Transplantation of mesenchymal stem cells (MSCs) has been considered an effective therapeutic treatment for a variety of diseases including bone fracture. However, there are associated complications along with MSCs transplantation. There is evidence to show that exosomes (Exos) derived from MSCs exert a similar paracrine function. In addition, repair capabilities of MSCs decline with age. Hence, this study aims to confirm whether the Exos protective function on osteogenic differentiation and fracture healing from aged MSCs was attenuated. This information was used in order to investigate the underlying mechanism. MSCs were successfully isolated and identified from young and aged rats, and Exos were then obtained. Aged-Exos exhibited significantly attenuated effects on MSCs osteogenic differentiation in vitro and facture healing in vivo. Using miRNA array analysis, it was shown that miR-128-3p was markedly upregulated in Aged-Exos. In vitro experiments confirmed that Smad5 is a direct downstream target of miR-128-3p, and was inhibited by overexpressed miR-128-3p. A series gain- and loss- function experiment indicated that miR-128-3P serves a suppressor role in the process of fracture healing. Furthermore, effects caused by miR-128-3P mimic/inhibitor were reversed by the application of Smad5/siSmad5. Taken together, these results suggest that the therapeutic effects of MSCs-derived Exos may vary according to differential expression of miRNAs. Exosomal miR-128-3P antagomir may act as a promising therapeutic strategy for bone fracture healing, especially for the elderly.

中文翻译：

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老年大鼠间充质干细胞的外泌体miRNA-128-3p通过靶向Smad5调节成骨和骨折愈合

间充质干细胞（MSCs）的移植被认为是对包括骨折在内的多种疾病的有效治疗方法。然而，伴随MSCs移植存在相关的并发症。有证据表明，源自MSC的外泌体（Exos）具有类似的旁分泌功能。另外，MSC的修复能力随年龄而下降。因此，本研究旨在证实Exos对老年MSCs成骨分化和骨折愈合的保护功能是否减弱。使用此信息是为了调查潜在的机制。从幼鼠和老年鼠中成功分离并鉴定了MSC，然后获得了Exos。Aged-Exos在体外对MSC的成骨分化和体内断裂修复表现出明显的减弱作用。使用miRNA阵列分析显示，miR-128-3p在Aged-Exos中显着上调。体外实验证实Smad5是miR-128-3p的直接下游靶标，并被过表达的miR-128-3p抑制。一系列增益和损失功能实验表明，miR-128-3P在骨折愈合过程中起抑制作用。此外，通过应用Smad5 / siSmad5可以逆转由miR-128-3P模拟物/抑制剂引起的效应。综上所述，这些结果表明，MSCs衍生的Exos的治疗效果可能会根据miRNA的差异表达而有所不同。外泌体miR-128-3P antagomir可能是有希望的骨折愈合治疗策略，尤其是对于老年人。体外实验证实Smad5是miR-128-3p的直接下游靶标，并被过表达的miR-128-3p抑制。一系列增益和损失功能实验表明，miR-128-3P在骨折愈合过程中起抑制作用。此外，通过应用Smad5 / siSmad5可以逆转由miR-128-3P模拟物/抑制剂引起的效应。综上所述，这些结果表明，MSCs衍生的Exos的治疗效果可能会根据miRNA的差异表达而有所不同。外泌体miR-128-3P antagomir可能是有希望的骨折愈合治疗策略，尤其是对于老年人。体外实验证实Smad5是miR-128-3p的直接下游靶标，并被过表达的miR-128-3p抑制。一系列增益和损失功能实验表明，miR-128-3P在骨折愈合过程中起抑制作用。此外，通过应用Smad5 / siSmad5可以逆转由miR-128-3P模拟物/抑制剂引起的效应。综上所述，这些结果表明，MSCs衍生的Exos的治疗效果可能会根据miRNA的差异表达而有所不同。外泌体miR-128-3P antagomir可能是有希望的骨折愈合治疗策略，尤其是对于老年人。一系列增益和损失功能实验表明，miR-128-3P在骨折愈合过程中起抑制作用。此外，通过应用Smad5 / siSmad5可以逆转由miR-128-3P模拟物/抑制剂引起的效应。综上所述，这些结果表明，MSCs衍生的Exos的治疗效果可能会根据miRNA的差异表达而有所不同。外泌体miR-128-3P antagomir可能是有希望的骨折愈合治疗策略，尤其是对于老年人。一系列的增益和损失功能实验表明，miR-128-3P在骨折愈合过程中起抑制作用。此外，通过应用Smad5 / siSmad5可以逆转由miR-128-3P模拟物/抑制剂引起的效应。综上所述，这些结果表明，MSCs衍生的Exos的治疗效果可能会根据miRNA的差异表达而有所不同。外泌体miR-128-3P antagomir可能是有希望的骨折愈合治疗策略，尤其是对于老年人。