Abstract:Objective To investigate the progress of chronic Ulcerative Colitis (UC) model induced by dextran sulfate (DSS) in mice. Methods 2.5% DSS solution were provided ad libitum for 5 days, and tap water for were supplied for another 5 days in one induction cycle. Male C57BL/6 mice were undergone continuous three cycles of induction to establish the chronic UC model. The weight, disease activity index (DAI), organ index, colon length of mice and pathological changes of colon tissue were determined. The level of myeloperoxidase (MPO) in colon tissue, cytokines such as IL-1β in serum and colon were detected. Results During the three cycles, all mice had diarrhea, bloody stool, weight loss, colon length shortening and pathological injury, which were aggravated after DSS administration and relieved after drinking water administration. The content of MPO in colon gradually increased. The spleen index and the levels of IL-1β, IL-6, IL-17A, TGF-β and TNF-α in serum increased continuously or fluctuating. The contents of IL-1β, IL-6 and IL-17A in colon increased significantly in the first or second cycle, and then decreased slowly. There was no significant change in TNF-α in colon. The concentrations of IL-10 in serum and colon fluctuated up and down, and decreased to a level lower than or remained the same as that in normal group at the end of the experiment. Conclusion Chronic UC model can be successfully induced by 2.5%DSS solution, which is characterized by alternating symptoms of "attack-remission". The persistent systemic inflammatory reaction and overactivation of colonic neutrophils reflect the characteristics of recurrent UC to some extent. It can be used as a tool for analying the pathological changes and interrention opportunities of UC, as well as for discovering and evaluating UC therapeutic drugs.