Molecular and Microstructural Imaging of Cardiomyocyte Apoptosis and Autophagy

描述（由申请人提供）：缺血再灌注期间心肌损伤的演变仍不完全清楚。心肌细胞（CM）可以通过坏死、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是特别感兴趣的，因为两者都是高度调节和能量需要的过程，在再灌注过程中易于调节。因此，这项建议的总体目标是使用新的分子和微观结构成像技术，最近在我们的中心开发，在体内心肌细胞凋亡和自噬的图像。通过使用这些技术，我们的目标是更好地了解程序性CM死亡如何发生在心肌再灌注过程中，以及如何防止这种情况。该提议的中心假设是，由于存在于该区域中的缺血和再灌注的平衡，中层心肌中的CM最容易发生细胞凋亡，但是它们也最容易通过自噬的发展进行挽救，自噬通过去除功能障碍的线粒体和其他促凋亡刺激物来保护CM。使用AnxCLIO-Cy 5.5进行CM凋亡的MRI和荧光成像，一种由参与CM自噬的溶酶体组织蛋白酶激活的近红外荧光染料，以及扩散光谱MRI来可视化心肌纤维结构，我们旨在：1）确定缺血严重程度和再灌注程度的透壁变化如何影响心肌细胞凋亡和自噬的发展，2）研究后适应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。所提出的成像方法是高度平移的，并且将允许在细胞水平上的CM损失的方面与可以在小鼠和人类中获得的心肌结构和功能的读数相关。拟议的研究有可能通过促进增加挽救中层心肌细胞的策略的发展来显著影响临床护理，从而将高度透壁和耐受性差的心肌梗死转化为耐受性良好的内膜下梗死。 公共卫生相关性：心肌（心脏肌肉）可以通过多种方式对血液供应不足做出反应，其中一些可能是保护性的，而另一些则是有害的。我们的目的是在这个建议中使用新的分子和微观结构成像技术，以更好地了解心肌急性损伤的反应，从而促进新的心脏保护策略的发展。这些策略的发展有可能显著减少心力衰竭患者人数的迅速增加，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.