The Study Of The Expression Of Hepatocyte Growth Factor In Mandibular Distraction Osteogenesis

Objective 1. Distraction Osteogenesis (DO) was an important clinical technology developed in recent years, which had a great potential in clinical applications and gave us a new way to study the basic mechanisms of bone regeneration. For further research of DO, a kind of nicer animal model of mandibular distraction osteogenesis in rabbits was established and a feasible and reproducible way to construct the model was detected in this experiment.2. HGF were a kind of important receptor protein molecules, which plays an important role in many physiologic and pathologic courses. HGF had been found very important in vessels developing and bone absorption and other respects, but the affection of HGF in DO had not been reported yet. HGF can transmit and direct cells to combine with multiple components and other cells in tissue in order to manage cells'setting down, migration and differentiation. In this study, we were to investigate the expression and distribution of HGF in course of DO on the basis of the established DO animal model and to detect the action and mechanism about HGF in bone regeneration of DO, in order that we might find a new way to improve bone regeneration of DO.Methods 1.16 mature rabbits weighting between 3.3～3.5 kilograms were used in this study. Under general anesthesia, an incision on the skin along the inferior margin of mandible was performed. The soft tissue was separated and the surface of bone was exposed. Then mandibular osteotomy was done on the edentulous area about 1 mm before the first premolar. In operation,bone marrow and the inferior alveolar artery should be carefully protected. The cut bone was fixed by a self-prepared bilateral extra-oral bone-supported distractor. Then periosteum was sutured and the wound was closed seriously. The bone stumps were fixed in situ for 7 days after operation(latency period), then distractors were activated at a speed of 0.25 millimeter every 6hours for 7 days before they were fixed(consolidation period). Four rabbits were killed randomly at the end of latency period, the end of distraction, the 14th and 28th day of consolidation period separately.2.44 adult New Zealand white rabbits were selected and divided randomly into 3 groups:DO, bone fracture and normal group. There were 20,20 and 4 rabbits in each group separately. DO models were made according to the method mentioned above. Bone fracture models were established in the same way with DO but not been distracted. Animals were killed and specimens were taken. Distribution and expression of HGF were observed by H-SCORE semi-quantitative technique, and the results were managed with statistic methods.Results 1. All animals' mandibles were prolonged successfully. The distraction gaps were found padded with neogenesis bone tissue gradually under X-ray examination. Histology section:Fibroblasts were found arranged along the direction of the tensile force after distraction.The medial and distal cortices of the gaps were connected with osteotyluses at the end of the latency period. At the side of the fibrous zone, neogenetic bone tissue was found formatted near the cortex of the bone stumps and marrow cavities. At the 14th day of the consolidation period, more bone trabeculae and less fibrous tissue were seen in the distraction zone. To the 28th day of consolidation period, calcified bone trabecula can be found in the center of the fissure, and neogenetic bone trabeculae were replaced by lamellar bone. Intramembranous ossification is the main manner of the osteogenesis during DO.2. The expression of HGF was found both in the DO and bone fracture groups. The expression of HGF on OC was seen only early after operation. Normal bone tissue was found no positive staining. The expression of HGF in the DO and bone fracture groups were found a week after operation and raised to the peak value at the 2nd or 3rd weeks post operation and then declined gradually to normal. The staining intensity of group of DO was higher than that of the bone fracture group. Conclusions 1.In this experiment, the animal model of bilateral mandibular distraction osteogenesis in rabbits was well established, which can be easily repeated. In the meanwhile, two different interventions can be applied on both sides of the mandible in this model. The model is very useful for further study of DO.2. Tension force may be one of the mechanisms which can activate the expression of HGF. HGF play an important role in promoting angiopoiesis of DO by transmitting and directing EC to adhere to ECM.