hair, then they may be considered to have been the latest thing to make them white overnight.

The authors of the new study, Harvard researcher Ya-Chieh Hsu, and her team hope to explore the problem as scientifically as possible. In a recent paper published in the journal Nature, they focused on stem cells. Stem cells are the basis for building a variety of cells in the body, including those that regulate hair growth.

“In the field of stem cell science, we have more advanced tools than ever before, and this field has begun to overlap with neurobiology in very exciting ways,” associate professor Xu said. “

Her team subjected black-haired mice to various pressures, such as limiting their activity. Over time, the mice in the stress-affected experimental group did show more white hair than the mice in the control group. The researchers then systematically listed factors that could cause hair to turn white, such as the immune system tracking hair-related cells. In the end, they ruled out all other possibilities, leaving only one option.

“We looked at many different possibilities, including immune attack, cortisol levels, and so on, and then we realized that the real driver was the sympathetic nervous system, which triggers mammals’ fighting or flight responses,” Xu explained.

The sympathetic nervous system governs our immediate and unconscious response to stress, thanks to neural networks throughout the body. Our skin is also part of this network, with sympathetic nerves wrapping each follicle. Inside the hair follicles, there are some stem cells that can be converted into cells that stain when hair is regenerated, which is melanin stem cells. Normally, some melanin stem cells are always retained in the hair follicles (at least before the slow aging process begins), but this is not the case in mice that experienced excessive stress in the study.

“We found that stress causes sympathetic nerves to release the neurotransmitter norepinephrine, which is then absorbed by melanocytes stem cells. This allows all the stem cells to be activated, so they are converted into pigment-producing cells,” Xu said. In just a few days, the stem cell bank of renewable pigments will dry up. Once they disappear, they can no longer produce pigment. “

Of course, mice are not human, so more research is needed to confirm that the same basic processes can occur in us. However, the team believes the human situation is much the same, because both mice and humans have these pigment-making stem cells, as well as similarly functional sympathetic nervous systems. “While we want a close connection between the two, there is no conclusive evidence, ” Mr. Xu said.

As is often the case in scientific research, Xu Yajie’s research not only provides a possible answer to an ancient question, but also opens the door to a new set of questions. For example, the team was surprised to find that the rat’s “war or flight” response caused such harm because it evolved like a button to avoid danger. Over the past few decades, scientists have begun to reveal in many ways that stress is a double-edged sword for our health. Continuing to study stem cells’ behavior under pressure may also reveal other negative effects.

“The serious impact of stress on these particular stem cells avoids the question of how other stem cells in the human body may be affected,” Associate Professor Xu said. “