Stem cells offer promise for hair growth

Penn researchers successfully transplant cells that lead to new hair follicles

Researchers at the University of Pennsylvania School of Medicine have isolated stem cells responsible for hair follicle growth. The findings, published in the April issue of Nature Biotechnology, may serve as the foundation for new hair loss and skin grafting treatments.

Hair grows from cells located at the base of the hair follicle. Hair follicles continuously cycle through growth, rest, and re-growth phases. In many people with hair loss, however, the follicles do not cycle correctly, with a growing number of abnormal follicles entering longer resting phases and producing only tiny invisible hairs.

Penn researchers suspected that stem cells located within the follicle bulge were responsible for hair growth. To test their theory, they used sophisticated cell labeling techniques to track the decedents of the stem cells during normal hair growth and isolate them in adult mice. They transplanted a slurry of these cells into the skin of a different set of adult mice with no immune systems. (The absence of an immune system prevented the mice from rejecting the stem cell transplant.)

Within four weeks, the transplanted cells made new hair follicles that produced new hair. “Now that we can isolate stem cells involved in hair growth, we can develop targets for manipulating hair growth,” says study principal investigator George Cotsarelis, MD, Director of the Penn Hair and Scalp Clinic and Assistant Professor of Dermatology. Penn researchers hope to one day isolate stem cells in an adult scalp and transplant those cells to other areas of the scalp, generating new follicles and hair growth. Using the stem cell transplant as a treatment for hair loss, however, is at least 10 years away, says Cotsarelis.

The findings have implications not only for hair growth, but also for burn treatments. “The cells that we have isolated not only make hair follicles, but also can make other skin cells,” says Cotsarelis. “These stem cells are there for your lifetime and have a huge capacity to proliferate and regenerate.” Current skin grafting treatments fail to generate hair growth and often lead to unsightly scars. One day, doctors may be able to isolate and use stem cells in skin grafts for burn patients, generating better grafts with hairs.