Epithelial Angiogenic Signaling in Polycystic Diseases of the Liver

描述（由申请人提供）：我们研究的更广泛目标是了解上皮细胞对损伤的反应，特别是胆管上皮细胞在肝脏修复和再生中的作用。肝内胆管树疾病（“胆管病”）是影响儿科和年轻成人人群的严重慢性衰弱性肝病。多囊肝病是一组遗传性胆管疾病，其特征在于胆管上皮的进行性囊性扩张，可能导致需要肝移植的并发症。这些疾病是特别的科学兴趣，因为它们与改变功能的蛋白质定位在初级纤毛。成人显性多囊肾病（ADPKD）是由多囊蛋白-1或-2的遗传缺陷引起的。这些蛋白质作为机械感受器起作用，并且参与调节细胞分化和上皮形态发生的信号传导途径。上皮血管生成信号传导，特别是VEGF和血管生成素-1，在ADPKD的胆管上皮细胞（胆管细胞）中显示上调，可能在肝脏疾病的发病机制中发挥作用。本提案中提出的假设是，源自胆管上皮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。该假说将通过三个具体目标进行检验：1）检查ADPKD患者胆管上皮中遗传缺陷与血管生成信号上调之间的关系; 2）研究参与自分泌VEGF和血管生成素-1介导的刺激胆管细胞生长和存活的细胞内途径; 3）研究血管生成信号传导的阻断是否减少ADPKD小鼠模型中的体内肝囊肿生长。这些问题将解决在体外和体内使用小鼠与多囊蛋白-1或多囊蛋白2的条件灭活。这些研究将a）增加我们对分泌上皮中VEGF调节和信号传导的理解，B）更好地阐明VEGF/血管生成素信号传导在肝脏疾病中的作用，c）提供关于导致ADPKD中囊肿进行性生长的机制的重要信息，d）提供抗血管生成治疗在ADPKD中控制肝和肾囊肿生长的作用的重要概念证据。 公共卫生相关性：多囊肝病是一组遗传性疾病，其特征是胆管细胞的异常发育。这导致形成多个胆管微小错构瘤，逐渐扩张为肉眼可见的囊肿，分散在整个肝脏。虽然肝功能通常在这些疾病中得以保留，但可能会发生严重的囊肿并发症（占位效应，出血，感染或破裂），并需要紧急肝移植，因为目前没有任何形式的医学治疗可用于预防胆管囊肿扩大。在这些疾病中异常过表达的血管生成生长因子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肿扩大的原因。在本申请中，我们的目标是使用具有遗传缺陷的动物繁殖这种疾病，以了解其原因并开发治疗其并发症的新方法。具体来说，我们将测试抗血管生成策略。预计针对肝脏设计的治疗策略也可能对肾脏有效，肾脏功能受损导致这些患者发病。此外，阻断疾病进展的能力不仅使这些患者受益，而且可以为其他人的移植保留器官。

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.