The role of Axin2+ stem cells in ulcer healing during colitis.

Axin2 干细胞在结肠炎溃疡愈合中的作用。

• 批准号: 9138122
• 负责人: Terrence A. Barrett
• 金额: --
• 依托单位: VA MEDICAL CENTER - LEXINGTON, KY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-10-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9138122
• 关键词: AXIN2 gene; Area; Biochemical; Cell Proliferation; Cells; Clinical Markers; Colitis; Colon; Colon Carcinoma; Data; Disease; Elements; Epithelial; Epithelial Cells; Event; Excision; Exhibits; Failure; Flare; Gene Expression; Gene Targeting; General Population; Generations; Goals; Granulation Tissue; Hospitalization; Human; Impairment; In Vitro; Incidence; Inflammatory Bowel Diseases; Intestines; Island; Lasers; Mediating; Medical; Messenger RNA; Microscopy; Molecular; Molecular Profiling; Mucous Membrane; Mus; Natural regeneration; Operative Surgical Procedures; Oral; Patients; Play; Population; Prevalence; Recovery; Refractory; Reporter; Risk; Role; Signal Transduction; Stem cells; Steroid therapy; Steroids; Structure; Surface; Symptoms; Ulcer; Ulcerative Colitis; Veterans; WNT Signaling Pathway; Work; beta catenin; cell type; clinical remission; design; disability; healing; improved; insight; monolayer; mouse model; novel; prevent; prospective; public health relevance; repaired; self-renewal; stem cell population; therapeutic target

 DESCRIPTION (provided by applicant): A major cause of colon removal surgery in veterans with inflammatory bowel disease (IBD) is a failure of medically-induced mucosal healing. Mucosal healing is a reliable clinical marker of recovery after IBD therapy as it is associated with durable clinical remission. Despite the importance of mucosal repair, we continue to have a poor understanding of many of the cellular and molecular elements that mediate ulcer healing. The current proposal focuses on the role of colonic (epithelial) stem cells (CSC) in ulcer healing during colitis. Wnt/β-catenin signaling in stem cells promotes cell proliferation as well as self-renewal, both essential functions needed for ulcer healing and restitution of the mucosal barrier. A central tenant of this proposal is the hypothesis that Wnt/β-catenin signaling plays an integral role in mucosal repair in IBD and that steroids delay ulcer healing my impairing Wnt/β-catenin signaling. In mucosal ulceration, as seen in IBD, there is replacement of surface mucosa with granulation tissue that is re-epithelialized with new crypt structures. We suspect that active Wnt signaling is required for several steps through this sequence of events from stage 1) generation of an intestinal epithelial cell (IEC) monolayer, to stage 2) formation of epithelial invaginations, to stage 3) formation of crypt islands on ulcer surfaces and finally stage 4) regeneration of mature crypts (Fig 3). Biochemical data from our lab indicate Wnt/β-catenin signaling is increased during ulcer healing in colitis in mice and IBD patients. In studies to interrogate the role of Wnt signaling in ulcer healing, we discovered that IEC expressing mRNA for the Wnt target gene Axin2 expand in ulcer margins, on ulcer surfaces, and within newly-formed crypt structures in the middle of ulcers. Studies using a novel Axin2 reporter mouse model indicate that Axin2+ IEC are pluripotent and capable of growing colonoid structures in vitro from a single cell. Together the preliminary data suggest that Axin2+ IEC represent a novel ISC population that forms new crypt structures during ulcer healing. In Aim 1, Axin2lacZ/+ and Axin2 CreERT2/+; R26RmTmG/+ mice will be used to study ulcer-associated Axin2+ IEC localization and gene expression profiles of this new stem cell population, as well as perform lineage tracing during ulcer healing in DSS colitis. In Aim 2 we will examine ulcer healing in mice treated with steroids. New studies will utilize Axin2-specific expression of stabilized β-catenin to examine its role in ulcer healin during steroid therapy. Aim 3 studies will interrogate the role of Axin2+ IEC in human IBD and will analyze the mechanisms by which steroids impair ulcer healing. The goal of these studies will be to determine if untreated UC patients exhibit increased Axin2 expression, Wnt signaling and stem cell gene expression in areas of ulcer healing (Aim 3A) and determine whether steroid therapy reduces levels of Axin2 expression and stem cell activation in areas of delayed ulcer healing in a prospective trial of UC patients treated with steroids for a colitis flare (Aim 3B). Together the studies proposed will provide valuable insights into the molecular mechanisms that govern ulcer healing in colitis. The goal is to determine areas where therapeutic targets can be designed to safely accelerate ulcer healing and reverse the negative impact of steroids on mucosal repair in colitis.

