Scientists reporting in the Proceedings of the National Academy of Sciences say they have for the first time successfully grown human hairs using dermal papilla cells taken from the inside of hair follicles.
The method could significantly expand the use of hair transplantation to women with hair loss as well as to men in early stages of baldness.
“About 90 percent of women with hair loss are not strong candidates for hair transplantation surgery because of insufficient donor hair. This method offers the possibility of inducing large numbers of hair follicles or rejuvenating existing hair follicles, starting with cells grown from just a few hundred donor hairs. It could make hair transplantation available to individuals with a limited number of follicles, including those with female-pattern hair loss, scarring alopecia, and hair loss due to burns,” explained senior author Dr Angela Christiano from the Columbia University Medical Center.
Such patients gain little benefit from existing hair-loss medications, which tend to slow the rate of hair loss but usually do not stimulate robust new hair growth.
“Dermal papilla cells give rise to hair follicles, and the notion of cloning hair follicles using inductive dermal papilla cells has been around for 40 years or so. However, once the dermal papilla cells are put into conventional, two-dimensional tissue culture, they revert to basic skin cells and lose their ability to produce hair follicles. So we were faced with a Catch-22: how to expand a sufficiently large number of cells for hair regeneration while retaining their inductive properties,” said co-author Prof Colin Jahoda from Durham University, UK.
The team found a clue to overcoming this barrier in their observations of rodent hair. Rodent papillae can be easily harvested, expanded, and successfully transplanted back into rodent skin, a method pioneered by Dr Jahoda several years ago.
The main reason that rodent hair is readily transplantable, the researchers suspected, is that their dermal papillae tend to spontaneously aggregate, or form clumps, in tissue culture. The team reasoned that these aggregations must create their own extracellular environment, which allows the papillae to interact and release signals that ultimately reprogram the recipient skin to grow new follicles.
“This suggested that if we cultured human papillae in such a way as to encourage them to aggregate the way rodent cells do spontaneously, it could create the conditions needed to induce hair growth in human skin,” said study first author Dr Claire Higgins from the Columbia University Medical Center.
To test their hypothesis, the team harvested dermal papillae from 7 human donors and cloned the cells in tissue culture. No additional growth factors were added to the cultures.
After a few days, the cultured papillae were transplanted between the dermis and epidermis of human skin that had been grafted onto the backs of mice. In five of the seven tests, the transplants resulted in new hair growth that lasted at least six weeks.
DNA analysis confirmed that the new hair follicles were human and genetically matched the donors.
“This approach has the potential to transform the medical treatment of hair loss. Current hair-loss medications tend to slow the loss of hair follicles or potentially stimulate the growth of existing hairs, but they do not create new hair follicles. Neither do conventional hair transplants, which relocate a set number of hairs from the back of the scalp to the front,” Dr Christiano said.
“Our method, in contrast, has the potential to actually grow new follicles using a patient’s own cells. This could greatly expand the utility of hair restoration surgery to women and to younger patients – now it is largely restricted to the treatment of male-pattern baldness in patients with stable disease.”
Bibliographic information: Claire A. Higgins et al. Microenvironmental reprogramming by three-dimensional culture enables dermal papilla cells to induce de novo human hair follicle growth. PNAS, published online October 21, 2013; doi: 10.1073/pnas.1309970110