Scientists Make Skin Grow New Hair Follicles By Itself
The study is published in the journal Nature.
Dr George Cotsarelis and colleagues from the Department of Dermatology, Kligman Laboratories, University of Pennsylvania School of Medicine, in Philadelphia, US, found that when skin is wounded, 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.
So far the results have only been achieved in mice, but the hope is the same is true of human skin.
The company Follica, which Dr Cotsarelis helped to set 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 envisage a commercial application similar to that used to treat teenage acne. A dermabrasion gel that gently damages the skin and kicks off the wounding process, together with a topical cream to switch on the follicle generating genes.
It's still early days 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 previously been associated with hair follicles started 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.
Hair growth occurred irrespective of the age of the mice, although the hair was colourless.
In a second experiment they used genetically engineered mice that expressed higher levels of a protein called Wnt. These mice produced twice 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."
Half a century 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 for good.
Perhaps it's because the regeneration occurs after skin damage that it has taken so long to discover wondered Dr Cotsarelis:
"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 avenues into how skin works, it "provides convincing evidence that the skin has remarkable powers of regeneration, not just repair," said Desmond Tobin, a cell biologist at the University of Bradford, UK, in an introductory article in the same edition of the journal.
Existing baldness treatments are described as "long and slow" by Carol Michaelides, a consultant at the Philip Kingsley Trichological Clinic in London, and the chances of success decrease with age and the amount of hair loss.
"The accepted baseline is 30 hairs per square centimetre," said 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", she added.
"Wnt-dependent de novo hair follicle regeneration in adult mouse skin after wounding."
Mayumi Ito, Zaixin Yang, Thomas Andl, Chunhua Cui, Noori Kim, Sarah E. Millar and George Cotsarelis.
Nature 447, 316-320 (17 May 2007).
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