Study On Osteogenesis Of Bovine Bone Scaffolds Treated With Three Methods In Synergy With BMP2 In Animal Models Of Different Bone Defects

ObjectiveTo compare the osteogenic effects between true bone ceramics,decalcified bone matrix and freeze-dried bone xenograft scaffold materials in different types of bone defects animal models,and to analyze the synergistic effect of BMP2 combined with above three materials.Methods1.Three kinds of scaffold materials were prepared by physical and chemical methods,tested by mechanical strength,scanning electron microscopy and cytotoxicity..2.Three kinds of scaffolds were combined with BMP-2 for repairing femoral condyle defect in rats,and semi-quantitative analysis was performed by gross observation histological score,Micro-CT analysis and hematoxylin-eosin staining.3.Three kinds of scaffolds were combined with BMP-2 for repairing rat tibia defect,and semi-quantitative analysis,X-ray film and scoring were performed by gross observation histological score,hematoxylin-eosin staining and calcein staining.Results1.Material characterization?.The maximum compressive strength of the TBC stent is 1.022±0.09Mpa,the yield strength is 0.46±0.06Mpa;the maximum compressive strength of the DBM stent is 1.73±0.45Mpa,and the yield strength is 1.02±0.49Mpa.There was no significant difference in the maximum compressive strength between the two(P>0.05),and there was no statistically significant difference in the yield strength(P>0.05).The maximum compressive strength of FDB is 12.81±5.29Mpa,and the yield strength is 9.82±4.3Mpa.The maximum compressive strength and yield strength of FDB are the largest,and there are statistical differences compared with the other two materials;?.The pore diameter of the TBC stent is 185-462um.The DBM scaffold has a pore size between 217 and 342 um and the FDB pore size between 404 and 560um.The three scaffold materials are porous structures.?.The RGR(relative proliferation rate)of TBC,DBM and FDB were 95.74±3.43%,89.12±5.68%and 82.89±5.72%,respectively.The TBC was compared with FDB,the statistical difference was significant(P<0.01),TBC and There was a statistically significant difference between DBM and PDB(P>0.05).There was no statistical difference between DBM and FDB(P>0.05).2.Comparison of repair effects of three materials in femoral condyle defect model.?.The femoral condyle of rats was observed by Hitchcock adhesion degree grading.There was significant difference between the different groups at the 8th week(P<0.05).?.In the fourth week,the autologous bone group scored the highest of HE staining score,which was 7.8±0.4,followed by the TBC/BMP-2 and FDB/BMP-2 groups,which were 6.0±0.7 and 4.4±0.5,respectively.After the three scaffold materials were combined with BMP-2,the other two scaffold materials except the DBM group were significantly improved(P<0.001).In the eighth week,the DBM group scored the lowest,which was 2.0±0.7;the autologous bone group scored the highest,which was 8.8±0.4,followed by TBC/BMP-2,TBC,FDB/BMP-2,which were 6.2±0.4,5.8±0.4 and 5.0±0.7 respectively.Except for the FDB group,the other two scaffold materials did not significantly increase after compounding with BMP-2(P<0.001).?.The bone volume/total volume(BV/TV)score was the highest in the TBC/BMP-2 group,and there was a statistically significant difference between the DBM/BMP-2 group and the FDB/BMP-2 group(P<0.01).There was no significant difference between the BMP-2 group and the FDB/BMP-2 group(P>0.05).There were significant differences between the three scaffolds and BMP-2 before and after treatment(P<0.01).The Trabecular Thickness(TT)was the largest in the TBC/BMP-2 group,followed by the TBC group.There was no significant difference between the two groups(P>0.05).The smallest trabecular thickness was in the DBM group.Followed by the FDB group,the difference between the two groups was not statistically significant(P>0.05).There was no statistically significant difference between DBM and FDB after complexing with BMP-2(P>0.05);TBC/BMP-2 and DBM/BMP-2,TBC/BMP-2 and DBM/BMP-2,There was significant statistical difference between TBC and DBM,TBC and FDB(P<0.01).3.Comparison of the repair effects of three materials in the humeral defect model.?The degree of adhesion of Hitchcock in rat tibia at the eighth week was statistically different between the uncombined BMP-2 groups(P<0.05).There was no statistical difference between the two groups.Difference(P>0.05).?The fourth week of the TBC group have the lowest histological score of 0.8±0.4.The score of autologous bone group was the highest,5.8±0.4,followed by the DBM/BMP-2 group,4.2±0.4.These scaffolds were improved in different degrees after being combined with BMP-2.There were statistical differences between the TBC/BMP-2 group and the DBM/BMP-2 group,TBC/BMP-2 group and FDB/BMP-2 group.At the eighth week,the scores of DBM/BMP-2 and autologous bone group were the highest,6.2±0.4,followed by TBC/BMP-2 group,which were 4.5±0.7.The FDB group scored the lowest,1.2±0.4.BMP-2 can improve the osteogenic effect of TBC and DBM scaffold materials,respectively,and there is no statistical difference between FDB scaffold materials before and after composite BMP-2(P>0.05).There was a statistically significant difference between the two stents after BMP-2(P<0.05)..?At the eighth week,there was no obvious sign of "double track sign"for the material that was not combined with BMP-2 after the implantation of the defect site,and the three scaffold materials were combined with BMP-2.After the double-track sign,the mineralization deposition rate of DBM/BMP-2 group was the highest,and the difference was statistically significant(P<0.05).There was no significant difference between TBC/BMP-2 and FDB/BMP-2(P>0.05).?.X-ray score:There was no significant difference between the two groups in the TBC group and the TBC/BMP-2 group(P>0.05).There was a statistically significant difference between the DBM group and the DBM/BMP-2 group(P<0.01);the difference between the FDB group and the FDB/BMP-2 group was statistically significant(P<0.01);the autologous bone group was compared with the TBC/BMP-2 group and the FDB/BMP-2 group.Statistical differences,P>0.05,were statistically different from the other groups,P<0.05.ConclusionsThis experiment shows that although the three scaffold materials have differences in mechanical strength and bone conduction,osteoinductive activity still plays a crucial role in the repair of bone defects.The three scaffold materials have a significant improvement in bone defect repair ability after compounding with BMP-2.In the femoral condyle bone defect model,due to the influence of local bleeding,BMP-2 may be diluted by the blood flow and may not function well.At the same time,due to the large number of surrounding cells,bone conduction performance can promote osteogenesis better in this model.However,in the humeral defect model,because the local activity of the unfixed humeral defect may affect the bone conduction performance of the scaffold material,it is necessary to add BMP-2 to improve its osteoinductive properties.The osteoinductive material is more suitable for the defect repair of this model.