凋亡MSCs刺激单核-巨噬细胞分泌外泌体对急性心肌梗死心肌修复的新机制

The inflammatory cells play a key role in cardiomyocyte regeneration therapy after acute myocardial infarction. Our preliminary study had found the main mechanism of the MSCs transplantation was that monocytes/macrophages infiltrating into the infarction zone phagocytized dead MSCs and subsequently secreted a variety of cytokines such as Ang-1, VEGF-α, IGF-1 which contributed to the repairation of the myocardium. Then we further found that the activated macrophages were able to secret a number of exosomes which can lead to better microenvironment in the infarction zone.However,in view of the complexity of the composition for exosomes, we still know little about the exact contents and mechanisms in the repairation of the myocardium.Thus,we give the hypothesis that the cirtical mechanism of MSCs repairation after AMI is the exosomes excreted by the macrophages which phagocytied apoptic MSCs. So,we will ① to explore the mechanisms of macrophage exosomes stimulated by apoptotic MSCs,screen the ingredients of the exosomes which are benefit to the viability of cardiac cells as well as the differentiation of cardiac stem cells ex vivo.②to explore the regulative mechanisms of exosomes secreted by macrophages through NF-kappa B/Heparanase/Sydecan-1 pathway. ③ to verify the efficacy of the exosomes derived from macrophages phagocytized apopotic MSCs in vivo in AMI mouse model. This study will give the new idea that the exosomes secreted by the macrophages which had phagocytized the dead MSCs are the main mechanism in myocardial MSCs repairation.

急性心肌梗死（AMI）后心肌细胞再生治疗中炎症细胞起着关键作用。我们的前期研究表明，MSCs移植治疗AMI主要是浸润至梗死区的巨噬细胞吞噬凋亡MSCs，分泌Ang-1、VEGF和IGF-1等细胞因子，促进了损伤心肌的修复；进一步研究发现，活化的巨噬细胞能分泌较多外泌体，改善干细胞移植微环境；但外泌体成分复杂，其发挥保护作用的组分及机制未明。我们提出假说：巨噬细胞吞噬凋亡的MSC后分泌的外泌体在AMI后心肌修复中起关键作用。据此，本项目以吞噬了凋亡MSCs的巨噬细胞及外泌体为研究对象，拟：①阐述巨噬细胞外泌体对心肌细胞活力以及心肌干细胞分化的影响，筛选有益心肌存活和修复的外泌体成分；②探讨经NF-kappa B/Heparanase/Sydecan-1路径调节巨噬细胞外泌体的机制；③体内验证"好"外泌体抑制心肌损伤、促进干细胞再生的作用机制。本研究将揭示AMI后干细胞移植治疗的新机制。

急性心肌梗死(AMI)后干细胞移植仍是治疗策略之一，然而研究表明骨髓间充质干细胞（MSC）移植进入心梗心脏内大部分发生凋亡，但仍发挥保护作用，我们前期体外研究表明凋亡的MSCs可被巨噬细胞吞噬，吞噬后巨噬细胞分泌多种生长因子，进而减少缺氧条件下心肌细胞凋亡，体内研究表明将MSCs经尾静脉注射进入心梗小鼠体内后，可发挥心脏保护作用，但具体机制仍不明确。本研究发现1.缺血缺氧条件下，MSCs凋亡明显增加，且这些凋亡的MSCs能被巨噬细胞吞噬，2.吞噬了凋亡MSCs的巨噬细胞分泌的外泌体可促进巨噬细胞向M2极化，同时减少缺氧条件下乳鼠心肌细胞的凋亡水平，3.在体研究表明，将吞噬了凋亡MSCs的巨噬细胞分泌的外泌体注射进入心梗老鼠心脏内可减少心肌细胞的凋亡水平、降低心梗面积进而提高心功能，4.凋亡MSCs被巨噬细胞吞噬后可改变巨噬细胞分泌外泌体所携带的生物活性物质，其分泌的外泌体携带多种与炎症相关的miRNA，进而发挥炎症调节作用，诱导巨噬细胞M2极化，改善心功能。通过本研究我们发现干细胞对心肌梗死后心脏的保护机制主要通过改变巨噬细胞分泌的外泌体发挥作用，外泌体携带多种炎症相关的miRNA发挥免疫调节作用，促进巨噬细胞极性改变从而提高心功能，本研究为急性心肌梗死的干细胞治疗带来新思路。