Effects of exogenous nerve growth factor on the expression of BMP-9 and VEGF in the healing of rabbit mandible fracture with local nerve injury

Abstract Background The fracture of mandible remains one of the most facial fractures and its healing is a complex process, involving nerve and growth factors. Currently, nerve growth factor not only benefits maintenance of sympathetic neurite growth, but also takes part in intricate regulatory network to stimulate other growth factors such as bone growth protein and vascular endothelial growth factor, which promote together essential osteogenesis and angiogenesis to physiological bone formation, growth and fracture healing. Therefore, it is necessary to analysis the combination of nerve growth factor, bone growth protein-9 and vascular endothelial growth factor to accelerate healing rate of mandible fracture. Methods The models of mandible fracture with local nerve injury established in forty-eight rabbits were randomly divided into nerve growth factor group (NGF group), gelatin sponge group (GS group), blank group and intact group with 12 rabbits in each group. The fracture healing was observed with visual and X-ray after the operation, then callus tissue in mandibular fracture area were collected for HE staining observation, and quantitative RT-PCR was used to detect the expression of BMP-9 and VEGF in callus at different stages. Results The combined results of macroscopic observation, X-ray examination and histological section showed that a large number of osteoblasts and some vascular endothelial cells were found around the trabecular bone in NGF group and the amount of callus formation and reconstruction were better than GS group at 2th weeks after the operation. Quantitative RT-PCR result indicated that the expression levels of BMP-9 mRNA and VEGF mRNA in the four groups reached the highest value at the second week, and then decreased with time. At the same time, the content of BMP-9 and VEGF in callus tissue in mandibular fracture area increased significantly in NGF group than GS group. Conclusion The exogenous NGF could improve the expressions of BMP-9 and VEGF in the early stage of mandibular fracture to accelerate healing of mandible fracture. This work provides a new foundation and theoretical basis to make clear mechanism of fracture healing, thereby promoting patients’ fracture healing and reducing their disability rate.