New activators and inhibitors in the hair cycle clock: targeting stem cells' state of competence.

J Invest Dermatol. 2012 May;132(5):1321-4. doi: 10.1038/jid.2012.38.
New activators and inhibitors in the hair cycle clock: targeting stem cells' state of competence.
Plikus MV.

Department of Dermatology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

The timing mechanism of the hair cycle remains poorly understood. However, it has become increasingly clear that the telogen-to-anagen transition is controlled jointly by at least the bone morphogenic protein (BMP), WNT, fibroblast growth factor (FGF), and transforming growth factor (TGF)-β signaling pathways. New research shows that Fgf18 signaling in hair follicle stem cells synergizes BMP-mediated refractivity, whereas Tgf-β2 signaling counterbalances it. Loss of Fgf18 signaling markedly accelerates anagen initiation, whereas loss of Tgf-β2 signaling significantly delays it, supporting key roles for these pathways in hair cycle timekeeping.