Three-dimensional intestinal villi epithelium enhances protection of human intestinal cells from bacterial infection by inducing mucin expression

Current in vitro cell culture models do not reflect human physiology, and various efforts have been made to enhance existing models. Reconstitution of three-dimensional (3D) tissue structure has been one of the strategies, since 3D tissue structure provides essential cellular environmental cues for cell functions. Previously, we developed a novel hydrogel microfabrication technique for constructing an accurate 3D replica of human intestinal villi epithelium. In this study, genetic and physiological properties of the 3D villi model were examined to gain a better insight into the barrier function of gut epithelium and its interaction with microbes. Gene expression study of Caco-2 on the 3D villi scaffold revealed that expression of MUC17, which is one of the transmembrane mucins, was highly enhanced in the 3D villi model, compared to a monolayer culture. Cells on the scaffold were almost immune to bacterial infection, while MUC17 knockdown in Caco-2 cells restored bacterial infectivity. The 3D villi model also exhibited changes in the barrier function compared to the 2D model, manifested by changes in transepithelial electrical resistance (TEER) and permeability of FITC-dextran. Knockdown of MUC17 resulted in reduction of tight junction protein expression and further increase in permeability, suggesting an important role of MUC17 in the barrier function against pathogens and xenobiotics. Our study suggests that mimicking the 3D tissue architecture of the small intestine induces physiological changes in human intestinal cells.