Proteasome inhibitors stimulate both bone formation and hair growth by similar mechanisms.

We propose that the remodeling process that occurs in localized areas on endosteal bone surfaces and in Haversian canals shares many features in common with the mammalian hair cycle. In both, there are phases of resorption or regeneration, a transition phase, and then a phase of growth, termed anagen in the hair follicle, and formation in the bone remodeling cycle. Furthermore, we suggest that these processes both use the same molecular mechanisms, and specifically the Hedgehog-BMP-Wnt signal transduction cascades. We have found that proteasome inhibitors, which enhance bone formation by effects on these cascades, also stimulate anagen induction and hair growth in the murine and human hair follicle, and propose they do so by effects on similar or identical molecular targets.