卷曲受体蛋白4在高脂血症大鼠种植体周围组织中的早期表达

Early expression of Frizzled 4 in peri-implant tissues of hyperlipidemic rats

目的探讨卷曲受体蛋白4(Frizzled4)在高脂血症大鼠种植体周围组织中早期的表达.方法48只成年雄性SD大鼠,随机分为实验组和对照组,每组24只.分别喂食高脂饲料和普通饲料8周.均于股骨干骺端植入直径1.5 mm、长2.5 mm的种植体.分别于术后第1天、第3天、第5天和第28天时处死大鼠,获取种植体周围骨组织.用Inveon MM CT扫描组织标本,扫描完成后将图像中种植体周围1 mm区域设置为兴趣区(ROI),进行ROI内三维重建,分析骨小梁参数:骨小梁体积/ROI体积(BV/TV)、骨小梁厚度(Tb.Th)、骨小梁数目(Tb.N)、骨小梁间隙(Tb.S).RT-PCR法检测成骨细胞、破骨细胞分化标志物Runt相关转录因子2(RUNX2)、组织蛋白酶K(CTSK)和Frizzled4的基因表达情况,Western blotting法检测Frizzled4蛋白表达情况.结果实验组种植体植入第1天、第3天时,实验组和对照组BV/TV、Tb.S、Tb.Th和Tb.N比较差异无统计学意义(P>0.05).植入第5天、第28天时,实验组BV/TV、Tb.Th和Tb.N均低于对照组,而Tb.S高于对照组,差异有统计学意义(P<0.05).实验组种植体植入第1天、第3天、第5天和第28天后,Runx2 mRNA表达水平均低于对照组,而CTSK mRNA表达水平高于对照组,差异有统计学意义(P<0.05).对照组种植体植入3 d内,Frizzled4 mRNA和蛋白表达水平明显增加,第5天、第28天时有所下降,但是仍高于实验组(P<0.05).实验组植入3 d内,Frizzled4 mRNA和蛋白表达水平明显下降,并且在第5天、第28天时升高(P<0.05).对照组种植体植入3 d内,Wnt/β-catenin蛋白表达水平明显增加,第5天,第28天时有所下降,但是仍高于实验组(P<0.05).实验组植入3 d内,Wnt/β-catenin蛋白表达水平显著上升,并且在第5天、第28天下降(P<0.05).结论高脂血症可抑制种植体的早期骨结合,这种作用可能与下调Frizzled4的表达有关,未来需要进一步地进行机制研究.

Objective To investigate the early expression of Frizzled 4 in peri-implant tissues of hyperlipidemic rats.Methods A total of 48 adult male SD rats were randomly divided into two groups,with 24 rats in either group.Rats in the experimental group were fed with high fat diet,while rats in the control group were fed with common diet for 8 weeks.Implants 1.5 mm wide and 2.5 mm long were implanted into the metaphyseal end of femur.The rats were sacrificed on the 1st,3rd,5th and 28th days after operation to obtain bone tissues around the implant.The tissues were scanned with Inveon MM CT and 1 mm area around the implant was set as the area of interest(ROI).Three-dimensional reconstruction was performed in ROI.Bone trabecular parameters were analyzed,including trabecular volume/ROI volume(BV/TV),trabecular thickness(Tb.Th),trabecular number(Tb.N)and trabecular space(Tb.S).The gene expressions of osteoblasts,osteoclast differentiation markers Runt-related transcription factor 2(RUNX2),cathepsin K(CTSK)and Frizzled 4 were detected with RT-PCR.The protein expression of Frizzled 4 was determined with Western blotting.Results There were no significant differences in BV/TV,Tb.S,Tb.Th and Tb.N between the two groups on the 1st and 3rd day of implantation(P>0.05).On the 5th and 28th days of implantation,the experimental group had lower BV/TV,Tb.Th and Tb.N but higher Tb.S than the control group(P<0.05).On the 1st,3rd,5th and 28th days of implantation,the experimental group had lower mRNA expression of Runx2 but higher mRNA expression of CTSK than the control group(P<0.05).In the control group,the mRNA and protein expressions of Frizzled 4 increased significantly on the 3rd day of implantation,and decreased on the 5th and 28th days,but were still higher than those in the experimental group(P<0.05).In the experimental group,both mRNA and protein expressions of Frizzled 4 decreased significantly on the 3rd day of implantation,but increased on the 5th and 28th days(P<0.05).In the control group,the protein expression of Wnt/β-catenin increased significantly on the 3rd day of implantation,and decreased on the 5th and 28th days,but was still higher than that in the experimental group(P<0.05).In the experimental group,the expression of Wnt/β-catenin increased significantly on the 3rd day of implantation,but decreased on the 5th and 28th days(P<0.05).Conclusion Hyperlipidemia can inhibit early osseointegration of implants,which may be related to the downregulation of Frizzled 4 expression.The exact mechanism needs further research.