Growth Regulation of the Intrahepatic Biliary Tree

描述（由申请人提供）：胆管细胞是慢性胆汁淤积性肝病如原发性胆汁性肝硬化（PBC）和原发性硬化性胆管炎（PSC）的靶细胞，其特征在于不同大小的胆管细胞（即，小的和大的）。胆管细胞分化和胆道重塑是维持胆道质量和功能恢复的关键，在这些毁灭性的肝脏疾病的发病机制。阐明调节小胆管细胞和大胆管细胞对胆汁淤积和肝损伤/毒素的不同再生反应的细胞内机制将在开发用于治疗胆汁淤积性肝病的治疗策略中发挥关键作用。在慢性肝胆损伤期间，双能肝祖细胞群被激活以刺激胆管细胞和肝细胞。如果人和啮齿类动物胆管内存在具有多能性的小胆管细胞，则这些细胞应具有在肝损伤期间分化成大胆管细胞或肝细胞的能力，例如大胆管细胞或肝细胞丢失或再生机制受阻的疾病状况。肝内胆管细胞的可塑性被认为是一个谱系的终末分化细胞可以直接分化成另一个谱系或经历转分化。因此，特定的细胞亚群，如表达已知的胆管祖细胞标志物的小胆管细胞，可以假设在暴露于某些病理条件时含有多能细胞群。我们提出了一个中心假设，即小胆管细胞通过在疾病条件下获得肝祖细胞和大胆管细胞的表型来促进胆道损伤的恢复。在本申请中提出了多能基因和微小RNA作为小胆管细胞中的标志物的系统研究，所述小胆管细胞具有胆汁淤积性肝损伤的治疗潜力。中心假设将通过三个具体目标进行评估。首先，我们将区分多能性 参与小和大胆管细胞中组织修复相关细胞功能的功能性信号传导途径。其次，我们将鉴定小胆管细胞中参与分化/再生相关细胞功能的TGF-β依赖性miRNA。最后，我们将在特定的动物模型中确定小胆管细胞及其相关的miRNA对加速转基因和慢性胆汁淤积性肝损伤的形态和功能恢复的作用。将在体内评价细胞移植物/miRNA操作对胆管细胞生长和分化的治疗效果。新的见解的生理作用和机制的分子和功能异质性在人类胆管上皮细胞将获得。同时，在小胆管细胞/胆管定向祖细胞的生长、分化和重塑的调节中获得的基础知识有望推进胆管细胞生物学/病理生理学领域。

DESCRIPTION (provided by applicant): Cholangiocytes are the target cells in chronic cholestatic liver diseases such as primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC), which are characterized by the damage, proliferation and differentiation of cholangiocytes of different sizes (i.e., small and large). Cholangiocyte differentiation and biliar remodeling are critical for the maintenance of biliary mass and the functional recovery during the pathogenesis of these devastating liver diseases. The elucidation of the intracellular mechanisms regulating the differential regenerative responses of small and large cholangiocytes to cholestasis and liver injury/toxins will play a pivotal role in the development o therapeutic strategies for the treatment of cholestatic liver diseases. During chronic hepatobiliary injury, a population of bipotent liver progenitor cells becomes activated to replenis both cholangiocytes and hepatocytes. If small cholangiocytes with multipotential capacity exist within human and rodent bile ducts, these cells should possess the ability to differentiate into either large cholangiocytes or hepatocytes during liver damage, such as diseased conditions in which large cholangiocytes or hepatocytes are lost or regenerative mechanisms are hampered. The plasticity of intrahepatic cholangiocytes has been postulated that terminally differentiated cells of one lineage may directly differentiate into another lineage or undergo trans-differentiation. Therefore, specific subpopulations of cells, such as small cholangiocytes that express known biliary progenitor cell markers, can be hypothesized to contain a multipotent cell population when exposed to certain pathological conditions. We propose the central hypothesis that small cholangiocytes contribute to the recovery of biliary injury through acquiring the phenotypes of liver progenitor cells and large cholangiocytes under diseased conditions. Systematic investigation of pluripotent genes and microRNAs is proposed in this application as markers in small cholangiocytes with the therapeutic potentials for cholestatic liver injury. The central hypothesis will be evaluated by three specific aims. First, we will distinguish pluripotent functional signaling pathways involved in tissue repair-related cellular functions in small and large cholangiocytes. Second, we will identify TGF-� dependent miRNAs involved in differentiation/regeneration-related cellular functions in small cholangiocytes. Last, we will determine the effects of small cholangiocytes and their-associated miRNAs on accelerating the morphologic and functional recovery of transgenic and chronic cholestatic liver injury in specific animal models. Therapeutic effects of cell engraft/miRNA manipulation on biliary cell growth and differentiation will be evaluated in vivo. Novel insights into the physiological roles and mechanisms of molecular and functional heterogeneity in human biliary epithelium will be obtained. Meanwhile, the fundamental knowledge obtained in the regulation of growth, differentiation and remodeling by small cholangiocytes/biliary committed progenitors is expected to advance the field of cholangiocyte biology/ pathophysiology.