Hypercholesterolemia in Cardiac Function, Survival and Repair

描述（由申请人提供）：越来越多的机制和转化研究支持使用基于细胞的治疗来修复因梗死而破坏的心肌组织并恢复心脏功能。成体原始细胞群的几个表型不同的亚群已被证明可以改善心肌梗死（MI）和心力衰竭动物模型的心脏结构和功能。干细胞治疗的小型临床试验已经概括了缺血性心肌病患者的这些有益效果。最近心脏干细胞（CSC）的发现引发了人们对开发有前途的心脏修复/再生干细胞疗法的强烈希望，因为CSC天生就具有重建心脏组织的功能。在最近的研究中，我们发现冠状动脉内输送CSCs给急性或慢性MI大鼠和慢性MI猪改善心脏功能和再生新的心脏细胞。然而，需要心脏修复治疗的人类患者通常具有一系列心血管风险因素，如高胆固醇血症（HC），糖尿病，高血压等。随着最近对患者细胞疗法的兴趣激增，了解这些风险因素对细胞介导的心脏修复的影响非常重要。特别是，HC是一种非常普遍的风险因素，并导致一系列病理生理学后果。因此，本提案的总体目标是研究HC对CSC介导的心脏修复的影响。我们的基本假设是，根据具体情况，胆固醇在CSC介导的心脏修复中可能是有益的或有害的。我们提出，血浆胆固醇的轻度升高或LDL-胆固醇的最低限度氧化修饰形式的存在预处理心肌和CSC;预处理CSC的细胞植入和增强的旁分泌信号传导机制的预处理心肌微环境的组合协同工作，以增强CSC介导的心脏修复。我们进一步提出，血浆胆固醇的显著升高或LDL-胆固醇的完全氧化形式的存在引起对CSC和心肌的氧化损伤，导致用于心脏修复的细胞疗法的功效丧失。我们将在3个特定目标下使用存在不同修饰的LDL的体外培养的CSC和心肌细胞以及具有不同血浆胆固醇水平的MI的体内大鼠模型来测试这些假设。目的1将确定HC对CSC介导的体内心脏修复的影响;目的2将确定LDL对CSC功能和体外修复能力的影响;目的3将确定体外用不同修饰的LDL预处理CSC是否会改变体内心脏修复治疗的疗效。鉴于血浆胆固醇是一种可改变的风险因素，但也是细胞功能所必需的，了解这种普遍的风险因素对基于干细胞的治疗的影响将具有翻译和机制的重要性。该项目将为急需的临床前框架提供新的见解，以开发用于心血管风险因素患者心脏修复的细胞疗法。

DESCRIPTION (provided by applicant): Mounting mechanistic and translational studies support the use of cell-based therapies to repair myocardial tissue destroyed by infarction and to restore cardiac function. Several phenotypically distinct subsets of adult primitive cell populations have been shown to improve cardiac structure and function in animal models of myocardial infarction (MI) and heart failure. Small clinical trials of stem cell therapy have recapitulated these beneficial effects in patients with ischemic cardiomyopathy. Recent discovery of cardiac stem cells (CSCs) has sparked intense hope for the development of promising stem cell therapies for cardiac repair/regeneration because CSCs are inherently programmed to reconstitute cardiac tissue. In recent studies, we found that intracoronary delivery of CSCs to rats with either acute or chronic MI and to pigs with chronic MI ameliorated cardiac function and regenerated new cardiac cells. However, human patients needing cardiac reparative therapies generally possess an array of cardiovascular risk factors such as hypercholesterolemia (HC), diabetes, hypertension etc. With the recent surge of interest in cell therapies for patients, it is important to understand the impact of these risk factors on cell-mediated cardiac repair. In particular, HC is a highly prevalent risk factor and contributes to a range of pathophysiological consequences. Hence, the overall goal of this proposal is to investigate the impact of HC on CSC-mediated cardiac repair. Our fundamental hypothesis is that depending on the specific conditions, cholesterol can be beneficial or detrimental in CSC-mediated cardiac repair. We propose that mild elevations of plasma cholesterol or the presence of the minimally oxidatively modified form of LDL-cholesterol precondition both the myocardium and the CSCs; the resulting combination of a primed myocardial microenvironment for cell engraftment and enhanced paracrine signaling mechanisms of preconditioned CSCs work in concert to enhance CSC-mediated cardiac repair. We further propose that marked elevations of plasma cholesterol or the presence of the completely oxidized form of LDL- cholesterol provoke oxidative injury to both the CSCs and the myocardium, leading to loss of efficacy of cell therapies for cardiac repair. We will test these hypotheses under 3 specific aims using both in vitro cultured CSCs and cardiomyocytes in the presence of differently modified LDLs and in vivo rat models of MI with different levels of plasma cholesterol. Aim 1 will determine the effects of HC on CSC-mediated cardiac repair in vivo; Aim 2 will determine the effects of LDLs on CSC function and reparative capability in vitro; and Aim 3 will determine whether pretreatment of CSCs with differently modified LDLs in vitro alters the efficacy of cardiac reparative therapy in vivo. Given that plasma cholesterol is a modifiable risk factor, but is also essential for cellular function, understanding the effects of this prevalent risk factor on stem cell-based therapies will have translational and mechanistic importance. This project will provide novel insights into a much-needed preclinical framework to develop cell-based therapies for cardiac repair in patients with cardiovascular risk factors.