Dissection of barrier dysfunction in organoid-derived human intestinal epithelia induced by Giardia duodenalis

Background and Aims: The protozoa Giardia duodenalis is a major cause of gastrointestinal illness worldwide, but underlying pathophysiological mechanisms remain obscure, partly due to the absence of adequate cellular models. We aimed to overcome these limitations and to recapitulate the authentic series of events in the primary human duodenal tissue by using the human organoid system. Methods: We established a compartmentalized cellular transwell system with electrophysiological and barrier properties akin to duodenal mucosa and dissected the events leading to G. duodenalis-induced barrier breakdown by functional analysis of transcriptional, electrophysiological and tight junction components. Results: Organoid-derived cell layers of different donors showed a time- and parasite load-dependent leak flux indicated by collapse of epithelial barrier upon G. duodenalis infection. Transcriptomic analysis suggested major expression changes in genes contributing to ion transport and tight junction structure. SLC12A2/NKCC1- and CFTR-dependent chloride secretion was reduced early after infection, while changes in the tight junction composition, localization and structural organization occurred later as revealed by immunofluorescence analysis and freeze fracture electron microscopy. Conclusion: Data suggest a previously unknown sequence of events culminating in intestinal barrier dysfunction upon G. duodenalis infection ignited by alterations of cellular ion transport followed by breakdown of the tight junctional complex and loss of epithelial integrity. The newly established organoid-derived model to study G. duodenalis infection will help enable further molecular dissection of the disease mechanism and, thus, can help to find new options treating disease and infection, in particular relevant for chronic cases of giardiasis.