In the Spring and Autumn Period, When Wu Zixuan was avoiding the chase, his hair was all white overnight and his face was different. Jin Yong in the “shooting hero” borrowed a lamp master’s mouth, described only eighteen-nine-year-old aunt because of “fear, sorrow, regret, disappointment, sadness, all sorts of mood sniping, the side of the side has produced countless white hair … … See her hair one by one from black to gray, from gray to white.” Today, a team of leading academic journals, Nature, reveals how stress gives rise to white hair, as part of a sledgeout study paper by Professor Yajie Xu of Harvard University and the Harvard Stem Cell Institute.
These “one-night whiteheads” stories are artistically processed, but from everyday experience, many people still associate stress and hair’s easy whitening.
So what is the basis behind this claim? To make scientific proof, the research team led by Professor Xu Yajie explored the experimental model of the hairy, black-bright mice.
Professor Xu Yajie is the head of the study (Photo: Harvard University website)
In the study, lead author Dr Bing Zhang and colleagues first examined the effects of different pressures on mouse hair. They used a variety of stress models, some of which caused acute psychological stress in mice, chronic and unpredictable mild psychological stress, and some of which caused physical stress. In just a few days, no matter what type of stress they are subjected to, the mice’s newly grown body hair will change from black to gray and gray to white.
All three of the stress orstresses tested prompted mice to whiten their body hair, with the most effective and powerful effects caused by body pressure (injection of capsaicin analogue RTX causes pain) (Photo: Supplied
Like our black hair, the hairs of small black mice are black and bright, depending on melanocyte synthetic melanin at the bottom of the hair follicle. If you lack melanocytes, or if you can’t synthesize melanin properly, the newly grown hair will turn white.
But further analysis of the cells in the mouse hair follicles found that the differentiated melanocytes were not disturbed during stress, and that melanin synthesis was normal, so the original hair remained black for the first few days. However, another stem cell that is closely related to melanocytes is rapidly declining. These stem cells are melanocytes (MeSC), the equivalent of a “storage” of melanocytes, which differentiate them when activated.
Because Of the rapid decline of MeSC, there are no new differentiated meddles of the following, and the new hairs are “inkless”. Even more profound is that due to stress caused the “storage” of melanocytes to disappear, the loss of hair pigment is not a momentary, but permanent!
What are the possible reasons for meSC’s loss? (Image source: Resources)
Next, the scientists went on to ask how the brain senses stress and how it quickly transmits signals to the skin, causing the loss of melanin stem cells.
The team examined potential causes, such as stress, which allowed the adrenal glands to secrete some stress-related hormones into the bloodstream, or stress, which could cause immune cells to attack the hair follicles, among other experimental methods, such as cell ablation, hormone-receptor knockout, and adrenal excision. However, the results showed that the whitening of the mice’s hair was not related to immune attack, and hormones secreted by the adrenal glands.
But they found that norepinephrine was crucial. Since the role of the adrenal gland, the hormone’s main source, has been ruled out, the researchers have noticed another source of norepinephrine: the sympathetic nerve. When we are stressed, the sympathetic nervous system is activated, triggering a “war or flight” response. When nervous, the heart beats faster and shortness of breath, are the expression of sympathetic nervous excitement. And near the MeSC of the skin follicles, there are many ends of the sympathetic nerve.
The red color shows the melanin stem cells at the bottom of the hair follicle, surrounded by a green sympathetic nerve (Copyright Bing Zhang and Xu Yajie)
Experiments showthat that in acute stress, the sympathetic nerve is highly activated, releasing a large amount of norepinephrine at once, which allows the MeSC, which was supposed to remain resting, to rapidly begin to multiply. After abnormal proliferation, they quickly divide and eventually migrate along the follicles. In this way, the stores of melanocytes are irreversibly depleted and the hairs begin to turn white.
On weekdays, each of us bears all kinds of pressures, some from the family, some from study and work, some from the social environment. On the effects of stress on the body, academic senile has also shared a number of studies in the past, such as that stress makes DNA age faster, and long-term stress can cause immune cells to “collapse.” And the new study tells us that stress does speed up hair whitening.
Into the winter vacation and Spring Festival, a busy year to the end, finally can temporarily unload the burden. Here, we also wish all readers friends a good rest, relax and enjoy a stress-reducing holiday.
References: Bing Zhang et al., (2020) Hyperofthel drives slosion of melanocyte stem cells. Nature. DOI: 10.1038/s41586-020-1935-3