The role of Pitx2 in heart injury and regeneration.

项目摘要 这项提案描述了一项研究配对样同源域2(PITX2)作用的五年计划 心肌梗死后细胞损伤反应和纤维化瘢痕形成过程中的信号转导。MI帐户 每年全球数百万人的死亡。因此，开发一种有效的再生疗法是 现代心血管生物学的主要目标。当Pitx2在心肌细胞中过表达时，它能够 部分修复小鼠心肌梗死模型的心肌。Pitx2功能是由上游诱导和促进的 核因子红系2样蛋白(Nrf2)，一种已知的氧化还原平衡调节因子。与大多数再生不同- 诱导心肌细胞周期重入的促进因素，Pitx2信号转导对心肌细胞 心肌细胞增殖。相反，Pitx2调节抗氧化剂清道夫和成分的表达。 在呼吸链中，两者都对细胞生存和动态平衡至关重要。我们的初步研究还表明， Pitx2在肌成纤维细胞活性和纤维化形成中的作用。因此，将Pitx2作为治疗学的靶点提供了 专注于细胞存活和消除纤维化的替代策略。然而，对Pitx2的深入研究是 是设计有效的目标策略所必需的。具体目标1将检验以下假设 Pitx2过表达通过诱导E3泛素蛋白表达促进Nrf2降解 连接酶Rbx1。这种拟议的负反馈环路可能会促进Nrf2的退化，Nrf2是 Pitx2的核转位和活性。我们的目的是解释为什么Pitx2在心肌中过表达 心肌梗死后心肌部分修复。具有修饰的Pitx2和/或Rbx1表达的转基因小鼠将 对MI进行检验，检验假设。我们还将通过以下方式测试改进的治疗策略 在梗塞心肌细胞中同时过表达Pitx2和Nrf2。具体目标2将重点放在 Pitx2信号的下游效应，并验证心肌细胞中Pitx2活性抑制 心肌梗死后心脏成纤维细胞向肌成纤维细胞的转化。初步数据显示，Pitx2信号在 心肌细胞可以影响肌成纤维细胞的活性。我们提出了心肌细胞和心肌细胞之间的相互作用 心肌成纤维细胞，由Pitx2协调，可以调节心肌梗死后纤维化的形成。鼠标模型，带 改良的Pitx2表达和体外原代细胞培养将用于检测心肌细胞是如何起源的 信号转导可以调节成纤维细胞向肌成纤维细胞的转化、肌成纤维细胞的迁移和细胞外基质的沉积。

Project Summary This proposal describes a five-year program to investigate the roles of paired-like homeodomain 2 (Pitx2) signaling during cellular injury response and fibrotic scar formation after myocardial infarction (MI). MI accounts for millions of deaths worldwide annually. Therefore, developing an effective regenerative therapy is one of the major goals of modern cardiovascular biology. Pitx2, when overexpressed in cardiomyocytes, is capable of partially repairing myocardium in a mouse MI model. Pitx2 function is induced and promoted by the upstream nuclear factor erythroid 2 like 2 (Nrf2), a known regulator of redox balance. Unlike most of the regeneration- promoting factors that induce cell cycle reentry in cardiomyocytes, the Pitx2 signaling only has a mild effect on cardiomyocyte proliferation. Instead, Pitx2 regulates the expression of antioxidant scavengers and components of respiratory chain, both are critical for cell survival and homeostasis. Our Preliminary studies also suggest a role of Pitx2 in myofibroblast activity and fibrosis formation. Therefore, targeting Pitx2 for therapeutics provides alternative strategies which focus on cell survival and removing fibrosis. However, an in-depth study of Pitx2 is needed for designing an efficient targeting strategy. The Specific Aim 1 will test the hypothesis that overexpression of Pitx2 promotes the degradation of Nrf2 by inducing the expression of E3 ubiquitin-protein ligase Rbx1. This proposed negative feedback loop may promote the degradation of Nrf2, a key factor for the nuclear translocation and activity of Pitx2. We aim to explain why Pitx2 overexpression in myocardium can only partially repair the myocardium after MI. Transgenic mice with modified Pitx2 and/or Rbx1 expression will be subjected to MI to examine the hypothesis. We will also test an improved therapeutic strategy by overexpressing Pitx2 and Nrf2 simultaneously in infarcted cardiomyocytes. The Specific Aim 2 will focus on the downstream effects of Pitx2 signaling and test the hypothesis that Pitx2 activity in cardiomyocytes inhibits the transition of cardiac fibroblasts to myofibroblasts after MI. Preliminary data suggest that Pitx2 signaling in cardiomyocyte can affect myofibroblast activity. We proposed an interaction between cardiomyocytes and cardiac fibroblasts, coordinated by Pitx2, that can regulate fibrosis formation after MI. Mouse models with modified Pitx2 expression and in vitro primary cell cultures will be used to examine how cardiomyocyte-derived signaling can regulate fibroblast-to-myofibroblast transition, myofibroblast migration, and ECM deposition.