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

摘要 我们利用miR145发现了microRNA miR145在抑制心肌纤维化中的一种新功能- 有缺陷的小鼠。也有报道称miR145增强了肺纤维化，miR145可以推动 肌成纤维细胞(MyoF)在心脏和肺成纤维细胞(FBS)中分化。这些数据加在一起表明 心脏和肺纤维化之间的机制差异可能反映了细胞类型的不同 MiR145对FBS的贡献和不同作用。初步数据显示，miR145目标 促纤维化的转化生长因子B信号通路的组成部分，它是心脏和肺的中枢介质 纤维化症。此外，我们还证明了下游的转化生长因子效应物Periostin(Postn)在 心脏和肺纤维化中的肌纤维。Postn已被证明在肝纤维化的形成中起重要作用。 在FB-myoF转换过程中被激活的许多器官。更多初步数据显示， 在心脏内，系统地删除Postn与减少纤维化有关，但与心脏不同的是， POSTN会导致肺纤维化加重。本申请的总体目标是定义不同的单元格- 导致心脏和肺纤维化的具体机制。我们的数据表明，抑制 通过miR145发出的信号和/或移除像Postn这样的对转化生长因子有反应的下游效应子可能是 被用来调节纤维化。我们的中心假设是心脏和肺纤维化表现出不同 由于贡献细胞群体和器官特定转录环境的差异而导致的机制。 虽然转化生长因子B信号驱动了Postn的病理和上调，但细胞微环境决定了 疾病的发展。心肌纤维化主要表现为应激诱导的CFs活化，而 肺纤维化包括上皮到间质的转变、炎症和常驻FB的激活。 使用细胞特有的功能损失和功能增益策略来调节miR145，我们将确定 导致miR145在心脏和肺纤维化中的不同功能的细胞类型。本公司- 研究人员团队能够很好地检验这一假设，并拥有合作和 专业知识。礼来公司的实验室已经培育出一种新的miR145转基因小鼠品系，并对 微核糖核酸分析。康威实验室在心脏和肺部疾病方面拥有丰富的经验。 模型，以及在Postn和FB激活方面的专业知识。AIMS的目标是确定特定的细胞类型 为了阐明新的独特机制，需要miR145来调节纤维化 与肺和心脏纤维化有关。目标1)描述不同的管理机制 心脏和肺纤维化。目的2)确定miR145转基因是否有谱系限制性过表达 改变肺和/或心脏纤维化。这些预期结果将阐明有助于 通过确定miR145如何调节细胞特异性纤维化来实现心脏和肺纤维化。

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.