Signaling mechanisms governing myocardial fibrosis in diseased heart

几乎每一种形式的进行性心力衰竭(HF)都与纤维化增加有关。目前没有 批准的治疗方法，专门针对患病心脏的心肌纤维化。直到最近，对HF的研究 在很大程度上仅限于心肌细胞，主要是由于心脏成纤维细胞(CF)特异性的不可用 老鼠模型。最近，我们使用了新的Cf特异性小鼠模型来证明Cf-GSK- 3β在缺血心脏中是有害的。这种成功地利用CF特异的基因打靶提供了一种 进一步利用这些最新优化的模型来了解CFS的作用及其 在活体心肌疾病过程中的激活。拟议研究的长期目标是确定新的 治疗心肌纤维化和继发性心衰的治疗靶点。三个具体目标是 旨在确定负责调控的关键信号通路和潜在的主要机制 心肌纤维化的症状。目的1：阐明Cf-GSK-3α调控纤维化的分子机制 缺血心脏的重塑。葛兰素史克-3家族由α和β两种异构体组成。与我们的 最近关于葛兰素史克-3β的报告，我们的初步研究表明，Cf特异性缺失葛兰素史克-3α是保护性的， 心肌梗死后。基于这一观察结果，我们推测CF-GSK-3α在心肌梗死后的过程中是有害的 纤维性重塑。这一假设将通过使用CF-葛兰素史克-3αKO(Periostin-cre)和他莫昔芬- 诱导成纤维细胞特异性αKO(TCF21-cre)小鼠模型。目标2：定义分子 Cf特异性缺失GSK-3β导致不良心肌纤维化的机制。我们假设 GSK-3β、SmadD-3和β-连环蛋白作为一个完整的中枢促纤维化信号级联起作用。我们会 将我们的GSK-3βfl/fl小鼠与sMAD-3fl/fl和β-cateninl/fl小鼠杂交，以确定是否抑制sMAD-3 β-连环素轴足以消除β-3 KO小鼠心肌纤维化。目标3：确定 整合素α1β1(itgα1β1)与促纤维化的sMAD-3和p38信号通路的相互作用机制 确定这种相互作用在调节心肌纤维化中的作用。我们的初步数据表明 即使在没有转化生长因子-β-1治疗的情况下，机械拉伸也会导致Smad3的激活。占优势的 在CFs中表达的整合素是ITGα1β1。为此，我们将对ITGα1β1的假设进行负向检验 调节转化生长因子-β-1/sMAD-3和p38通路，从而对心肌纤维化起关键作用 改建。所提出的方法是创新的，因为它利用了新的CF-C-R来改变现状。 特异性功能丧失小鼠模型及从中分离出的细胞，以了解其分子机制 病变心脏的心肌纤维化。因此，新的研究领域有望成为可能。 这项拟议的研究具有非常重要的意义，因为它提出了预防肝纤维化重塑的新策略 生病的心脏。

Virtually every form of progressive heart failure (HF) is associated with increased fibrosis. Currently there is no approved therapy to specifically target myocardial fibrosis in the diseased heart. Until very recently, HF studies have been largely limited to cardiomyocytes, primarily due to unavailability of cardiac fibroblast (CF)-specific mouse models. Recently, we used novel CF-specific mouse models to demonstrate that deletion of CF-GSK- 3β is detrimental in the ischemic heart. This successful utilization of CF-specific gene targeting provides a unique opportunity to further employ these newly optimized models to understand the role of CFs and their activation in myocardial disease process in vivo. The long-term goal of the proposed studies is to identify new therapeutic targets for the treatment of myocardial fibrosis and subsequent HF. Three specific aims are designed to identify the key signaling pathways and underlying primary mechanisms responsible for regulation of myocardial fibrosis. Aim 1: To elucidate the molecular mechanism by which CF-GSK-3α regulates fibrotic remodeling in the ischemic heart. The GSK-3 family consists of two isoforms, α and β. In stark contrast to our recent report with GSK-3β, our preliminary studies suggest that CF-specific deletion of GSK-3α is protective, post-MI. Based on this observation we hypothesize that CF-GSK-3α is deleterious in the process of post MI fibrotic remodeling. This hypothesis will be tested by employing CF-GSK-3α KO (periostin-cre) and tamoxifen- inducible fibroblast specific GSK-3α KO (TCF21-cre) mouse models. Aim 2: To define the molecular mechanisms by which CF-specific deletion of GSK-3β leads to adverse myocardial fibrosis. We hypothesize that GSK-3β, SMAD-3 and β-catenin function as an integrated central profibrotic signaling cascade. We will cross our GSK-3βfl/fl mice with SMAD-3fl/fl and β-cateninfl/fl mice to determine whether inhibition of the SMAD-3 and β-catenin axis is sufficient to abolish myocardial fibrosis in GSK-3βKO mice. Aim 3: Determine the mechanisms by which Integrin α1β1 (ITGα1β1) cross-talks with the profibrotic SMAD-3 and p38 pathways and identify the role of this interaction in regulation of myocardial fibrosis. Our preliminary data suggest that mechanical stretch couples to SMAD-3 activation even in the absence of TGF-β1 treatment. The predominant integrin expressed in CFs is ITGα1β1. In this aim, we will test the hypothesis that ITGα1β1 negatively regulates the TGF-β1/SMAD-3 and p38 pathways and thus exerts a critical break on myocardial fibrotic remodeling. The proposed approach is innovative, because it departs from status quo by utilizing novel CF- specific loss of function mouse models and isolated cells from them to understand the molecular mechanism of myocardial fibrosis in diseased heart. New research horizons are expected to become attainable as a result. The proposed research is highly significant, since it proposes novel strategies to prevent fibrotic remodeling in diseased heart.