Molecular and Microstructural Imaging of Cardiomyocyte Apoptosis and Autophagy

描述（由申请人提供）：缺血再灌注过程中心肌损伤的演变尚不完全清楚。现在有充分的证据表明，心肌细胞（CM）可以通过坏死、凋亡或自噬对损伤作出反应。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和需要能量的过程，可在再灌注期间调节。因此，本提案的总体目标是利用我们中心最近开发的新型分子和微观结构成像技术，对体内心肌细胞凋亡和自噬进行成像。通过使用这些技术，我们旨在更好地了解程序性CM死亡是如何在心肌再灌注期间发生的，以及如何预防这种情况。该建议的中心假设是，由于心肌中存在缺血和再灌注平衡，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对CM细胞凋亡进行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，以及弥散谱MRI显示心肌纤维结构，我们的目标是：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。所提出的成像方法具有高度的可转译性，可以将细胞水平上的CM损失与小鼠和人类的心肌结构和功能读数相关联。该研究有可能通过促进策略的发展来显著影响临床护理，从而增加挽救的心肌细胞，从而将高度跨壁和不良耐受性的心肌梗死转化为耐受性良好的心内膜下梗死。

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.