Hair-Cycle-Dependent Expression of Parathyroid Hormone-Related Protein and Its Type I Receptor: Evidence for Regulation at the Anagen to Catagen Transition

The document from 2003 reported that parathyroid hormone-related protein (PTHrP) and its type I receptor (PTH1R) are involved in the regulation of the hair cycle in mice, particularly at the transition from the growth phase (anagen) to the regression phase (catagen). PTHrP expression was found to be dynamically regulated by the hair cycle and was not present in the interfollicular epidermis. PTH1R expression was also dependent on the hair cycle and was found in the developing dermis. Overexpression of PTHrP in transgenic mice resulted in hair that was 30-40% shorter due to premature entry into the catagen phase. Additionally, cross-breeding experiments with fibroblast growth factor-5-knockout mice indicated that PTHrP and fibroblast growth factor-5 regulate the anagen to catagen transition independently. This study suggests that PTHrP signaling is significant in hair follicle biology and could be a target for treating hair growth disorders.