聚己内酯/β-磷酸三钙支架联合骨髓间充质干细胞与骨形态发生蛋白2修复股骨缺损OA

BACKGROUND:Polycaprolactone/β-tricalcium phosphate composite materials have shown good potential in bone tissue engineering,but the effect of their combined application with bone marrow mesenchymal stem cells and bone morphogenetic protein-2 for repairing large segmental bone defects needs systematic evaluation. OBJECTIVE:To investigate the in vitro osteogenic efficacy of 3D printed polycaprolactone/β-tricalcium phosphate scaffolds alone and in combination with bone marrow mesenchymal stem cells and bone morphogenetic protein-2,as well as their in vivo effect on the repair of large segmental femoral defects in rats. METHODS:Cylindrical polycaprolactone/β-tricalcium phosphate composite scaffolds(4 mm in diameter,6 mm in height)with a pore size of 500 μm and a porosity of 70％were prepared using fused deposition modeling 3D printing technology.Third-passage allogeneic rat bone marrow mesenchymal stem cells were seeded onto the scaffolds at a concentration of 1×106 cells/scaffold and cultured for 24 hours.Recombinant human bone morphogenetic protein-2(10 μg/scaffold)was loaded onto the scaffolds using a surface adsorption-freeze-drying method.Scaffold morphology,cytocompatibility,and osteogenic performance were detected in vitro.Rat models of mid-femoral large segmental bone defect(6 mm)were established and randomly divided into four groups(n=10 per group):polycaprolactone/β-tricalcium phosphate scaffold alone group(Group A),polycaprolactone/β-tricalcium phosphate scaffold+bone marrow mesenchymal stem cells group(Group B),polycaprolactone/β-tricalcium phosphate scaffold+bone morphogenetic protein-2 group(Group C),and polycaprolactone/β-tricalcium phosphate scaffold+bone marrow mesenchymal stem cells+bone morphogenetic protein-2 group(Group D).Postoperative general condition and survival rate of animals were observed.Specimens were collected at 4 and 8 weeks after surgery.Bone volume fraction and trabecular parameters were analyzed by Micro-CT scanning.Compressive strength and compressive modulusof the femur were detected bycompression test.New bone tissue morphology was observed by hematoxylin-eosin staining and Masson's trichrome staining.Runt-related transcription factor 2 expression was detected by immunofluorescence staining. RESULTS AND CONCLUSION:(1)One rat in Group A died due to deep anesthesia,and one rat in Group C was excluded due to incision infection.All rats in Groups B and D survived.(2)At 4 weeks after surgery,continuous callus bridging was observed in the bone defect area of Group D,and bone volume fraction and bone mineral density were higher than those in the other groups(P＜0.05).At 8 weeks after surgery,bone defects in Group D were completely healed,the bone volume fraction was significantly higher than that in Groups A,B,and C(all P＜0.05),the compressive strength recovered to approximately 75％of normal femur,and the compressive modulus recovered to approximately 68％.(3)Hematoxylin-eosin and Masson staining showed that the new bone trabeculae in Group D were thick and orderly arranged,with mature lamellar bone structure.The percentage of Runt-related transcription factor 2 immunofluorescence positive area and the expression levels of osteogenic genes(Runt-related transcription factor 2 and type Ⅰ collagen)were highest in Group D(P＜0.05).Overall,these findings indicate that polycaprolactone/β-tricalcium phosphate scaffold combined with bone marrow mesenchymal stem cells and bone morphogenetic protein-2 synergistically promotes early bridging and mechanical function reconstruction of large segmental femoral defects in rats,and this"scaffold-cell-growth factor"composite strategy provides an experimental basis for optimizing bone tissue engineering scaffolds.