Researchers at UT Southwestern Medical Center have identified the skin cells that cause hair to go bald and to turn gray – findings that could one day help develop possible treatments for gray hair and baldness. The team actually stumbled upon these cells while studying a disorder called Neurofibromatosis Type 1, a rare genetic disease that causes tumors to grow on nerves.
“Although this project was started in an effort to understand how certain kinds of tumors form, we ended up learning why hair turns gray and discovering the identity of the cell that directly gives rise to hair,” said Dr. Lu Le of UT Southwestern, in a news release. “With this knowledge, we hope in the future to create a topical compound or to safely deliver the necessary gene to hair follicles to correct these cosmetic problems.”
The researchers found that a protein called KROX20, which is commonly associated with nerve development, turns on in skin cells that become the hair shaft. This protein then causes these hair cells to produce a protein called stem cell factor (SCF), which researchers say is essential for hair pigmentation. When they removed the SCF gene in hair cells in mouse models, the hair turned white. And when the researchers went on to delete the cells that produce KROX20, they found that no hair grew and the mice eventually went bald.
Researchers already knew that skin stem cells contained in a bulge area of hair follicles are involved in hair growth and that SCF is important for pigmented cells. However, they didn’t know what happens after those stem cells move down to the base of hair follicles and which cells in the hair follicles produce SCF – or that cells involved in hair shaft creation make the KROX20 protein.
As the team noted, when both of these molecules KROX20 and SCF are expressed in a cell, they move up from the bulb, interact with pigment-producing melanocyte cells, and grow into pigmented (healthy, colored) hairs. But without SCF, the hair in mouse models was gray, and then turned white with age. And without KROX20-producing cells, no hair grew.
Now, Dr. Le and his team are working on to find out if the KROX20 in cells and the SCF gene stop working properly as people age, as well as whether it is associated with graying, hair thinning seen in older people and male pattern baldness. The team hopes their study could also provide answers about why we age in general as hair graying and hair loss are among the first signs of aging.