Experimental Studies On Injectable Chitosan/β-TCP/rhBMP-2 Composite In Repairing The Rabbit Mandible Defects

Objective:To evaluate the repaired efficacy and mechanism of scaffolds for chitosan / beta-Tricalcium phosphate(CS/β-TCP) as an injectable bone tissue engineering scaffold material of recombinant human bone morphogenetic protein(rhBMP-2) on mandible of rabbits.To approach the possibilities of applications as an injectable bone surrogate and provide theoretical evidence for the clinical practices.Methods:Twenty-four healthy New Zealand White Rabbits were selected,and the 15 mm×6 mm bilateral mandibular defects were made by dental drill.Then the animals were randomly divided into 4 groups composed of CS/β-TCP /rhBMP-2 group,CS/β-TCP group,autograft group and blank contrast group,the defects were made synchronously,implanted with differert materials according to different groups. 2,4 and 8 weeks after operation the specimen were harvested and examined by gross observation,X-ray observation,histological observation,including hematoxylin eosin (HE) staining,collagenⅠ(COLⅠ)immunochemical staining and scanning electron microscope(SEM) and Statistical analysis of images.Result:(1)Gross observation demonstrated that the size and thickness of osteotylus in every defect increased gradually.And,in every experimental time,the size of osteotyluses in CS/β-TCP/rhBMP-2 group is equivalent with autograft group,there were more osteotyluses than others.(2)X-ray observation demonstrated that the area of photic zone in every group diminished gradually.2 weeks after operation,there were some opacity areas in the edge and the center of the recovery area in CS/β-TCP/rhBMP-2 group and autograft group,4 weeks after operation,there were some opacity areas in the center of the recotery area in CS/β-TCP group and BC group,8 weeks after operation,there was no photic zone in CS/β-TCP/rhBMP-2 group and autograft group,while,the photic zone in other groups also decreased.(3)Histological observation demonstrated that,in every experimental time, there were more bone matrixs in CS/β-TCP/rhBMP-2 group and autograft group than which in CS/β-TCP group and BC group.The bone matrixs in CS/β-TCP/rhBMP-2 group have not significant difference with autograft group.There are least bone matrixs in BC group.(4) The bone density of each group gradually increased with time.The bone density of CS/β-TCP/rhBMP-2 group was significant difference from CS/β-TCP group and BC group.(5) ESEM demonstrated that,4 weeks after operation,the bone bed and the materials were connected with fibrous bone,the materials degraded.8 weeks after operation,the bone bed and the materials in CS/β-TCP/rhBMP-2 group were connected with bone,the gap between them disminished,the degradation of the materials were so obvious that the complete structure of materials couldn't be found.(6) Statistical analysis of images demonstrated that,There was significant difference among the areas of bone regeneration of all groups(F=53.292 P=0.000).There was no significant differentce between CS/β-TCP/rhBMP-2 group(Mean=22.96%) and autograft group (Mean=22.63%).The two groups was better than blank contrast group (Mean=10.35%) and CS/β-TCP group(Mean=10.73%).There was significant differentce among all weeks,the proportion of area of bone regeneration increased with time.Conclusion:Osteogenic effect of injectable CS/β-TCP/rhBMP-2 composite in repairing the rabbit mandible defects is considerable with autograft group.CS/β-TCP/rhBMP-2 group,which compared with CS/β-TCP group and blank contrast group,could advance the reparative process of bone defect,promote the earlier period healing,which had good foreground of clinical application.