Exosomes secreted from miRNA-29b-modified mesenchymal stem cells repaired spinal cord injury in rats

Exosomes, a kind of extracellular vesicle, are promising therapeutic agents for spinal cord injury (SCI). This article aimed to investigate effects of exosomes secreted from miRNA-29b-modified bone marrow mesenchymal stem cells (BMSCs) on SCI. Exosomes were extracted from BMSCs transfected with miRNA-29b or negative control (miR NC). SCI rats were injected intravenously with exosomes (control exosomes, miRNA-29b exosomes) and BMSCs (miR NC, miRNA-29b) through the tail vein. The expression of miRNA-29b in spinal cord tissues of SCI rats was detected by qRT-PCR. The hind limb motor function was evaluated by Basso Beattie Bresnahan (BBB) score. The histopathological damage and neuronal regeneration in spinal cord tissues was observed by HE staining and immunohistochemistry, respectively. The injection of miRNA-29b exosomes and miRNA-29b BMSCs both significantly increased the expression of miRNA-29b in spinal cord tissues of SCI rats (P<0.05). Compared with SCI rats, rats in the miRNA-29b exosomes and the miRNA-29b groups exhibited improved SCI, including increased BBB score, NF200 and GAP-43 positive neurons, as well as decreased contractile nerve cell numbers and GFAP positive neurons (all P<0.05). The relieving degree of SCI was significantly higher in the miRNA-29b exosomes group than in the miRNA-29b BMSCs group (P<0.05). Exosomes secreted from miRNA-29b-modified BMSCs were effective in the repair of SCI in rats.

外泌体（Exosomes）作为一类细胞外囊泡（extracellular vesicle），是极具应用前景的脊髓损伤（spinal cord injury, SCI）治疗制剂。本研究旨在探讨经微小RNA-29b（miRNA-29b）修饰的骨髓间充质干细胞（bone marrow mesenchymal stem cells, BMSCs）分泌的外泌体对脊髓损伤的治疗效果。研究人员从转染了miRNA-29b或阴性对照（negative control, miR NC）的骨髓间充质干细胞中提取外泌体，通过尾静脉向脊髓损伤模型大鼠注射外泌体（分为对照外泌体组、miRNA-29b外泌体组）以及骨髓间充质干细胞（分别转染miR NC、miRNA-29b）。采用实时荧光定量聚合酶链反应（qRT-PCR）检测脊髓损伤大鼠脊髓组织中miRNA-29b的表达水平；通过Basso Beattie Bresnahan（BBB）评分对大鼠后肢运动功能进行评估；分别采用苏木精-伊红（HE）染色与免疫组化技术观察脊髓组织的病理损伤及神经元再生情况。实验结果显示，注射miRNA-29b外泌体与miRNA-29b修饰的骨髓间充质干细胞，均可显著上调脊髓损伤大鼠脊髓组织中miRNA-29b的表达量（P<0.05）。与单纯脊髓损伤模型大鼠相比，miRNA-29b外泌体组与miRNA-29b修饰骨髓间充质干细胞组大鼠的脊髓损伤均得到改善，具体表现为BBB评分升高，神经丝蛋白200（NF200）及生长相关蛋白43（GAP-43）阳性神经元数量增加，同时皱缩神经元数量与胶质纤维酸性蛋白（GFAP）阳性神经元数量均显著降低（所有指标P<0.05）。其中，miRNA-29b外泌体组对脊髓损伤的缓解效果显著优于miRNA-29b修饰骨髓间充质干细胞组（P<0.05）。本研究证实，经miRNA-29b修饰的骨髓间充质干细胞分泌的外泌体可有效修复大鼠脊髓损伤。