Background/Aims: Mesenchymal stem cells (MSCs) are multipotent progenitor cells currently under investigation for its efficacy as the treatment for inflammatory bowel disease. In this study, we evaluated the efficacy of tonsil-derived mesenchymal stem cells (T-MSCs) as a novel source of mesenchymal stem cells and traced their localization in a murine model of acute colitis induced by dextran sulfate sodium (DSS). Methods: C57BL/6 mice were randomly assigned to the following three groups: the

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... mal control group, DSS colitis group (DSS+phosphate buffered saline), and T-MSC group (DSS+T-MSCs, 110 6 ). The severity of colitis was assessed by determining the severity of symptoms of colitis, colon length, histopathologic grade, and levels of inflammatory cytokines. T-MSCs labeled with PKH26 were traced in vivo. Results: The T-MSC group, compared with the DSS colitis group, showed a significantly lower disease activity index (11.3±1.5 vs. 8.3±1.9, p=0.015) at sacrifice and less reduction of body weight (-17.1±5.0% vs. -8.1±6.9%, p=0.049). In the T-MSC group, the histologic colitis score was significantly decreased compared with the DSS colitis group (22.6±3.8 vs. 17.0±3.4, p=0.039). IL-6 and IL-1β, the pro-inflammatory cytokines, were also significantly reduced after a treatment with T-MSCs. In vivo tracking revealed no PKH26-labelled T-MSCs in the colonic tissue of mice with acute colitis. Conclusions: In the acute colitis model, we demonstrated that the administration of T-MSCs ameliorates inflammatory symptoms and histology. Moreover, the anti-inflammatory activities of T-MSCs were independent of gut homing. (Korean J Gastroenterol 2017;69:119-128)