Scientists transplanted scalp cells from one person to another and, for the first time ever, grew new hair on a human without the use of drugs.
The approach could someday enable just about any head to sprout hair, researchers said.
It also raises hopes of someday spurring the growth of new tissue or even whole organs inside patients, such as cartilage in arthritic joints.
"You can use a few cells to basically regenerate an entire organ. To me, that's the mind-blowing part," said Angela Christiano, a Columbia University baldness researcher who did the genetic analysis for the British experiment, reported in Thursday's issue of the journal Nature.
The researchers, led by biologist Colin Jahoda at Durham University, in England, took cells at the bottom of hair pores -- or follicles -- from Jahoda's own scalp and from a colleague's. These cells from the so-called dermal sheath were then transplanted into the forearm of Jahoda's wife.
Within five weeks, the transplanted tissue -- no bigger than the head of a pin -- made a total of five fully grown hairs in the woman's arm.
The transplanted tissue "is telling the cells of the recipient: You will make a hair follicle," Jahoda said. The new hair was genetically male. It was longer, thicker and darker than arm hair, but it combined some characteristics of both donor and recipient.
Such success had been achieved before only in animal experiments.
Current baldness treatments include hair grafts and certain drugs. Drugs can slow hair loss or even produce new hair, but only in a limited number of people. In grafts, hair is lifted from one section of a man's scalp and transplanted whole into a bald spot on his head. However, the process requires a slow, expensive and potentially painful series of operations.
The new work suggests the possibility of a quicker procedure with less cutting and the creation of new hair in just about anyone. The cells could be removed from a person's own scalp or, if that person cannot produce good quality cells, they could be collected from someone else. They could then be multiplied through laboratory cloning before being transplanted.
Toupees are not out yet, however. It is not yet clear whether such newly grown hair will last, pop up at the correct angle, and satisfy several other requirements for cosmetically acceptable treatments, researchers said. The microsurgery used in the experiment is complex, too.
The research buttresses the theory that transplanted hair cells somehow bypass the body's normal rejection mechanism for foreign tissue.
The researchers picked Jahoda's wife partly because she is not related by blood to him or the other donor. Yet she showed no signs of tissue rejection.
"Having the hair as an immunologically privileged organ would be very, very important," said Dr. Michael Bernstein, a hair transplant surgeon who is medical director of the New Hair Institute in Los Angeles.
He said Jahoda's technique may give hope mainly to old people who want new hair, patients with bad burns, or others who for genetic reasons fail to make their own hair. He predicted that bald men will be able to have their own hair cloned within 15 years or so.