The technique centers on the behavior of human dermal papilla cells, the ones that make up the base of hair follicles. While the idea of using dermal papilla cells to generate new hair growth has been around for about 40 years, scientists have had a hard time doing it since the cells simply revert back to basic skin cells when they’re put into a culture. Rodent papillae, however, don’t have that problem, because they clump together and make it easier for the cells to communicate with each other.
Taking a cue from the rodent example, the Columbia researchers figured out how to encourage the human papillae to aggregate in a culture. After harvesting samples from human donors, the researchers transplanted the cells between the dermis and epidermis of human skin and grafted them onto the backs of mice. After a few days, scientists found that the hair was growing like normal. Sure, the human hair was growing on the backs of mice, but they matched up with the donors perfectly.
A magical hair growth tonic is probably still at least a few years away, if it's coming at all. But at least we’re headed in the right direction. More here.