Recapitulation of the parathyroid hormone‐related peptide–Indian hedgehog pathway in the regenerating deer antler

Parathyroid hormone (PTH)‐related peptide (PTHrP) and the PTH/PTHrP receptor (PPR) play an essential role in controlling growth plate development. The aim of the present study was to use the deer antler as a model to determine whether PTHrP and PPR may also have a function in regulating cartilage and bone regeneration in an adult mammal. Antlers are the only mammalian appendages that are able to undergo repeated cycles of regeneration, and their growth from a blastema involves a modified endochondral process. Immunohistochemistry was used to establish sites of localization of PTHrP and PPR in antlers at different stages of development. The pattern of Indian Hedgehog (IHH) and transforming growth factor‐beta1 (TGFβ1) distribution was also investigated, because PTHrP expression in the developing limb is regulated by IHH and during embryonic growth plate formation TGFβ1 acts upstream of PTHrP to regulate the rate of chondrocyte differentiation. In the antler blastema (