Epithelial and stromal remodeling in murine Crohn's disease-like ileitis.

BACKGROUND AND AIMS: Inflammatory bowel disease is characterized by progressive epithelial, immune, and stromal dysfunction. Human datasets yield important insights yet are inherently descriptive, requiring animal models for in vivo mechanistic interrogation. The SAMP1/YitFc (SAMP) mouse model develops spontaneous Crohn's disease (CD)-like ileitis while allowing controlled manipulation of pathophysiologic pathways. To understand cell-specific disease-associated transcriptional changes, we defined the single-nucleus transcriptomes of inflamed SAMP ilea using single-nucleus RNA-sequencing (snRNA-seq). METHODS: We performed whole-ileum snRNA-seq on SAMP (n=4) and control AKR/J (n=3) mice using the gut-optimized CitraPrep protocol, generating 58,349 high-quality nuclei across epithelial, immune, and stromal lineages. We corroborated SAMP-associated changes with immunofluorescent staining, Western blotting, spatial transcriptomic, and human single-cell RNA-sequencing data. RESULTS: We observed a primary type 2 immune phenotype in SAMP compared to AKR mice, but most transcriptional changes occurred in stromal and epithelial, not immune, cells. Stromal remodeling included increased fibroblast-derived Igf1. In SAMP epithelium, expansion of tuft cells and emergence of SAMP-specific Pcsk6+ crypt enterocytes were observed and confirmed in human CD patients. Finally, we identified cross-compartmental changes in cell-cell signaling, including enterocyte-to-type 3 innate lymphoid cell (ILC3) communication and enhanced global Igf1 signaling. These features recapitulate known, as well as novel, characteristics of CD and extend our understanding of disease-associated multicellular networks. CONCLUSION: This atlas of ileitis-prone SAMP mice provides a high-resolution resource for dissecting conserved and novel mechanisms of inflammation and tissue remodeling. Herein, we uncover disease-associated transcriptional changes conserved in human CD, presenting a translational platform for future mechanistic and therapeutic studies.