Signaling Mechanisms Governing Myocardial Fibrosis in Diseased Heart

几乎每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，专门针对心肌纤维化在患病的心脏。直到最近，HF研究 主要限于心肌细胞，主要是由于心脏成纤维细胞（CF）特异性 小鼠模型。最近，我们使用新的CF特异性小鼠模型来证明CF-GSK- 3β在缺血性心脏中是有害的。这种成功利用CF特异性基因靶向提供了一种新的治疗方法。 这是进一步利用这些新优化的模型来了解CF及其 激活在体内心肌疾病过程中的作用。拟议研究的长期目标是确定新的 用于治疗心肌纤维化和随后的HF的治疗靶点。三个具体目标是 旨在确定负责调节的关键信号通路和潜在的主要机制 心肌纤维化目的1：阐明CF-GSK-3α调控肝纤维化的分子机制 缺血心脏的重塑GSK-3家族由α和β两种亚型组成。与我们的 最近关于GSK-3β的报道，我们的初步研究表明，GSK-3α的CF特异性缺失是保护性的， 心梗后基于这一观察，我们假设CF-GSK-3α在MI后的过程中是有害的 纤维化重塑该假设将通过使用CF-GSK-3α KO（骨膜素-cre）和他莫昔芬- 诱导型成纤维细胞特异性GSK-3α KO（TCF 21-cre）小鼠模型。目的2：确定分子 GSK-3β的CF特异性缺失导致不利的心肌纤维化的机制。我们假设 GSK-3β、SMAD-3和β-catenin作为整合的中枢促纤维化信号级联发挥作用。我们将 将我们的GSK-3βfl/fl小鼠与SMAD-3 fl/fl和β-连环蛋白fl/fl小鼠杂交，以确定SMAD-3的抑制是否 β-catenin轴足以消除GSK-3βKO小鼠的心肌纤维化。目标3：确定 整合素α1β1（ITGα1β1）与促纤维化SMAD-3和p38通路交叉作用的机制， 确定这种相互作用在心肌纤维化调节中的作用。我们的初步数据显示， 即使在没有TGF-β1处理的情况下，机械拉伸也与SMAD-3活化偶联。的主要 在CF中表达的整合素是ITGα1β1。为此，我们将检验ITGα1β1负性表达的假设， 调节TGF-β1/SMAD-3和p38通路，从而在心肌纤维化中发挥关键作用。 重塑所提出的方法是创新的，因为它从现状出发，利用新的CF- 特定的功能丧失小鼠模型和分离的细胞，以了解分子机制， 病变心脏的心肌纤维化。预计新的研究视野将因此而变得可实现。 这项研究具有重要意义，因为它提出了新的策略来预防肝纤维化重塑。 心脏病

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.