Combined Administration of BMP-2 and HGF Facilitate Bone Regeneration through Angiogenic Mechanisms

Abstract

Promotion of bone repair contributes to the shortening of the treatment period and improvement of the therapeutic effect in large bone defects. The purpose of the present study was to determine the optimal condition for the administration of growth factors to facilitate bone repair and explore the significance of angiogenesis in bone regeneration in vivo. Critical-size calvarial defects were created in the parietal bones of adult ddY mice, and the defects were treated with gelatin sponges impregnated with growth factors BMP-2, FGF-2, and HGF, alone or in combination. The bone regeneration at 1, 2, 3, and 4 weeks was evaluated using micro-computed tomography and histological observation. Critical-size calvarial defects were also created in Flk1-GFP mice to analyze angiogenesis in the early phase of bone repair. The proliferation of Flk1-GFP positive endothelial cells during bone repair was quantitatively evaluated using immunohistochemistry for Ki67. Treatment with a combination of BMP-2 and HGF (BMP-2+HGF) significantly induced more new bone formation within the bone defects compared with the other groups. Compared with BMP-2 alone, bone regeneration was rapidly increased by BMP-2+HGF from 3 weeks of the beginning of the treatment. The number of FLK1-GFP and Ki67 double positive cells in the defect areas of mice administered BMP-2+HGF at 1 week was larger than that in those administered BMP-2 alone. These results indicate that the combination of BMP-2 and HGF was markedly efficient in bone regeneration due to the promotion of angiogenesis in the early phase of bone repair.