1220 GMT April 20, 2019
One team, with members from Japan, the US and the Netherlands, found that accumulated DNA damage was at least partly to blame — the other team, working at the University of Colorado, discovered a certain protein that appears to be responsible for causing follicle stem cells to enter their dormant cycle, Medical Xpress reported.
Both teams have published papers in the journal Science, describing their studies and results. Mingxing Lei and Cheng-Ming Chuong with the University of Southern California offer a perspectives piece on the work done by the two teams in the same journal issue, and more fully explain the on/off growing cycle of scalp hair in mammals.
Understanding why people lose their hair as they age might benefit people looking to avoid baldness, but it might also offer a whole new understanding of the way that stem cells work. In one of the two studies, the researchers sought to find the answer to a question that plagues dermatologists and other researchers — is alopecia caused by environmental factors, or is it because of some internal mechanism? The team was not able to prove definitively that it is likely more due to the latter, but found strong evidence that suggests the root cause is accumulated damage to DNA over the course of many cell mutations. To come to that conclusions, they took skin samples from aged mice and found DNA damage had led to the breakdown of a protein called Collagen 17A1 and that led to follicle stem cells being transformed into a type of skin cell, which eventually got sloughed off. To find out if the same applied to humans, the researchers studied hair follicles taken from a large group of women between the ages 22 and 70. In addition to lower levels of Collagen 17A1, they also found that follicles were smaller in the older women.
To better understand the hair cycle, the second team of researchers focused on follicle stem cells during both phases of hair growth — the growing (anagen) and resting (telogen) phases — and in so doing they found that a protein called Foxc1 appeared to be the trigger for keeping hair growth dormant — when the gene that caused it to be expressed was removed, the follicles stayed in the 'on' phase indefinitely. Not a cure for baldness, of course, but certainly an interesting discovery.