Activation of CGRP receptor-mediated signaling promotes tendon-bone healing.

Abstract

Calcitonin gene-related peptide (CGRP), an osteopromotive neurotransmitter with a short half-life, shows increase while calcitonin receptor-like (CALCRL) level is decreased at the early stage in bone fractures. Therefore, the activation of CALCRL-mediated signaling may be more critical to promote the tendon-bone healing. We found CGRP enhanced osteogenic differentiation of BMSCs through PKA/CREB/JUNB pathway, contributing to improved sonic hedgehog (SHH) expression, which was verified at the tendon-bone interface (TBI) in the mice with <i>Calcrl</i> overexpression. The osteoblast-derived SHH and slit guidance ligand 3 were reported to favor nerve regeneration and type H (CD31^hiEMCN^hi) vessel formation, respectively. Encouragingly, the activation or inactivation of CALCRL-mediated signaling significantly increased or decreased intensity of type H vessel and nerve fiber at the TBI, respectively. Simultaneously, improved gait characteristics and biomechanical performance were observed in the <i>Calcrl</i> overexpression group. Together, the gene therapy targeting CGRP receptor may be a therapeutic strategy in sports medicine.