Hormones and follicles
Glucocorticoids and regulatory T-cells activate hair growth
Elizaveta Minina, PCR.news
It is known that regulatory T cells are an important component of the stem cell niche and they play one of the key roles in their activation. As shown by the authors of an article published in Nature Immunology (Liu et al. Glucocorticoid signaling and regulatory T cells cooperate to maintain the hair-follicle stem-cell niche), under the action of glucocorticoids, regulatory cells activate the stem cells of hair follicles, providing hair regeneration.
Scientists from the Salk Institute for Biological Research (La Jolla, USA) and Fudan University (Shanghai) investigated the role of glucocorticoid hormones and regulatory T cells in autoimmune diseases - multiple sclerosis, Crohn's disease and asthma. They characterized the expression of steroid hormone receptors in different populations of regulatory T cells and noticed that regulatory skin T cells express them especially actively. In addition, it turned out that the resident skin T-cells of all steroid receptors express only the glucocorticoid receptor and that during hair regeneration after depilation, the level of these hormones in the skin increases. (Glucocorticoids are produced not only in the adrenal glands, but also locally in the skin, as part of a reaction to damage or inflammation.)
Scientists have tested whether glucocorticoids affect the behavior of skin regulatory T-cells. They showed that the glucocorticoid signaling pathway has no effect on the expression of the Foxp3 gene in these cells and, therefore, does not transfer them to a resting state. To further clarify the role of glucocorticoids in the activity of resident skin regulatory T-cells, the authors removed the hair on the back of wild-type mice and mice knocked out by the glucocorticoid receptor, and observed the rate of hair restoration. While wild-type mice completely regrown their hair in 15 days, less than 20% of the hair cover had been restored in knockout mice by this time. In knockout mice, the activity of hair follicles was significantly suppressed. This allowed the authors to conclude that glucocorticoids are critically needed for the activation of follicles by regulatory T cells.
Left: After hair loss, skin cells (blue) of a normal mouse can activate hair follicle stem cells (red). Right: Mouse cells without glucocorticoid receptors in their regulatory T cells cannot activate hair follicle stem cells. Figure from the press release of Hair-raising research: Salk scientists find surprising link between immune system, hair growth – VM.
Scientists have found that the glucocorticoid signaling pathway through the interaction of the receptor with Foxp3 activates the production of TGF-β3 in regulatory T cells. This cytokine activates stem cells in hair follicles. It is important to note that the absence of a glucocorticoid receptor on skin regulatory T-cells affected only hair growth and had no effect on the immune homeostasis of the skin.
"For a long time, regulatory T cells have been studied in terms of how they reduce excessive immune responses in autoimmune diseases," says lead author Ye Zheng from the Salk Institute for Biological Research. "We have now identified an upstream hormonal signal and a downstream growth factor that actually promote hair growth and regeneration, completely independent of suppressing the immune response." Ye Zheng added that glucocorticoids are often prescribed in acute cases of autoimmune alopecia, when attacks by the immune system cause hair loss. Obviously, glucocorticoids not only suppress the immune response, but also stimulate the activation of hair follicle stem cells through regulatory skin T cells producing TTGF-β3.
Portal "Eternal youth" http://vechnayamolodost.ru