Biopsy-derived colonoid air-liquid interface monolayers reveal persistent mucosal defects in ulcerative colitis patients

Background: The Inflammatory Bowel Disease (IBD) ulcerative colitis (UC) is characterized by colonic mucosal inflammation and barrier dysfunction. We hypothesize that UC causes persistent defects in mucosal homeostasis, evident even in the absence of active inflammation, contributing to disease chronicity. Methods: To test this, we grew patient biopsy-derived sigmoid colonoids into air-liquid interface (ALI) monolayers, characterizing them through microscopy, proteomics, bulk RNAseq, and their susceptibility to UC patient-isolated Escherichia coli pathobiont p19A. Results: Non-IBD ALI monolayers formed uniform crypt-like structures and a thick mucus layer containing all epithelial-derived proteins previously identified in human colonic mucus. In contrast, ALI monolayers from UC patients displayed a range of impairments, classified as a mild phenotype with distorted architecture and a thinner, more permeable mucus layer to a severe phenotype with defects in cellular differentiation and an inability to produce a mucus layer. Transcriptome analysis identified activated pathways associated with extracellular matrix formation and cell signaling, including numerous cancer-associated genes in UC ALI monolayers, which also proved significantly more susceptible to E. coli p19A. Conclusions: Taken together, the culturing of patient biopsies into ALI colonoid monolayers provides a powerful model to assess human colonic mucosal development, healing, homeostasis, and mucus barrier function, revealing that UC-derived colonoid monolayers display a range of developmental and functional defects that persist in the absence of inflammation.