Functional dynamics of dysbiosis in a gnotobiotic transfer model of Crohn`s disease-like ileitis: Impact of diet and inflammation

炎症性肠病（IBD）发病率的增加被认为是环境和个体风险因素的结果。慢性炎症的疾病机制研究的一个主要焦点是肠道微生物生态系统及其与肠粘膜的相互作用。克罗恩病是主要影响末端回肠的两种主要IBD表型之一。尽管多种易感基因表明微生物触发因子在克罗恩病发病机制中的作用，但许多IBD相关小鼠模型仅靶向结肠中的慢性炎症，并且仍然缺乏肠道微生物群在形成自发发展的小肠慢性炎症过程中的功能证据。本项目的目的是在克罗恩病样回肠炎的独特小鼠模型（杂合Tnf ΔARE/+小鼠）中鉴定和机械表征疾病相关微生物群。第一个实验表明，Tnf ΔARE/+小鼠的抗生素治疗（万古霉素/甲硝唑）抑制回肠炎症，支持微生物因素在小肠疾病发病机制中起重要作用的假设。回肠病理学的改善与粘膜相关和管腔细菌多样性的显著变化相关，但与细胞密度无关，如通过16 S rRNA基因扩增子的高通量序列分析所测量的。基于这些发现，我们将使用内源性微生物群的分离细菌菌株在无菌和经抗肿瘤治疗的Tnf ΔARE/+小鼠中引发（目标1）或预防（目标2）复发性病理。选定的微生物群与疾病易感宿主的相互作用将在上皮（回肠）和T细胞水平上进行分析，目标是先天和抗原特异性机制。总之，我们建议使用克罗恩病样回肠炎的少数模型系统之一来研究非感染性肠道微生物群在引发小肠慢性炎症中的功能作用。

The increasing incidence of inflammatory bowel diseases (IBD) is considered to be the consequence of environmental and individual risk factors. A major focus of research into disease mechanisms underlying chronic inflammation is the gut microbial ecosystem and its interaction with the intestinal mucosa. Crohn’s disease is one of the two major IBD phenotypes mostly affecting the terminal ileum. Despite the fact that a variety of susceptibility genes suggest a role for microbial triggers in the pathogenesis of Crohn’s disease, numerous IBD-related mouse models target chronic inflammation only in the colon and functional evidence for the intestinal microbiota in shaping a spontaneously developing, chronic inflammatory process of the small intestine is still lacking. The aim of the present project is to identify and mechanistically characterize a disease-relevant microbiota in a unique murine model for Crohn’s disease-like ileitis (heterozygous Tnf ΔARE/+ mice). First experiments showed that antibiotic treatment (vancomycin/metronidazole) of Tnf ΔARE/+ mice inhibited ileal inflammation, supporting the hypothesis that microbial factors play an essential role in the disease pathogenesis of the small intestine. Improvement of ileal pathology was associated with marked changes in mucosa-associated and luminal bacterial diversity, but not cell density, as measured by high-throughput sequence analysis of 16S rRNA gene amplicons. Based on these findings, we will use isolated bacterial strains of the endogenous microbiota to initiate (Objective 1) or prevent (Objective 2) recurrent pathology in germ-free and antibiotic-treated Tnf ΔARE/+ mice. The interplay of selected microbiota with the disease-susceptible host will be analyzed at the epithelial (ileum) and T cell level targeting innate and antigen-specific mechanisms. In summary, we propose to use one of the few model systems for Crohn’s disease-like ileitis to study the functional role of the non-infectious intestinal microbiota in initiating chronic inflammation of the small intestine.