间质干细胞成骨过程中外泌体内miRNA-222-5p对肌腱细胞损伤的修复作用及其机制

Effects and mechanism of mesenchymal stem cell osteogenesis-derived exosomes deliver miRNA-222-5p on tendon cell injury repair

目的:探讨间质干细胞成骨过程中外泌体转运的miRNA-222-5p对肌腱细胞损伤的修复作用及其机制。方法:收集、分离和鉴定间质干细胞外泌体。小鼠跟腱切断后1周安乐死后取其肌腱,分离培养肌腱细胞,得到肌腱细胞损伤模型(损伤组);将成骨分化过程中的间质干细胞与肌腱细胞共培养(共培养组);将miRNA-222-5p模拟物转染进间质干细胞,成骨分化过程中的间质干细胞与肌腱细胞共培养(miRNA-222-5p组)。通过克隆形成、Transwell观察间质干细胞分泌外泌体及外泌体转运的miRNA-222-5p对肌腱细胞损伤修复的能力;qPCR、Western-blot和荧光染色检测成软骨和成骨相关蛋白的相对mRNA和相对蛋白表达水平;通过Western-blot检测信号通路因子的表达。结果:电镜观察外泌体直径为40~100 nm,形态为典型的杯口状结构。外泌体标志蛋白热休克蛋白70、多配体聚糖结合蛋白1、肿瘤转移抑制因子9、肿瘤转移抑制因子63和肿瘤易感基因101的相对表达量分别为2.56±0.22、2.06±0.42、1.96±0.32、1.94±0.38、1.86±0.33,与正常对照组比较差异均有统计学意义(P<0.05)。克隆形成试验后细胞群落数量:损伤组(4.00±0.58)个、共培养组(7.25±0.48)个、miRNA-222-5p组(16.00±1.35)个,差异有统计学意义(F=46.550,P<0.001)。Transwell试验后细胞数量:损伤组(37±4)个、共培养组(78±3)个、miRNA-222-5p组(168±8)个,差异有统计学意义(F=454.100,P<0.001)。qPCR、Western-blot和荧光染色检测结果显示,与损伤组相比,共培养组细胞中Sry相关HMG盒9、Ⅱ型胶原纤维α1基因、蛋白聚糖、骨形态发生蛋白2、Runt相关转运因子2和骨桥蛋白的mRNA和蛋白质表达量增加;与共培养组相比,miRNA-222-5p组细胞mRNA和蛋白质表达量均增加(P<0.05)。Western-blot结果显示,与损伤组相比,共培养组核因子κB、细胞外调节蛋白激酶2、信号传导与转录激活因子3、信号传导与转录激活因子5和细胞信号转导分子2的表达水平升高;与共培养组相比,miRNA-222-5p组的表达升高(P<0.05)。结论:间质干细胞与跟腱细胞共培养可促进跟腱细胞成骨分化,同时间质干细胞来源的外泌体可通过转运miRNA-222-5p进一步促进跟腱细胞成骨分化。其机制可能与损伤肌腱中信号通路因子核因子κB、细胞外调节蛋白激酶2、信号传导与转录激活因子3、信号传导与转录激活因子5和细胞信号转导分子2的表达上调有关。

Objective To investigate the repair effects and mechanism of mesenchymal stem cell osteogenesis-derived exosomes deliver miRNA-222-5p on tendon cell injury.Methods Mesenchymal stem cell exosomes were collected,isolated and characterized.The mice achilles tendon was collected after cutting one week later.The tendon cells were isolated and cultured to obtain a tendon cell injury model(injury group).The subjects were divided into three groups.During the process of osteogenic differentiation,mesenchymal stem cells were co-cultured with tendon cells(co-culture group).Further,miRNA-222-5p mimics were transfected into mesenchymal stem cells,the co-cultured mesenchymal stem cells and tendon cells during the process of osteogenic differentiation(miRNA-222-5p group).Clone formation and Transwell were used to detect the ability of mesenchymal stem cells to secrete exosomes and exosomes transported miRNA-222-5p to repair damaged tendon cells.qPCR,Western-blot and fluorescence staining were used to detect the expression levels of cartilage-related proteins and bone-related proteins on mRNA and protein.Western-blot was used to detect the expression of signal pathway factors.Results The shape of the exosomes was a typical cup-like structure.The exosome proteins marker was all expressed positively(P<0.05).After counting the colony formation and Transwell test,the number of cell communities and cell invasion were significantly increased in the co-culture group compared with those in the injury group.The number of those in miRNA-222-5p group were significantly increased compared with those in co-culture group(P<0.05).The qPCR,Western-blot and fluorescent staining test results showed that the mRNA and protein expression levels of SOX-9,COL2A1,ACAN,BMP2,Runx2,and OPN in the co-culture group were significantly increased compared with the injury group.The mRNA and protein expression levels of the above proteins in the miRNA-222-5p group were significantly increased compared with those in co-culture group(P<0.05).We also detected the protein expression levels of signal pathway related factors.Western-blot results showed that the expression levels of NF-κB,Erk2,STAT3,STAT5 and Smad2 in the co-culture group were significantly increased compared with those in the injury group.The expression levels of the above factors in the miRNA-222-5p group were significant increased compared with the co-culture group(P<0.05).Conclusion The co-culture of mesenchymal stem cells and achilles tendon cells could promote the osteogenic differentiation of achilles tendon cells.Exosomes derived from mesenchymal stem cells could further promote the osteogenic differentiation of achilles tendon cells by transporting miRNA-222-5p.The mechanism may be related to the up-regulation of signal pathway factors in injured tendons,including NF-κB,Erk2,STAT3,STAT5 and Smad2.