HGF and Signaling Pathways in Hepatic Tissue Assembly

HGF 和肝组织组装中的信号通路

• 批准号: 6862635
• 负责人: GEORGE K MICHALOPOULOS
• 金额: $ 29.85万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6862635
• 关键词: bile ducts; biological signal transduction; cell cell interaction; cell cycle; cell differentiation; cell proliferation; embryogenesis; epidermal growth factor; gene expression; genetically modified animals; hepatocellular carcinoma; hepatocyte growth factor; histogenesis; immunocytochemistry; implant; in situ hybridization; laboratory mouse; laboratory rat; liver; liver cells; liver regeneration; mitogens; tissue /cell culture

DESCRIPTION (provided by applicant): The purpose of this grant application is to explore new findings from our work as well as new models recently developed in our lab, in order to understand the mechanisms controlling assembly and formation of liver tissue. Gene array analysis of organoid cultures, composed of reassembled hepatic cellular elements, led to better understanding of the mechanisms by which dexamethasone, HGF and EGF regulate hepatic tissue assembly. We also found, unexpectedly, that in cultures maintained in the absence of dexamethasone HGF and EGF there is high proliferative activity, presumably driven by novel mitogen(s) not predicted from the literature derived from hepatocyte cultures or from whole animal, liver regeneration, models. The focused list of these potential mitogens identified from the gene array analysis will be studied in detail until the signaling molecules regulating this process are determined. After this is accomplished, the role of these mitogens in liver early embryogenesis, overall tissue repair and early carcinogenesis will be studied. We will also pursue further analysis of the role of HGF in liver embryology by utilizing an imported colony of Met -/+ mice, heterozygous for deletion of the HGF receptor (cMet). The livers of Met -/- embryos will be carried out alive further and beyond the day of embryonic lethality and will be studied as embryonic implants in the peritoneal cavity. We have recently developed this model and found out that it allows development and organization of all epithelial elements seen in mature liver including hepatocyte plates and bile ductules, even though mature portal triads do not appear. These studies will finally determine whether embryonic defects seen in livers of HGF -/- and Met -/- mice are primary to the genetic deletions or secondary to the placental anomalies seen in these embryos. The pathways leading to development of biliary ductules in wild type and Met -/- embryo livers after embryonic implantation will also allow determination of the importance of HGF as a key factor for biliary development, an item which has been often postulated but never proven. In addition to mitogenic signals, liver tissue assembly and repair also depends on the capacity of cellular elements to function as tissue restricted facultative stem cells for each other. Biliary cells can transdifferentiate to hepatocytes via the "oval cell" pathway. We have now shown that hepatocytes can transdifferentiate to biliary epithelium, in culture and in the whole animal. This relationship between hepatocytes and biliary epithelium establishes a new paradigm of organ stability in which mature, fully differentiated, cell types can function as "stem cells" for each other The signaling pathways and molecular determinants (growth and transcription factors) regulating this process will be studied in cultures, whole animals and embryonic implants. The above studies will provide insights and better understanding of the dynamics of liver tissue formation and provide paradigms with general applicability to other models of formation and maintenance of complex tissues.

描述(申请人提供)：这项资助申请的目的是从我们的工作中探索新的发现以及我们实验室最近开发的新模型，以了解控制肝组织组装和形成的机制。对由重组的肝细胞元件组成的有机培养物进行基因阵列分析，有助于更好地理解地塞米松、HGF和EGF调节肝组织组装的机制。我们还意外地发现，在没有地塞米松、肝细胞生长因子和表皮生长因子的培养中，有高的增殖活性，推测是由新的有丝分裂原(S)驱动的，而从文献中没有预测来自肝细胞培养或来自整个动物的肝再生模型。从基因阵列分析中确定的这些潜在有丝分裂原的重点清单将被详细研究，直到调节这一过程的信号分子被确定为止。在此之后，这些有丝分裂原在肝脏早期胚胎发生、整体组织修复和早期癌变中的作用将被研究。我们还将利用HGF受体(CMET)缺失杂合子的进口Met-/+小鼠群体，进一步分析HGF在肝脏胚胎学中的作用。Met-/-胚胎的肝脏将被活着进行，并将在胚胎死亡之日之后进行，并将作为胚胎植入腹膜腔进行研究。我们最近开发了这个模型，并发现它允许成熟肝脏中所有上皮细胞的发育和组织，包括肝细胞板和胆管，即使成熟的门静脉三联体没有出现。这些研究将最终确定HGF-/-和Met-/-小鼠肝脏中的胚胎缺陷是基因缺失的主要原因，还是这些胚胎中出现的胎盘异常的次要原因。胚胎植入后导致野生型和蛋氨酸/胚胎肝脏胆小管发育的途径也将有助于确定HGF作为胆道发育的关键因素的重要性，这一点经常被假设但从未得到证实。除了有丝分裂信号外，肝组织的组装和修复还取决于细胞元件相互之间作为组织限制性兼性干细胞的能力。胆汁细胞可通过“卵圆细胞”途径转分化为肝细胞。我们现在已经证明，在培养和整个动物中，肝细胞可以转分化为胆管上皮细胞。肝细胞和胆管上皮之间的这种关系建立了一种新的器官稳定性范例，在这种范例中，成熟的、完全分化的细胞类型可以相互发挥“干细胞”的作用。调节这一过程的信号通路和分子决定因素(生长和转录因子)将在培养物、整个动物和胚胎植入中进行研究。上述研究将提供对肝组织形成动力学的洞察和更好的理解，并为复杂组织的形成和维持的其他模型提供普遍适用的范例。