Hypoxia Signaling and Spontaneous Pulmonary Fibrosis in a Novel Mouse Model

描述(申请人提供)：特发性肺纤维化(IPF)是一种致命的不治之症，每年导致40,000名美国人死亡。随着老龄人口的增长，IPF的患病率从20例/10万人跃升至30例/10万人。尽管存在巨大的公共卫生负担，但IPF的起源和进展性质的分子基础仍然难以捉摸。这种知识差距的延续阻碍了IPF靶向治疗的发展。因此，长期目标是确定肺中有助于IPF启动和进展的分子、机制和细胞类型，这将有助于IPF靶向治疗的发展。虽然目前的损伤诱导纤维化动物模型正在产生机械性的见解，但随着纤维化随着时间的推移而消退，这些模型仍然存在固有的局限性。 排除了参与PF进展的分子驱动因素的识别。因此，本项目的目标是通过发展、表征和提炼一种表现出疾病进行性的PF小鼠模型来填补这一重大空白，概括IPF的一些临床病理特征。反复损伤呼吸道上皮细胞(RECs)会引起细胞应激，引发与分子变化相关的异常上皮修复，使RECs发生纤维化。这些REC分泌纤维化信号，激活驻留的成纤维细胞/间充质细胞，促进纤维化。一种这样的上皮应激因素是对上皮细胞的慢性缺氧反应，众所周知，这会在体外改变RECs的结构和功能。此外，基于我们提供的体内数据，我们将检验一个中心假设，即起源于肺上皮的异常低氧反应使RECs发生纤维化，从而促进体内的PF。我们将利用自发性和进行性肺泡性肺炎的小鼠模型来描述启动肺泡性肺炎的分子/机制。由于体内传导和肺泡上皮细胞(AECs)中VHL基因的缺失而引发慢性低氧信号，该模型发展缓慢超过3个月。这一模型与临床上IPF患者出现的缓慢进展的纤维化特征有很好的相关性。我们发现，体内RECs的低氧反应触发了Wnt/？-catenin、转化生长因子？？和CXCR4/SDF-1信号的激活，这与它们在PF中的作用以及在IPF患者中的研究结果一致。目的#1利用系统生物学方法，定义肾小管上皮细胞中最早启动PF的分子事件和激活Wnt/？连环蛋白和转化生长因子途径的分子。目的研究CXCR4/SDF-1基因在人肾小管上皮细胞中的调控，探讨促纤维化的肾小管上皮细胞在激活原代人肾实质成纤维细胞纤维化表型中的旁分泌作用。该项目的结果将是重要的，揭示了定义驱动PF的早期分子事件的分子/机制。在促纤维化的上皮细胞中发现的分子和信号网络将具有很高的预后、诊断和治疗价值。具有特征性的小鼠模型在建立新的IPF靶向治疗的临床理论方面具有巨大的临床前研究潜力。

DESCRIPTION (provided by applicant): Idiopathic PF (IPF) is a lethal, incurable disease killing 40,000 Americans every year. As the aged population has grown, the prevalence of IPF has jumped from 20 to 30 cases/100,000 individuals. Despite this enormous public health burden, the molecular basis of the origins and progressive nature of IPF remains elusive. Continuation of this knowledge gap has stymied the development of targeted therapies for IPF. Thus, the long-term goal is to define molecules, mechanisms and cell types in the lung that contribute to the initiation and progression of IPF that will aid in the development of targeted therapies for IPF. While mechanistic insights are being generated from current animal models of injury-induced fibrosis, these models remain inherently limited as the fibrosis resolves over time, precluding the identification of molecular drivers participating in the progression of PF. Therefore, the objective of the present project is to fill this significant gap by developing, characterizing and refining a mouse model of PF exhibiting progressive nature of the disease, recapitulating some of the clinico-pathological features of IPF. Repeated injury to the respiratory epithelial cells (RECs) causes cellular stress, triggering aberrant epithelial repair associated with molecular alterations that render RECs profibrotic. These RECs secrete fibrogenic signals, activating resident fibroblasts/mesenchymal cells, contributing to fibrosis. One such epithelial stress factor is chronic hypoxic response to the epithelial cells, which is known to alter structure and function of RECs in vitro. In addition, based on our in vivo data presented here, we will test the central hypothesis that aberrant hypoxic responses originating in the lung epithelium render RECs profibrotic, contributing to PF in vivo. We will delineate molecules/mechanisms initiating PF utilizing a mouse model of spontaneous and progressive PF that slowly develops over 3 months due to chronic hypoxia signaling elicited by deletion of Vhl gene in the conducting and alveolar airway epithelial cells (AECs) in vivo. This model correlates well with slow progressive features of fibrosis seen in IPF patients in the clinic. We show that hypoxic response in the RECs in vivo triggers activation of Wnt/ß-catenin, TGF-ß and CXCR4/SDF-1 signaling, consistent with their role in PF and findings in IPF patients. Aim#1 will define earliest molecular events initiating PF and molecules activating Wnt/ß-catenin and TGF-pathways in the RECs using systems biology approaches. Aim #2 will ascertain the regulation of CXCR4/SDF-1 genes in human RECs and examine the paracrine roles of profibrotic RECs in activating fibrogenic phenotype of primary human parenchymal fibroblasts. The outcome of the project will be significant, revealing molecules/mechanisms defining early molecular events driving PF. The molecules and signaling networks identified in the profibrotic epithelia would have high prognostic, diagnostic and therapeutic utility. The characterized mouse model holds immense potential for pre-clinical studies in building clinical rationale for emerging targeted therapies of IPF.