Defining the role of Factor Inhibiting HIF (FIH) as a key regulator of extracellular matrix homeostasis

细胞外基质(ECM)是体内细胞和组织功能最重要的调节因子之一。细胞外基质的动态重塑对于发育、伤口愈合和正常的器官动态平衡是必不可少的。当ECM重塑过度或失控时，就会出现危及生命的病理情况，如器官纤维化。细胞外基质被定义为包围所有固体组织中细胞的各种蛋白质和糖的集合。尽管ECM在历史上一直被认为主要是履行结构和生物力学的作用，但近年来ECM提供负责控制个体和集体细胞行为的背景信息的能力已经得到越来越多的认识。ECM的生物力学特性受基质成分的特定组成和浓度以及糖基化、转谷氨酰胺和交联化等翻译后修饰的严格控制。我们最近发现，纤维化的肺组织比正常肺组织更僵硬，这是由于骨型胶原蛋白交联性增加，这促进了纤维化的进展。通过人体体外和组织分析，我们证实了HIF途径的激活推动了这种病理性的骨型交联体，这是通过氧独立激活HIF信号-称为假缺氧-通过失去抑制HIF的因子(FIH)的活性来确定的。此外，我们还发现，高HIF基因签名评分对肺纤维化的死亡率有很强的预测作用，与肺生理学严重程度无关。因此，我们的假设是，FIH功能丧失导致假性缺氧表型，从而推动进行性纤维化。这个项目的目的是使用先进的原代人类细胞和组织模型，辅以系统和定量生物学方法来确定：(1)FIH缺失的肺成纤维细胞的整体转录图谱；(2)FIH缺失后肺成纤维细胞的生物学和分子变化；(3)FIH活性丧失对ECM自身稳定性的影响。本项目将确定FIH作为细胞外基质重构的关键调节因子的作用。

The extracellular matrix (ECM) is one of the most important regulators of cellular and tissue function in the body. Dynamic remodeling of ECM is essential for development, wound healing and normal organ homeostasis. Life-threatening pathological conditions, such as organ fibrosis, arise when ECM remodeling becomes excessive or uncontrolled. The ECM is defined as the diverse collection of proteins and sugars that surrounds cells in all solid tissues. Although the ECM has historically been perceived as fulfilling a primarily structural and hence biomechanical role, the ability of the ECM to provide the contextual information responsible for controlling both individual and collective cellular behavior has been increasingly recognized in recent years. The biomechanical properties of the ECM are tightly controlled by the specific composition and concentration of matrix components, and also by post-translational modifications, such as glycosylation, transglutamination and cross-linking. We have recently identified that fibrotic lung tissue is stiffer than normal due to increased 'bone' type collagen cross-linking and that this promotes fibrosis progression. Through human in vitro and tissue analyses we identified that HIF pathway activation drives this pathologic 'bone type' crosslinking, and that this is determined through oxygen-independent activation of HIF signalling - termed pseudohypoxia - by loss of activity of Factor Inhibiting HIF (FIH). Furthermore, we identified that a high HIF gene signature score is strongly predictive of mortality of lung fibrosis independent of lung physiology severity. Thus, our hypothesis is that loss of function of FIH creates a pseudohypoxic phenotype that drives progressive fibrosis. The aims of this project are to use advanced primary human cell and tissue based models complemented by systems and quantitative biology approaches to determine:(1) global transcriptomic profiling of FIH-depleted lung fibroblasts;(2) biological and molecular changes following FIH depletion in lung fibroblast;(3) the impact of loss of FIH activity on ECM homeostasis.This project will define the role of FIH as a key regulator of extracellular matrix remodelling.