A new animal model of postsurgical bowel inflammation and fibrosis: the effect of commensal microflora.

OBJECTIVE: Ileocaecal resection (ICR) is common in Crohn's disease. Inflammation and fibrosis frequently recur at the site of anastomosis or in the small intestine (SI). No animal models of postsurgical inflammation and fibrosis exist. A model of ICR was developed in interleukin 10 (IL10) null and wild-type (WT) mice to test the hypothesis that ICR promotes postsurgical inflammation and fibrosis in the SI or anastomosis of genetically susceptible IL10 null, but not WT or germ-free (GF)-IL10 null mice.
METHODS: GF-IL10 null mice were conventionalised (CONV) and 3 weeks later randomised to ICR, transection (T) or no treatment (NoTx). Age-matched conventionally raised (CONV) WT and GF-IL10 null mice received ICR, T or NoTx. Animals were killed 28 days later. Histological scoring, real-time PCR for tumour necrosis factor alpha and collagen, and immunostaining for CD3(+) T cells assessed inflammation and fibrosis.
RESULTS: After ICR, CONV-IL10 null, but not CONV-WT mice, developed significant inflammation and fibrosis in the SI and inflammation in anastomosis compared with NoTx or T controls. Fibrosis occurred in the anastomosis of both CONV-IL10 null and CONV-WT mice following ICR. GF-IL10 null mice developed little or no inflammation or fibrosis in the SI or anastomosis after ICR.
CONCLUSIONS: ICR in CONV-IL10 null mice provides a new animal model of postsurgical inflammation and fibrosis in the SI and anastomosis. Absence of inflammation and fibrosis in the SI of CONV-WT and GF-IL10 null mice following ICR indicates that postsurgical small bowel disease occurs only in genetically susceptible IL10 null mice and is bacteria dependent.