Experimental Study On Repair Of Mandible Defects By Bone Marrow Derived Osteoblasts Combined With Demineralized Bone In Rabbits

Objective To investigate the osteogenetic capability and effect of tissue engineering bone in repairing mandible defects in rabbits, which was constructed by autogenous bone marrow derived osteoblasts and allogeneic demineralized bone.Methods The bone marrow derived osteoblasts of 20 New Zealand white rabbits were isolated, cultured and proliferated then seeded into the demineralized bone to construct tissue-engineering bone in vitro. The tissue engineering bone and demineralized bone were used respectively to repair the mandible defects in rabbits, and the latter was as the control. The bone formation was evaluated grossly, radiographically, histologically at 2, 4,8,12 weeks after transplantation. The relative bone density of defects in experimental and control sides were recorded and compared by using the computer analysis system on the x-ray image.Results Gross observation showed that the process of new bone growth in control defect was lagged when compared with experimental defect. At the 12th week the defect in experimental side was completely filled with new bone .In the 12-week control implant, partial defect was remained at the inferior margin. Radiographically, at the second week, both of experimental and control defect were radiolucent in the x-ray image, but the experimental defect had higher density and presented little bone callus image at the marginal region. At the 4th week, bone callus image presented in the marginal and center region of experimental defect, and the bone callus image increased greatly and had higher density at the 8th week. At the 12th week, the experimental defect was filled with bone callus image. In the control defect, spot-like bone callus image presented in the marginal region of defect at the 4th week. At the8th week, the region of bone callus image connected and increased. At the 12th week, higher density was observed, but a radiolucent region remained in the inferior part of defect far away from the host bone. There was statistically significant difference (P<0.05) between the relative density of the experimental defect and the control defect at the each time point within the four groups. Histologically, in the 2-week implant of experimental side, there was newly formation bone tissue in the center of implant with large amounts of bone trabecula from the host bone penetrated into the implant. In the 4-week implant and 8-week implant of experimental side, the new trabecular bone developed towards lamellar bone at center region. At the 12th week, the new bone was similar to host bone .In the control implant, the major osteogenetic pattern was "creeping substitute". There was a large amount of fibrous tissue growing between new bone and demineralized bone during new bone formation.Conclusion The tissue engineering bone constructed by autogenous bone marrow derived osteoblasts and allogeneic demineralized bone has the capability of osteogenesis, osteoconduction and osteoinduction with better osteogenetic effect and quality than demineralized bone implant, and is an ideal graft in repair of mandible defects.