Epithelial Angiogenic Signaling in Polycystic Diseases of the Liver

描述(由申请人提供)：我们研究的更广泛的目标是了解上皮细胞对损伤的反应，特别是胆管上皮在肝脏修复和再生中的作用。肝内胆管疾病(“胆管病”)是影响儿童和青年人群的严重的慢性衰弱肝病。多囊性肝病是一组遗传性胆管病，其特征是胆管上皮呈进行性囊性扩张，可能导致需要肝移植的并发症。这些疾病具有特别的科学价值，因为它们与初级纤毛上定位的蛋白质功能改变有关。成人显性多囊肾病(ADPKD)是由多囊蛋白-1或-2基因传递缺陷引起的。这些蛋白质作为机械感受器发挥作用，并参与调节细胞分化和上皮形态发生的信号通路。上皮性血管生成信号，尤其是血管内皮生长因子和血管生成素-1，在ADPKD的胆管上皮细胞(胆管细胞)中上调，可能在肝脏疾病的发病机制中起作用。本研究提出的假说是胆管上皮细胞产生的自分泌和旁分泌血管生成信号是ADPKD肝囊肿生长和疾病进展的机制之一。这一假说将通过三个特定的目标进行验证：1)检测遗传缺陷与ADPKD患者胆管上皮细胞血管生成信号上调之间的关系；2)研究自分泌血管内皮生长因子和血管生成素-1介导的胆管细胞生长和存活所涉及的细胞内通路；3)研究阻断血管生成信号是否可以减少ADPKD小鼠模型中肝囊肿的生长。这些研究将在体外和体内利用条件灭活多囊蛋白-1或多囊蛋白2的小鼠来解决。这些研究将a)提高我们对VEGF在分泌上皮细胞中的调节和信号转导的理解，b)更好地阐明VEGF/Angiopoietin信号在肝病中的作用，c)为ADPKD囊性病变的进行性生长机制提供重要信息)为抗血管生成治疗在ADPKD中控制肝肾囊肿生长的作用提供重要的概念证据。 公共卫生相关性：多囊肝病是一组遗传性疾病，其特征是排列在胆管内的细胞发育异常。这会导致多发性胆管微小错构瘤的形成，这些错构瘤逐渐扩大为肉眼可见的囊肿，散布在肝脏各处。虽然肝功能通常在这些疾病中得到保护，但可能会出现严重的囊性并发症(肿块效应、出血、感染或破裂)，需要紧急肝移植，因为目前还没有任何形式的药物治疗来防止胆囊肿扩大。在这些疾病中，血管生成生长因子异常过度表达，刺激胆管细胞的生长，可能是导致肝脏疾病严重并发症的囊性增大的原因。在这项应用中，我们的目标是使用具有遗传缺陷的动物来复制这种疾病，以了解其原因并开发治疗其并发症的新方法。具体地说，我们将测试抗血管生成策略。预计为肝脏设计的治疗策略也可能对肾脏有效，肾脏的功能障碍导致这些患者的发病率。此外，阻止疾病发展的能力不仅对这些患者有利，还可以为其他人的器官移植腾出空间。

DESCRIPTION (provided by applicant): The broader goal of our studies is to understand how epithelia react to damage and in particular the role of the biliary epithelium in the repair and regeneration of the liver. Diseases of the intrahepatic biliary tree ("cholangiopathies") are severe chronic debilitating liver diseases affecting the pediatric and young adult population. Polycystic liver diseases, a group of genetic cholangiopathies, are characterized by progressive cystic dilations of the biliary epithelium that may cause complications requiring liver transplantation. These diseases are of particular scientific interest because of their association with an altered function of proteins localized on the primary cilia. Adult Dominant Polycystic Kidney Disease (ADPKD) is caused by genetically transmitted defect in polycystin-1 or -2. These proteins function as mechanoceptors, and are involved in signaling pathways that regulate also cell differentiation and epithelial morphogenesis. Epithelial angiogenic signaling, particularly VEGF and Angiopoietin-1, were shown to be upregulated in biliary epithelial cells (cholangiocytes) from ADPKD and may play a role in the pathogenesis of liver disease. The hypothesis addressed in this proposal is that autocrine and paracrine angiogenic signals originating from the biliary epithelium are one of the mechanisms responsible for liver cysts growth and disease progression in ADPKD. This hypothesis will be tested trough three specific aims: 1) to examine the relationships between genetic defects and up-regulation of angiogenic signaling in the biliary epithelium of ADPKD patients; 2) to study the intracellular pathways involved in autocrine VEGF- and angiopoieting-1 mediated stimulation of cholangiocyte growth and survival; 3) To study if blockade of angiogenic signaling reduces liver cysts growth in vivo in ADPKD mouse models. These questions will be addressed in vitro and in vivo using mice with conditional inactivation of polycystin-1 or polycystin 2. These studies will a) increase our understanding of VEGF regulation and signaling in secretory epithelia, b) better clarify the role of VEGF/angiopoietin signaling in liver diseases c) provide important information on mechanisms leading to the progressive growth of cysts in ADPKD d) provide an important proof of concept for the role anti-angiogenic therapy to control the growth of liver and kidney cysts in ADPKD. Public Health Relevance: Polycystic liver diseases are a group of inherited conditions characterized by an abnormal development of the cells that line the bile ducts. This leads to the formation of multiple biliary microhamartomas that progressively dilate to macroscopic cysts, scattered throughout the liver. Although liver function is usually preserved in these disorders, severe cyst complications (mass effect, hemorrhage, infection or rupture) may develop and require urgent liver transplantation, since no forms of medical treatment are currently available to prevent biliary cyst enlargement. Stimulation of the growth of bile duct cells by angiogenic growth factors aberrantly overexpressed in these disorders may be responsible for the cyst enlargement that leads to the severe complications of the liver disease. In this application we aim to use animals with genetic defects that reproduce this disease in order to understand its cause and to develop new ways to treat its complications. Specifically, we will test antiangiogenic strategies. It is expected that therapeutic strategies devised for the liver may also be effective in the kidney, functional impairment of which contributes to morbidity in these patients. Moreover, the ability to block progression of the disease would not only benefit these patients but could spare organs for transplantation of others.