 描述（由申请人提供）： 患有炎症性肠病（IBD）的退伍军人结肠切除手术的一个主要原因是医学诱导的粘膜愈合失败。粘膜愈合是IBD治疗后恢复的可靠临床标志，因为它与持久的临床缓解相关。尽管粘膜修复的重要性，我们仍然有一个贫穷的理解，许多细胞和分子的元素，介导溃疡愈合。目前的建议集中在结肠（上皮）干细胞（CSC）在结肠炎溃疡愈合中的作用。干细胞中的Wnt/β-连环蛋白信号传导促进细胞增殖以及自我更新，这两种功能都是溃疡愈合和粘膜屏障恢复所需的基本功能。该提议的核心租户是Wnt/β-连环蛋白信号传导在IBD的粘膜修复中起着不可或缺的作用并且类固醇通过损害Wnt/β-连环蛋白信号传导来延迟溃疡愈合的假设。在粘膜溃疡中，如在IBD中所见，表面粘膜被肉芽组织替代，肉芽组织用新的隐窝结构再上皮化。我们怀疑，从阶段1）肠上皮细胞（IEC）单层的产生，到阶段2）上皮内陷的形成，到阶段3）溃疡表面上的隐窝岛的形成，以及最后阶段4）成熟隐窝的再生，这一系列事件中的几个步骤需要活性Wnt信号传导（图3）。来自我们实验室的生化数据表明，在小鼠和IBD患者的结肠炎溃疡愈合期间，Wnt/β-连环蛋白信号传导增加。在询问Wnt信号传导在溃疡愈合中的作用的研究中，我们发现表达Wnt靶基因Axin 2的IEC mRNA在溃疡边缘、溃疡表面和溃疡中间新形成的隐窝结构内扩展。使用新的Axin 2报告小鼠模型的研究表明，Axin 2 + IEC是多能的，并且能够在体外从单细胞生长结肠样结构。总之，初步数据表明Axin 2 + IEC代表了在溃疡愈合期间形成新的隐窝结构的新型ISC群体。在目标1中，Axin 2lacZ/+和Axin 2CreERT 2/+; R26 RmTmG/+小鼠将用于研究溃疡相关的Axin 2 + IEC定位和该新干细胞群的基因表达谱，以及在DSS结肠炎的溃疡愈合期间进行谱系追踪。在目标2中，我们将检查用类固醇治疗的小鼠的溃疡愈合。新的研究将利用稳定的β-连环蛋白的Axin 2特异性表达来检查其在类固醇治疗期间在溃疡愈合中的作用。目的3研究将询问Axin 2 + IEC在人类IBD中的作用，并将分析类固醇损害溃疡愈合的机制。这些研究的目的是确定未经治疗的UC患者在溃疡愈合区域是否表现出Axin 2表达、Wnt信号传导和干细胞基因表达增加（Aim 3A），并确定在接受类固醇治疗的UC患者结肠炎发作的前瞻性试验中，类固醇治疗是否降低了溃疡延迟愈合区域的Axin 2表达和干细胞活化水平（Aim 3B）。这些研究将为结肠炎溃疡愈合的分子机制提供有价值的见解。其目的是确定可以设计治疗靶点的领域，以安全地加速溃疡愈合并逆转类固醇对结肠炎粘膜修复的负面影响。