Background: Calcitonin gene-related peptide (CGRP) is a neuropeptide distributed in bone tissue involved in bone remodeling. Previously we demonstrated that CGRP can promote proliferation and migration of endothelial cells, relating to the expression of vascular endothelial growth factor (VEGF) and focal adhesion kinase (FAK).
Methods: CGRP1 receptor expression in human umbilical vein endothelial cells (HUVECs) was examined by immunofluorescence microscopy and real-time PCR. Tube formation was measured by a Matrigel tube formation assay. VEGF protein and mRNA levels were quantified by ELISA and real-time PCR, respectively. The expression of VEGF receptor 1 (FLT1) and VEGF receptor 2 (KDR) were measured by real-time PCR and immunoblotting assays.
Results: CGRP significantly induced vascular tube formation of outgrowth HUVECs in a Matrigel. The expression of FLT and KDR were significantly increased by CGRP, and CGRP enhanced the expression of CGRP1 receptors. Compared to the known angiogenesis regulator VEGF(165), CGRP had an equal or stronger effect on migration and tube formation, but not on proliferation of endothelial cells. The upregulation of calcitonin receptor-like receptor (CRLR), FAK, VEGF and its two main receptors (FLT1, KDR) by CGRP was also more pronounced than that obtained by VEGF(165).
Conclusion: It is concluded that CGRP is a strong proangiogenic growth factor, thereby contributing to bone development and remodeling by promoting angiogenesis.