AIMS/HYPOTHESIS Diabetic peripheral neuropathy (DPN) is one of the major complications of diabetes, which contributes greatly to morbidity and mortality. There is currently no effective treatment for this disease. Exosomes are cell-derived nanovesicles and play an important role in intercellular communications. The present study investigated whether mesenchymal stromal cell (MSC)-derived exosomes improve neurological outcomes of DPN. METHODS Exosomes were isolated from the medium of cultured mouse MSCs by ultracentrifugation. Diabetic mice (BKS.Cg-m+/+Leprdb/J, db/db) at the age of 20 weeks were used as DPN models. Heterozygous mice (db/m) of the same age were used as the control. MSC-exosomes were administered weekly via the tail vein for 8 weeks. Neurological function was evaluated by testing motor and sensory nerve conduction velocities, and thermal and mechanical sensitivity. Morphometric analysis was performed by myelin sheath staining and immunohistochemistry. Macrophage markers and circulating cytokines were measured by western blot and ELISA. MicroRNA (miRNA) array and bioinformatics analyses were performed to examine the exosomal miRNA profile and miRNA putative target genes involved in DPN. RESULTS Treatment of DPN with MSC-exosomes markedly decreased the threshold for thermal and mechanical stimuli and increased nerve conduction velocity in diabetic mice. Histopathological analysis showed that MSC-exosomes markedly augmented the density of FITC-dextran perfused blood vessels and increased the number of intraepidermal nerve fibres (IENFs), myelin thickness and axonal diameters of sciatic nerves. Western blot analysis revealed that MSC-exosome treatment decreased and increased M1 and M2 macrophage phenotype markers, respectively. Moreover, MSC-exosomes substantially suppressed proinflammatory cytokines. Bioinformatics analysis revealed that MSC-exosomes contained abundant miRNAs that target the Toll-like receptor (TLR)4/NF-κB signalling pathway. CONCLUSIONS/INTERPRETATION MSC-derived exosomes alleviate neurovascular dysfunction and improve functional recovery in mice with DPN by suppression of proinflammatory genes.

中文翻译：

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间充质基质细胞源性外泌体改善了糖尿病小鼠模型的周围神经病变。

目的/假说糖尿病周围神经病变（DPN）是糖尿病的主要并发症之一，它极大地增加了发病率和死亡率。目前尚无对该疾病的有效治疗方法。外泌体是细胞衍生的纳米囊泡，在细胞间通讯中起重要作用。本研究调查了间充质基质细胞（MSC）衍生的外泌体是否可以改善DPN的神经学结果。方法采用超速离心法从培养的小鼠骨髓间充质干细胞中分离外泌体。将20周龄的糖尿病小鼠（BKS.Cg-m + / + Leprdb / J，db / db）用作DPN模型。将相同年龄的杂合小鼠（db / m）用作对照。每周通过尾静脉给予MSC外泌体8周。通过测试运动神经和感觉神经的传导速度来评估神经功能，以及热和机械灵敏度。通过髓鞘鞘染色和免疫组织化学进行形态分析。巨噬细胞标志物和循环细胞因子通过western blot和ELISA测定。进行了MicroRNA（miRNA）阵列和生物信息学分析，以检查DPN中涉及的外泌体miRNA图谱和miRNA假定靶基因。结果MSC-外泌体治疗DPN明显降低了糖尿病小鼠的热和机械刺激阈值，并增加了神经传导速度。组织病理学分析表明，MSC外泌体显着增加了FITC-右旋糖酐灌注血管的密度，并增加了坐骨神经表皮内神经纤维（IENF）的数量，髓鞘厚度和轴突直径。蛋白质印迹分析表明，MSC外泌体治疗分别减少和增加了M1和M2巨噬细胞表型标记。而且，MSC-外泌体基本上抑制了促炎细胞因子。生物信息学分析表明，MSC外泌体包含大量靶向Toll样受体（TLR）4 /NF-κB信号通路的miRNA。结论/解释MSC衍生的外泌体可通过抑制促炎基因减轻DPN小鼠的神经血管功能障碍并改善其功能恢复。