Molecular and Microstructural Imaging of Cardiomyocyte Apoptosis and Autophagy

描述(申请人提供)：缺血再灌注期间心肌损伤的演变仍不完全清楚。目前已有文献表明，心肌细胞可通过坏死、凋亡或自噬对损伤做出反应。然而，这些不同形式的心肌细胞(CM)损伤的全部意义以及它们之间的相互作用仍然知之甚少。心肌细胞(CM)凋亡和自噬之间的相互作用特别令人感兴趣，因为两者都是高度调控的，需要能量的过程都可以在再灌注期间进行调节。因此，这项建议的总体目标是使用我们中心最近开发的新的分子和微结构成像技术来成像活体心肌细胞的凋亡和自噬。通过使用这些技术，我们的目标是更好地了解心肌再灌注期间程序性CM死亡是如何发生的，以及如何防止这种情况发生。这一建议的中心假设是，由于存在缺血和再灌注的平衡，中段心肌中的CM最容易发生凋亡，但它们也最容易通过自噬的发展来挽救，自噬通过去除功能失调的线粒体和其他促凋亡刺激来保护CM。利用AnxCLIO-Cy5.5进行MRI和CM自噬相关溶酶体组织蛋白激活的近红外荧光染料CM的MRI和荧光成像，以及扩散光谱MRI显示心肌纤维结构，我们的目的是：1)确定缺血严重程度和再灌注程度的跨壁变化如何影响心肌细胞凋亡和自噬的发生；2)研究后处理对心肌细胞凋亡和自噬的影响；3)确定心肌细胞凋亡和自噬对心肌纤维结构完整性的影响。建议的成像方法是高度翻译的，并将允许在细胞水平上的CM丢失的方面与在小鼠和人类中都可以获得的心肌结构和功能的读数相关联。这项拟议的研究有可能对临床护理产生重大影响，因为它有助于制定策略，增加对心肌中期细胞的挽救，从而将高度跨壁和耐受性差的心肌梗死转变为耐受性良好的心内膜下心肌梗死。 公共卫生相关性：心肌(心肌)可以通过几种方式对血液供应不足作出反应，其中一些可能具有保护作用，另一些可能是有害的。我们的目标是使用新的分子和微结构成像技术来更好地了解心肌对急性损伤的反应，从而促进新的心脏保护策略的发展。这种策略的发展有可能显著减少迅速上升的心力衰竭患者的数量，因此具有重大的临床和公共卫生意义。

DESCRIPTION (provided by applicant): The evolution of myocardial injury during ischemia reperfusion remains incompletely understood. It is now well documented that a cardiomyocyte (CM) can react to injury by undergoing necrosis, apoptosis or autophagy. However, the full significance of these various forms of cardiomyocyte (CM) injury, as well as their interaction with each other, remains poorly understood. The interplay between cardiomyocyte (CM) apoptosis and autophagy is of particular interest since both are highly regulated and energy requiring processes that are amenable to modulation during reperfusion. The overall aim of this proposal is thus to use novel molecular and microstructural imaging techniques, recently developed in our centers, to image cardiomyocyte apoptosis and autophagy in vivo. By using these techniques we aim to better understand how programmed CM death occurs during myocardial reperfusion and how to prevent this. The central hypothesis of this proposal is that CMs in the midmyocardium are the most susceptible to apoptosis due to the balance of ischemia and reperfusion that exist in this zone, but that they are also the most amenable to salvage through the development of autophagy, which protects the CM by removing dysfunctional mitochondria and other pro-apoptotic stimuli. Using AnxCLIO-Cy5.5 for MRI and fluorescence imaging of CM apoptosis, a near-infrared fluorochrome activated by the lysosomal cathepsins involved in CM autophagy, and diffusion spectrum MRI to visualize myocardial fiber architecture we aim to: 1) determine how the transmural variation in the severity of ischemia and the degree of reperfusion influence the development of cardiomyocyte apoptosis and autophagy, 2) study the effects of postconditioning on cardiomyocyte apoptosis and autophagy 3) determine the impact of cardiomyocyte apoptosis and autophagy on the integrity of myocardial fiber architecture. The proposed imaging approach is highly translational and will allow aspects of CM loss at the cellular level to be correlated with readouts of myocardial structure and function that can be obtained in both mice and humans. The proposed study has the potential to impact clinical care significantly by facilitating the development of strategies to increase the salvage midmyocardial cardiomyocytes, and thus convert highly transmural and poorly tolerated myocardial infarcts into well-tolerated subendocardial infarcts. PUBLIC HEALTH RELEVANCE: The myocardium (heart muscle) can respond to a lack of blood supply in several ways, some of which may be protective and others deleterious. We aim in this proposal to use novel molecular and microstructural imaging techniques to better understand the response of the myocardium to acute injury, and thus to facilitate the development of novel cardio-protective strategies. The development of such strategies has the potential to significantly reduce the rapidly rising number of patients with heart failure, and is thus of major clinical and public health significance.