Strategic activation of endogenous c-kit+ progenitor cells for cardiac regeneration

 描述(由申请人提供)：心力衰竭的患病率继续上升，发病率和死亡率令人无法接受。目前，已有600多万美国人被诊断为心力衰竭，每年相关的医疗费用估计为350亿美元，而且还在上升。心力衰竭的最重要原因是缺血性心肌病，缺血事件导致的心肌细胞丢失是疾病的主要驱动因素。由于心脏再生的速度有限(据估计，在正常衰老期间，每年有1%的新心肌细胞形成)，剩余心肌细胞的工作量增加，导致心肌肥大，最终导致心力衰竭。由于心力衰竭最重要的驱动力是心肌细胞的丧失，因此在成人心脏中发现的心脏前体细胞可以在培养时产生所有的心脏谱系，这揭示了促进心脏再生的可能性。到目前为止，使用培养的CPC进行细胞治疗一直是促进心脏再生的主要方法。然而，大多数注射的细胞在几周内死亡，心脏功能的最终改善可能是由内源性CPC介导的。目前的建议将确定刺激CPC以促进内源性再生的方法。我们的长期目标是了解内源性CPC如何被激活以响应心脏损伤，以及是什么决定了CPC在体内的命运，最终目标是找到促进内源性心脏再生的策略。我们最近发表了允许对内源性心脏祖细胞进行谱系追踪的遗传小鼠模型，并将在整个提案中使用这些小鼠模型。在内源性CPC的遗传谱系追踪中，我们注意到有许多内皮细胞生成，但只有少数心肌细胞生成。然而，我们假设内源性CPC可以被激活以增强它们的心源性潜力。建议的小鼠遗传模型和特定信号通路的操作将用于确定促进心脏再生的策略。我们的具体目标是1)确定不同刺激是否以及如何激活内源性心脏c-kit+CPC向心脏谱系发展，2)确定阻断内皮细胞命运是否会激活内源性c-kit+CPC成为心肌细胞，以及3)确定Notch1信号对c-kit+祖细胞向内皮细胞和心肌细胞的增殖和分化的重要性程度。这项研究的目的是确定能够刺激内源性心脏前体细胞产生更多心肌细胞的途径。未来的研究将采用促进内皮祖细胞增殖和分化的策略，以促进心脏再生。

 DESCRIPTION (provided by applicant): The prevalence of heart failure continues to rise with unacceptable rates of morbidity and mortality. Currently, over 6 million Americans have been diagnosed with heart failure with an associated annual health care expense estimated at 35 billion US dollars and rising. The single most important cause for heart failure is ischemic cardiomyopathy, where loss of cardiomyocytes due to ischemic events is the main driver of disease. Due to limited rates of cardiac regeneration (estimated at 1% new cardiomyocyte formation per year during normal aging), the workload on remaining cardiomyocytes is increased, giving rise to cardiac hypertrophy and ultimately heart failure. Since the most important driver of heart failure is loss of cardiomyocytes, the discovery of cardiac progenitor cells (CPCs) in the adult heart that can give rise to all cardiac lineages when cultured uncovered the possibility of enhancing cardiac regeneration. Up until this point cell therapy using cultured CPCs has been the main method used to enhance cardiac regeneration. However, most injected cells die within weeks and the ultimate improvement in cardiac function is likely mediated by endogenous CPCs. The current proposal will identify ways of stimulating CPCs to enhance endogenous regeneration. Our long-term goal is to understand how endogenous CPCs are activated in response to cardiac injury and what determines CPC fate decisions in vivo with the ultimate objective of finding strategies that enhance endogenous cardiac regeneration. We recently published genetic mouse models that allow lineage tracing of endogenous cardiac progenitor cells and will use these mouse models throughout this proposal. Upon genetic lineage tracing of endogenous CPCs we noted many endothelial cells being generated, but only few cardiomyocytes. However, we hypothesize that endogenous CPCs can be activated to enhance their cardiogenic potential. The proposed genetic mouse models and manipulations of specific signaling pathways will be used to identify strategies to enhance cardiac regeneration. Our specific aims are to 1) Determine whether and how different stimuli activate endogenous cardiac c-kit+ CPCs toward cardiac lineage, 2) Determine whether blocking endothelial fates will activate endogenous c-kit+ CPCs to become cardiomyocytes, and 3) Establish to what extent Notch1 signaling is important for c-kit+ progenitor proliferation and differentiation toward both endothelial cells and cardiomyocytes. The goal of this study is to define pathways that can stimulate endogenous cardiac progenitor cells to produce more cardiomyocytes. Future studies will employ strategies to enhance the proliferation and differentiation of eCPCs to improve cardiac regeneration.