Animal models of inflammatory bowel disease: novel experiments for revealing pathogenesis of colitis, fibrosis, and colitis-associated colon cancer.

Inflammatory bowel disease (IBD), comprising Crohn's disease and ulcerative colitis, is a lifelong disease that manifests with chronic intestinal inflammation, sequential fibrosis, and an increased risk of colitis-associated colon cancer (CAC). The combined effects of genetic, immunological, environmental, and microbial factors render it difficult to determine the specific mechanism underlying the induction and perpetuation of IBD. Various animal models of IBD have contributed enormously to the understanding of IBD pathogenesis in terms of genomics, transcriptomics, proteomics, microbiome, and drug development of novel therapeutics. Although comprehensive research on IBD has been enabled by advanced technologies, such as genetically engineered models, there is a great need to develop relevant in vivo models of colitis and fibrosis. Here, we review 4 categories of animal models of acute and chronic intestinal inflammation, fibrosis, and CAC: chemically induced, genetically engineered, T cell transfer, and spontaneous gene mutation models.