Stress can be bad for your hair. It is known to be capable of causing premature graying. Scientists believe stress is one of the causes of baldness (alopecia). But its mechanisms of action on hair follicles have been poorly understood.
Hair follicle tissues in humans and some mammals regenerate regularly. Their stem cells work cyclically, then multiplying intensively, then resting. During the growth phase, the follicle is renewed, the hair grows intensively. The second phase is accompanied by their inactivity, at which time the hair falls out more easily. Substantial hair loss occurs if the new regeneration cycle is delayed.
Stress hormone causes hair loss
The authors of the new study studied mice under chronic stress. They found that animal hair follicle stem cells stay in the resting phase without regenerating longer than usual.
Chronic stress in mice increases the level of the hormone corticosterone, which is produced in the adrenal cortex. In another experiment, the administration of this hormone to ordinary mice reproduced its effect that scientists observed under stress: hair follicles began to regenerate worse, their stem cells became less active.
Scientists point out that the equivalent of corticosterone in humans is cortisol. It also rises with stress and is known as the “stress hormone”.
How stress affects hair growth
Next, scientists focused on the follicles to see if the stress hormone has a direct effect on them. Corticosterone binds to a specific receptor in stem cells. The researchers bred mice without this receptor in the follicles, that is, excluded the effect of the hormone on them. It didn’t work: the stress hormone kept hair falling out. Then scientists “removed” these receptors from the hair papillae – structures that are located under the follicle. After that, the resting period of the stem cells was shortened, and under the influence of stress, the hair continued to grow as usual.
The papilla is very important for the activation of follicle stem cells. However, its performance in chronic stress has not been studied previously. In a new study, the researchers determined that stress appears to be preventing the papilla from producing the Gas6 protein.
In an experiment, the introduction of Gas6 into the skin improved hair growth both under stress and without stress. According to scientists, the mechanism associated with this substance can potentially be used to develop methods to combat hair loss. However, first it is necessary to investigate in humans the processes that were demonstrated in this study in mice.