Alveolar epithelial-mesenchymal transition (EMT) in pulmonary fibrosis

描述（由申请方提供）：新出现的证据表明，特发性肺纤维化（IPF）由上皮损伤和异常伤口修复引起，上皮-成纤维细胞串扰失调导致上皮细胞凋亡、基质重塑和进行性纤维化。我们最近的工作提出了一种新的范式，其中肌成纤维细胞，在基质沉积和结构重塑的IPF中的关键效应细胞，可以通过上皮间质转化（EMT）从肺泡上皮细胞（AEC）衍生。EMT可以被视为细胞可塑性的极端形式，其特征在于上皮标志物的丧失、细胞骨架重组和转变为纺锤形形态，同时获得间充质标志物。长期以来，EMT被认为在肿瘤的发生和侵袭过程中的细胞转分化中发挥作用。越来越多的人认识到，在上皮应激/损伤后，上皮细胞可以产生成纤维细胞，从而通过经历EMT而促成纤维化的发病机制。然而，在这种情况下EMT的机制知之甚少。转化生长因子（TGF-β）是诱导纤维化的“主开关”，在EMT中起着关键作用，最近的研究表明，Wnt/β-连环蛋白通路在IPF的AEC中起着激活作用。一个示范作用，- 连环蛋白信号在EMT的发展和肿瘤进展的背景下，以及TGF-β在EMT和IPF中的中心作用，表明这两种途径之间的相互作用可能是介导AEC中EMT的主要因素。本提案的总体目标是研究AEC中EMT的分子机制，重点是TGF-β和Wnt/β-catenin通路之间的串扰。我们的主要假设是：1）AEC中的EMT涉及TGF-β和Wnt/β-catenin通路之间的相互作用，2）AEC中TGF-β诱导的EMT是Smad依赖性的，3）AEC中EMT的调节将为IPF患者的管理提供新的治疗方法。这些假设将通过解决以下具体目标来研究：1）探索Wnt/<$-连环蛋白通路在AEC中EMT中的作用; 2）研究AEC中TGF-<$诱导的EMT的Smad依赖性; 3）表征Wnt/<$-连环蛋白和TGF-<$通路在介导AEC中EMT中的相互作用;以及，4）研究Wnt/<$-连环蛋白通路的调节对AEC中EMT的影响。我们将利用AEC分化的良好表征的体外模型（其中表型可以通过实验调节），建立的纤维化和EMT动物模型以及IPF患者的肺组织来研究这些相互作用在AEC中EMT的作用及其与人类疾病的相关性。了解导致EMT的精确分子相互作用有望确定肺纤维化的新治疗靶点，这些靶点可以抑制这种毁灭性疾病的进展，并为IPF患者的管理提供新的治疗选择。公共卫生相关性。特发性肺纤维化（IPF）是一种病因不明的进行性疾病，目前尚无有效治疗方法。我们最近证明，肺上皮衬里细胞本身可能通过上皮-间充质转化（EMT）过程转化为成纤维细胞而导致纤维化，这表明中断/预防EMT的策略可能对IPF有益。了解激活EMT的分子/信号应有助于开发治疗IPF和其他纤维化肺部疾病的新策略。

DESCRIPTION (provided by applicant): Emerging evidence suggests that idiopathic pulmonary fibrosis (IPF) results from epithelial injury and abnormal wound repair, with dysregulated epithelial-fibroblast crosstalk leading to epithelial apoptosis, matrix remodeling and progressive fibrosis. Our recent work suggests a novel paradigm in which myofibroblasts, key effector cells in matrix deposition and structural remodeling in IPF, may be derived from alveolar epithelial cells (AEC) through epithelial-mesenchymal transition (EMT). EMT can be viewed as an extreme form of cell plasticity characterized by loss of epithelial markers, cytoskeletal reorganization and transition to a spindle- shaped morphology concurrent with acquisition of mesenchymal markers. EMT has long been known to play a role in cellular transdifferentiation during development and tumor invasion. It is increasingly being recognized that, following epithelial stress/injury, epithelial cells can give rise to fibroblasts and thereby contribute to the pathogenesis of fibrosis by undergoing EMT. However, mechanisms underlying EMT in this context are poorly understood. Transforming growth factor (TGF-¿), implicated as a 'master switch' in induction of fibrosis, plays a pivotal role in EMT, and recent studies suggest a role for activation of the Wnt/¿-catenin pathway in AEC in IPF. A demonstrated role for ¿-catenin signaling in EMT in the context of development and tumor progression, and the central role of TGF-¿ in EMT and IPF, suggest that interactions between these two pathways may be a major factor mediating EMT in AEC. The overall goal of this proposal is to investigate molecular mechanisms underlying EMT in AEC, focusing on crosstalk between TGF-¿ and Wnt/¿-catenin pathways. Our main hypotheses are that 1) EMT in AEC involves interactions between TGF-¿ and Wnt/¿-catenin pathways, 2) TGF-¿-induced EMT in AEC is Smad-dependent and 3) modulation of EMT in AEC will provide new therapeutic approaches to management of patients with IPF. These hypotheses will be investigated by addressing the following Specific Aims: 1) Explore the role of Wnt/¿-catenin pathway in EMT in AEC; 2) Investigate Smad-dependence of TGF-¿-induced EMT in AEC; 3) Characterize interactions between Wnt/¿-catenin and TGF-¿ pathways in mediating EMT in AEC; and, 4) Investigate effects of modulation of Wnt/¿-catenin pathway on EMT in AEC. We will utilize well-characterized in vitro models of AEC differentiation (in which phenotype can be experimentally modulated), established animal models of fibrosis and EMT, and lung tissue from patients with IPF to investigate the role of these interactions in EMT in AEC and its relevance to human disease. Understanding the precise molecular interactions that lead to EMT promises to lead to identification of novel therapeutic targets for pulmonary fibrosis that could inhibit progression of this devastating disease and provide new therapeutic options for management of patients with IPF. PUBLIC HEALTH RELEVANCE. Idiopathic pulmonary fibrosis (IPF) is a progressive disorder of unknown etiology with no effective treatment. We recently demonstrated that lung epithelial lining cells may themselves contribute to fibrosis by changing into fibroblasts through a process called epithelial-mesenchymal transition (EMT), suggesting that strategies for interrupting/preventing EMT could be of benefit in IPF. Understanding the molecules/signals that activate EMT should lead to development of novel strategies for treatment of IPF and other fibrotic lung disorders.