Differentiation of Alveolar Epithelium in Pulmonary Fibrosis

描述(由申请人提供)： 间质性肺纤维化(IPF)发病机制的早期事件与损伤的肺泡上皮修复错误有关，在损伤的肺泡上皮，增殖的肺泡II型(AT2)细胞不能有效地分化为I型(AT1)细胞。这会导致不可逆转的损伤、纤维化和功能丧失。正常情况下控制AT2细胞分化为AT1的机制尚不清楚，因此受这些致病事件影响的调节分子或途径尚不清楚。在这个方案中，我们将应用最近建立的正常人类肺泡上皮细胞分化的体外模型和肺纤维化大鼠的体内模型的新概念来研究新的、相互作用的信号通路和核因子，我们预测这些信号通路和核因子在纤维化肺疾病中被错误地调节，例如特发性肺纤维化。我们的数据表明，肺纤维化中硫酸盐化细胞外基质(ECM)的过度增加改变了分化过程中关键因子FoxA1和WNT7A的有效性，并刺激调节因子的转变，即使在高硫酸盐化的ECM环境中也有利于增殖。我们将证明FOXA2在发育过程中弥补无效的FoxA1，在这些条件下受到青睐，并上调Wnt7b，后者促进增殖而不是分化。肺泡上皮细胞继续试图通过产生更多的TGF2来实现分化，而不是稳定增殖和表型，这不仅维持了这个问题，而且促进了EMT和更多的纤维化。需要解决的具体假设是：在间质性肺纤维化中，过高的硫酸盐化ECM水平有利于FOXA2的持续表达，并促进TGF？肺泡上皮细胞中的信号转导，它们共同增加Wnt7b的表达和信号转导，导致持续的增殖、停滞的分化和阻止生成完全成熟的AT1细胞。为了解决这一假设，我们将通过组织化学方法检测轻度或重度IPF患者中这些分子和相关分子的表达水平。这些研究的结果有望支持这一基本假设，即细胞外基质中固定的完整和脱落的细胞周围硫酸盐成分改变了肺泡上皮细胞的微环境-这构成了这些细胞如何相互作用的关键决定因素，它们的增殖潜力，以及通过影响对WNT和TGF2信号的明确反应和特定的基因调控而分化的命运。它们将提供必要的必要信息，以更好地了解肺纤维化中基本的细胞-细胞和细胞-ECM关系，以及指导其发病机制。与公共卫生相关：肺纤维化是一种原因不明的疾病，它会导致肺内表面僵硬，从而显著降低肺功能。纤维肺疾病发展的一个潜在的重要因素可能是排列在肺内表面的细胞通过分裂和分化进行自我更新的能力受损。这笔赠款将定义调控影响表达的具体变化，这些影响阻止细胞有效分化并促进组织创伤。(摘要结束)

DESCRIPTION (provided by applicant): Early events in the pathogenesis of interstitial pulmonary fibrosis (IPF) have been linked to faulty repair of injured alveolar epithelium where proliferating alveolar type II (AT2) cells do not effectively differentiate into type I (AT1) cells. This leads to irreversible damage, fibrosis, and loss of function. The mechanisms that normally control the process of differentiation of AT2 cells into AT1s are poorly understood, so regulatory molecules or pathways that are affected by these pathogenic events have not been elucidated. In this proposal, we will apply new concepts developed from recent in vitro modeling of normal human alveolar epithelial cell differentiation and in vivo modeling of pulmonary fibrosis is rats to study novel, interactive signaling pathways and nuclear factors that we predict are incorrectly regulated in fibrotic lung diseases, such as idiopathic pulmonary fibrosis. Our data indicates that excessive increases in sulfated extracellular matrix (ECM) as seen in pulmonary fibrosis, alters the effectiveness of key factors in the differentiation process, FoxA1 and Wnt7A, and stimulates a shift to regulatory factors which favor proliferation even in a high sulfated ECM environment. We will show that FoxA2, known to compensate for ineffective FoxA1 in development, is favored under these conditions and upregulates Wnt7B, which promotes proliferation over differentiation. Instead of stabilization of proliferation and phenotype, alveolar epithelial cells continue to attempt to achieve differentiation by producing more TGF2, which not only sustains the problem but promotes EMT and more fibrosis. The SPECIFIC HYPOTHESIS to be addressed is: The excessively high level of sulfated ECMs in interstitial pulmonary fibrosis favors sustained expression of FoxA2 and promotes TGF? signaling in alveolar epithelium, which together increase Wnt7B expression and signaling resulting in sustained proliferation, stalled differentiation, and prevention of the generation of fully mature AT1 cells. To address this hypothesis, we will examine the levels of expression of each of these and related molecules by histochemistry in patients with mild or severe stages of IPF. Results of these studies are expected to support the fundamental hypothesis that fixed whole and shed fragments of pericellular sulfated components of extracellular matrices alter the microenvironment of alveolar epithelial cells - which constitutes a critical determinant of how these cells interact, their proliferative potential, and differentiated fate by influencing defined responses to WNT and TGF2 signaling and specific gene regulation. They will provide essential information needed to better understand basic cell-cell and cell-ECM relationships in pulmonary fibrosis and the mechanisms that steer its pathogenesis. PUBLIC HEALTH RELEVANCE: Pulmonary fibrosis is a disease of unknown origin which causes stiffening of internal surfaces of the lung, which significantly reduces lung function. A potentially significant contributing factor to the development of fibrotic lung disease may the impaired ability of cells which line internal surfaces of the lung to renew themselves by dividing and differentiating. This grant will define specific changes in the expression of modulatory influences which prevent cells from effectively differentiating and promote tissue scaring. (End of Abstract)