Background: Stem cell-released exosomes (EXs) have shown beneficial effects on regenerative diseases. Our previous study has revealed that EXs of endothelial progenitor cells (EPC-EXs) can elicit favorable effects on endothelial function. EXs may vary greatly in size, composition, and cargo uptake rate depending on the origins and stimulus; notably, EXs are promising vehicles for delivering microRNAs (miRs). Since miR-210 is known to protect cerebral endothelial cell mitochondria by reducing oxidative stress, here we study the effects of miR-210-loaded EPC-EXs (miR210-EPC-EXs) on ischemic brain damage in acute ischemic stroke (IS). Methods: The miR210-EPC-EXs were generated from EPCs transfected with miR-210 mimic. Middle cerebral artery occlusion (MCAO) surgery was performed to induce acute IS in C57BL/6 mice. EPC-EXs or miR210-EPC-EXs were administrated via tail vein injection 2 hrs after IS. To explore the potential mechanisms, inhibitors of the vascular endothelial growth factor receptor 2 (VEGFR2)/PI3 kinase (PI3K) or tyrosine receptor kinase B (TrkB)/PI3k pathways were used. The brain tissue was collected after treatments for infarct size, cell apoptosis, oxidative stress, and protein expression (VEGFR2, TrkB) analyses on day two. The neurological deficit score (NDS) was evaluated before collecting the samples. Results: 1) As compared to EPC-EXs, miR210-EPC-EXs profoundly reduced the infarct volume and improved the NDS on day two post-IS. 2) Fewer apoptosis cells were detected in the peri-infarct brain of mice treated with miR210-EPC-EXs than in EPC-EXs-treated mice. Meanwhile, the oxidative stress was profoundly reduced by miR210-EPC-EXs. 3) The ratios of p-PI3k/PI3k, p- VEGFR2/VEGFR2, and p-TrkB/TrkB in the ipsilateral brain were raised by miR210-EPC-EXs treatment. These effects could be significantly blocked or partially inhibited by PI3k, VEGFR2, or TrkB pathway inhibitors. Conclusion: These findings suggest that miR210-EPC-EXs protect the brain from acute ischemia- induced cell apoptosis and oxidative stress partially through the VEGFR2/PI3k and TrkB/PI3k signal pathways.

中文翻译：

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miR-210引发的内皮祖细胞外泌体减轻急性缺血性脑损伤

背景：干细胞释放的外泌体（EX）已显示出对再生疾病的有益作用。我们之前的研究表明，内皮祖细胞（EPC-EX）的 EX 可以对内皮功能产生有利的影响。根据来源和刺激因素，EX 的大小、成分和货物吸收率可能会有很大差异；值得注意的是，EX 是一种很有前景的 microRNA (miR) 传递工具。由于已知 miR-210 通过减少氧化应激来保护脑内皮细胞线粒体，因此我们在此研究加载 miR-210 的 EPC-EX (miR210-EPC-EX) 对急性缺血性中风 (IS) 缺血性脑损伤的影响。方法：miR210-EPC-EX 由转染 miR-210 模拟物的 EPC 产生。进行大脑中动脉闭塞 (MCAO) 手术以诱导 C57BL/6 小鼠急性 IS。 IS后2小时通过尾静脉注射施用EPC-EX或miR210-EPC-EX。为了探索潜在的机制，使用了血管内皮生长因子受体 2 (VEGFR2)/PI3 激酶 (PI3K) 或酪氨酸受体激酶 B (TrkB)/PI3k 通路的抑制剂。治疗第二天收集脑组织，进行梗塞面积、细胞凋亡、氧化应激和蛋白质表达（VEGFR2、TrkB）分析。在收集样本之前评估神经功能缺损评分（NDS）。结果：1) 与 EPC-EX 相比，miR210-EPC-EX 显着减少了梗塞体积，并改善了 IS 后第二天的 NDS。 2) 在用miR210-EPC-EX处理的小鼠的梗塞周围脑中检测到的凋亡细胞比用EPC-EX处理的小鼠要少。同时，miR210-EPC-EXs 显着降低了氧化应激。 3)miR210-EPC-EXs治疗提高了同侧脑中p-PI3k/PI3k、p-VEGFR2/VEGFR2和p-TrkB/TrkB的比率。这些作用可以被 PI3k、VEGFR2 或 TrkB 通路抑制剂显着阻断或部分抑制。结论：这些研究结果表明，miR210-EPC-EXs部分通过VEGFR2/PI3k和TrkB/PI3k信号通路保护大脑免受急性缺血诱导的细胞凋亡和氧化应激。