Stem cell niche and Wnt in liver injury and regeneration.

干细胞生态位和 Wnt 在肝损伤和再生中的作用。

• 批准号: 8521271
• 负责人: Bruce Mao Zheng Wang
• 金额: $ 6.21万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-14 至 2014-07-13
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8521271
• 关键词: Address; Adult; Appearance; Automobile Driving; Binding; Binding Sites; Bioinformatics; Biological Assay; Cell Maintenance; Cell Proliferation; Cell Therapy; Cells; Cirrhosis; Development; Elements; Enhancers; Exhibits; Genes; Genetic Enhancer Element; In Vitro; Injury; Injury to Liver; Lead; Link; Liver; Liver Regeneration; Liver diseases; Measures; Mediating; Modeling; Morbidity - disease rate; Mus; Mutation; Natural regeneration; Physiological; Play; Population; Protein Family; Replacement Therapy; Reporter; Reporter Genes; Research; Role; Signal Pathway; Signal Transduction; Stem cells; Stimulus; Therapeutic; Tissues; Transcriptional Regulation; Transgenic Mice; Transgenic Organisms; United States; Work; adult stem cell; base; improved; in vivo; inhibitor/antagonist; injured; insight; liver injury; loss of function; mortality; novel; oval cell; regenerative; repaired; response; response to injury; stem cell niche; tissue regeneration; tissue repair; transcription factor

DESCRIPTION (provided by applicant): Oval cells are adult liver progenitor cells that play a physiologic role in liver regeneration and have attractive therapeutic potential. They are believed to reside in a niche within the periportal region. However, the signals that activate oval cells after injury are not known. The Wnt family of proteins plays important roles in adult stem cell maintenance in a variety of mammalian tissues. Wnt signaling is also involved in liver development and repair. Evidence suggests that Wnt signaling is central to the injury response that activates oval cells. A main unanswered question in tissue repair is how injury leads to activation of the signals necessary for rebuilding the tissue. Pursuing a novel line of research, the Nusse lab has identified a transcriptional control element (called CAIRE, for Cis Acting Injury Responsive Element) that governs the expression of Wnt in response to injury. Through the use of reporter genes linked to this enhancer, CAIRE function has been examined in various tissues. In preliminary work, the lab has shown that it is in the periportal region of the liver and responds to injury. The hypothesis is that CAIRE undergoes activation in response to liver injury that activates the oval cell compartment. It induces oval cell proliferation by driving local Wnt expression, which is required for the regenerative response. A specific signaling pathway exists upstream of CAIRE that controls CAIRE activity and Wnt expression. The proposed studies will address these hypotheses. First, the role of CAIRE in three distinct forms of liver injury that exhibit different degrees of oval cell activation will be examined. CAIRE reporter expression is expected in injury that activates the oval cell population. Next, transgenic mice in which CAIRE conditionally activates the Wnt inhibitor Dkk will be generated to determine if local Wnt signaling driven by CAIRE is required for the oval cell regenerative response. Wnt inhibition is expected to result in decreased oval cell regeneration after injury. Lastly, transcription factors that bind to and activate CAIRE will be identified. Bioinformatics will be used to identify potential transcription factors that bind to CAIRE. These factors will be examined for direct binding to CAIRE. Based on these results, mutations will be made in transcription factor binding sites within CAIRE. Transgenic mice will be made to assess for loss-of- function. These mice are expected to have decreased oval cell regenerative response. These studies will provide the first evidence of an upstream activator of Wnt expression. They will add to the evidence for a key role for Wnt signaling in liver injury and the subsequent regenerative response involving oval cells. Lastly, the results will give insight into the role of the niche in linking the injury response to tissue regeneration.

描述（由申请人提供）：卵圆细胞是成体肝祖细胞，在肝再生中发挥生理作用，并具有吸引人的治疗潜力。它们被认为位于门静脉周围区域内的一个壁龛中。然而，损伤后激活卵圆细胞的信号尚不清楚。Wnt蛋白家族在多种哺乳动物组织中的成体干细胞维持中起重要作用。Wnt信号也参与肝脏发育和修复。有证据表明，Wnt信号是激活卵圆细胞的损伤反应的核心。组织修复中一个主要的未回答的问题是损伤如何导致重建组织所必需的信号的激活。Nusse实验室进行了一系列新颖的研究，确定了一种转录控制元件（称为CAIRE，代表顺式作用损伤反应元件），该元件控制Wnt在损伤后的表达。通过使用报告基因连接到这个增强子，CAIRE功能已在各种组织中进行了检查。在初步工作中，实验室已经表明它位于肝脏的门静脉周围区域，并对损伤做出反应。假设CAIRE在肝损伤后激活卵圆细胞区室。它通过驱动再生反应所需的局部Wnt表达来诱导卵圆细胞增殖。CAIRE上游存在一条特异性信号通路，控制CAIRE活性和Wnt表达。拟议的研究将解决这些假设。首先，将检查CAIRE在三种不同形式的肝损伤中的作用，这些肝损伤表现出不同程度的卵圆细胞活化。预期CAIRE报告基因表达在激活卵圆细胞群的损伤中。接下来，将产生CAIRE条件性激活Wnt抑制剂Dkk的转基因小鼠，以确定卵圆细胞再生反应是否需要CAIRE驱动的局部Wnt信号传导。Wnt抑制预期导致损伤后卵圆细胞再生减少。最后，将鉴定结合并激活CAIRE的转录因子。生物信息学将用于识别与CAIRE结合的潜在转录因子。将检查这些因子与CAIRE的直接结合。基于这些结果，将在CAIRE内的转录因子结合位点中进行突变。将制备转基因小鼠以评估功能丧失。预期这些小鼠具有降低的卵圆细胞再生反应。这些研究将提供Wnt表达的上游激活剂的第一个证据。他们将为Wnt信号在肝损伤和随后涉及卵圆细胞的再生反应中的关键作用提供证据。最后，研究结果将深入了解小生境在连接损伤反应与组织再生中的作用。