MSC来源exosomes在急性心肌梗死损伤修复中的作用及机制

Clinical phase I and II studies have shown that mesenchymal stem cells (MSCs) transplantation is beneficial to the repair of acute myocardial infarction (AMI), but is restrained by the low survival rate of transplanted MSCs, aggravation of stenosis, and safety issue. We have demonstrated that exosomes secreted by human umbilical cord MSC(ucMSC-exosome) exhibit the similar therapeutic effects on impaired cardiomyocytes to that of ucMSCs. The non-cell-based transplantation of exosomes may overcome the deficiencies that observed in ucMSCs, which possess a better prospective for clinical use. There is an urgent need to evaluate the roles and the mechanisms of action of ucMSC-exosomes in AMI tissue injury repair.This research is aimed to isolate and purify exosomes that fulfill the requirement of pre-clinical studies from normal and Akt gene modified ucMSC, establish the standard protocol for using ucMSC-exosomes in rat AMI model, seek for the critical targets and molecular pathways by which ucMSC-exosomes perform their therapeutic effects,and monitor the safety of ucMSC-exosomes for long-term use. This project will provide an experimental basis for the commercialization of ucMSC-exosomes, an alternative approach and a novel strategy for AMI therapy.

临床I期和II期实验已经证实间质干细胞（MSC）能修复急性心肌梗死(AMI)损伤，但MSC存在移植存活率低、加重狭窄及致瘤安全性隐患等不足使得其临床应用受到限制。我们发现脐带MSC旁分泌的活性成分exosomes（ucMSC-exosomes）能修复损伤心肌，同时又能避免MSC的许多不足，较MSC更具有临床应用前景。因此，ucMSC-exosomes用于AMI损伤修复治疗作用及机制值得进一步研究。本研究将分离纯化能满足临床前试验的质量标准ucMSC-exosomes及Akt修饰MSC来源的exosomes，结合大鼠AMI模型，建立ucMSC-exosomes对AMI损伤修复治疗方法，寻找ucMSC-exosomes对AMI损伤修复的关键靶点及分子通路，并评价其长期应用的安全性，为ucMSC-exosomes产品化提供实验基础，为AMI的治疗提供一个可供选择的基于MSC的非细胞疗法和新思路。

基于干细胞对缺血性心脏病治疗的旁分泌机制，本研究旨在分离人脐带间质干细胞来源的exosomes（hucMSCs-exosomes），研究hucMSCs-exosomes及过表达Akt人脐带间质干细胞来源的exosomes（Akt-hucMSC-exosomes）对大鼠AMI损伤修复作用及机制，并比较全面地评估了人脐带间充质干细胞来源的exosomes (hucMSC-exosomes)的安全性。本研究成功分离鉴定hucMSCs-exosomes 和Akt-hucMSC-exosomes，通过尾静脉输注hucMSCs-exosomes能够减少缺氧诱导的大鼠心肌细胞凋亡，改善AMI大鼠左室心肌收缩功能并减少胶原沉积，对大鼠AMI损伤具有修复作用，Akt-hucMSC-exosomes较hucMSC-exosomes具有更强的AMI损伤修复作用。研究表明其修复作用机制与促进血管形成相关，并主要通过高表达PDGF-D促进血管形成在急性心肌梗死中起着保护作用。在exosomes修复心肌梗死过程中，exosomes中富含的miR-92b及miR-125b可能是通过调节Smad7进而促进心功能恢复。hucMSC-exosomes的安全性研究表明hucMSC-exosomes不会引起溶血反应，对注射点的血管、肌肉及周围组织都没有刺激性，不含有过敏原和致热源，对血常规指标没有不良影响，对AMI模型的大鼠体重的降低有一定的缓解作用，并且对肝功能、肾功能都没有副作用，各项结果都显示hucMSC-exosomes的应用安全可靠。本研究提示hucMSCs-exosomes可为AMI临床治疗提供可选择的方法和思路，为更深入研究MSCs成分治疗组织损伤提供实验依据。