Liver Pathobiology: insights through the lens of rare diseases

项目摘要/摘要 慢性肝病(CLD)是一个重大的全球健康问题，影响着全球超过10亿人，并导致 每年多达200万人死亡。慢性肝损伤通常是静止性的，但如果持续，可能会导致肝纤维化， 可进展为肝硬变和临床上显著的门脉高压并发症(如腹水， 食道静脉曲张出血和肝性脑病)。这些临床症状是最常见的 导致慢性阻塞性肺疾病死亡的原因，而肝移植是唯一可用的治疗措施。自.以来 肝移植的需求仍然远远超过可用的供体器官，即终末期肝脏 疾病是全球第11大致死原因。因此，分子理解的进展 肝损伤和病理生物学的研究对于开发新的诊断、预后和治疗工具至关重要， 目的降低未来对肝移植的需求。几年来，我的研究主要集中在 对病因不明的罕见肝表型个体的研究作为发现新事物的路线图 肝细胞癌发病机制及治疗的分子机制(S) 常见的肝病。作为这项持续努力的一部分，我们最近发现，在一个小的 GTP酶被命名为GIMAP5，导致肝窦内皮细胞毛细血管形成和肝功能障碍。拿走 现有的Gimap5功能丧失(LOF)突变小鼠模型的优势，该模型概括了 在Gimap5缺陷者中所见的肝窦内皮细胞毛细血管表型，我们证明 Gimap5在肝内皮细胞中表达，在这些细胞中选择性缺失导致肝窦形成 内皮细胞(LSEC)去分化为毛细血管内皮细胞(CECs)。此外，单细胞RNA- Gimap5缺陷和Gimap5充足小鼠分离的肝内皮细胞的序列分析 显示CEC几乎完全取代了健康的LSEC。重要的是，LSEC去分化为CEC 是一种在肝纤维化中描述的事件，一般来说，与肝损伤的病因无关。在此，我们建议 确定在维持LSEC特性和防止肝窦内皮细胞方面的关键因素 通过毛细作用完成以下两个目标：(1)识别细胞的外在信号线索 通过GIMAP5来维持LSEC的同一性；以及(2)研究Gimap5在肝脏中的信号转导途径 内皮细胞。总而言之，这一提议产生的知识有可能识别小说 将CECs转化为健康的LSECs的治疗目标，并通过这种方式开发新的非侵入性肝脏治疗方法 纤维化、肝硬变和门脉高压，这是尚未得到满足的主要医疗需求。

PROJECT SUMMARY/ABSTRACT Chronic liver disease (CLD) is a major global health problem that affects over 1 billion people globally and leads up to 2 million deaths annually. Chronic liver injury is typically silent, but when persistent may lead to liver fibrosis, which can progress to cirrhosis and clinically significant portal hypertension complications (such as ascites, esophageal variceal hemorrhage, and hepatic encephalopathy). These clinical signs are the most common cause of mortality from CLD, and for which liver transplantation is the only available curative intervention. Since the demands for liver transplantation still far exceeds the supply of available donor organs, end-stage liver disease represents the 11th leading cause of death worldwide. Hence, advances in the molecular understanding of liver injury and pathobiology are critical to develop novel diagnostic, prognostic and therapeutic tools, with the goal to decrease the demand for liver transplantation in the future. For several years, my research has focused on the study of individuals with rare liver phenotypes of unknown etiology as a roadmap to uncover novel molecular mechanism(s) underlying liver pathology that may be relevant to the pathogenesis and treatment of common liver diseases. As part of this ongoing effort, we recently found that recessive genotypes in a small GTPase, named GIMAP5, cause liver sinusoidal endothelial cell capillarization and liver dysfunction. Taking advantage of an available Gimap5 loss-of-function (LOF) mutant mouse model, which recapitulates the sinusoidal endothelial cell capillarization phenotype seen in Gimap5-deficient humans, we demonstrate that Gimap5 is expressed in liver endothelial cells and its selective deletion in these cells lead to liver sinusoidal endothelial cell (LSEC) de-differentiation into capillarized endothelial cells (CECs). Furthermore, single cell RNA- sequencing analysis of sorted liver endothelial cells isolated from Gimap5-deficient and Gimap5-sufficient mice shows a near complete replacement of healthy LSECs by CECs. Importantly, LSEC de-differentiation into CECs is an event described in liver fibrosis, in general, independent of the etiology of liver injury. Here, we propose to define the key contributors in maintaining LSEC identity and preventing hepatic sinusoidal endothelial cell capillarization through the completion of the following two aims: (1) identify the cell extrinsic cues that signal through GIMAP5 to maintain LSEC identity; and (2) characterize the Gimap5 signal transduction pathway in liver endothelial cells. Collectively, the knowledge generated by this proposal has the potential to identify novel therapeutic targets to revert CECs into healthy LSECs, and this way develop new non-invasive therapies for liver fibrosis, cirrhosis and portal hypertension, which represent a major unmet medical need.