The Experimental Study Of Bone Defect Repair By Ectopic Osteogenesis Using 3D Printed Porous Tantalum Scaffold Loaded With BMP-2 And Axial Vascular Bundle

Research purposeThe 3D printing technology was used to create a personalized porous tantalum scaffold,combined with the axial vascular bundle,and loaded bone morphogenetic protein-2(BMP-2)ectopic osteogenesis to repair the proximal humerus bone defect in rabbits,providing a theoretical basis for the clinical repair of large segment bone defects.Methods1.Adjust the laser power and scanning spacing of the 3D printer,and obtain the best process parameters through density detection and mechanical property detection.Porous tantalum scaffold materials with porosity of 400μm,600μm and 800μm were designed and printed.The best scaffolds were selected through the general morphology,microscopic characterization,co-culture of scaffolds and cells and mechanical properties test.2.Ectopic osteogenic scaffold material was prepared in the bursa of rabbit supraspinatus muscle using the principle of in vivo bioreactor,and the osteogenic and angiogenic effects of the scaffold material were evaluated.The experiment was divided into 4 groups:Group A was a 3D printed porous tantalum 3D center loaded with BMP-2 loaded with axial vascular bundle group;Group B was 3D printed porous tantalum center with axial vascular bundle.Group C was 3D printed porous tantalum loaded BMP-2 group;Group D is 3D printed porous tantalum group.The stents were implanted into the bilateral symmetric supraspinatus muscle bursae of each rabbit.The stents were removed at 6 and 12 weeks after surgery,and the osteogenesis and angiogenesis were observed by HE staining and CD31 and ALP immunohistochemistry.3.Rabbit proximal humerus bone defect model was prepared,and different methods were used to repair the bone defect.The effect of bone defect repair in different groups was observed 6 weeks later.The experiment was divided into three groups:composite scaffold(CS)was implanted with rabbit supratinus muscle for 6 weeks,with ectopic scaffold implanted near the humerus defect.porous tantalum(PT)group implanted porous tantalum 3D printed into the defect of humerus.The blank control group(BC)treated the humerus defect without treatment.6 weeks after the operation,the animals were sacrificed to take the humerus bone defect repair area tissue,gross observation and X-ray imaging to evaluate the repair of bone defect.Miro-CT scan imaging was used to observe the repair of bone defects in each group,and bone formation was evaluated by quantitative data analysis.At the same time,Miro-CT scan of proximal humerus was performed after barium sulfate vascular perfusion to observe the local vascular distribution in the defect repair area,and quantitative analysis was performed.The humerus specimens were stained with hard tissue sections to observe the bone growth in the defect repair area.Result1.Through the optimization of 3D printing process parameters,it is found that the tantalum metal printing sample has the best indicators when the laser power is 260W and the scanning interval is 0.055mm.When the porosity of porous tantalum scaffolds was 80%,all the scaffolds with three pore sizes were conducive to the growth of cells and blood vessels.Porous tantalum scaffolds have similar structure to normal cancellous bone,and the mechanical properties of scaffolds are between cancellous bone and cortical bone.2.Through HE staining and immunohistochemical quantitative analysis,it was found that the internal tissues of group A(3D printed porous tantalum combined with BMP-2 group with axial vascular bundle in the center)had significantly better effects on osteogenesis and angiogenesis than the other three groups.3.6 weeks after implantation of the humerus defect site in rabbit,the composite scaffold group had completely fused with the surrounding normal bone,and the transplantation area was rich in blood transport.It showed better bone induction,bone conduction and bone integration ability than the other two groups.Conclusion3D printing porous tantalum scaffold supported by BMP-2 vascularization after ectopic osteogenesis can repair rabbit bone defects and the repair effect is good,providing a theoretical basis for further clinical application.