RESUMEN
BACKGROUND: Pediatric Crohn's disease is characterized by a higher incidence of complicated phenotypes. Murine models help to better understand the dynamic process of intestinal fibrosis and test therapeutic interventions. Pre-pubertal models are lacking. We aimed to adapt a model of chronic colitis to pre-pubertal rats and test if a polymeric diet rich in TGF-ß2 could reduce TNBS-induced intestinal inflammation and fibrosis. METHODS: Colitis was induced in 20 five-week-old Sprague-Dawley male rats by weekly rectal injections of increasing doses of TNBS (90 mg/kg, 140 mg/kg and 180 mg/kg) for 3 weeks, while 10 controls received phosphate-buffered saline. Rats were anesthetized using ketamine and chlorpromazine. After first administration of TNBS, 10 rats were fed exclusively MODULEN IBD® powder, while remaining rats were fed breeding chow. Colitis was assessed one week after last dose of TNBS by histopathology and magnetic resonance colonography (MRC). RESULTS: Histological inflammation and fibrosis scores were higher in TNBS group than controls (p < 0.05 for both). MRC showed increased colon wall thickness in TNBS group compared to controls (p < 0.01), and increased prevalence of strictures and target sign (p < 0.05). Colon expression of COL1A1, CTGF, α-SMA and COX-2 did not differ between TNBS rats and controls. TNBS colitis was not associated with growth failure. Treatment with MODULEN IBD® was associated with growth failure, increased colon weight/length ratio (p < 0.01), but did not affect histological scores or MRI characteristics. Colon expression of α-SMA was significantly lower in the MODULEN group versus controls (p = 0.005). CONCLUSION: Features of chronic colitis were confirmed in this model, based on MRC and histopathology. Treatment with MODULEN did not reverse inflammation or fibrosis.