Mechanisms of Bile Duct Morphogenesis

描述(由申请人提供)：本提案侧重于胆道系统的形态发生，胆道系统是将胆汁从肝细胞输送到肠道的管道。沿着其复杂的分支结构的任何一点的胆管功能障碍都可能是发病率和死亡率的来源，而重建正常的胆管完整性对于损伤的恢复至关重要。这项建议中描述的实验将提供关于如何沿着整个胆管树建立连通性的洞察力，描绘Notch-一种其缺陷导致人类胆管缺陷的途径-调节肝脏发育的机制，并确定该途径在成人胆管功能中的作用。这项研究的长期目标是了解肝脏如何实现并保持其三维结构。该实验将使用CRE/LOX技术和实时成像技术来检测活体胆管形态发生的几个参数：肝外-肝内胆管连接的形成，胆管-小管连接的形成，以及胆管细胞极性和小管形成的建立。该提案的一个中心目标是测试Notch信号通过启动细胞“小管发生程序”来控制胆管发育的假设，这一过程的特定候选介体将在体外测试它们在小管形成中的作用。此外，还将研究Notch信号如何与其他已知的胆管发育调节因子(如HNF1B、HNF6、TGFb)协调。最后，我们建议进行实验，以验证Notch信号通过维持导管细胞的完整性和在空间上组织对损伤的反应，在一生中继续对肝脏生物学产生影响的假设。公共卫生相关性：目前，对终末期肝功能衰竭患者唯一有效的治疗方法是移植。另一种方法的发展面临的一个主要挑战是无法概括正常的肝细胞组织(形态发生)和体外功能。这项研究的最终目的是描述引导肝脏正常分化和形态发生的事件，从而设计出合理的肝脏再生和替代方法。

DESCRIPTION (provided by applicant): This proposal is focused on morphogenesis of the biliary system, the conduit for transport of bile from hepatocytes to the intestine. Dysfunction of the bile ducts at any point along its intricate branched structure can be a source of morbidity and mortality, and re-establishment of normal biliary integrity is essential for recovery from injury. The experiments described in this proposal will provide insight into how connectivity is established along the entirety of the biliary tree, delineate the mechanisms by which Notch - a pathway whose deficiency causes bile duct deficiency in humans - regulates liver development, and determine the role of this pathway in the function of adult bile ducts. The long-term objective of this research is to understand how the liver achieves and maintains its three dimensional architecture. The proposed experiments will employ Cre/lox technology and real-time imaging to examine several parameters of biliary morphogenesis in vivo: formation of the extrahepatic-intrahepatic biliary junction, formation of the ductal-canalicular junction, and the establishment of biliary cell polarity and tubule formation. A central goal of the proposal is to test the hypothesis that Notch signaling controls bile duct development by initiating a cellular "tubulogenesis program," and specific candidate mediators of this process will be tested for their role in tubulogenesis in vitro. In addition, studies will be performed to examine how Notch signals are coordinated with other known regulators of bile duct development (e.g. HNF1b, HNF6, TGFb). Finally, experiments are proposed that will test the hypothesis that Notch signaling continues to exert an effect on liver biology throughout life, by maintaining ductal cell integrity and spatially organizing the response to injury. PUBLIC HEALTH RELEVANCE: At present, the only effective treatment for patients with end-stage liver failure is transplantation. A major challenge to the development of alternative approaches is the inability to recapitulate normal liver cell organization (morphogenesis) and function outside of the body. The ultimate goal of this research is to delineate the events that guide differentiation and morphogenesis of the liver normally, and thereby devise rational approaches to liver regeneration and replacement.