Paracrine TGFß Signaling Counterbalances BMP-Mediated Repression in Hair Follicle Stem Cell Activation

Hair follicle (HF) regeneration begins when communication between quiescent epithelial stem cells (SCs) and underlying mesenchymal dermal papillae (DP) generates sufficient activating cues to overcome repressive BMP signals from surrounding niche cells. We uncovered a hitherto unrecognized DP transmitter, TGFβ2, which activates Smad2/3 transiently in HFSCs concomitant with entry into tissue regeneration. We used microarrays to detect the genes specifically affected by TGFß receptor II-deficient mice upon HFSC activation. Hair follicle stem cells (HFSCs) of hair gem (HG) and bulge, and total skin keratinocytes were FACS-purified from the mouse back skin at 2nd telogen-to-anagen transition stages.