Hypoxia and cardiac stem cell homing

描述（由申请人提供）：缺血性心脏病是导致充血性心力衰竭的主要原因。最终的治疗方法是追求基于干细胞的再生。骨髓是干细胞的主要储存库。心肌缺血诱导的基质衍生因子-11 （SDF-11）通过SDF-1与CXC趋化因子受体4 （CXCR4）结合，在募集循环BM-derived stem cells （BMSC）到缺血心肌中进行心脏修复中起关键作用。除了外源性干细胞外，越来越多的有力证据表明心脏具有内源性再生潜力。常住性心脏干细胞（CSCs）可用于成人心脏的自我更新。然而，缺血引起的心肌损伤通常是不可逆的。内源性心脏修复失败的机制包括：心肌梗死（MI）后常驻CSCs的急性耗竭，CSCs增殖和自我更新不足，无法快速重建心脏中的CSC群体，以及心肌缺血诱导的有限和短暂的内源性归巢信号（如SDF-11）。我们建议通过体外从心脏中分离和扩增CSCs，在心肌梗死后全身输注，并通过SDF-11/CXCR4信号通路将其招募到缺血心肌，来补充心脏修复的干细胞库。然而，主要的挑战仍然存在，包括正常情况下CSCs的CXCR4表达水平低，移植细胞的存活率低，这限制了干细胞在体内的修复能力。我们提出了一系列体外和体内实验来验证缺氧预处理可以通过调节CXCR4的表达来增加CSC的归巢，并通过细胞保护来提高急性缺血心肌归巢细胞的存活率。此外，重组腺相关病毒（rAAV）介导的SDF-1基因治疗可能使我们能够对慢性心肌缺血患者进行CSC移植。为了验证这些假设，我们提出以下具体目标：(1)评估缺氧诱导的心脏干细胞归巢：CXCR4和HIF-11在细胞募集和保留中的作用。(2)探讨缺氧预处理是否能提高居家CSC的存活率，并探讨其作用机制。(3)探讨rAAV病毒介导的SDF-11基因治疗慢性缺血心肌诱导CSC归巢的可能性。

DESCRIPTION (provided by applicant): Ischemic heart disease is the leading cause of congestive heart failure. The ultimate therapy would pursue stem cell-based regeneration. Bone marrow (BM) can be regarded as the major reservoir of stem cells. Stromal-derived factor-11 (SDF-11) induced by myocardial ischemia plays a critical role for recruiting circulating BM-derived stem cells (BMSC) to ischemia myocardium for heart repair via binding of SDF-1 to CXC chemokine receptor 4 (CXCR4). Besides exogenous stem cells, compelling evidence has accumulated suggesting that the heart has endogenous regenerative potential. Resident cardiac stem cells (CSCs) are potentially available for self-renewing of adult heart. However, myocardial damage from ischemia is usually irreversible. Proposed mechanisms for the failure of endogenous heart repair include: acute depletion of resident CSCs after myocardial infarction (MI), inadequate proliferation and self-renewal of CSCs to rapidly reconstitute CSC population in heart, and limited and transient endogenous homing signals (e.g. SDF-11) induced by myocardial ischemia. We propose to replenish the stem cell pool for heart repair, by isolating and expanding CSCs from heart in vitro, infusing them systemically back in vivo post MI, and recruiting them to the ischemic myocardium using SDF-11/CXCR4 signal pathway. However, major challenges remain, including low level of CXCR4 expression of CSCs under normal conditions, the poor survival of grafted cells, which has limited the reparative capacity of stem cells in vivo. We propose a series of in vitro experiments and in vivo experiments to verify that hypoxia preconditioning can be utilized to increase CSC homing via regulation of CXCR4 expression and enhance survival of homed cells via cytoprotection in acute ischemic myocardium. In addition, recombinant adeno-associated virus (rAAV) mediated SDF-1 gene therapy may permit us to conduct CSC transplantation for patients with chronic myocardial ischemia. To test these hypotheses, we propose the following Specific Aims: (1) To evaluate hypoxia induced cardiac stem cell homing: role of CXCR4 and HIF-11 in cell recruitment and retention. (2) To determine whether hypoxia-preconditioning can enhance homed CSC survival and characterize the mechanism. (3) To investigate the possibility of homing CSC to chronic ischemia myocardium via rAAV virus mediated SDF-11 gene therapy.