PROJECT SUMMARY This project will develop novel in vitro models of the human gastrointestinal (GI) tract for understanding natural cellular responses to microbes and the induction of immune tolerance and activation. The development of gastrointestinal organoids, 3-D permanent cultures of complex primary epithelial cell populations embedded in an extracellular matrix, has revolutionized research in gastrointestinal development, microbiology and immunology in the past 5 years. For our project, we have assembled a trans-disciplinary team of investigators with expertise in bioengineering (Wilking, Chang), immunology (Bimczok, Jutila), and human microbiome research (Walk) to significantly advance 3-D gut organoid-microbiome co-culture systems. Our team has recently established a millifluidic gut-on-a chip-platform, the GoFlowChip, that recapitulates luminal and basal flow in human intestinal organoids. In parallel investigations, we have established co-cultures of primary human monocyte-derived DCs and human gastric spheroids that we have successfully infected with H. pylori. Here, we seek to leverage the unique capabilities of our two models and combine them into a single analytical platform to study antigen sampling from the gastrointestinal lumen for the induction of adaptive mucosal immunity or tolerance. Specifically, we seek to define and quantify the contributions of candidate mechanisms including transepithelial dendrite formation and Fc-receptor-dependent transcytosis that enable mononuclear phagocytes (MNPs) to acquire luminal antigens. We hypothesize that distinct mechanisms of MNP antigen acquisition are reproduced and can be quantitatively analyzed using the GOFlowChip platform and that colonizing bacteria and fluid dynamics regulate epithelial antigen transport. To test our hypotheses, we will (1) Develop and validate a chip-based organoid-DC co-culture system with luminal and basolateral flow capacity. (2) Quantify the net effect of biologic complexity on GI organoid biology and MNP interaction. (3) Elucidate the mechanisms involved in bacterial antigen sampling from the gastrointestinal lumen by human MNPs. This approach will enable us to optimize our integrated GoFlowChip co-culture system as a powerful new tool for the field for studies on vaccine or drug delivery and on the impact of intestinal microbiota on antigen sampling. The proposed research is conceptually innovative, because it integrates all three necessary cell types (epithelial, microbial, and immune) involved in mucosal host-microbe interactions. The GoFlowChip platform is technologically innovative, because it replicates a complex, oxygen-utilizing epithelium and a microbially colonized lumen, is the first to incorporate fluidics into 3-D organoid cultures, and reproduces the intimate interactions that naturally occur between the gastrointestinal epithelium and sentinel MNPs. The proposed research is significant, because it will provide an incredibly powerful new tool to address fundamental, mechanistic questions in human mucosal biology, microbiology, and immunology in the context of human health and disease.

NARRATIVE Gastrointestinal immunity and homeostasis depend on the complex interplay between the epithelium, luminal microbes and immune cells in the basolateral compartment. The GoFlowChip combines all of these players in a novel organ-on-a-chip design with luminal and basal fluidics. This innovative platform will enable the field to analyze the mechanisms underlying phagocytic antigen sampling and a variety of other key GI-related biological functions in a validated and reproducible human tissue culture system.