It is well known that chronic stress can lead to hair loss, but it remains a mystery how stress can actually cause hair loss – so far. A new study by Harvard University researchers may provide clues.
In a recent study published in the journal Nature, researchers found that the stress hormone binds hair cells to a “prolonged rest period,” which means that new hair growth stops longer than usual.
First, it is important to understand the three stages of hair growth: growth, rest, and breakage. In the first case, the hair follicle cells move and hair is produced continuously, in the second the hair stays in a relaxed state but can still shed, and in the final stage – decay – the hair falls out.
According to the study, “During the rest period, the stem cells are quiet and the hair flows easily. Hair loss can occur when the hair follicles fall out and the stem cells do not regenerate new tissue. ”
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The researchers looked specifically at the adrenal glands, which produce the stress hormone corticosteroid, and the relationship between hair loss in mice. (In rats, corticosteroids are thought to be equivalent to the stress hormone cortisol produced in humans.)
The researchers surgically removed the adrenal glands from the rats. Later, in the removed adrenal glands, the hair follicles in rats found that they had a shorter rest period but more often than not. When rats administered corticosteroids, their hair growth slowed to normal.
For more than nine weeks, the researchers administered corticosteroids to non-rats whose adrenal glands were still intact. They found that these rats had elevated corticosterone levels and reduced their hair growth, noting that their hair follicles had a longer rest period than usual.
The real shock came when we were depleted of stress hormones. Under normal circumstances, the hair follicles grow back and forth – the rest of the animal’s life span. But when we remove stress hormones in abnormal conditions, the stem cell compartment becomes too short and even as rats get older, they enter the developmental stage to regenerate new hair follicles and hair, ”said Ya-Chih Hussein, Alvan and Esta Star Associate Professor Stem Cell And Rehabilitation Biology and senior author of the study, for Technology Networks.
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The researchers shaved off the adrenal glands. Nineteen days later, they had a completely renewed coat, the adrenal glands did not shrink, and the shaved mice were still mostly bald.
“Therefore, even the normal level of stress hormones in the body is an important regulator of rest. The stress elevates the existing adrenal gland – hair follicle axis, which makes it harder for hair follicle stem cells. Enter the development stage to renew new haircuts, ”Hussein explained in the next press release on the findings of the study.
After identifying the link between stress hormone and hair follicle stem cell activity, the researchers explored the biological mechanism behind it.
“At first we asked if the stress hormone directly controls the cells and tests the corticosteroid receptor, but this was a mistake. Instead, we find that the stress hormone actually works on the underlying skin cells. The hair follicle, known as the papilla of the skin, was described by another researcher, Sekuyu Choi.
“Dermal papilla is known to be important in stimulating hair follicle stem cells, but the underlying causes of dermal papilla have not changed when stress levels change. Researchers have shown that hair follicles can activate hair follicles. ”
Although more research is needed, the authors hope that some genetic therapies may be used in the future to combat hair loss in humans.
“Adding gas 6 was enough to stimulate the hair follicle stem cells that were at rest during normal and stressful conditions and to promote hair growth,” Choi said. “In the future, gas 6 pathways can be exploited by stimulating stem cells to promote hair growth.
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“When we look for cellular factors, we usually look at the surrounding skin. Although there are important environmental factors, our findings suggest that the main modifier for hair follicle stem cell activation is actually far from the adrenal gland and it works by changing the threshold needed for cell activation.”
You may have systematic control of stem cell behavior in a particular organ that plays a very important role, and we will learn more and more examples of these ‘organ interactions’. Tissue biology is related to the physiology of the body. We still have a lot to learn in this area, but we always remember that in order to understand stem cells, we often need to think beyond the skin.