Scientists studying anti-inflammatory immune cells called Tregs discovered that defects in these cells may be responsible for hair loss called alopecia areata.
Alopecia areata is a common autoimmune skin disease where the immune system attacks hair follicles, causing the hair to fall out in round patches on the scalp. There is often hair loss on the face and sometimes other areas of the body. There is no cure for alopecia areata.
When the researchers temporarily removed the Tregs from the skin of laboratory mice, they discovered that patches of hair that had been shaved were not regrowing. Curious at this unexpected result, they observed the skin of the mice using imaging techniques that allowed them to see that the hairs that were regrowing had Tregs gathering around the follicle stem cells.
“Our hair follicles are constantly recycling. When a hair falls out, the whole hair follicle has to grow back,” one of the scientists, Professor Michael Rosenblum, an immunologist and dermatologist at University of California San Francisco, told the Independent.
“This has been thought to be an entirely stem cell-dependent process, but it turns out Tregs are essential. If you knock out this one immune cell type, hair just doesn’t grow. It’s as if the skin stem cells and Tregs have co-evolved, so that the Tregs not only guard the stem cells against inflammation but also take part in their regenerative work. The stem cells rely on the Tregs completely to know when it’s time to start regenerating,” he explained.
“We think of immune cells as coming into a tissue to fight infection, while stem cells are there to regenerate the tissue after it’s damaged,” said Rosenblum. “But what we found here is that stem cells and immune cells have to work together to make regeneration possible.”
Rosenblum suggested that further research into Tregs’ role in hair regrowth could lead to improved treatments for hair loss in general beyond only the autoimmune-type alopecia areata. Other types of alopecia include hereditary androgenetic alopecia, also known as pattern hair loss, and traction alopecia, which is caused by pulling force being applied to hair roots.
It is uncertain, though, whether this kind of research could benefit one group of alopecia sufferers — those who have permanent hair loss caused by drugs such as chemotherapy drug Taxotere.
“Treatments exist for types of alopecia that are that are hereditary and those related to autoimmune diseases, and new treatments are being developed all the time. Unfortunately, for people affected by Taxotere, these treatments are unlikely to work because the hair follicle is damaged or altered, with the stem cells necessary for hair growth terminated or replaced by non-functional cells,” says Beau Darley III of Beasley Allen Law Firm of Montgomery, Alabama. The firm is representing individuals who have permanently lost their hair after cancer treatment in litigation against Sanofi-Aventis, the manufacturer of Taxotere.