树突状细胞源Exosomes介导miR-92a调控小鼠心肌梗死后氧化应激和血管新生的作用研究

Angiogenesis is a key mechanism in myocardial repair after myocardial infarction (MI), which is closely associated with oxidative stress. Dendritic cell(DC) is highly involved in the process of oxidative stress and cardiac remodeling after MI. With DC depletion, post-infarction myocardial angiogenesis is impaired, resulting in aggravation of myocardial remodeling. However, the mechanism remains unclear. MicroRNA-92a(miR-92a) plays a complex role in the progression of cardiac angiogenesis. Our preliminary study revealed that the expression of miR-92a was significantly increased in both DC and exosomes derived from DC (DEX). We hypothesize that DEX-miR-92a can promote cardiac angiogenesis through oxidative stress reduction in cardiac microvascular endothelial cell(CMEC) after MI. In vitro, fluorescent labeling and confocal laser scanning microscope were used to observe the secretion of DEX and transfer of endogenous DEX between DC and CMEC initially. The effects of DEX-miR-92a on improving oxidative stress were then investigated through migration and tube formation of CMEC, and luciferase assay was used to confirm the target gene of miR-92a. In vivo, based on MI model of conditional DC knockout mice, we evaluated the relationship between the expression of DEX-miR-92a, oxidative stress and cardiac angiogenesis, and simultaneously studied the positive effects on cardiac angiogenesis via injection of DEX-miR-92a through the tail vein. This project presents an innovative theory in which Dendritic cells(DC) can improve cardiac remodeling after MI through secretion of DEX-miRNAs.

血管新生是心肌梗死（MI）后心肌修复的关键环节，而氧化应激反应与血管新生关系密切。树突状细胞（DC）参与MI后氧化应激和心肌重构过程，DC缺失导致MI后心肌微血管（CMV）新生障碍。我们发现心肌细胞坏死液刺激DC分泌外泌体microRNA-92a（DEX-miR-92a）显著增高，而miR-92a是CMV新生的重要调控因子。因此假设：MI后DC分泌DEX-miR-92a抑制心肌微血管内皮细胞（CMEC）氧化应激进而引起CMV新生。本研究拟采用荧光标记技术证实DC分泌DEX-miR-92a；体外研究DEX-miR-92a对CMEC氧化应激、成管功能、迁移能力的调控机制；再基于条件性DC敲除小鼠MI模型并回输DEX-miR-92a，在体确立DEX-miR-92a抑制氧化应激并引起CMV新生和改善心肌重构的效应。本项目提出了MI后DC分泌DEX-miRNAs抑制氧化应激反应参与CMV的新见解。

树突状细胞（DC）参与心肌梗死（MI）后氧化应激和心肌重构过程，DC缺失导致MI后心肌微血管新生障碍。在该项目中，我们发现DC起源的外泌体miR-92a可以靶向抑制KLF2的表达，从而参与血管的发育、改善内皮细胞增殖、迁移能力及促进损伤血管内皮的修复，从而减轻心脏氧化应激反应，促进血管新生，改善心功能。另外，我们针对DC进行了一些其他方面的探索性研究。我们在体外模拟高脂血症小鼠心梗和RAS被激活的内环境，发现 ox-LDL在AngⅡ的基础上进一步诱导DCs免疫成熟、迁移和炎症反应，LOX-1-TLR4-MyD88信号通路参与了DCs成熟和炎症反应在高脂血症合并心肌梗死发生和发展的过程。在此基础上，我们发现ACEI能够减少DCs向心肌组织的浸润，并减少外周血DCs数量，抑制DCs的脾脏动员，改善MI后的炎症反应和心室重构，而通过抑制AT2受体的表达，可以减弱ACEI对DC的上述作用，说明AT2受体可能部分参与了心肌梗死后ACEI对DC的抗炎作用和心室重构的影响。同时，高脂状态下，ACEI的这些作用也被抑制，其机制可能与TLR4-MyD88-NF-ΚB信号通路的激活有关。在针对miRNA进行研究时，我们还发现miR-19a可通过下调NHE-1的表达和减轻钙超载，从而减弱缺氧诱导的心肌细胞凋亡。我们的研究结果提示，树突状细胞在心梗后心肌重塑、动脉粥样硬化乃至血脂代谢过程中发挥了复杂的作用，其作用机制包括miRNA、外泌体等。针对上述作用机制的更深入研究有助于我们发现治疗疾病的新靶点。