Differential response of patient-derived intestinal organoids to site-specific mucosal bacteria in pediatric inflammatory bowel disease

Objective: Inflammatory bowel disease (IBD) is secondary to an abnormal immune response to the microbiota. There is evidence of impaired stem cell signatures in IBD contributing to impaired epithelial repair. We therefore aimed to study the role of the microbiome in the intestinal stem cell population in paediatric IBD cases, a group without confounding treatments or comorbidities, by directly studying the interaction between patient-isolated bacteria and the epithelium. Design: We established a unique biobank with matched intestinal organoids and cultured mucosally adherent bacteria from 36 paediatric patients. To determine the bacterial effect on host epithelial cells, closely related bacterial isolates from control and IBD patients were selected for microinjection into their corresponding organoid line. Results: Whilst no differences were observed between control and IBD-derived organoids following injury, transcriptional profiling revealed differential gene expression between uninjured control and IBD- derived organoids. Furthermore, following microinjection of an isolate originating from a control patient, there was upregulation of inflammatory signalling pathways, whereas this was not observed with a closely related isolate originating from an IBD patient. Conclusion: This demonstrates the feasibility of isolating bacteria and generating organoids from the same biopsy tissue, to explore personalised host-microbe interactions. The microinjections show the individual nature of responses, with closely related bacteria inducing very different epithelial responses, with downstream implications for immune response. This highlights the importance of understanding host-microbe interactions in a strain and site-specific manner, and developing techniques for personalised microbiome-based therapeutics.