Substance P has been observed to be increased in the lesions of both patients with FOP and with acquired HO.185 In a murine model of Achilles tendon HO formation, substance P delivery alone promoted HO formation and increased expression of BMP2; the addition of calcitonin gene‐related peptide (CGRP) in conjunction with substance P mitigated this effect. This evidence concerns the gene TAC1 and fibrodysplasia ossificans progressiva.