Myocardial Regeneration with Adult Stem Cells

描述(申请人提供)：缺血性心肌病和心肌梗死(MI)的典型特征是心肌(心肌细胞)和血管(由内皮细胞和平滑肌细胞组成)不可逆转的丧失，这是维持心脏完整性和功能所必需的。最近对成体和胚胎干细胞的识别引发了通过干细胞移植直接重新填充这些组织的尝试，作为一种新的治疗选择。有关成体干细胞/祖细胞心肌再生的报道激起了人们对使用这些细胞的热情，然而，关于它们的治疗潜力，更具体地说，是什么机制导致了观察到的治疗效果，仍然存在许多悬而未决的问题。首先，尽管各种成人BM来源的干细胞被用于尝试再生心肌，但目前还没有令人信服的人类成年干细胞被证明具有诱导新生血管和心肌生成的治疗能力，这是成功的心肌组织再生的两个关键组成部分。其次，体内显示的治疗效果与成体干细胞/祖细胞(Transn)分化为特定细胞系的程度存在一定程度的差异。第三，尽管慢性心梗后心力衰竭是干细胞治疗最具临床相关性的候选方法之一，但这种治疗方法几乎没有被研究过。我们最近在成人和大鼠骨髓(BM)中发现了一种新的SC群体，它可以在单个细胞水平上分离出来，并可以扩展到超过120个群体倍增(&gt；连续9个月)。这些干细胞显示出分化为三个胚层的细胞的潜力：中胚层(内皮细胞、平滑肌细胞和心肌细胞)、内胚层和神经外胚层。我们将这些细胞称为骨髓来源的多潜能干细胞(BMSCs)。因此，我们推测移植人骨髓间充质干细胞(HBMSC)可以改善缺血性心脏病动物模型的心功能，其机制可能不仅包括细胞分化，还可能包括多种体液因子的传递。在具体目标1中，我们将探讨心肌人骨髓间充质干细胞移植在急性和慢性缺血性心力衰竭模型中的治疗作用，这两种模型是临床上最相关的SC治疗候选对象。在特定目的2中，利用上述实验获得的心脏标本，我们将探索局部细胞和旁分泌机制，以介导hBMSC移植的治疗效果。更具体地说，这将包括hBMSC的细胞分化，hBMSC与宿主心肌的融合，多种旁分泌因子的表达，以及宿主心肌的增殖和促存活作用。在特殊目的3中，我们将研究人骨髓间充质干细胞移植的系统效应。具体地说，我们将研究心肌hBMSC移植是否能诱导宿主循环干/祖细胞的动员和募集，并进一步探索使用细胞因子增强这一自然过程的可能性，从而提高治疗效果。我们预计，这项提案中概述的实验结果将为新型骨髓来源的人类干细胞在受损心肌再生中的应用提供新的见解，并可能为急性和慢性心力衰竭提供新的治疗策略。

DESCRIPTION (provided by applicant): Ischemic cardiomyopathy and myocardial infarction (MI) are typified by the irreversible loss of cardiac muscle (cardiomyocytes) and vasculature (composed of endothelial cells and smooth muscle cells), which are essential for maintaining cardiac integrity and function. The recent identification of adult and embryonic stem cells has triggered attempts to directly repopulate these tissues by stem cell transplantation as a novel therapeutic option. Reports describing provocative and hopeful examples of myocardial regeneration with adult stem/progenitor cells have furthered enthusiasm for the use of these cells, however many unanswered questions remain regarding their therapeutic potential and, more specifically the mechanisms responsible for the observed therapeutic effects. First, although various adult BM-derived stem cell populations have been employed in an attempt to regenerate myocardium, currently no human adult stem cells have been convincingly shown to have the capacity to induce both a therapeutic level of neovascularization and cardiomyogenesis, two of the key components for successful myocardial tissue regeneration. Second, there has been a degree of discrepancy between the therapeutic effect demonstrated in vivo and the magnitude of adult stem/progenitor (trans)differentiation into specific cell lineages. Third, although chronic post-MI heart failure is one of the most clinically relevant candidates for stem cell therapy, this therapeutic approach has been virtually uninvestigated. We recently identified a novel SC population within adult human and rat bone marrow (BM), which can be isolated at a single cell level and can be expanded for more than 120 population doublings (PDs)(> 9 consecutive months). These stem cells demonstrated a potential for differentiation into cells of all three germ layers; mesoderm(endothelium, smooth muscle cells and cardiomyocytes), endoderm and neuroectoderm. We refer to these cells as BM-derived multipotent stem cells (BMSCs). Accordingly we hypothesize that transplantation of human BMSC (hBMSC) may improve cardiac function in animal models of ischemic heart diseases and the mechanisms may encompass not only cellular differentiation but also delivery of multiple humoral factors. In Specific Aim 1, we will explore the therapeutic impact of myocardial hBMSC transplantation in acute and chronic models of ischemic heart failure, which are the two most clinically relevant candidates for SC therapy. In Specific Aim 2, using cardiac samples obtained from the above experiments, we will explore local cellular and paracrine mechanisms which can mediate the therapeutic effect of hBMSC transplantation. More specifically, this will encompass cellular differentiation from hBMSC, fusion between hBMSC and host myocardium, expression of muitiple paracrine factors, and proliferative and pro-survival effects on host myocardium. In SpecificAim 3, we will investigate the systemic effect of hBMSC transplantation. Specifically,we will examine whether myocardial hBMSC transplantation can induce mobilization and recruitment of host circulating stem/progenitor cells and furthermore, explore the possibility of augmenting this natural process with the use of cytokines, thereby enhancing therapeutic efficacy. We anticipate that the results of the experiments outlined in this Proposal will yield new insight into the application of novel BM-derived human stem cells for regeneration of damaged myocardium, and potentially suggest novel therapeutic strategies for acute and chronic forms of heart failure.