VEGF Modulates Angiogenesis and Osteogenesis in Shockwave-Promoted Fracture Healing in Rabbits

Abstract

Strong vascular endothelial growth factor (VEGF) expression of osteoprogenitors was found in callus site during fracture healing. The aim of this study was to investigate whether VEGF modulates the angiogenesis and osteogenesis in shockwave-promoted fracture healing in rabbits. Twenty-seven Japanese rabbits were used in the study. A fracture of left tibia with 5 mm gap was created, and the fracture was stabilized with an external fixator. The rabbits were randomly divided into three groups. Group I was the control group and received no shockwave therapy. Group II received shockwave therapy, and group III was pretreated with bevacizumab, a monoclonal antibody against VEGF, before receiving shockwave. Radiographs of the tibia were obtained at 1, 4, and 8 wk. Bone mineral density was performed at 8 wk. The rabbits were euthanized at 8 wk, and the bone specimens were subjected to histomorphological examination and immunohistochemical analysis. At 8 wk, radiographs showed considerably better bone healing and remodeling of the fracture in group II compared with groups I and III, whereas no discernable difference was noted between group I and group III. The BMD values were significantly higher in group II than groups I and III, but no difference noted between group I and group III. In histomorphological examination, significant increases in bone tissue was were noted in group II compared with groups I and III, but no difference was noted between group I and group III. In immunohistochemical analysis, significant increases in VEGF, vWF, PCNA, BMP-2 and osteocalcin, and a decrease in TUNEL expression were observed in group II compared with groups I and III, but no statistical difference was noted between group I and group III. Significant increases in VEGF and angiogenic and osteogenic growth factors were noted in shockwave-promoted bone healing. Pre-treatment with bevacizumab inhibited VEGF and in turn, attenuated the effect of shockwave. It appears that VEGF modulates angiogenesis and osteogenesis in shockwave-promoted bone healing in rabbits.