GRIM-19协同STAT3在促进心肌细胞增殖保护梗死心肌中的作用及机制研究

To enforce the re-entry into cell cycle of cardiomyocytes for myocardial regeneration to compensate a significant loss of cardiomyocytes is an ideal method to repair cardiac injury after myocardial infarction (MI), which remains a hot topic for regeneration medicine. Our preliminary data suggest that GRIM-19 (gene associated with retinoid-interferon-induced mortality 19) is critical for cardiomyocyte proliferation which involves mediating HIF1α and c-Myc up-regulation. This set of data suggests GRIM-19 is an important regulator of self-renew for cardiomyocytes. Thus, in the present proposal, we will utilize newly generated tamoxifen inducible cardiac specific (under myh6-Cre) GRIM-19 and STAT3 (loxP) knock-out mice models and use a MI model to elucidate the following scientific questions: 1) moderate down-regulation of GRIM-19 can trigger cardiomyocyte proliferation and generate newer cardiomyocytes, which would significantly improve post-MI remodeling; 2) STAT3 is responsible for GRIM-19 induced cardiac regeneration process which involves increased c-Myc transcription activity; 3) HIF1α as a cofactor of STAT3 facilitates the effect of GRIM-19 on cardiac repair. Completion of this research project would not only further enhance our understand of cardiac regeneration and but also provide new therapeutic approach for treating patients with MI.

增强心肌细胞增殖能力促进心肌细胞再生是恢复心肌梗死后心功能理想的治疗方法，是再生医学的研究热点。本项目组前期研究心脏线粒体复合体I一重要因子即细胞死亡调节因子GRIM-19 (gene associated with retinoid-interferon-induced mortality 19)时，发现适度下调GRIM-19可使心肌细胞重新进入细胞周期，并上调c-Myc和HIF1α的表达。由此推测适度下调GRIM-19可增强心肌细胞增殖修复梗死心肌。本项目拟利用条件性可诱导心肌特异性GRIM-19和STAT3敲除小鼠旨在阐明适度下调GRIM-19可以通过与STAT3协同调控c-Myc转录活性促进心肌细胞增殖和抗凋亡能力达到心肌梗死后修复心肌的作用及HIF1α作为STAT3的协同因子在其中的作用模式。本项目的实施可望揭示心肌梗死后心肌再生一新调控机制，为临床应用提供理论依据。

心肌梗死引起心肌细胞的坏死，继而被纤维瘢痕组织替代，最终导致心力衰竭。成年心肌细胞一直被认为终末分化细胞不能增殖再生。最近的研究表明,哺乳动物成年心肌细胞有较弱的自行增殖再生能力。因此探索促进心肌增殖的机制和策略对于心脏的再生修复具有重要意义。本课题主要研究了GRIM-19（即NDUFA13）对心肌缺血再灌注损伤的作用和对心肌细胞增殖的作用及相关机制。结果表明：1）心肌特异性敲除GRIM-19的杂合子小鼠（Tam-Myh6Cre- GRIM-19flox/+）在GRIM-19下调的同时可以保持心脏正常的形态和生理功能，并且在缺血再灌注过程中可以明显减少应激带来的损伤和凋亡；2）心肌GRIM-19下调明显减少了缺血再灌注带来的永久性心肌死亡面积，有效保存存活心肌组织；3）通过抑制线粒体复合物I和II，Tam-Myh6Cre- GRIM-19flox/+小鼠心肌细胞线粒体剩余氧耗量较野生型老鼠明显增加，其泄露的电子和氧气结合产生的微量H2O2可以明显增加心肌细胞本底的低能ROS值；4）H2O2的增加可导致STAT3二聚化的增加，从而调控Bcl2的含量起到保护心肌的作用，而这个可以被双氧水消除剂NAC消除的过程本身可能和其下游诱导的一系列心肌缺血再灌注保护作用相互联系；5）心肌GRIM-19下调明显增加心尖切除后心肌细胞增殖的能力和心脏功能；6）心肌GRIM-19下调可引起心肌细胞中YAP的表达增加，特异性下调心肌YAP可逆转GRIM-19下调带来的心肌修复作用。该项目发现了GRIM-19对缺血再灌注和心脏再生修复的作用及相关分子机制，为缺血性心脏病患者提供了潜在的治疗靶点与新的策略。