A small intestinal organoid model of non-invasive enteric pathogen-epithelial cell interactions

Organoids mirror in vivo tissue organization and are powerful tools to investigate the development and cell biology of the small intestine. However, their application for the study of host-pathogen interactions has been largely unexplored. We have established a model using microinjection of organoids to mimic enteric infection, allowing for direct examination of pathogen interactions with primary epithelial cells in the absence of confounding variables introduced by immune cells or the commensal microbiota. We investigated the impact of Paneth cell α-defensin antimicrobial peptides on bacterial growth. We demonstrate that organoids form a sealed lumen, which contains concentrations of α-defensins capable of restricting growth of multiple strains of Salmonella enterica serovar Typhimurium for at least 20 h postinfection. Transgenic expression of human defensin 5 in mouse organoids lacking functional murine α-defensins partially restored bacterial killing. We also found that organoids from NOD2(-/-) mice were not impaired in α-defensin expression or antibacterial activity. This model is optimized for the study of non-invasive bacteria but can be extended to other enteric pathogens and is amenable to further genetic manipulation of both the host and microbe to dissect this critical interface of host defense.