| objective 1. To study the cellular biocompatibility and in vitro adhesion between a new type PLGA scaffold and bone marrow stem cells(BMSCs)so as to provide a basis for the preparation of scaffolds that can load many factors.2. To construct tissue engineering bone with BMSCs and PLGA scafford loading BMP, and to investingate the effect of this tissue engineering bone implants on healing of segmental bone defects.3. To investigate the dose-effect correlation between tissue engineering bone loading BMP at different densities and new bone formation in vivo.Methods 1. The bone marrow was aspirated from the ilia of some 2-months old New Zealand Rabbits,Adherent cells were selected as BMSCs after whole marrow was cultured.There were 3 groups of experiments:PLGA group, β —TCP group and control group.BMSCs were Inoculated onto the PLGA and β —TCP with a concentration of 1 × 10~6 / ml.The implanted cells and materials were retrieved and observed at different times with phase contrast microscope,scaning electron microscope,and flow cytometry(FCM).the proliferation and alkaline phosohatase activity were tested.2. A 15mm bone defect experimental model in the right radius of New Zealand white rabbit was made,the animals were divided into three groups at random, BMP 5mg with PLGA carrier and about 1×10~6 BMSCs was implanted in the experimental group, PLGA and about 1×10~6 BMSCs was implanted in the control group,and onlyPLGAwas planted in the blank group. The osteogenesis of the bone in the defect area was observed by regular roentgenography, the histological changes of the bone defect tissue in 4th, 8th, 12th week after operation were studied and the new bone formation was measured by image analysis.3. A 15mm bone defect experimental model at the right radius of New Zealand rabbit was made. 24 animals of this model were divided into three groups at random. PLGA scaffords loaded with 5mg BMP and about 1X 106BMSCs were implanted in Group 1(10 rabbits); PLGA scaffords loaded with 2.5mg BMP and about 1X106 BMSCs were implanted in Group 2(7 rabbits); PLGA scaffords loaded with lmg BMP and about 1 X 106 BMSCs were implanted in Group 3(7 rabbits). The osteogenesis at the defect area was observed by regular roentgenography, Histological changes at the bone defects at 4th, 8th, 12th weeks after operation were studied and the new bone formation was measured by image analysis. Biomechanical analysis was done 12 weeks after operation.Results 1. BMSCs adhered well to PLGA and P -TCP, the PLGA scaffold has no obviously effect on cell proliferation and cell cycle.2. The results revealed that the bone defect in the experimental group had best repaired that seen in the control and blank group, there was only fibration in the blank group at 12th week.3. A large quantity of callus was found in all the 3 groups 4 weeks after repair. At the 12th week, the complete bone healing rate was 7/8, 3/5, 3/5, respectively in Group 1, 2 and 3. Group 1 had the largest quantity of new bone measured by histopathological study and X-ray analysis, and at the 12th week,the medullary cavity in this group became united. The compress stiffness. Torsion stiffness and the maximal load were better than those in other groups.Conclusions 1. This PLGA scaffold possesses good cellular biocompatibility, and it can be used as a carrier of many factors in bone tissue engineering.2. This tissue engineering bone constructed by BMSCs and PLGA scafford thatloaded with 5mg BMP is capable of repairing segmental bone defect.3. The tissue engineering bone constructed by BMSCs and PLGA scaffords that loaded with 5mg BMP is more capable of repairing segmental bone defect than the 2.5mg group and lmg group, the best concentration of BMP in PLGA scafford is 4 X l(T2mg/mlii3...
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