Improving Animal Model of Induced Colitis by Acetic Acid in Terms of Fibrosis and Inflammation Incidence in the Colon

Background:One of the animal models of colitis is induced by acetic acid, which mimics some features of ulcerative colitis disease. In order to increase the similarity of this model to human IBD and determine the suitable duration of acid contact to the colon and the day of induction of colitis were investigated in this study. Methods Fifty rats were randomly separated into five groups (n = 10) with different durations (30 s, 5, 10, and 20 min) of exposure of the colon to 4% acetic acid and colitis was investigated for 0-9 days. The extent of the mucosal ulcers, colon tissue thickening, and mucosal bleeding were scored by the Gerald classification system score. Slides of tissues were prepared for pathologic assay using the modified Wallace method. Results In all groups, inflammation was severe three days after the colitis induction, but no inflammation was observed in the 30 s group after five days. Acid contact with the colon surface did not result in fibrosis for the 30 s and the colon fibrosis was mild in 5 min group and severe in 10 and 20 min groups. The tissue damage was higher in groups of 20, 10, 5 min, and 30 s, respectively. Over time, the recovery rates in the 30 s and 5 min groups were higher than other groups. Conclusion Our results showed that the evaluation of the disease process from 3 days to nine days after a 10 min contact of acid to the colon is a suitable model that mimics the histological features of the disease.