Stress hormones: How stress relieves hair

It is known that chronic stress is not good for us – this is also reflected in abundance of hair: psychological stress can lead to hair loss. A study in mice now sheds light on the mechanisms behind this effect. Consequently, the stress hormone corticosterone leads to less cleavage activity of hair follicle stem cells in rodents. Experiments show that blocking the responsible signaling pathway can also stimulate hair growth. These results could be passed on to humans, and at least prospects are emerging for developing treatment options for stress-related hair loss.

Hair becomes thinner and flabby – For many people, hair loss is a stressful note when looking in the mirror. First of all, it is important to note that hair loss can have very different causes. So predisposition, deficiency symptoms, or autoimmune reactions could be the basis. However, chronic stress is also known to be one of the factors that can cause hair thinning. However, it is not yet clear which mechanisms this effect depends on. In order to gain basic insights, researchers working with Sekyu Choi of Harvard University in Cambridge conducted experiments on animals often used as human models: mice.

Hair roots in sight

As they explain, hair growth in rodents with fur depends to a large extent on principles similar to those found in humans. It is divided into three stages: growth, degeneration and rest. As the hair follicle grows, it constantly creates an elongated stem in the hair follicle. This formation depends on the activity of the hair follicle stem cells. During the degeneration stage, growth stops and the lower part of the hair follicle shrinks. During the ensuing rest, the hair falls out. Later the cycle begins again. Therefore it was suspected that increased hair loss during stress was due to the early transition of the follicle into the resting phase. Specifically, stress hormones could be the mastermind.

In order to follow this pathway in the mouse model, Choi and colleagues subjected some rodents to experimental stress over a period of nine weeks and investigated the effect on hair growth. They were initially able to confirm that this treatment resulted in decreased hair growth associated with increased levels of the stress hormone corticosterone in the blood. As they explain, corticosterone is the animal equivalent to the human stress hormone cortisol, which is produced by the adrenal gland. To confirm the role of the adrenal glands and corticosterone in mice, the scientists removed tissue from some test animals. The resting stages of hair follicles associated with fall were shown to be shortened in these mice. However, when the scientists artificially administered the stress hormone corticosterone to the animals, this effect disappeared. In turn, this confirmed that the stress hormone affects hair root growth.

Causes and treatment options are shown

As the researchers explain, it was suggested that the effect depends on the sensitivity of specific cells in the hair follicle to glucocorticoids. This hormone is known to act via glucocorticoid receptors. So the researchers turned off this signal receptor in a targeted manner in different cells in the root region of mice’s hair. It turns out that it is not the hair follicle stem cells that directly interact with the hormone, but rather the cells underneath – the so-called dermal papillae. Subsequent molecular genetic studies enabled them to demonstrate the role these cells play in transmitting signals. According to this, the glucocorticoid stress hormone prevents the formation of a protein called GAS6 in the dermal papillae. This substance, in turn, is responsible for stimulating the hair follicle stem cells: GAS6 stimulates the cell division necessary for the hair growth phase.

The researchers were able to demonstrate this by using genetic engineering to artificially increase GAS6 production in the dermal papillae of mice. This stimulated hair growth in test animals when they were exposed to chronic stress or given corticosteroids. These results clarified: Secretion of corticosterone in the event of chronic stress leads to inhibition of GAS6 production in dermal papillae. But the negative effect associated with hair growth can be eliminated by the artificial supply of GAS6.

From a human perspective, these results look promising as they show potential causes and treatment options for stress-related hair loss. However, there are still some open questions that need to be clarified in this context, the researchers note. Above all, it is questionable to what extent the results in mice can be transmitted to humans. Because despite the many similarities, there are also differences between the growth of our hair and the processes of rodents with fur. It can influence the effectiveness of methods to reverse stress-related hair follicle stem cell inhibition. Therefore, extensive follow-up examinations are now necessary. Dennoch sind die Ergebnisse ausgesprochen vielversprechend, betont der Dermatologe Rui Yi von der Northwestern University in Chicago in einem Kommentar zur Studie: „Vielleicht wird es eines Tages möglich sein, a die negativen Auswirkungen vretronischem Haufen sufenz, die negativen Auswirkungen vretronischem stufenz Auswirkungen vretronischem Haufen Results.

Those: Nature, doi: 10.1038 / s41586-021-03417-2

March 31, 2021

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