间充质干细胞（MSC）移植的心脏修复和再生作用可能与旁分泌机理有关，目前对旁分泌因子生物属性及作用机理知之甚少。MSC表达CD73蛋白，催化生成的细胞外腺苷对T细胞免疫有调节作用。本课题首先通过移植CD73缺失MSC和重组CD73蛋白以及MSC细胞膜成分，揭示CD73在腺苷生物合成中的意义；其次通过分析MSC心脏移植后心肌组织中腺苷浓度、炎症介质释放、免疫细胞浸润以及M1∕M2巨噬细胞的分化过程，揭示MSC移植对免疫反应，尤其是T细胞免疫的调节作用；最后以抗体耗竭CD4阳性细胞和制备免疫细胞A2a和A2b受体缺失嵌合体小鼠，研究腺苷介导免疫调制作用的潜在靶点。总之，本课题将以MSC→CD73→腺苷→T细胞A2a受体→炎症介质释放→M1∕M2巨噬细胞分化→心肌修复和再生为研究轴线，从腺苷的生物合成，作用靶点和功能分析等方面，阐明腺苷作为干细胞旁分泌因子介导免疫调制作用的心肌修复和再生作用。

The regenerative effects of mesenchymal stem cell (MSC)-based therapy for ischemic heart disease have been suggested to be mediated by a paracrine mechanism by which MSC generates indirectly therapeutic benefits by releasing soluble bioactive factors that may exert various biological impacts on cardiac repair, including myogenesis, angiogenesis and immunomodulation. However, the biological nature of the paracrine factors has not been well documented. Our previous study showed that the extracellular adenosine (Ado) which was enzymatically catalyzed by ecto-5-nucleotidase (CD73) modulated T-cell immunity after tissue damage, suggesting adenosine may serve as a paracrine factor that modulates the local inflammatory response after ischemic injury. In pursuit of such knowledge, we then aim to reveal the mechanistic insight into the adenosine-mediated immunomodulation in the cardiac protection after MSC therapy. Firstly, we will transplant MSC from CD73 knock-out mice and the membrane fraction of MSC as well as recombinant CD73 peptide to prove the crucial role of CD73-built Ado in the immunomodulation in cardiac protection and repair after injury. Secondly, we will analyse the interstitial concentration of Ado, intensity of cardiac inflammation, composition of the infiltrated immune cells and the subsequent polarization of M1/M2 macrophages to demonstrate the obligated role of Ado-mediated immunomodulation in MSC-induced cardiac protection. Finally, we will exhaust CD4 T cells by using a specific antibody and generate chimeric mice lacking immune cell-specific A2a/A2b receptor by the means of bone marrow transplantation to analyze the cellular target and intracellular cascade of Ado-mediated immunomodulation in cardiac protection. Therefore, this proposal will follow the research axis of MSC→CD73→ Ado → Treg/Th cells →A2a/A2b receptors → cytokine/chemokine release → M1/M2 polarization → cardiac regeneration to identify extracellular adenosine as a pivotal paracrine factor that regulates T-cell immunity and promotes cardiac repair. This novel finding will provide the mechanistic basis of CD73-based therapy for ischemic heart disease.