Cardiac Mesenchymal Stem Cells and Myocardial Fibrosis: Role of Platelet Derived Growth Factor Receptor Signaling

该项目的中心目标是评估PDGF/PDGFR信号传导、炎症信号传导 反应调节驻留的心脏间充质干细胞（cMSCs）在衰竭中的功能结果 心中缺血性心肌损伤启动了两个自我放大事件的级联反应， 组织修复最初的事件是由浸润性促炎性免疫反应的协同作用介导的。 细胞虽然，修复最初，延长浸润的活化单核细胞/巨噬细胞群体内 损伤的心肌进一步加重炎症反应，延迟创伤表现 治愈慢性这些过程诱导细胞外基质（ECM）重塑通过激活细胞增殖， 产生胶原的肌成纤维细胞。虽然本质上是多能的，但MSC通常分化为肌成纤维细胞， 在体内的许多病理，表明组织微环境的影响是至关重要的， 引导MSC命运。cMSC在缺血性HF的病因学和进展中的确切作用尚不清楚。 更重要的是，在衰竭的心脏中调节cMSC功能和分化的因素尚不清楚。 明白在急性心肌梗死（MI）和慢性心力衰竭（HF）期间， 大量的促炎性心脏巨噬细胞。更重要的是，慢性HF中的巨噬细胞扩张 伴随着促进心脏纤维化的肌成纤维细胞的持续活化。血小板衍生生长 血小板源性生长因子（PDGF）是公认的组织纤维化和血管生成的介质。像巨噬细胞，骨髓间充质干细胞 分泌PDGF并表达PDGF受体（PDGFRs），导致富含PDGF和PDGF反应性 心脏衰竭的微环境然而，重要的是，cMSC定位的PDGF信号传导， 对慢性炎症和巨噬细胞浸润等因素的反应，调节cMSC的命运， HF的反应未知。在这项提案中，我们将测试这一假设，即增强的cMSC定位 PDGF信号优先引导cMSC朝向肌成纤维细胞命运（并远离内皮细胞 命运），从而增加纤维化和减少血管生成和修复。三个目标是 被求婚目的1将明确PDGFR信号转导和巨噬细胞相互作用在体外巨噬细胞凋亡中的作用。 来自正常和衰竭心脏的cMSC的分化命运。目的2将确定在体内的作用， 缺血性HF期间cMSC定位的PDGFR对LV重构和功能的影响这些研究将使用 转基因小鼠的PDGFR的诱导性和cMSC特异性消融。目标3将建立治疗 再灌注-MI后cMSC细胞疗法与体内PDGFR抑制联合使用的功效。 这些研究将使用临床批准的PDGFR抑制剂甲磺酸伊马替尼（Gleevac®）。统称 拟议的研究将回答与HF相关的关键问题， 心肌纤维化中改变的cMSC命运，以及cMSC和药理学的潜在治疗用途 PDGFR抑制以诱导组织修复。 !

The central objective of this project is to evaluate how PDGF/PDGFR signaling, inflammatory signaling responses modulate the functional outcomes of resident cardiac mesenchymal stem cells (cMSCs) in failing hearts. Ischemic myocardial injury initiates a cascade of two self-amplifying events that intend to promote tissue repair. The initial events are mediated by the concerted action of infiltrating pro-inflammatory immune cells. Although, reparative initially, prolonged infiltration of activated monocyte/macrophage populations within the injured myocardium further exaggerate inflammatory responses and delay the manifestation of wound healing. Chronically these processes induce extracellular-matrix (ECM) remodeling by activating proliferation of collagen producing myofibroblasts. Although multipotent in nature, MSCs often differentiate into myofibroblasts in vivo in a number of pathologies, suggesting that tissue microenvironment influences are paramount in guiding MSC fate. The precise role of cMSCs in the etiology and progression of ischemic HF is unknown. More importantly, factors regulating cMSC function and differentiation in the failing hearts are not clearly understood. During both acute myocardial infarction (MI) and chronic heart failure (HF), there is increased abundance of pro-inflammatory cardiac macrophages. More importantly, macrophage expansion in chronic HF is accompanied by sustained activation of myofibroblasts that promote cardiac fibrosis. Platelet derived growth factor (PDGF) is a well-recognized mediator of tissue fibrosis and angiogenesis. Like macrophages, MSCs secrete PDGF and express PDGF receptors (PDGFRs), resulting in a PDGF-rich and PDGF-responsive microenvironment in the failing heart. Importantly, however, whether cMSC-localized PDGF signaling, in response to such factors as chronic inflammation and macrophage infiltration, regulates cMSC fate and responses in HF is unknown. In this proposal we will test the hypothesis that augmented cMSC-localized PDGF signaling preferentially channels cMSCs toward a myofibroblast fate (and away from an endothelial cell fate) in the failing heart, thereby augmenting fibrosis and reducing angiogenesis and repair. Three aims are being proposed. Aim 1 will define the role of PDGFR signaling and macrophage interactions on the in vitro differentiation fate of cMSCs derived from normal and failing hearts. Aim 2 will determine the in vivo role of cMSC-localized PDGFRs on LV remodeling and function during ischemic HF. These studies will use transgenic mice with inducible and cMSC-specific ablation of PDGFRs. Aim 3 will establish the therapeutic efficacy of cMSC cell therapy after reperfused-MI when used in combination with PDGFR inhibition in vivo. These studies will use the clinically approved PDGFR inhibitor imatinib mesylate (Gleevac®). Collectively the proposed studies will answer critical questions relevant to HF related to both the pathophysiological import of altered cMSC fate in myocardial fibrosis, and the potential therapeutic use of cMSCs and pharmacological PDGFR inhibition to induce tissue repair. !