A scientific trial of a skin transplant procedure had the unexpected side-effect of causing hair from a man's head to grow on a woman's arm.
Although further tests have not been done, the method could contribute to a solution in the centuries-old search for an answer to baldness.
An estimated 40 per cent of the male population suffers from varying degrees of baldness. A research team from Britain and the US discovered the new way to transplant donor hair follicles that do not get rejected.
The breakthrough in hair growth is described today in the science journal, Nature, by researchers from Durham University, the Royal Victoria Infirmary at Newcastle-upon-Tyne and Columbia University, New York.
The team is talking about true transplants from a donor to a recipient, not the more familiar and ghastly business of punching out little plugs of hair from the back of the head and moving them to the front.
Despite great advances in human tissue and organ transplantation, the researchers point out, rejection was a constant threat and one which made hair transplants from a donor an impossibility - until now. Instead of using complete hair follicles, the specialised cells which produce growing hair, they transplanted only "dermal sheath tissue" from the base of the follicles.
When the cells were transplanted, not only were they not rejected, they promptly began growing new follicles and hair within three to five weeks after the graft. None of these cells showed any sign of rejection when examined between 41 and 77 days after the graft.
The researchers carried out these experiments on themselves, choosing individuals who would be completely incompatible in normal transplant terms. To add to the challenge, the transplants were from the heads of males to the inner forearm of a female.
They examined the follicles and found them to be perfectly normal. They also did a DNA analysis, which showed that the base of the follicle carried male DNA while the top working part carried female DNA.
The researchers say the dermal sheath tissues have been shown to be "immunoprivileged": they have a "special immune status" which means that the recipient's immune system doesn't try to destroy and reject them.
The researchers state with some excitement that the discovery about immunoprivilege "might be used in tissue and organ engineering" to prevent organ rejection, but also admit, "more immediately, might be used in new treatments for hair loss". Now their main challenge might be to avoid getting crushed in the stampede to their door.
