With enough time, every blonde, brunette, and redhead goes silver, but scientists had been unable to pin down the cellular basis behind gray hair. By examining two strains of mutant mice, however, researchers finally have unveiled a root cause for this inevitable part of aging.
Mice with mutations in either of two genes, known as Bcl2 and Mitf, go gray months faster than normal mice. After analyzing hair follicles from both mutant strains, David Fisher and his colleagues at Harvard Medical School in Boston found some telling activity in stem cells within each follicle's base.
These stem cells are responsible for producing melanocytes, a type of cell that manufactures and stores the pigment in hair and skin. As the rodents aged and their hair began turning gray, the melanocyte stem cells gradually died off inside each follicle, Fisher's team reports. Additionally, some stem cells began differentiating into melanocytes while still within the base of a follicle instead of after migrating into the follicle's bulb, as they do in mice that go gray later. In a follicle's base, the melanocytes are useless for coloring hair.
The researchers found a similar mechanism at work in the gray hairs of normal mice and in people.
While the findings, slated to appear in an upcoming Science, may eventually lead scientists to a graying-prevention scheme, Fisher says that his interest is "not on the cosmetic." Instead, he and his coworkers have set their sights on new treatments for melanoma, a skin cancer caused by melanocytes multiplying uncontrollably.
David E. Fisher
Department of Pediatric Hematology/Oncology
Melanoma Program in Medical Oncology
Dana-Farber Cancer Institute
44 Binney Street
Boston, MA 02115