Mechanisms of cardiac and pulmonary fibrosis in relation to TGF-beta signaling and miR-145 function

总结 我们使用miR 145-miR-145在抑制心脏纤维化中鉴定了microRNA miR 145的新功能。 缺陷小鼠还报道了miR 145增强肺纤维化，并且miR 145可以驱动肺纤维化。 心肌和肺成纤维细胞（Fbs）内的肌成纤维细胞（myoF）分化。这些数据表明 心脏和肺纤维化之间的机制差异可能反映了细胞类型的差异， miR 145对Fbs的贡献和不同作用。初步数据显示，miR 145靶向 促纤维化TGF β 1信号通路的组成部分，其是心脏和肺的中枢介质， 纤维化此外，我们已经表明，下游TGF β效应物，骨膜蛋白（Postn），是上调， 心肌纤维化和肺纤维化。Postn已被证明在肝纤维化中起重要作用， 许多器官在Fb-myoF转换期间被激活。其他初步数据显示， 在心脏内，Postn的系统性缺失与纤维化减少相关，但与心脏不同， 导致肺纤维化增加。本申请的总体目标是定义不同的细胞- 导致心脏和肺纤维化的特定机制。我们的数据表明， 通过miR 145的TGF β信号传导和/或TGF β-应答性下游效应物如Postn的去除可能是 用于调节纤维化。我们的中心假设是心脏和肺纤维化表现出不同的 由于贡献细胞群和器官特异性转录环境的差异， 虽然TGF β信号传导驱动病理和Postn的上调，但细胞微环境决定了 疾病进展。心脏纤维化主要通过应激诱导的CFs激活来表现， 肺纤维化涉及上皮细胞向间充质细胞的转化、炎症和驻留的Fb活化。 使用细胞特异性功能丧失和功能获得策略来调节miR 145，我们将确定miR 145的表达。 在心脏和肺纤维化中对miR 145的对比功能有贡献的细胞类型。这一合作- 调查人员小组有能力检验这一假设，他们有合作的以往记录， 专业知识礼来实验室已经产生了一种新的miR 145转基因小鼠品系， microRNA分析康威实验室在心脏和肺部疾病方面拥有丰富的经验 模型，以及Postn和Fb激活方面的专业知识。目的是确定细胞类型特异性 需要miR 145来调节纤维化，目的是阐明新的独特机制 与肺和心脏纤维化有关。目标1）描述差异管理的机制 心肺纤维化目的2）确定miR 145转基因的谱系限制性过表达是否 改变肺和/或心脏纤维化。这些预期成果将阐明有助于 通过测定miR 145如何调节细胞特异性纤维化来研究心脏和肺纤维化。

SUMMARY We identified a novel function for microRNA miR145 in the suppression of cardiac fibrosis using miR145- deficient mice. It has also been reported that miR145 enhances pulmonary fibrosis, and that miR145 can drive myofibroblast (myoF) differentiation within both cardiac and lung fibroblasts (Fbs). Together these data suggest that mechanistic differences between cardiac and pulmonary fibrosis may reflect differences in cell type contribution and dissimilar actions of miR145 upon Fbs. Preliminary data reveal that miR145 targets components of the profibrotic TGFß signaling pathway, which is a central mediator of cardiac and pulmonary fibrosis. Furthermore, we have shown that a downstream TGFß effector, Periostin (Postn) is upregulated in myoFs in cardiac and pulmonary fibrosis. Postn has been proven to play an important role in fibrogenesis in many organs in which it is activated during the Fb-myoF transition. Additional preliminary data reveal that within the heart, systemic deletion of Postn correlates with decreased fibrosis but unlike the heart, the absence of Postn results in elevated lung fibrosis. The overall objective of this application is to define the distinct cell- specific mechanisms that contribute to cardiac and pulmonary fibrosis. Our data suggest that suppression of TGFß signaling by miR145 and/or removal of TGFß-responsive downstream effectors like Postn may be employed to modulate fibrosis. Our central hypothesis is that cardiac and pulmonary fibrosis exhibit different mechanisms due to variances in the contributing cell populations and organ-specific transcriptional milieu. While TGFß signaling drives both pathologies and upregulation of Postn, the cell microenvironment dictates disease progression. Cardiac fibrosis manifests primarily through stress-induced activation of CFs, while pulmonary fibrosis involves epithelial-to-mesenchymal transitions, inflammation and resident Fb activation. Using cell-specific loss-of-function and gain-of-function strategies to modulate miR145, we will determine the cell types that contribute to the contrasting functions of miR145 in cardiac and pulmonary fibrosis. This co- investigator team is well positioned to test this hypothesis, with a prior track record of collaboration and expertise. The Lilly lab has generated a novel miR145 transgenic mouse strain, and is experienced with microRNA analyses. The Conway lab brings extensive experience in both cardiac and pulmonary disease models, and expertise in Postn and Fb activation. The goal of the aims is to determine the cell type-specific requirement of miR145 to regulate fibrosis with the intent of elucidating novel distinctive mechanisms associated with pulmonary and cardiac fibrosis. Aim 1) Delineate the mechanisms that differentially govern cardiac and pulmonary fibrosis. Aim 2) Determine if lineage-restricted overexpression of a miR145 transgene alters pulmonary and/or cardiac fibrosis. These expected outcomes will elucidate mechanisms contributing to cardiac and pulmonary fibrosis via determination of how miR145 regulates cell-specific fibrosis.