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Methotrexate‐induced mucositis in mucin 2‐deficient mice

The mucin Muc2 or Mycin2 (Muc2), which is the main structural component of the protective mucus layer, has shown to be upregulated during chemotherapy‐induced mucositis. As Muc2 has shown to have protective capacities, upregulation of Muc2 may be a counter reaction of the intestine protecting against mucositis. Therefore, increasing Muc2 protein levels could be a therapeutic target in mucositis prevention or reduction. Our aim was to determine the role of Muc2 in chemotherapy‐induced mucositis. Mucositis was induced in Muc2 knockout (Muc2−/−) and wild type (Muc2+/+) mice by injecting methotrexate (MTX). Animals were weighed and sacrificed on Days 2–6 after MTX treatment and jejunal segments were analyzed. Before MTX treatment, the small intestine of Muc2+/+ and Muc2−/− mice were similar with respect to epithelial morphology and proliferation. Moreover, sucrase‐isomaltase and trefoil factor‐3 protein expression levels were comparable between Muc2+/+ and Muc2−/− mice. Up to Day 3 after MTX treatment, percentages of weight‐loss did not differ. Thereafter, Muc2+/+ mice showed a trend towards regaining weight, whereas Muc2−/− mice continued to lose weight. Surprisingly, MTX‐induced intestinal damage of Muc2−/− and Muc2+/+ mice was comparable. Prior to MTX‐injection, tumor necrosis factor‐α and interleukin‐10 mRNAs were upregulated in Muc2−/− mice, probably due to continuous exposure of the intestine to luminal antigens. Muc2 deficiency does not lead to an increase in chemotherapy‐induced mucositis. A possible explanation is the mechanism by which Muc2 deficiency may trigger the immune system to release interleukin‐10, an anti‐inflammatory cytokine before MTX‐treatment. J. Cell. Physiol. 210: 144–152, 2007. © 2006 Wiley‐Liss, Inc.