Generation and Phenotypic Analysis of the IL-10RAR104W/R104W Mouse Model.

Background: Very-early-onset inflammatory bowel disease (VEO-IBD) is a form of IBD that manifests in infants and young children, with a significant proportion of them carrying interleukin 10 receptor alpha (IL-10RA) mutations. Despite the increasing incidence rate, the pathogenesis of VEO-IBD remains elusive, and treatment options are limited. The utilization of a humanized mouse model holds promise for further investigation into VEO-IBD. Previous study has revealed that VEO-IBD patients had a homozygous C > T mutation at IL-10RA position 301, which can be pathogenic.

Methods: We generated the corresponding point mutation mouse model via CRISPR/Cas9 technology. Subsequently, we performed various experiments to assess the colitis phenotype in mice and conducted a preliminary exploration of the model's utility.

Results: The mouse model progressively developed spontaneous colitis between 6 and 12 weeks. Hematoxylin and eosin (H&E) staining revealed abnormal colonic structure and massive local immune cell infiltration. The mouse model has abnormal levels of inflammatory cytokines in the colonic tissue, with an expansion of F4/80+ macrophages, CD4+ T cells, and B220+ B cells. Among the macrophages, the level of tissue-resident macrophages associated with anti-inflammation was reduced in IL-10RAR104W/R104W mice, while the level of immature macrophages associated with pro-inflammation was increased. Furthermore, we found that bone marrow transplantation can alter the composition of intestinal macrophage populations and treat intestinal inflammation in mutant mice. Finally, the result of subcutaneous tumor-bearing experiments indicated a faster tumor growth rate in the mutant mice.

Conclusions: In summary, we have successfully constructed a humanized mouse model with a stable spontaneous colitis phenotype, which is a valuable model for the therapeutic exploration of VEO-IBD.