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BMPER Enhances Bone Formation by Promoting the Osteogenesis-Angiogenesis Coupling Process in Mesenchymal Stem Cells

Background/Aims: During bone repair and remodeling, osteogenesis is coupled with angiogenesis. Bone morphogenetic protein (BMP) antagonists are important modulators of BMP signaling and bone homeostasis. Several investigations have demonstrated that one ‘BMP antagonist’, BMP-binding endothelial cell precursor-derived regulator (BMPER), participates in the regulation of BMP signaling. In this study, we examined the role of BMPER in the osteogenesis-angiogenesis coupling process. Methods: Human bone mesenchymal stem cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs) were used in this experiment. After overexpressing or silencing BMPER with lentiviruses or siRNA, hBMSCs were stimulated by BMP-2, and osteogenic differentiation activity was detected by alkaline phosphatase and alizarin red staining. VEGF and endostatin release were assessed by ELISA. HUVEC migration was detected by the cell scratch test and transwell migration assay, and in vitro angiogenesis was determined by the tube formation assay. Bone formation was assessed using in vivo femoral monocortical defect and ectopic bone formation models. Results: BMP-2 upregulated BMPER expression. Overexpression of BMPER remarkably enhanced BMP-2-induced osteogenic differentiation, while suppression of BMPER effectively inhibited this process both in vitro and in vivo. In addition, overexpression of BMPER promoted BMP-2-induced VEGF expression in vitro and vascularization in the ectopic bone formation model. Conclusion: BMPER functions as a positive regulator of the osteogenesis-angiogenesis coupling process in hBMSCs, suggesting a novel therapeutic role of BMPER in the regenerative capacity of bone repair.