Human enteroid monolayers: A novel, functionally stable model for investigating oral drug disposition

To further the development of an in vitro model that faithfully recapitulates drug disposition of orally administered drugs, we investigated the utility of human enteroid monolayers to simultaneously assess intestinal drug absorption and first-pass metabolism processes. We cultured human enteroid monolayers from 3 donors, derived via biopsies containing duodenal stem cells that were propagated and then differentiated atop permeable Transwell inserts, and confirmed transformation into a largely enterocyte population via RNA sequencing analysis and immunocytochemistry (ICC) assays. Proper cell morphology was assessed and confirmed via bright field microscopy and ICC imaging of tight junction proteins and other apically and basolaterally localized proteins. Enteroid monolayer barrier integrity was demonstrated by elevated transepithelial electrical resistance that stabilized after 10 days in culture and persisted for 42 days. These results were corroborated by low paracellular transport probe permeability at 7 and 21 days in culture. The activity of a prominent drug metabolizing enzyme, CYP3A, was confirmed at 7, 21, and 42 days culture under basal, 1α,25(OH)₂ vitamin D₃-induced, and 6',7'-dihydroxybergamottin-inhibited conditions. The duration of these experiments is particularly noteworthy, because, to our knowledge, this is the first study to assess drug metabolizing enzymes and transporters expression/function for enteroids cultured for greater than 12 days. The sum of these results suggests enteroid monolayers are a promising ex vivo model to investigate and quantitatively predict an orally administered drug's intestinal absorption and/or metabolism. SIGNIFICANCE STATEMENT: This study presents a novel ex vivo model of the human intestine, human intestinal organoid (enteroid) monolayers that maintain barrier function and metabolic functionality for up to 42 days in culture. The incorporation of both barrier integrity and metabolic function over an extended period within the same model is an advancement over historically used in vitro systems, which either lack one or both of these attributes or have limited viability.