NEW hair has been grown from stem cells plucked from the follicles of one mouse and implanted into another. The work is a significant advance that will stimulate research into ways to treat baldness.
鈥淭his is what I鈥檝e been shooting for for over 14 years,鈥� says George Cotsarelis of the University of Pennsylvania School of Medicine in Philadelphia. 鈥淚鈥檓 just in nirvana.鈥�
For years, biologists have known that a part of the hair follicle called the bulge contains stem cells that give rise to hair and help heal skin wounds. But until recently no one had managed to separate these cells from the surrounding tissue. Cotsarelis and his team did it by getting the bulge stem cells to produce a green fluorescent protein. Standard cell-sorting machines were then able to separate out the cells (Nature Biotechnology, DOI: 10.1038/nbt950).
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Earlier this year, Elaine Fuchs鈥檚 group at the Rockefeller University in New York City used another strategy to isolate the cells (Science, vol 303, 359). But Cotsarelis鈥檚 team has gone further by transplanting the stem cells onto other mice. The cells produced hair and all its associated skin structures: follicles, epidermis and sebaceous glands.
鈥淗ere you have two very talented groups taking different approaches and coming to similar conclusions,鈥� says Anthony Oro, a dermatology researcher at Stanford University in California. 鈥淭hat gives us a lot of confidence in these results.鈥�
Both groups used gene chips to find out which genes are switched on in the stem cells, allowing more of the genes involved in hair production to be identified. The work also provides a signature that researchers can use to identify the same kind of cells in people. 鈥淲e鈥檝e known where these cells are for a while, but now we finally have the prospect of getting our hands on a lot of them,鈥� Oro says.
If these stem cells could be isolated from individuals, multiplied in the lab and then re-implanted into that person鈥檚 scalp, it could be a great improvement over current hair transplant techniques, which involve moving hair from the surviving fringes to the bald spot. Such work could also help improve treatments for burns victims, Cotsarelis says: 鈥淥ne problem with a burn is that the wound is never covered with hair.鈥� However, Cotsarelis does not have the funding to pursue this long-term project.
The most significant outcome of his work may be to boost research into the balding process. Normal balding is not caused by the loss of hair follicles 鈥� bald men have just as many as their more hirsute counterparts. The problem is that the follicles switch to producing colourless, almost invisible hairs (快猫短视频, 13 October 2001, p 28). This is thought to be due to a shortening of the follicles鈥� growth cycle, but the cause of this change is not known. If human bulge stem cells can be isolated, Cotsarelis says, it might be possible to screen for drugs that will reverse this process.
The work could also yield insights into other diseases. Many forms of skin cancer are thought to be caused by ultraviolet damage to the bulge stem cells.