αCGRP Regulates Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells Through ERK1/2 and p38 MAPK Signaling Pathways

As a typical neuropeptide richly distributed in central and peripheral nervous systems, alpha-calcitonin-gene-related peptide (alpha CGRP) has recently been found to play a crucial role in bone development and metabolism, but the mechanisms involved are not fully uncovered. Here, this study aimed to investigate the effects and underlying molecular mechanisms of alpha CGRP in regulating the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Using microarray technology, gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) analyses revealed that osteogenic properties of BMSCs were facilitated and mitogen-activated protein kinase (MAPK) signaling pathway was upregulated by alpha CGRP in this process. Through western blot assay, we proved that alpha CGRP led to an increased phosphorylation level of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 MAPK signaling cascades in a time-dependent manner. And alpha CGRP could promote differentiative capacity of BMSCs, showing upregulated mRNA and protein expression level of alkaline phosphatase (Alp), collagen type 1 (Col-1), osteopontin (Opn), and runt-related transcription factor 2 (Runx2), as well as increased ALP activity and calcified nodules. The addition of ERK1/2 or p38 MAPK inhibitor-U0126 or SB203580, resulted in an impaired osteogenic differentiation of BMSCs. Besides, inactivation of this signal transduction had negative impacts on proliferative activity and apoptotic process of alpha CGRP-mediated BMSCs. Our findings demonstrated that MAPK signaling pathway, at least in part, was responsible for the enhanced BMSCs' osteogenesis induced by alpha CGRP, which might offer us promising strategies for bone-related disorders.