The role of c-met in liver biology

c-met 在肝脏生物学中的作用

• 批准号: 8552759
• 负责人: Snorri Thorgeirsson
• 金额: $ 25.44万
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8552759
• 关键词: Address; Adhesions; Adult; Area; Biliary; Biology; CCL2 gene; Carbon Tetrachloride; Cell Differentiation process; Cell Line; Cell Proliferation; Chronic; Cytoskeletal Modeling; DNA Damage; Development; Dystrophic Calcification; Epidermal Growth Factor Receptor; Epithelial; Experimental Animal Model; Fibrosis; Gene Expression Profile; Gene Targeting; Genes; Genetic; Goals; Growth; Healed; Hepatic; Hepatic Fibrogenesis; Hepatocyte; Hepatocyte Growth Factor; Immunohistochemistry; Inflammatory; Injury; Knockout Mice; Liver; Liver Fibrosis; Liver Regeneration; Liver Stem Cell; Maintenance; Malignant neoplasm of liver; Mediating; Mediator of activation protein; Metabolism; Modeling; Monitor; Morphogenesis; Natural regeneration; Necrosis; Pathway interactions; Phase; Play; Proto-Oncogene Proteins c-akt; RANTES; Receptor Protein-Tyrosine Kinases; Regulation; Research; Resolution; Resources; Role; STAT3 gene; Signal Pathway; Signal Transduction; Stem Cell Research; Stem cells; Time; Tissue Survival; Tissues; Western Blotting; adult stem cell; biological adaptation to stress; cancer site; cholangiocyte; healing; in utero; intercellular communication; liver cell proliferation; meetings; mouse model; receptor; regenerative therapy; self-renewal; stellate cell; stem; transcriptomics; tumorigenesis

Our most recent results in this project include: (1)EGFR and c-Met are involved in both activation and differentiation of hepatic progenitor cell (HPC) . However, the underlying mechanisms have not been elucidated. Here we have addressed the impact of EGFR and c-Met signaling on the differentiation of HPC into heptatocytic and biliary epithelial lineages using clonally derived progenitor cell lines from EGFRfl/fl and Met fl/fl conditional knockout mice.Precise control of lineage commitment and maintenance of stem/progenitor cells is crucialfor regeneration of diseased liver. We have used a combination of genetic and pharmacological approaches to address the role of Egfr and Met, two principal liver receptor tyrosine kinases (RTK), in hepatocyte-billiary epithelial lineage decisions of hepatic progenitor cells (HPCs). We have shown that Met and Egfr collaborate to increase the HPC self-renewal growth through activation of ERK pathway. Met is a key RTK responsible for hepatocyte differentiation via strong activation of AKT and STAT3, whereas Egfr is an essential mediator of the Notch1 pathway required for cholangiocyte specification and branching morphogenesis. Unlike Met, genetic loss of Egfr was beneficial for HPC-mediated liver regeneration by switching HPC differentiation towards hepatocytes rather than cholangiocytes. This establishes both cooperative and uniquefunctions of Met and Egfr regulatory network as a mechanism of HPC expansion and directed differentiation with implications for regenerative therapies; and (2)HGF/c-Met signaling plays a pivotal role in hepatocyte survival and tissue remodeling during liver regeneration. HGF treatment accelerates resolution of fibrosis in experimental animal models. We have utilized Met(fl/fl);Alb-Cre(+/-) conditional knockout mice and a carbon tetrachloride(CCl(4))-induced liver fibrosis model to formally address the role of c-Met signaling in hepatocytes in the context of chronic tissue injury. Histological changes during injury (4weeks) and healing phase (4weeks) were monitored by immunohistochemistry; expression levels of selected key fibrotic molecules were evaluated by western blotting, and time-dependent global transcriptomic changes were examined using a microarray platform. Loss of hepatocyte c-Met signaling altered hepatic microenvironment and aggravated hepatic fibrogenesis. Greater liver damage was associated with decreased hepatocyte proliferation, excessive stellate cell activation and rapid dystrophic calcification of necrotic areas. Global transcriptome analysis revealed a broad impact of c-Met on critical signaling pathways associated with fibrosis. Loss of hepatocyte c-Met caused a strong deregulation of chemotactic and inflammatory signaling (MCP-1, RANTES, Cxcl10) in addition to modulation of genes involved in reorganization of the cytoskeletal network (Actb, Tuba1a, Tuba8), intercellular communications and adhesion (Adam8, Icam1, Itgb2), control of cell proliferation (Ccng2, Csnk2a, Cdc6, cdk10), DNA damage and stress response (Rad9, Rad52, Ercc4, Gsta1 and 2, Jun). Our study demonstrates that deletion of c-Met receptor in hepatocytes results in pronounced changes in hepatic metabolism and microenvironment, and establishes an essential role for c-Met in maintaining the structural integrity and adaptive plasticity of the liver under adverse conditions.

本课题的最新研究结果包括：（1）EGFR和c-Met参与肝祖细胞（HPC）的活化和分化。然而，其潜在机制尚未阐明。在此，我们使用来自EGFRfl/fl和Met fl/fl条件敲除小鼠的克隆衍生祖细胞系，研究了EGFR和c-Met信号对HPC分化为肝细胞和胆管上皮细胞谱系的影响。我们已经使用了遗传学和药理学的方法来解决的Egfr和Met，两个主要的肝受体酪氨酸激酶（RTK），在肝祖细胞（HPC）的肝细胞-胆汁上皮谱系决定的作用。我们已经表明，Met和Egfr合作，通过激活ERK途径增加HPC自我更新生长。Met是通过强烈激活AKT和STAT 3负责肝细胞分化的关键RTK，而Egfr是胆管细胞特化和分支形态发生所需的Notch 1途径的重要介质。与Met不同，Egfr的遗传缺失通过将HPC分化向肝细胞而不是胆管细胞转变而有利于HPC介导的肝再生。这建立了Met和Egfr调控网络作为HPC扩增和定向分化机制的协同和独特功能，并对再生治疗具有意义;（2）HGF/c-Met信号传导在肝细胞存活和肝再生过程中的组织重塑中起关键作用。HGF治疗加速实验动物模型中纤维化的消退。我们利用Met（fl/fl）;Alb-Cre（+/-）条件性基因敲除小鼠和四氯化碳（CCl（4））诱导的肝纤维化模型来正式阐述慢性组织损伤背景下肝细胞中c-Met信号传导的作用。通过免疫组化监测损伤（4周）和愈合期（4周）的组织学变化;通过蛋白质印迹法评估所选关键纤维化分子的表达水平，并使用微阵列平台检查时间依赖性全局转录组学变化。肝细胞c-Met信号的丢失改变了肝脏微环境并加重了肝纤维化。肝细胞增殖减少、星状细胞过度活化和坏死区快速营养不良性钙化与更严重的肝损伤相关。全局转录组分析揭示了c-Met对与纤维化相关的关键信号通路的广泛影响。肝细胞c-Met的缺失导致趋化和炎症信号的强烈失调（MCP-1、RANTES、Cxcl 10）的调节，以及参与细胞骨架网络重组的基因的调节。（Actb，Tuba 1a，Tuba 8），细胞间通讯和粘附（Adam 8，Icam 1，Itgb 2），细胞增殖控制（Ccng 2，Csnk 2a，Cdc 6，cdk 10），DNA损伤和应激反应（Rad 9，Rad 52，Ercc 4，Gsta 1和2，Jun）。我们的研究表明，肝细胞中c-Met受体的缺失导致肝脏代谢和微环境的显著变化，并建立了c-Met在不利条件下维持肝脏结构完整性和适应性可塑性的重要作用。