Does stress stop human hair follicle growth?

Does stress stop human hair follicle growth?  A study published in Nature on March 31 pointed out that stress does cause baldness. Experiments in mice have proved that stress can cause the body to secrete stress hormones, which can cause the hair follicle development system to shut down and hair growth to stop.

According to Ya-Chieh Hsu, associate professor of stem cell and regenerative biology at Harvard University, hair follicles are the organs responsible for hair growth, and there are two stages: “growth” and “dormancy”. In the growth phase of hair follicles, hair follicle stem cells divide continuously to make hair grow. In the dormant period, the stem cells stop dividing, and the hair stops growing and gradually falls off.

Stress can cause hair loss, but the specific mechanism is unclear. To this end, the researchers did a series of experiments. First, they removed the adrenal glands of the mice so that they could not produce the adrenaline that causes increased stress. As a result, the frequency of hair follicles in these mice entering the growth phase was about three times that of control mice. In addition, the hair resting period of the mice in the control group was about 60 to 100 days, and the mice without adrenaline lasted less than 20 days.

Next, the researchers fed mice that had their adrenal glands removed, which is a hormone that has a similar effect to the human stress hormone cortisol. They found that the hair follicle growth period in mice was shortened. This shows that stress is suppressed in some form. Hair growth. The researchers applied a mild pressure environment to normal mice at intervals for up to nine weeks, and found that their corticosterone levels increased and hair growth was hindered.

In the next step, the researchers removed the corticosterone hormone receptor in the cells involved in mouse hair growth. The results showed that after the hair follicle stem cells removed the receptor, the hormone could still hinder hair growth; however, the mice’s dermal papilla cells were affected by the hormone receptor. After the body is removed, hair growth is not affected by hormones. It can be seen that the hormone receptors of dermal papilla cells are the “switches” for inhibiting hair growth.

When the dermal papilla cells are exposed to corticosterone, the production of a protein GAS6 is stopped. This protein functions to insert hair follicle stem cells to initiate hair growth. If there is no such protein, the hair follicles are still moving. GAS6 was injected into the skin of mice. Even if the animals were under pressure, the corticosterone level increased, and the hair still grew normally. Therefore, GAS6 is open

In summary, stress does not directly affect stem cells, but interferes with the signals that activate stem cell division. Corticosterone inserts into the receptors of the cells at the bottom of the hair follicle and inhibits the production of GAS6 protein. This causes the hair follicle stem cell division switch to turn off, and the hair stops growing.

Hsu said that the structure of corticosterone in rodents is similar to that of human cortisol, and the receptors are the same. Therefore, this set of chain reaction mechanisms may have certain similarities. In theory, an anti-stress alopecia treatment can be developed from this. Of course, whether it can be applied to humans, there are still several issues that need to be resolved.

First, we need to prove that cortisol can shut down the growth phase of hair follicles like corticosterone. Second, rodents and humans have different hair cycle timelines. Most mice have reached the maturity stage, and the resting period of hair follicles is getting longer and longer. By about 1.5 years of age, most of the hair follicles stop functioning. In contrast, 90% of human hair follicles are generally in the growth stage. Whether cortisol causes the hair follicles in these growth stages to be forcibly closed is also a question.

The last question is that the hair can fall off during the resting period, but it is not known when it will fall off. Therefore, there may be a mechanism for stress hormones. In addition to inhibiting growth, it can also accelerate the loss of hair.

In general, although there are many questions that need to be answered urgently, this mouse experiment confirmed that there is a solution to hair loss due to stress, and one of the breakthroughs may be the GAS6 protein pathway. If this kind of stress-induced hair loss is confirmed in humans, it will undoubtedly open a crucial step for the development of new treatment methods.

(source:internet, reference only)

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