Abstract: Objective: To prepare the velvet antler polypeptide-collagen/chitosan composite materials, and to investigate its promotive effect on cicatrization of mandibular defect and possible mechanism. Methods: The collagen and chitosan solution were mixed.The composite material was prepared by glutaraldehyde crosslinking method.The microstructure of the composite material was observed by transmission electron microscope (SEM).The unilateral mandibular defect models of 36 rabbits were established.The rabbits were divided into experiment and control groups,and each group was divided into 4-,8-and 12-week subgroups, and there were 6 rabbits in each sub group.The rabbits in experiment group were implanted with velvet antler polypeptide-collagen/chitosan composite materials and the rabbits in control group were treated.4,8 and 12 weeks after operation,the histology of bone defect and peripheral nerve reconstruction of the rabbit models were detected by CT; the expression of vascular endothelial growth factor (VEGF) in bone tissue of the rabbits was detected by immunohistochemistry;the ultrastructure of bone defect was observed by SEM. Results: The structure of composite materials had layered folds and the inner diameter of the stent became larger and mainly dominated by sheet structure,which was the ideal structure of biological materials.4 weeks after operation,the new bone was formatted in experiment group,most of the new bone like-tissue materials were degraded,and the VEGF expression showed an increasing trend; 8 weeks after operation,the trabecular bone in the bone defect of the rabbits in experiment group was increased obviously and the expression of VEGF was decreased.12 weeks after operation,the new bone formation and the density in experiment group was consistent with the normal tissue,and the expression level of VEGF returned to normal.At each the point after operation,the degree of bone defect healing and bone formation rate in experiment group were obviously prior to control group. Conclusion: Velvet antler polypeptide-collagen/chitosan composite material has the promotive effect on the fracture healing of mandibular defect of the rabbits and its possible mechanism may be related to promoting the expression of VEGF.

Key words: mandibular defect, vascular endothelial growth factor, bone tissue engineering, velvet antler polypeptide