M1型巨噬细胞来源的外泌体抑制心肌梗死后血管新生、心肌再生的机制

M1 type macrophages inhibit cardiac repair after myocardial infarction. We have found that M1 type macrophages release a large number of exosomes (M1-Exo) post myocardial infarction. By comparing the miRNA expression profiles of M1-Exo and M2-Exo, it was found that miR-155 and miR-200b/c were highly expressed in M1-Exo. We also found that M1-Exo played a role in inhibiting angiogenesis and the proliferation of cardiomyocytes by transferring miR-155 to endothelial cells and cardiomyocytes. Furthermore, we demonstrated that rac1, pak2, sirt1 and ampka2 were new target genes for miR-155, whereas akt1, bcl2, and enos were new target genes for miR-200b/c. Therefore, this project aim to verify the following hypothesis: after myocardial infarction, ischemia and hypoxia, TNFα, and IL-1β stimulate M1 type macrophages to release exosomes and transfer miR-155, miR-200b/c, and other miRNAs to endothelial cells and cardiomyocytes. Among them, miR-155 inhibits endothelial cell proliferation, migration and angiogenesis and inhibits myocardial regeneration by targeting rac1, pak2, sirt1, ampka2, and enos. miR-200b/c target akt1, bcl2, and enos. M1 macrophages aggravate myocardial damage, restrain angiogenesis and myocardial regeneration by exosomes secretion, leading to cardiac repair inhibition and promoted ventricular remodeling. The elucidation of this mechanism helps to illuminate the effect and mechanism of M1 macrophages on cardiac repair and cardiac remodeling from the new perspective of exosomes. It will also provide more ideas and scientific basis for clinical prevention and treatment of myocardial infarction.

M1型巨噬细胞抑制心肌梗死后的心脏修复。我们前期发现心梗后M1型巨噬细胞释放外泌体（M1-Exo）增加。miRNA表达谱分析表明miR-155、miR-200b/c等在M1-Exo中高表达。M1-Exo通过传递miR-155抑制血管形成能力及心肌细胞增殖。进而我们筛选出miR-155、miR-200b/c各自的几个新靶基因。因此本项目旨在验证如下科学假说：心梗后，受缺血缺氧、TNFα、IL-1β等刺激，M1型巨噬细胞以外泌体为载体，传递丰富的miRNAs至血管内皮、心肌细胞。其中miR-155、miR-200b/c分别通过新靶基因rac1、pak2、sirt1、ampka2和akt1、bcl2、enos等，抑制血管新生、心肌再生能力。最终抑制心脏修复、促使心室重构。该机制的阐明，有助于从外泌体这一新的角度阐明M1型巨噬细胞抑制心脏修复的机制，将为心肌梗死的临床防治提供更多的思路和科学依据。

心肌梗死后，巨噬细胞发挥的炎症反应是调控心脏修复、心室重构的重要环节。在不同的炎症环境下，巨噬细胞可分化为不同类型的细胞从而呈现不同的功能，主要分化为M1型巨噬细胞和M2型巨噬细胞两种类型。M1型巨噬细胞主要作用是分泌细胞炎症因子和趋化因子激活炎症，促进MMPs分泌、细胞外基质的降解和清除坏死组织及细胞碎片。然而炎症反应控制不良或过强的炎症反应会促进大量的M1型巨噬细胞浸润，M1型巨噬细胞能够抑制心肌梗死后的心脏修复，但是其潜在机制尚未完全阐明。外泌体（Exos）携带多种生物分子，通过介导细胞之间的物质信息传递，调节细胞存活、血管再生及免疫反应等功能，因而近年来其在心梗微环境中的作用受到了广泛关注。我们研究发现在心梗后的炎症反应期，细胞因子如GM-CSF、IFN-γ、TNF-α、IL-1β以及缺血缺氧等刺激能够诱导巨噬细胞分化为M1型巨噬细胞，并且M1型巨噬细胞能释放大量的外泌体（M1-Exo）。随后我们验证了M1-Exo抑制小鼠心肌梗死后心脏功能和血管新生并进一步发现M1-Exo抑制人冠脉内皮细胞细胞增殖、迁移和小管形成能力以及抑制心肌细胞增殖。通过miRNA表达谱分析表明miR-155在M1-Exo中高表达。M1-Exo能够通过传递miR-155至内皮细胞和心肌细胞并抑制血管新生及心肌细胞增殖。进而我们筛选出并验证了miR-155的几个新靶基因如RAC1、PAK2、Sirt1、AMPKα2和eNOS。本项目证实了如下科学假说：在心肌梗死微环境下，受缺血缺氧（OGD）、GM-CSF、IFN-γ、TNFα、IL-1β等刺激，M1型巨噬细胞以外泌体为载体，传递miR-155至血管内皮细胞和心肌细胞，通过靶向RAC1、PAK2、Sirt1、AMPKα2和eNOS等基因，抑制内皮细胞的增殖、迁移和血管形成能力，抑制心肌细胞增殖，进而抑制心肌梗死后的血管新生和心脏修复。该机制的阐明，有助于从外泌体这一角度阐明M1型巨噬细胞抑制心脏修复的机制，将为心肌梗死的临床防治提供更多的思路和科学依据。