TGF-β1 Expression And Histological Changes In Condyle In Response To Bilateral Mandibular Distraction Osteogenesis Of Canine

Objective: To investigate the effect of the bilateral distraction osteogenesis on condylar cartilage. Methods: 16 adult hybrid dogs were randomly divided into normal control group (4dogs) and experiment group (12dogs). Experiment dogs were performed bilateral mandibular osteo-distraction at a rate of 1mm/day with 7 days latency. The mean lengthening achieved was 10 mm. In experiment group, every 4 dogs were sacrificed and the bilateral condyles specimens were harvested at different time points : the 6th day in distraction period, the 2nd and 8th week in neutral fixation after completion of 10 days distraction. The changes of histological and superficial ultrastructure were obvered. Immunohistochemical technique was used to detect the expresstion of TGF-beta1. Result: Compared with normal control group, various degrees of irregularities and erosion were found in fibrocartilage of condyle in experiment group, including damage in fibrous layer, hyperplasia in hypertrophic chondrocyte layer and proliferative layer and osteogenic activity in cartilage layer. By SEM, destroyed agglutinating substance and disappeared ripple structure on the surface of condyles were found in distraction groups, but the changes would become recovered over time. TGF-beta1 positive staining was noted in fibrous layer cell, hypertrophic chondrocyte matrix , chondroblast, osteoblast and matrix in osteogenic activity areas. Atotal significant difference of TGF- β1 expression in condyle was found in all groups (p<0. 05) . A significant increase of TGF-β1 expression in condyle was found in the group being neutral fixation 2 weeks after completion of distraction when compared with the other groups except for the group being neutral fixation 8 weeks after completion of distraction (p<0. 05). Conclusion: Gradual bilateral mandibular distraction at a rate of 1mm/day for 10 days brought remodeled changes of condyle, but the changes were reversible over time. TGF-β1 may participate in cartilage repairing during the distraction osteogenesis.