Effects of Different Concentrations of rhBMP-2 on Mandibular Distraction Osteogenesis and its OPG Expression in Rabbits

Objective To investigate the Effects of different concentrations of rhBMP-2 on mandibular distraction osteogenesis and the expression of OPG in the period of distraction osteogenesis.Methods Unilateral mandibular osteotomies were performed in 48 mature rabbit,1.5 mg rhBMP-2 or 3 mg rhBMP-2 with the collagen carrier were implanted in the osteotomy side of mandibles.Only collagen sponge was implanted in control group.the mandibles of 48 rabbits were lengthened by 4 mm using a distractor,The animals were killed on 1,3,7,14 days of consolidation period.The distracted calluses were harvested and processed for immunohistochemistry study of OPG.Results The regenerated bone was found in the distraction gap after mandibular lengthening.Staining of OPG was localized in osteoblasts cell of the periosteal region after completion of distraction.The mandibular side treated with 1.5 mg rhBMP-2 gained greater amount of new bone formation than treated with collagen sponge,and the mandibular side treated with 3 mg rhBMP-2 harvested greater amount of new bone formation than treated with 1.5 mg rhBMP-2.OPG expression was found in the cytoplasm of osteoblasts and stained brown or dark brown by immunohistochemistry.In the mean time,OPG expression indicated there was siganificant difference between rhBMP-2 group and control group(P0.05),and 3 mg rhBMP-2 group had siganificant difference comparing with 1.5 mg rhBMP-2 group(P0.05).Conclusions The animal experiment shows rhBMP-2 could accelerate bone formation of mandibular distraction osteogenesis in rabbit and was concentration-dependent.rhBMP-2 could increase the expression of OPG.