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* = Presenting author

P041. Piroxicam-accelerated colitis in interleukin-10 knock out mice – a “new” model of human inflammatory bowel disease

K. Holgersen1, P.H. Kvist2, A.K. Hansen3, T.L. Holm4, 1Novo Nordisk-LIFE In Vivo Pharmacology Centre, Frederiksberg, Denmark, 2Novo Nordisk A/S, Department of Histology, Måløv, Denmark, 3University of Copenhagen, Department of Veterinary Disease Biology, Frederiksberg, Denmark, 4Novo Nordisk A/S, Department of Immunopharmacology, Måløv, Denmark

Background

Inflammatory bowel disease (IBD) is assumed to be triggered by a defective mucosal barrier, a dysregulated immune response and an excessive reactivity against the gut microbiota. The presence of these three factors leads to a breakdown of the intestinal homeostasis and chronic inflammation in the gut. Piroxicam acceleration of colitis (PAC) in IL-10 k.o. mice was original described by Berg et al. as a method for induction of chronic colitis, which integrates both barrier dysfunction and a dysregulated immune response. We hypothesise that this model could function as a novel tool in the preclinical research of IBD. However, the PAC IL-10 k.o. mouse model needs to be characterised further with respect to clinical features, underlying pathogenic mechanisms as well as its ability to respond to existing therapies.

Methods

The PAC IL-10 k.o. model was evaluated by clinical manifestations. Disease pathology was characterised by haematology, colonoscopy, histopathology of colon and ileum, cytokine profiling ELISAs, as well as FACS analyses. Mice were treated with the broad-spectrum antibiotic, ampicillin, to determine the role of commensal bacteria in disease progression. Model qualification was performed by examining the efficacy of treatment with known efficacious biologic therapies for IBD (e.g. anti-IL-12/23p40, anti-TNF α).

Results

The PAC IL-10 k.o. mice developed synchronised weight loss and bloody diarrhea and colonoscopy revealed a thickened mucosa with a granulomatous appearance. The number of granulocytes, macrophages and T lymphocytes was elevated in the blood and mesenteric lymph nodes compared to IL-10 k.o. and wild type control mice. ELISA analyses of colon homogenates indicated the involvement of neutrophils, activated macrophages and Th1/Th17 cells in the pathogenesis. Histological evaluation of both colonic and ileal biopsies showed hyperplasia and infiltration of immune cells in mucosa and submucosa. Disease progression could be ameliorated by prophylactic treatment with monoclonal antibodies targeting IL-12/23p40 and TNF α, as well as ampicillin.

Conclusion

The data show that the PAC IL-10 k.o. model fulfil the “three-factor model” and enables studies of barrier function, a dysregulated immune system and reactivity to the commensal microflora. The model develops symptoms which mimic Crohn's disease including ileitis, and reference drugs show predictive validity. Therefore, the PAC IL-10 k.o. mouse could be useful as an in vivo model of human IBD.