Although it was not their original intent, researchers from UT Southwestern Medical Center, Dallas, TX, have discovered that skin cells are directly responsible not only for turning hair gray but for balding as well. They published their study results in the journal Genes & Development. ￼ Researchers have discovered that skin cells control balding as well as the graying of hair.
“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 Lu Q. Le, MD, PhD, associate professor of dermatology with the Harold C. Simmons Comprehensive Cancer Center, UT Southwestern. “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.”
Dr. Le holds the Thomas L. Shields, MD Professorship in Dermatology, and is a member of the Hamon Center for Regenerative Science and Medicine, also in Dallas, TX. He and colleagues were studying neurofibromatosis type 1, a rare genetic disease that causes tumors to grow on nerves. KROX20 is a protein associated with nerve development and is activated in the skin cells that become the hair shaft. These hair progenitor cells also produce stem cell factor (SCF), another protein that is essential for hair pigmentation.
In their murine model, these researchers found that deletion of the SCF gene in the hair progenitor cells turned the animals’ hair white. In addition, when KROX20-producing cells were deleted, no hair grew and the mice became bald.
Hair production was already known to involve the stem cells in hair follicles, and SCF was known to be vital for pigmented cell formation. What was not known was what happens after these stem cells move down to the base of the hair follicles and which cells produced SCF.
These researchers discovered that the cells involved in making the hair shaft also produce the KROX20 protein and that the cells that contain functioning KROX20 and SCF move up from the base of hair follicles to interact with melanocyte cells (which produce pigment), and then grow into pigmented hairs.
In the mouse models, hair was gray without SCF, turning white with age, and without KROX20, no hair grew at all. Dr. Le and fellow researchers are now studying whether the KROX20 in cells and the SCF gene stop working with age, which leads to the gray and thinning hair seen in older adults. They are also researching whether this dysfunction can also lead to male pattern baldness.
The research was supported by the National Cancer Institute, Specialized Programs of Research Excellence (SPORE) grant, National Institutes of Health, the Dermatology Foundation, the Children’s Tumor Foundation, and the Burroughs Wellcome Fund.