Deep roots. For a hair follicle to begin a new phase of growth, an elusive group of cells called the hair germ (bright red) must be activated. This progression of images shows that the hair germ begins proliferating (green) before other cells do, suggesting a two-step mechanism.
Research from Rockefeller University reveals that a structure at the base of each strand of hair, the hair follicle, uses a two-step mechanism to activate its stem cells and order them to divide. The mechanism provides insights into how repositories of stem cells may be organized in other body tissues for the purpose of supporting organ regeneration.
So understanding and fixing the stem cells and the replenishment of stem cells in hair follicles could lead to a baldness cure and also to human regeneration of organs.
“We discovered that the dynamics of the hair follicle regeneration is a two-step process,” says Valentina Greco, a visiting postdoctoral fellow who, along with postdoctoral associate Ting Chen, spearheaded the project. “The hair germ, which is in constant contact with the dermal papilla, gets activated first and the bulge is then called to contribute later during growth.”
“Because the germ is in closer proximity to the dermal papilla, it may achieve a threshold of stimulatory signals sooner than the bulge,” explains Fuchs, who is also a Howard Hughes Medical Institute investigator. Previous work by her team has shown that two inhibitory signals, known as Wnts and BMP, are needed for hair follicle stem cells to activate. They have now identified an additional activation signal, a growth factor called FGF7, that is made by the dermal papilla and steadily increases throughout the resting phase. “We think that FGF7 might contribute, along with the Wnts and BMP inhibitory signals, to coax the hair germ to divide and proliferate,” says Fuchs.
Fuchs and her team believe that this dual organization of the stem cell niche could apply to other organs. “It could be that the two-step process we’ve identified is needed to achieve optimal organ regeneration, not only in the skin but also in the blood and intestine,” says Greco. “These organs have slow- and fast-cycling cells — much like the hair germ and the bulge — and have the capacity to self-renew and regenerate.”