Hair loss is a disease caused by the human immune system attacking its own hair follicles. Scientists at the Salk Institute in the United States have found an unexpected molecular target for hair loss treatment. The research paper published in natural immunology on June 23 describes how immune cells called regulatory T cells use hormones as messengers to interact with skin cells to produce new hair follicles and promote hair growth.
Researchers say that for a long time, people have been studying how regulatory T cells can reduce the excessive immune response in autoimmune diseases. The new study confirms that the upstream hormone signals and downstream growth factors that actually promote hair growth and regeneration are completely separated from the suppression of immune response.
The researchers studied the role of regulatory T cells and glucocorticoids in autoimmune diseases. Glucocorticoids are steroid hormones derived from cholesterol produced by the adrenal gland and other tissues. They induced hair loss in normal mice and mice lacking glucocorticoid receptors in regulatory T cells.
Two weeks later, the researchers saw significant differences between the mice. Normal mice regrow, but mice without glucocorticoid receptors can hardly regrow. The results showed that there must be some communication between regulatory T cells and hair follicle stem cells in order to regenerate hair.
The researchers used a variety of techniques to monitor multicellular communication, and then studied the expression of regulatory T cells and glucocorticoid receptors in skin tissue samples. They found that glucocorticoids direct regulatory T cells to activate hair follicle stem cells, leading to hair growth. This crosstalk between T cells and stem cells depends on the induction of TGF by glucocorticoid receptors in regulatory T cells- β TGF-beta3 then activates hair follicle stem cells to differentiate into new hair follicles and promote hair growth. Other analyses confirmed that this pathway is completely independent of the ability of regulatory T cells to maintain immune balance.
Researchers say that in cases of acute hair loss, immune cells attack skin tissue and cause hair loss. The usual remedy is to use glucocorticoids to suppress the skin’s immune response so that they do not attack the hair follicles all the time. The use of glucocorticoids has the dual benefit of triggering the production of TGF by regulatory T cells in the skin- β 3. Stimulate the activation of hair follicle stem cells.
This study shows that regulatory T cells and glucocorticoids are not only immunosuppressants, but also have regenerative function. Next, researchers will study other injury models and isolate regulatory T cells from injured tissues to monitor TGF- β 3 and other growth factor levels.