| Tissue engineering is a rapidly advanced field, which provide a new methods for bone defect reconstruction and spinal fusion. Bone mesenchymal stem cells contribute to the regeneration of mesenchymal tissues such as bone, cartilage, muscle, ligament, tendon, et al.The ideal scaffold materials of tissue engineering should have the good biocompatibility, proper biodegradation, porous structure and proper mechanical function, which will meet the need of the cells adhesiveness, growth, proliferation and differentiation. In this study, we choose BMSCs as seed cells and tricalcium phosphate as scaffold materials which had been proven excellent in bone tissue engineering. Objective:To investigate the methods of the proliferative and osteogenic activity of rabbits bone marrow mesenchymal stem cells in vitro, the osteogenic ability of tissue bone made of BMSCs and tricalcium phosphate composites, and the efficiency of tissue bone as bone graft substitute for posterior thoracic spinal fusion. Materials and methods:Study 1: Bone marrow was obtained from in New Zealand rabbits. Bone marrow stromal cells were separated from the bone marrow and cultured in DMEM conditional medium(containing dexamathasone, 3-glycerophosphate and L-ascorbic acid). The biological characteristics of cells were examined by phase-contrast microscopy, tansmission electron microscope, ALP stain type I collagen stain and Von Kossa calcium stain.Study 2: To constructe tissue bone choosing the BMSCs as the seed cells and the tricalcium phosphate as the scaffold materials. After 4 weeks ,12 weeks, the materials was taken out to do the histological examination so as to evaluate the osteogenesis of tissue bone.Study 3: Posterior thoracic spine fusion was carried out in 60 White New Zealand rabbits using one of the following graft materials: TCP granules plus cultured MSCs(group I); TCP granules plus fresh autogenous bone marrow(group);TCP granules alone(group I); and autogenous bone graft(group IV). The 12 rabbits(3 rabbits every group) were killed for histological analysis 4 weeks after surgery, and all the rest rabbits were killed 12 weeks after surgery to underwent the evaluation of radiography, computed tomography, manual palpation and histologic analysis. Results:Study I: The passage cultured BMSCs have multi-configuration changed from spindle-shaped appearance to a polygonal shape; In the earlier stage had the tendency to be the character of fibroblasts, and gradually transformed into multiplayer structure, contact inhibition was not observed. The cells showed positive reaction by ALP staining, type I immunohistochemical staining and Von Kossa calcium stain. Theosteoblasts.Study II: The tissue bone made from BMSCs -tricalcium phosphate composites produced new bone in 4 weeks and more in 10 weeks after surgery.Study III: The passage cultured BMSCs have multi-configuration changed from spindle-shaped appearance to a polygonal shape; In the earlier stage had the tendency to be the character of fibroblasts, and gradually transformed into multiplayer structure, contact inhibition was not observed. The cells showed positive reaction by ALP staining, type I immunohistochemical staining and Von Kossa calcium stain. The morphological characteristics and functions of cultured cells were similar to those of osteoblasts.The tissue bone made from BMSCs -tricalcium phosphate composites produced new bone in 4 weeks and 12 weeks respectively. The rate of fusion was significantly higher in group compared with group, group and group ; In group and group histological analysis showed abundance newly formed bone in contact with the implanted granules, but relatively little new bone formation in group In group, there were a reduced amount of newly formed bone and abundant fibrous tissue. In group , there were thin trabeculae of newly formed bone closed to the decorticated lamina and dead trabecular bone in the outer portion of the fusion mass. Conclusion:Bone marrow stromal cells can differentiate and proliferate to osteoblast phenotype when cultured...
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