BACKGROUND Mesenchymal stem cells (MSCs) are suspected to exert neuroprotective effects in brain injury, in part through the secretion of extracellular vesicles like exosomes containing bioactive compounds. We now investigate the mechanism by which bone marrow MSCs (BMSCs)-derived exosomes harboring the small non-coding RNA miR-29b-3p protect against hypoxic-ischemic brain injury in rats. METHODS We established a rat model of middle cerebral artery occlusion (MCAO) and primary cortical neuron or brain microvascular endothelial cell (BMEC) models of oxygen and glucose deprivation (OGD). Exosomes were isolated from the culture medium of BMSCs. We treated the MCAO rats with BMSC-derived exosomes in vivo, and likewise the OGD-treated neurons and BMECs in vitro. We then measured apoptosis- and angiogenesis-related features using TUNEL and CD31 immunohistochemical staining and in vitro Matrigel angiogenesis assays. RESULTS The dual luciferase reporter gene assay showed that miR-29b-3p targeted the protein phosphatase and tensin homolog (PTEN). miR-29b-3p was downregulated and PTEN was upregulated in the brain of MCAO rats and in OGD-treated cultured neurons. MCAO rats and OGD-treated neurons showed promoted apoptosis and decreased angiogenesis, but overexpression of miR-29b-3p or silencing of PTEN could reverse these alterations. Furthermore, miR-29b-3p could negatively regulate PTEN and activate the Akt signaling pathway. BMSCs-derived exosomes also exerted protective effects against apoptosis of OGD neurons and cell apoptosis in the brain samples from MCAO rats, where we also observed promotion of angiogenesis. CONCLUSION BMSC-derived exosomal miR-29b-3p ameliorates ischemic brain injury by promoting angiogenesis and suppressing neuronal apoptosis, a finding which may be of great significance in the treatment of hypoxic-ischemic brain injury.

中文翻译：

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骨髓间充质干细胞来源的外泌体microRNA-29b-3p通过激活PTEN介导的Akt信号通路来预防大鼠脑缺氧缺血性损伤。

背景技术间充质干细胞（MSC）被怀疑在脑损伤中发挥神经保护作用，部分是通过分泌细胞外囊泡，如含有生物活性化合物的囊泡来实现的。现在，我们研究了具有小的非编码RNA miR-29b-3p的骨髓MSC（BMSCs）衍生的外泌体保护大鼠免受缺氧缺血性脑损伤的机制。方法我们建立了大鼠大脑中动脉闭塞（MCAO）和原代皮层神经元或大脑微血管内皮细胞（BMEC）缺氧和缺糖（OGD）模型。从BMSC的培养基中分离出外来体。我们在体内用BMSC衍生的外泌体治疗了MCAO大鼠，同样在体外用OGD处理过的神经元和BMEC进行了治疗。然后，我们使用TUNEL和CD31免疫组织化学染色以及体外Matrigel血管生成测定法，测量了与凋亡和血管生成相关的特征。结果双荧光素酶报告基因检测结果表明，miR-29b-3p靶向蛋白磷酸酶和张力蛋白同源物（PTEN）。在MCAO大鼠的大脑和OGD处理的神经元中，miR-29b-3p的表达下调，PTEN的表达上调。MCAO大鼠和经OGD处理的神经元显示出促进细胞凋亡和减少血管生成的作用，但miR-29b-3p的过表达或PTEN的沉默可以逆转这些改变。此外，miR-29b-3p可能负调控PTEN并激活Akt信号通路。BMSCs衍生的外来体也对MCAO大鼠脑中的OGD神经元凋亡和细胞凋亡具有保护作用，在这里我们还观察到血管生成的促进。结论BMSC来源的外泌体miR-29b-3p可通过促进血管生成和抑制神经元凋亡来改善缺血性脑损伤，这一发现在治疗缺氧缺血性脑损伤中可能具有重要意义。