“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, Associate Professor of Dermatology at UT Southwestern.
The process involves KROX20, a protein commonly associated with nerve development, which activates in skin cells that become the hair shaft. This, in turn, makes hair precursor cells produce stem cell factor (SCF), essential for hair pigmentation.
In mouse models, deleting the SCF gene in the hair progenitor cells made the animal’s hair turn white. Furthermore, completely eliminating the KROX20-producing cells lead to mice becoming bald.
At the time of the discovery, Dr. Lu was studying Neurofibromatosis Type 1, a rare genetic disease that causes tumors to grow on nerves. He was intrigued to see that cells with functioning KROX20 and SCF move from the base of hair follicles, then interact with pigment-producing melanocyte cells and grow into pigmented hairs.
Hair is typically pigmented because of the presence of melanin in hair shafts, which is synthesized by follicular melanocytes and then transferred to the neighboring hair progenitors that give rise to hair shafts. It’s clear now that hair matrix progenitors that regulate hair growth and pigmentation are partly due to creating an SCF-dependent niche for follicular melanocytes.
“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”, noted Dr. Lu.