Intestinal Barrier: Mechanisms of Disruption and Strategies for Restoration in Ulcerative Colitis

Background: Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease. Intestinal barrier impairment represents a core pathogenic mechanism and a key therapeutic target for achieving mucosal healing and sustained remission. Methods: This narrative review summarizes intestinal barrier structure, disruption mechanisms, barrier-targeted therapies, and non-invasive monitoring approaches. A reproducible literature search was conducted in PubMed, Web of Science, and ClinicalTrials.gov from 2015 to 2026. Results: Barrier disruption in UC involves genetic susceptibility, proinflammatory cytokines, zonulin-mediated tight junction injury, gut microbiota dysbiosis, decreased short-chain fatty acids and secondary bile acids, impaired autophagy, and an abnormal mucin 2 (MUC2)-dependent mucus layer. Validated non-invasive monitoring tools include fecal calprotectin/lactoferrin, intestinal ultrasound, diffusion-weighted magnetic resonance imaging (MRI), and intravoxel incoherent motion (IVIM). Emerging therapies focus on tight junction stabilization, epithelial regeneration, autophagy regulation, MUC2 restoration, and microbiota modulation. Conclusions: Intestinal barrier dysfunction drives the initiation and progression of UC. Barrier-based monitoring and targeted repair strategies improve UC management. Future studies should develop personalized therapies, precise microbiota engineering, and multi-dimensional digital evaluation systems.