Effect of calcitonin-gene-related peptide on proliferation and osteogenesis in rat bone mesenchymal stem cells

Calcitonin-gene-related peptide (CGRP) is an important neurotransmitter in signaling pathways of osteogenesis in mature osteoblasts. The aim of this study was to investigate the function of CGRP in rat bone mesenchymal stem cells (rBMSCs) during the process of osteogenetic differentiation. CCK-8 method was adopted to test the effect of different concentrations of CGRP on rBMSCs proliferation and identify the optimal concentration of CGRP8-37 which was the antagonist of CGRP. PCR and Western blot were conducted to detect the mRNA and protein expression level of Ramp1 and CRLR. After osteogenic induction, alkaline phosphatase assay, Western blot and real-time qPCR were conducted to detect the protein of alkaline phosphatase (ALP), bone sialoprotein (BSP) and Runx2. Furthermore, Alizarin red staining and calciumion concentration measurement were used to test the differentiation and osteogenesis ability of rBMSCs in the later ossification differentiation period. Consequently, we found that receptors Ramp1 and CRLR of CGRP could be detected in rBMSCs. After osteogenic inducing culture, the expression levels of Runx2, ALP and BSP in rBMSCs were increased in CGRP groups compared with control groups, but the increase was attenuated in CGRP+CGRP8-37 and CGRP8-37 groups at both day 1 and 5. More mineral nodules and concentration of calcium ion were found in CGRP groups than other groups. Collectively, our findings suggest CGRP promotes the proliferation and osteogenic differentiation of BMSCs, but its receptor antagonist CGRP8-37 attenuates the effect.