Mechanisms of Oval Cell Activation and Differentiation

描述(申请人提供)：如啮齿类动物2/3部分肝切除模型所示，肝脏具有巨大的再生能力。当成熟的肝细胞不能在这一过程中发挥作用时，肝脏内的干细胞室被激活。这项研究建议的首要问题是：哪些系统信号调节干细胞介导的肝再生，这种调节的分子机制是什么？这项拟议的研究将确定涉及肝脏干细胞的激活、运输、扩增和分化的特定因素的作用和作用机制。以往的实验表明，结缔组织生长因子(CTGF)、Notch-1、WNT1、生长抑素(SST)、胰岛素样生长因子结合蛋白3(IGFBP3)在大鼠肝干细胞对2AAF/PH肝损伤的反应中起关键作用。所有这些因素都与TGFb有关。我们将从三个具体目标来描述这些关系。具体目标1将验证这样的假设，即TGF2/CTGF轴介导激活的门静脉成纤维细胞合成富含纤维连接蛋白的临时细胞外基质(ECM)，这是2-AAF/PH后肝干细胞群扩张所必需的。这一目的的主要目的是确定TGFb和CTGF在形成合适的肝干细胞增殖和迁移的细胞外微环境中的作用。特异性目标2将验证IGFBP3和SST介导肝脏干细胞在肝脏内转运的假设，以及SST在大鼠卵圆细胞对2AAF/PH的反应中增强CTGF上调的假设。这些因素在指导肝干细胞迁移中的作用以及这些途径与TGF2信号的相互作用将被阐明。特指目标3将验证这一假说，即Notch/Jagge和Wnt/Frizzleed信号在肝脏干细胞分化过程中的谱系选择中起着必要的作用。这些途径中的每一个都受到TGFb的影响，这些信号的整合似乎决定了分化的干细胞的表型。这些研究产生的数据将提供对肝脏干细胞调控的更完整的了解。这一知识将有助于指导干细胞移植治疗肝病的治疗策略的制定。

DESCRIPTION (provided by applicant): The liver has an enormous capacity to regenerate, as demonstrated by the 2/3 partial hepatectomy model in rodents. A stem cell compartment within the liver is activated when mature hepatocytes are unable to perform their role in this process. The overarching question of this research proposal is; which systemic signals regulate stem cell mediated liver regeneration and what molecular mechanisms underlie this regulation? The proposed research will identify the role and mechanism of action for specific factors involved in the activation, trafficking, expansion and differentiation of liver stem cells. Previous experiments have implicated connective tissue growth factor (CTGF), Notch-1, Wnt1, Somatostatin (SST), insulin-like growth factor binding protein 3 (IGFBP3) as playing key-roles in the liver stem cell response to 2- acetylaminofluorene/partial hepatectomy (2AAF/PH) liver injury in rats. All of these factors have a relationship to TGFb. We will characterize these relationships in three specific aims. Specific aim 1 will test the hypothesis that the TGF2/CTGF axis mediates the synthesis of a fibronectin rich provisional extracellular matrix (ECM) by activated portal fibroblasts that is required for the expansion of the liver stem cell population following 2-AAF/PH in rats. The main goal of this aim is to determine the role of TGFb and CTGF in forming the appropriate extracellular microenvironment for liver stem cell proliferation and migration. Specific aim 2 will test the hypothesis that IGFBP3 and SST mediate the trafficking of liver stem cells within the liver, and that SST potentiates the up-regulation of CTGF during the oval cell response to 2AAF/PH in rats. The role of these factors in directing the migration of liver stem cells and the interaction of these pathways with TGF2 signaling will be elucidated. Specific aim 3 will test the hypothesis that Notch/Jagged and Wnt/Frizzled signaling play a required role in lineage selection during liver stem cell differentiation. Each of these pathways is influenced by TGFb, and the integration of these signals appears to determine the phenotype of the differentiated stem cell. The data generated by these studies will provide a more complete understanding of the regulation of liver stem cells. This knowledge will help to guide the development of strategies for the therapeutic use of stem cell transplants for the treatment of liver disease.