It may be small comfort to anyone sporting a comb-over, but researchers have found a second genetic risk factor for baldness.
Two groups, working independently, found variants on chromosome 20 that are associated with male pattern baldness–the most common cause of hair loss in men, and the root of a multimillion-dollar industry devoted to protecting, nurturing, and transplanting hair.
A third report identifies a new kind of stem cell in the hair follicles of mice that, when transplanted onto the skin of hairless rodents, causes the animals to sprout tufts of hair.
These latest findings offer greater insight into the genetic underpinnings of male pattern baldness, and into the process that produces a glorious head of hair in the unafflicted. According to a research team led by Tim Spector of King’s College London, figuring out the genetic variants linked to the disorder could lead to gene therapies for baldness. The discovery of a risk factor on chromosome 20 may point to “an intriguing new potential target” for gene therapy.
All three studies were published online in Nature Genetics on October 12.
Genetic tests, the researchers say, could identify people who are likely to be troubled by a receding hairline and give them the benefit of early treatment, before they’re forced to smear sunblock on their naked scalps.
Despite its name, male pattern baldness, which is strongly hereditary, affects both women and men–40 percent of adults in all. There are a couple of drugs available that can slow hair loss and lead to new hair growth in some people, but the effect isn’t permanent: if a patient stops the regimen, his hair will fall out. Some people opt for hair transplants, but they’re time consuming and expensive.
However, this latest genetics work may have value beyond the bathroom mirror. People with male pattern baldness are more likely to suffer from cardiovascular disease, insulin resistance, and several other disorders. Scientists haven’t figured out the link, but “it is quite likely that there is one genetic connection,” says Axel Hillmer, formerly at the University of Bonn, in Germany, and now with the Genome Institute of Singapore, who led one of the teams that identified the risk factors on chromosome 20.
Male pattern baldness is also linked to variants in the androgen receptor gene on the X chromosome.
Hillmer, together with other researchers in Germany and Australia, genotyped several hundred men who began to go bald before the age of 40. They found five variants on chromosome 20 that were strongly associated with male pattern baldness.
“Our aim is eventually to identify all the genes that are involved,” Hillmer says.
In another study of nearly 2,000 balding men and women, researchers from Europe, Canada, and the United States also identified a link between variants on chromosome 20 and male pattern baldness. One in seven of the Caucasian men in that study had risk factors on both that chromosome and the X chromosome; they were seven times likelier to go bald than people without those variants. The effects of the same risk factors in women were less pronounced. Neither of the research groups found any evidence of interactions between genes at the two locations.
The prevalence of these genetic risk factors for baldness “varies strikingly worldwide,” Hillmer says, although it doesn’t fully explain geographic differences in the prevalence of male pattern baldness, such as the low incidence among Southeast Asians.
A separate study by researchers in Europe offers new insights into the functioning of hair follicles, at least in mice. It was previously thought that stem cells in hair follicles were limited to a specific part of the follicle, and that they seldom divided. But Rune Toftgård of the Karolinska Institute, in Sweden, and his colleagues discovered long-lived stem cells in mouse hair follicles that are very active. Elaine Fuchs, head of the laboratory of mammalian cell biology and development at The Rockefeller University, who wasn’t involved in the study, termed Toftgård’s research “compelling.”
“Even when they’re out of their normal location, they still have stem-cell properties,” Toftgard says.
When the researchers isolated these cells and transplanted them onto the skin of hairless mice, the cells regenerated into complete follicles, which sprouted hair. While that might seem like a promising approach for filling in thinning human hair, Lloyd E. King of Vanderbilt University, who wasn’t involved in the work, says that human and mouse follicles are different enough that such treatments are “unlikely to happen soon.”
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