长链非编码RNA MEG3/miR-1906/TLR4通路在卒中缺血再灌注损伤机制和治疗作用的研究

Our previous study has demonstrated that miR-1906 translated from activated astrocytes to neurons protects neurons against ischemic reperfusion injury after stroke by inhibiting the expression of TLR4. However, a prolonged ischemia resulted in higher miR - 1906 in the astrocytes but lower miR-11906 in the neurons. Our preliminary data shows that polarization of activated astrocytes after stroke, which is divided into proinflammatory (A1) and anti-inflammatory (A2) astrocytes. The A1 astrocytes highly express the long-noncoding RNA MEG3, which may sponge the miR-1906. In this project, ischemia induced activated astrocytes overexpress MEG3. Overexpression of MEG3 would reduce the translocation of miR-1906 from astrocytes to neurons by sponging the miR-1906. The low of miR-1906 within the astrocytes would promote the A2 to A1 by overexpression of TLR4. It would amplify ischemia-reperfusion injury. The recombinant virus vector with TetOn system in this promoter would deliver the MEG3 shRNA sequences into cells. It would express MEG3 shRNA in the presence of tetracycline, which would reduce the MEG3 level to release the miR-1906. The miR-1906 would promote the polarization of astrocytes from A1 to A2 and transfer to neurons to treat ischemia-reperfusion injury. This project is the further extension of the previous study, which would deepen the mechanism of MEG3/miR-1906/TLR4 in the pathophysiology of ischemic stroke and translate it from bench to bedside.

项目组前期研究发现星形胶质细胞经外泌体向神经元转运miR-1906，通过抑制TLR4表达减轻卒中的缺血再灌注损伤。但随着缺血时间延长，星形胶质细胞内miR-1906增多但通过外泌体转至神经元的miR-1906却显著减少。预实验显示卒中后星形胶质细胞极化为促炎型(A1)和抗炎型 (A2)。本项目认为卒中后星形胶质细胞内长链非编码RNA MEG3过表达，通过吸附miR-1906，导致TLR4过表达，促使星形胶质细胞极化为A1型，放大缺血再灌注损伤；含TetOn系统重组病毒载体携带MEG3的shRNA序列，在四环素存在下抑制MEG3水平，释放miR-1906，使活化的星形胶质细胞从A1型向A2型转化，促使miR-1906向神经元转移，治疗缺血再灌注损伤。本项目是前期研究的延伸，通过提出新的机制，有效弥补了前期研究的不足，将为卒中的治疗进一步打下理论基础。

【项目背景】血管再通治疗是缺血性卒中的标准治疗，然而血管再通带来的缺血再灌注损伤使得部分患者出现无效灌注。经过研究，我们发现miR-1906可以通过抑制神经元内TLR4表达减轻卒中的缺血再灌注损伤。miR-1906主要来自于星形胶质细胞，随着缺血时间的延长，来自星形胶质的miR-1906却显著减少。本项目主要就是探讨来自来自星形胶质细胞的miR-1906减少的机制，并且通过该机制来减轻缺血再灌注损伤。【研究内容】 MEG3吸附星形胶质细胞内miR-1906；MEG3抑制星形胶质细胞内miR-1906通过外泌体转移至神经元；A1型星形胶质细胞促进MEG3高表达；MEG3/miR-1906/TLR4促使星形胶质细胞向A1型极化；抑制MEG3治疗缺血再灌注损伤。【重要结果及关键数据】我们首先利用单细胞测序联合空间转录组测序法，将缺血半暗带中的星形胶质细胞分类，经过分析可分为A1型（促炎型）和A2型（抑炎型）。接着，利用流式分选A1型星形胶质细胞，发现其长链非编码RNA MEG3过表达，并且MEG3和miR-1906的水平呈负相关；进一步，我们证实MEG3可吸附miR-1906从而降低其水平。当A2型星形胶质细胞感染AD-MEG3高表达MEG3，iNOS/Arg1免疫荧光发现A1型比例，当TLR4被敲除后，该效应就被阻止。最后，将病毒注射到半暗带区域，抑制了MEG3的表达，在不同时间点收集脑组织，用TUNEL法观察梗死核心，半暗带及梗死对侧正常区域内神经元的凋亡，注射病毒可显著减少梗死半暗带区域内的神经元的死亡。【科学意义】本项目作为前期研究的延伸，探讨了缺血再灌注后不同类型星形胶质细胞的作用及相互转化的机制，有效弥补了前期研究的不足，将为卒中的治疗进一步打下理论基础。