The Study Of Establishing Animal Models Of Rabbit Mandibular Do With Gene-treatment And The Evaluation Of Regenerated Bone

Objectives:To establish animal models of rabbit mandibular distraction osteogenesis (DO) with bone mesenchymal stem cells(BMSCs)modifled with human bone morphogenetic protein-2(hBMP-2) gene. Research if there is stimulative effect of the gene therapy to the rabbit mandibular led a osteogenesis new bone formation. It will provide a theoretical basis for the sdudy of how to shorten the treatment cycle of DO.Materials and Methods:Thirty-six healthy adult New Zealand white rabbits were randomly divided into three groups with twelve in each, the experimental group (injected with autogenous MSCs modified with hBMP-2gene)、the positive control group(injected with autogenous MSCs) and the negative control group(injected with saline solution). All the right mandibles’cortical bone of the objects were completely disconnected and osteotomized as DO animal models with a small distractor installed in each. After a six-day latency, the distractors were activated at a rate of1.0mm/d, adding to7.0mm totally before consolidation. On the first day of consolidation period, the experimental group objects were injected with200μL autogenous MSCs modified with hBMP-2gene in the distraction gap, while the positive and negative control group was injected with200μL autogenous MSCs and saline solution, respectively. the rabbits were sacrificed respectively in the2nd and6th week of consolidation thus the bone regeneration of three groups can be further compared and analyzed through different methods such as radiological records were taken for bone healing evaluation, hematoxylin-eosin (HE) staining to compare the situation of regenerated bone, testing the Ca/P ratios to compare the degree of mineralization,and three-point bend testing was used to measure the mechanical strength of the bone regeneration of each group.Results:Experiment was successfully completed on all the objects. the rabbits were sacrificed respectively in the2nd and6th week of consolidation Specimens were harvested and processed for radiography, higher X-ray image density in the distracted area than the positive and negative control groups, but there was no significant difference between the positive and negative control groups; All groups’ new bone X-ray image density in the distracted area increases along with the consolidation period prolonged. HE staining observed that the new trabeculae of the experimental group appeared and matured earlier than the other two groups.The mean Ca/P ratios in the regenerated bone in the distracted callus for three groups at2or6weeks after distraction shown that the experimental group were significantly higher than the positive and negative control groups, the positive group had no significant difference when compared with the negative control group; The mechanical strength in the experimental group was greater than that in the positive and negative control groups by three-point bending testing. Conclusions: Surgical model of rabbit mandibular DO with hBMP-2-gene-modified autogenous BMSCs is practicable. Bone regeneration in distracted area of the experimental group injected with hBMP-2-gene-modified autogenous BMSCs happens faster than in the blank group, proving that autogenous MSCs modified by hBMP-2gene can effectively promote bone regeneration of rabbit mandibular DO, which will provide an experimental basis to shorten DO treatment cycle in clinic.