The hair follicle, at the base of each hair strand is like a mini-dispensable organ. Throughout our lifetime each hair follicle follows a cycle of growth, destruction and rest using an intrinsic stem cell population. Hair growth occurs through a two-step regeneration process.
There are signals namely Wnts, BMP, FGF7 which activate the hair follicle stem cells. One group of stem cells are located in a small compartment called the bulge. Another small cluster of stem cells are situated at the bottom of the bulge called the hair germ.
Germ is molecularly similar to bulge suggesting it to be originating from the bulge. After the end of the resting phase of the hair cycle activating signal generated from the dermal papilla causes germ cells to proliferate first and contribute to hair growth. In the second step of regeneration process the bulge cells start dividing.
The researchers at the Rockefeller University believe that this two-step regeneration process of the stem cell niche not only applies to the skin but also to other organs such as intestine.