Hyaluronan in Pulmonary Fibrosis and Asthma

（c） 控制组织重塑的分子机制仍不完全清楚。这个程序 细胞外基质在肺炎症和纤维化中的调节作用是近年来研究的热点。一 在慢性肺病的病理生物学中，一个关键的未回答的问题是， 疾病进展和不可逆的功能丧失。持续性肺部炎症和纤维化是导致 主要发病率和死亡率，无论是发生在气道中，如慢性哮喘，还是发生在气道中，如 特发性间质性肺炎，如特发性肺纤维化（IPF）。我们创造了一个 这项工作已经确定了糖胺聚糖透明质酸（HA）及其同源受体， 在非感染性肺损伤的情况下，在调节肺部炎症和纤维化中起重要作用。HA是 一种不寻常的大分子，它在细胞膜上合成并被挤出到细胞外。 并在炎症期间变得碎片化。我们实验室过去17年的工作 确定了HA在非感染性肺损伤中的不同功能，这取决于其细胞背景和其 表达和它呈现给相互作用的细胞的形式。HA在肺的背景下被修饰 炎症和分解产物积累促进炎症。我们还发现， HA在肺上皮细胞的细胞表面上表达，其具有针对非感染性的保护功能。 侮辱。相反，当肌成纤维细胞被引导过表达透明质酸合酶2（HAS 2）时， 其结果是损伤后发生严重的进行性纤维破坏性肺病，导致显著的死亡率。 IPF的病理特征之一是肺泡内皮细胞基底膜的破坏， 界面，我们开始研究成纤维细胞对基质的侵袭是否可能是 持续的纤维化我们发现从转基因小鼠中分离的成纤维细胞 在D-平滑肌肌动蛋白启动子的指导下过表达HAS 2的细胞具有侵袭性， 表型相对于转基因阴性对照成纤维细胞。我们还开发了第一个 靶向删除间充质细胞中的HAS 2，发现肺纤维化的发展 伤害受损。此外，我们还发现，使用一种新的方法， 导致气道纤维化的小鼠慢性哮喘模型。总的来说，该系统提供了独特的 在两个不同的模型系统中剖析控制持续性纤维化的机制的方法。 此外，我们还发现，从患有严重特发性白内障的患者中分离的成纤维细胞， 肺纤维化和慢性哮喘表现出侵袭性表型。 基于来自新型小鼠模型以及人类疾病的这些数据，我们已经生成了 假设持续的炎症和持续的纤维化是由累积的 HA片段和需要透明质酸的侵袭性成纤维细胞表型的发展 合成酶2和HA结合蛋白如CD 44。我们将在以下目标中检验这一假设： 具体目标1。确定透明质酸合成酶2（HAS 2）过度表达的机制 和CD 44调节严重的肺纤维化和侵袭性成纤维细胞表型的发展。 具体目标2。确定透明质酸合成酶2（HAS 2）和CD 44在调节 在慢性小鼠哮喘模型中使用小鼠哮喘表型和进行性气道重塑， 肌成纤维细胞中HAS 2的靶向过表达和肺上皮中HAS 2的缺失， 间充质细胞 具体目标3。确定HAS 2和CD 44在调节侵袭性成纤维细胞表型中的作用， IPF患者。 相关性（参见说明）： 本项目（项目1）是该计划全球目标的一个组成部分，旨在研究内源性 基质成分通过与同源受体相互作用驱动持续性肺部炎症和纤维化 导致侵袭性成纤维细胞表型的发展。项目1将与项目2密切配合 (Dr. Wright），因为这些概念将在表面活性剂缺乏的背景下进行研究。项目1还将 与项目3（Kraft博士）密切合作，以确定透明质酸及其受体在 小鼠和人哮喘病理生物学。

instrucfions): The molecular mechanisms that control tissue remodeling remain incompletely understood. This program has focused on elucidafing the role of extracellular matrix in regulafing lung inflammafion and fibrosis. A crifical unanswered question in the pathobiology of chronic lung diseases is what are the determinants of disease progression and irreversible loss of funcfion. Persistent lung inflammation and fibrosis is a cause of major morbidity and mortality whether it occurs in the ainways as in chronic asthma or in the interstifium as in idiopathic interstitial pneumonias such an idiopathic pulmonary fibrosis (IPF). We have generated a body of work that has identified the glycosaminoglycan hyaluronan (HA) and its cognate receptors as having important roles in regulating lung inflammation and fibrosis in the context of noninfectious lung injury. HA is an unusual macromolecule in that it is synthesized at the cell membrane and extruded into the extracellular milieu and becomes fragmented during inflammafion. Work from our laboratory over the last 17 years has identified distinct functions for HA in noninfectious lung injury depending on both the cellular context of its expression and the form in which it is presented to interacting cells. HA is modified in the context of lung inflammation and breakdown products accumulate that promote inflammation. We have also discovered that HA expressed on the cell surface of lung epithelial cells serves a protective function against noninfectious insults. In contrast, when myofibroblasts are directed to over-express hyaluronan synthase 2 (HAS2),.the result is a severe and progressive fibrodestructive lung disease after injury that causes significant mortality. One of the pathologic hallmarks of IPF is the destruction of basement membrane at the alveolar-endothelial interface and we began to investigate whether fibroblast invasion of matrix could be an important feature of unremitting fibrosis. We have made the exciting observation that fibroblasts isolated from transgenic mice that over-express HAS2 under the direction of the D-smooth muscle actin promoter have an invasive phenotype relative to transgene negative control fibroblasts. We have also developed the first model of targeted deletion of HAS2 in mesenchymal cells and found that the development of fibrosis following lung injury is impaired. In addifion, we have found a marked accumulation of HA in lung fissue using a novel chronic model of asthma in mice that causes ainway fibrosis. Collectively, this system offers unique approaches to dissect the mechanisms that control persistent fibrosis in two distinct model systems. Furthermore, we have also found that fibroblasts isolated from patients that have severe idiopathic pulmonary fibrosis and chronic asthma demonstrate an invasive phenotype. Based on these data from novel mouse models as well as human diseases we have generated the hypothesis that persistent inflammation and unremitting fibrosis is driven by both the accumulation of HA fragments and the development of an invasive fibroblast phenotype that requires hyaluronan synthase 2 and HA binding proteins such as CD44. We will test this hypothesis in the following Aims: Specific Aim 1. Determine the mechanisms by which over-expression of hyaluronan synthase 2 (HAS2) and CD44 regulate severe lung fibrosis and the development of an invasive fibroblast phenotype. Specific Aim 2. Determine the roles of hyaluronan synthase 2 (HAS2) and CD44 in regulafing the asthma phenotype and progressive ainway remodeling in a chronic model of mouse asthma using mice with targeted over-expression of HAS2 in myofibroblasts and deletion of HAS2 in lung epithelial and mesenchymal cells. Specific Aim 3. Determine the role of HAS2 and CD44 in regulating the invasive fibroblast phenotype in patients with IPF. RELEVANCE (See instructions): This project (Project 1) is an integral part of the global goal of this program to study the role of endogenous matrix components in driving unremitting lung inflammation and fitirosis by interacting with cognate receptors leading to the development of an invasive fibroblast phenotype. Project 1 will interface closely with Project 2 (Dr. Wright), as these concepts will be investigated in the context of surfactant deficiency. Project 1 will also interface closely with Project 3 (Dr. Kraft) to determine the roles of hyaluronan and its receptors in the pathobiology of asthma in mouse and man.