Skin Induced to Grow New Hair Follicles By Itself

They hope this discovery may one day lead to treatments for baldness and abnormal hair growth.

In the study, published in the May 17, 2007, issue of the journal Nature, Dr. George Cotsarelis and colleagues from the department of dermatology, Kligman Laboratories, University of Pennsylvania School of Medicine (Philadelphia, USA) found that when skin is injured, the cells of the epidermis take on the properties of stem cells and generate new hair follicles that are capable of growing new shafts of hair.

Up to now, the results have only been achieved in mice, but the hope is the same is true of human skin. The company Follica (Boston, MA, USA), which Dr. Cotsarelis helped to start up and in which he has a stake, hopes to develop and market a human follicle regrowth treatment based on a patent currently being filed by the university.

The researchers envision a commercial application similar to that used to treat teenage acne. A dermabrasion gel that gently damages the skin and triggers the wounding process, together with a topical cream to turn on the follicle generating genes, is in the planning stages. However, it is still early phases of development, according to Dr Cotsarelis. "If it all went perfectly, then possibly in two to three years we would have a product, but that's very optimistic,” he said.

Dr. Cotsarelis and colleagues took patches of skin from mice and observed the wounds as they healed over the following weeks. They noticed that skin cells that had not earlier been associated with hair follicles began to behave like stem cells and express genes that generate hair follicles during skin development. "The regenerated hair follicles establish a stem cell population, express known molecular markers of follicle differentiation, produce a hair shaft, and progress through all stages of the hair follicle cycle,” they wrote in their article.

Hair growth occurred irrespective of the age of the mice, although the hair was colorless. In a second experiment, the investigators utilized genetically engineered mice that expressed higher levels of a protein called Wnt. These mice produced two times the density of hairs in the normal mice under the same wounding conditions.

The research team concluded that, "these remarkable regenerative capabilities of the adult support the notion that wounding induces an embryonic phenotype in skin, and that this provides a window for manipulation of hair follicle neogenesis by Wnt proteins.”

Fifty years ago scientists suggested that follicle regrowth might be possible but until now nobody had proved it. It has been generally accepted that once hair follicles die off, through baldness or skin damage, they are lost forever. Perhaps, Dr. Cotsarelis conjectured, it is because the regeneration occurs after skin damage that it has taken so long to discover. "Most people studying skin wounding don't pay a lot of attention to hair follicles. They view wound closure as the end-point,” he said.

The discovery also opens up new insights into how skin works, it "provides convincing evidence that the skin has remarkable powers of regeneration, not just repair,” said Dr. Desmond Tobin, a cell biologist at the University of Bradford, UK, in an introductory article in the same issue of the journal.

Existing baldness treatments are described as "long and slow” by Dr. Carol Michaelides, a consultant at the Philip Kingsley Trichological Clinic in London, UK, and the chances of success decrease with age and the amount of hair loss. "The accepted baseline is 30 hairs per square centimeter,” said Dr. Michaelides. "This compares with several hundred in a healthy head. If the human scalp can be induced to make its own follicles, it would be a huge step forward.”


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