The role of Pitx2 in heart injury and regeneration.

项目摘要 该提案描述了一个为期五年的计划，以调查配对样同源结构域2（Pitx 2）的作用。 心肌梗死（MI）后细胞损伤反应和纤维化瘢痕形成过程中的信号传导。管理信息账户 每年全球有数百万人死亡。因此，开发一种有效的再生疗法是其中之一。 现代心血管生物学的主要目标。Pitx 2在心肌细胞中过表达时，能够 在小鼠MI模型中部分修复心肌。Pitx 2的功能是由上游的 核因子红细胞2样2（Nrf 2），一种已知的氧化还原平衡调节剂。与大多数的再生不同- 在心肌细胞中诱导细胞周期重入的促进因子中，Pitx 2信号传导仅对 心肌细胞增殖相反，Pitx 2调节抗氧化剂清除剂和成分的表达， 呼吸链，都是细胞生存和稳态的关键。我们的初步研究还表明， Pitx 2在肌成纤维细胞活性和纤维化形成中的作用。因此，靶向Pitx 2用于治疗提供了 替代策略，重点是细胞存活和消除纤维化。然而，对Pitx 2的深入研究是 设计一个有效的目标定位策略。具体目标1将检验以下假设： Pitx 2的过表达通过诱导E3泛素蛋白的表达促进Nrf 2的降解 连接酶Rbx 1。这种提出的负反馈回路可能会促进Nrf 2的降解，Nrf 2是导致细胞凋亡的关键因素。 核转位和Pitx 2活性。我们的目的是解释为什么心肌中Pitx 2的过度表达只能 部分修复MI后心肌。具有修饰的Pitx 2和/或Rbx 1表达的转基因小鼠将被 进行MI以检验假设。我们还将测试一种改进的治疗策略， 在梗死心肌细胞中同时过表达Pitx 2和Nrf 2。第二个目标将集中在 研究Pitx 2信号传导的下游效应，并检验心肌细胞中Pitx 2活性抑制心肌细胞中Pitx 2信号传导的假说。 心肌梗死后心脏成纤维细胞向肌成纤维细胞的转变。初步数据表明，Pitx 2信号在 心肌细胞可以影响肌成纤维细胞活性。我们提出了心肌细胞和 心脏成纤维细胞，由Pitx 2协调，可以调节MI后的纤维化形成。小鼠模型 修饰的Pitx 2表达和体外原代细胞培养将用于检查心肌细胞来源的 信号传导可以调节成纤维细胞到成肌纤维细胞的转变、成肌纤维细胞迁移和ECM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.