心肌梗死是危害人类健康的重大疾病，细胞移植是心肌组织修复最有前景的治疗手段之一，如何提高其修复疗效是关键问题。研究证明移植骨髓间充质干细胞（MSC）的疗效主要通过旁分泌起作用，而MSC所分泌的exosome起到了主要的作用。我们前期研究已发现缺氧处理MSC显著上调其瘦素和miR-210的表达，并证实瘦素在缺氧预处理MSC提高其修复功能中起重要作用。由此我们假设缺氧预处理所带来的MSC疗效提高主要是通过改变其分泌的exosome内含物贡献的，瘦素在调节exosome内含物中起重要作用。本研究拟进一步探索瘦素对MSC缺氧处理后exosome分泌的影响，明确瘦素对调节诸如miR-210等“有益”microRNA 的表达及募集到exosome中的作用，从新的角度揭示干细胞修复心肌的机制及提高疗效的途径，为今后开发以瘦素关联分子为靶标，利用exosome为制剂的新型心肌修复治疗方法提供理论依据。

Myocardial infarction is a major hazard disease to human health. Cell transplantation is one of the most promising treatment for myocardial tissue repair, and how to improve the repair efficacy is the key issue. The therapeutic effect of transplanted cells is thought through secretion of stimulaing factors, which is named as paracrine effect. Our preliminary study has shown that hypoxic preconditioning improved the therapeutic efficacy of bone marrow derived mesenchymal stem cells (MSC), which was associated with significantly upregulated expression of leptin and microRNA 210; wild-type MSC had more miR-210 in their secreted exosome and better enhanced myocardial repair capacity than leptin deficient MSC, suggesting that leptin plays an important role for hypoxic preconditioned MSC to promote cardiac repair. The proposed study will determine the signaling network of leptin in hypoxic preconditioned MSC and the role of leptin in controling content of exosome, by comparing MSCs from wild type,leptin deficient，and leptin receptor deficient mice. We will define the role of leptin on miR-210 expression, exosome secretion,and on paracrine effect of MSC preventing cardiomyocyte apoptosis, promoting the recruiting cardiac stem cells. By testing the "leptin-dependent" myocardial repair hypothesis in hypoxia preconditioned MSC threpay,we will define the mechanism by which stem cells repair myocardial tissue. The results will enhance our understanding of stem cell biology, enable us to refine cell-based therapeutic strategies, and develop new cell-free, exosome-based therapeutic reagent for the treatment of cardiovascular diseases.