BMP-2复合涂层多孔钛合金试件植入对兔股骨中段骨整合的影响

Effect of porous titanium alloy test piece with BMP-2 composite coating on bone integration of rabbit femur middle section

目的探讨骨形态发生蛋白2(BMP-2)复合涂层多孔钛合金试件植入对兔股骨中段骨整合的影响。方法构建多孔钛合金试件48件,随机取24件制备BMP-2复合涂层多孔钛合金试件。选择雄性新西兰兔24只,随机分为观察组、对照组,每组12只。对照组双侧股骨植入多孔钛合金试件,观察组双侧股骨植入BMP-2复合涂层多孔钛合金试件。多孔钛合金试件植入4、8周后,每组随机取6只,空气栓塞法处死,右侧股骨Micro-CT断层扫描,获取股骨骨体积分数(BVF)、组织矿物密度(TMD)和骨微观结构指标骨小梁相对体积(TBV)、骨小梁厚度(Tb.Th)、骨小梁间隙(Tb.Sp),并测试植入体与股骨结合强度(即拔出多孔钛合金试件时最大拔出力);左侧股骨于低真空扫描电镜下观察植入体-股骨界面骨形成情况,丽春红法染色检测植入体骨长入面积百分比,实时荧光定量PCR法检测植入体-股骨界面骨组织成骨相关基因Runt相关转录因子2(Runx2)、骨钙素(OCN)、成骨细胞特异性转录因子Osterix(Osx)表达。结果与对照组比较,观察组多孔钛合金试件植入4、8周股骨BVF、TMD、TBV、Tb.Th均显著升高,Tb.Sp均显著降低(P均<0.05)。两组多孔钛合金试件植入8周时植入体最大拔出力均显著高于多孔钛合金试件植入4周时,并且观察组多孔钛合金试件植入4、8周时植入体最大拔出力均显著高于对照组同期(P均<0.05)。多孔钛合金试件植入4周,对照组植入体-股骨界面有新生骨向植入体边缘生长,骨小梁细小且骨质间有较多空隙,而观察组植入体-股骨界面新生骨较对照组明显增多,骨小梁增粗融合且骨质间的空隙变小;多孔钛合金试件植入8周,对照组植入体-股骨界面可见大量新生骨在植入体表面爬行生长,骨小梁变粗融合且呈规则层状较整齐排列,而观察组植入体-股骨界面新生骨较对照组进一步增多,骨小梁变粗融合且呈规则层状整齐排列现象更加明显,板层骨明显形成,并在植入体与股骨之间形成完整的骨性界面。两组多孔钛合金试件植入8周时植入体骨长入面积百分比均显著高于植入4周时,并且观察组多孔钛合金试件植入4、8周时植入体骨长入面积百分比均显著高于对照组同期(P均<0.05)。与对照组比较,观察组多孔钛合金试件植入4、8周植入体-股骨界面骨组织Runx2、OCN、Osx相对表达量均显著升高(P均<0.05);观察组多孔钛合金试件植入8周植入体-股骨界面骨组织Runx2、OCN、Osx相对表达量均显著高于多孔钛合金试件植入4周时(P均<0.05),而对照组多孔钛合金试件植入4、8周植入体-股骨界面骨组织Runx2、OCN、Osx相对表达量比较差异均无统计学意义(P均>0.05)。结论BMP-2复合涂层多孔钛合金试件可促进兔股骨中段新生骨形成和骨长入,改善植入体-股骨界面骨组织微观结构,提高植入体与股骨结合强度,有利于兔股骨中段骨整合。

Objective To investigate the effect of bone morphogenetic protein-2(BMP-2)composite-coated porous titanium alloy test piece on bone integration in the middle femur of rabbits Methods Forty-eight porous titanium alloy test pieces were constructed,and 24 samples were randomly selected to prepare porous titanium alloy test pieces with BMP-2 composite coating.Twenty-four male New Zealand rabbits were randomly divided into the observation group and control group,with 12 in each group.The rabbits in the control group were implanted with porous titanium alloy test pieces in both femurs,and the rabbits in the observation group were implanted with BMP-2 composite-coated porous titanium alloy test pieces in both femurs.After 4 and 8 weeks of implantation of porous titanium alloy test pieces,6 rats in each group were randomly selected and killed by air embolism.Micro-CT scan of the right femur was performed to obtain the femoral bone volume fraction(BVF),tissue mineral density(TMD),and bone microstructure indicators,bone trabecular relative vol⁃ume(TBV),bone trabecular thickness(Tb.Th),bone trabecular space(Tb.Sp),and the bond strength between the implant and the femur(the maximum pullout force when the porous titanium alloy test piece was pulled out);the bone for⁃mation at the implant-femoral interface was observed in the left femur under the low vacuum scanning electron microscope,the percentage of bone ingrowth area of the implant was detected by the ponceau staining,and the expression levels of osteogenesis-related gene Runt related transcription factor 2(Runx2),osteocalcin(OCN),and Osteoblast-specific tran⁃scription factor Osterix(Osx)in the bone tissues at the implant-femoral interface were detected by real-time fluorescence quantitative PCR.Results Compared with the control group,the femur BVF,TMD,TBV and Tb.Th of porous titanium alloy test piece in the observation group significantly increased at 4 and 8 weeks after implantation,while the Tb.Sp signifi⁃cantly decreased(all P<0.05).The maximum pullout force of porous titanium alloy test pieces at 8 weeks of implantation in both groups was significantly higher than that at 4 weeks of implantation,and the maximum pullout force of porous titanium alloy test pieces at 4 and 8 weeks of implantation in the observation group was significantly higher than that in the control group(all P<0.05).The porous titanium alloy test pieces were implanted for 4 weeks.In the control group,new bone grew towards the edge of the implant at the implant-femur interface,with small bone trabeculae and more space between bones,while in the observation group,new bone at the implant-femur interface increased significantly,and bone trabecu⁃lae were thickened and fused,and the space between bones became smaller.After 8 weeks of implantation of the porous titanium alloy test pieces,a large number of new bones could be seen crawling and growing on the surface of the implant at the implant-femur interface of the control group,and bone trabeculae were thicker and fused and arranged in regular layer-like order,while the new bones at the implant-femur interface of the observation group further increased compared with the control group,bone trabeculae were thicker and fused and arranged in regular layer-like order,and lamellar bone was obvi⁃ously formed.And a complete bony interface was formed between the implant and the femur.The percentage of implant bone growth area at 8 weeks of implantation was significantly higher in both groups than that at 4 weeks of implantation,and the percentage of implant bone growth area at 4 and 8 weeks of implantation in the observation group was significantly higher than that in the control group(both P<0.05).Compared with the control group,the relative expression levels of Runx2,OCN and Osx in the interfacial bone tissues of the porous titanium alloy at 4 and 8 weeks after implantation signifi⁃cantly increased in the observation group(all P<0.05).The relative expression levels of Runx2,OCN and Osx in the interfacial bone tissues of porous titanium alloy at 8 weeks implantation were significantly higher than those of porous titani⁃um alloy at 4 weeks implantation(all P<0.05).There were no significant differences in the expression levels of Runx2,OCN or Osx in the interfacial bone tissues of the porous titanium alloy in the control group between 4 and 8 weeks after implantation(all P>0.05).Conclusion BMP-2 composite-coated porous titanium alloy test pieces can promote the for⁃mation of new bone and bone insertion in the middle part of rabbit femur,improve the microstructure of bone tissues at the implant-femur interface,improve the binding strength of implant and femur,and facilitate the bone integration in the mid⁃dle part of rabbit femur.