Background: Survivin, a member of the inhibitor of apoptosis protein (IAP) family, regulates mitosis and chromosome\nsegregation. The expression of survivin proceeds during embryonic development and in addition has already been\ndemonstrated in cancer cells. However, there is also evidence of survivin expression in differentiated tissues, including\nthe gastro-intestinal tract of adult rats. A study with human colon specimens exhibited survivin in most basal crypt\nepithelial cells of normal mucosa. There is rather limited information on survivin expression in the small intestine. In\norder to paint a more detailed and thus complete picture of survivin expression patterns in the gastrointestinal tract,\nwe used an immunohistochemical approach in normal adult rat small intestinal and ascending colonic tissue.\nMoreover, to get deeper insights in the regulation of survivin expression after tissue damage, we also studied its\nexpression in mesenteric ischemia-reperfusion (I/R) injury.\nMethods: Mesenteric ischemia-reperfusion injury was induced in male Wistar rats (six animals/group) by occlusion of\nthe superior mesenteric artery for 90 min and subsequent reperfusion for 120 min. Paraffin sections of untreated or\nischemically treated tissue were assessed immunohistochemically by survivin and Ki-67 staining.\nResults: Survivin could be detected in the small intestine and ascending colon of the normoxia group. It was expressed\nmainly in the epithelial cells of the crypts and only marginally in the villi. The individual small intestinal segments studied\nrevealed comparable staining intensities. Likewise, expression of survivin was detected in the ischemically damaged small\nintestine and ascending colon. The expression pattern corresponded to the normoxic animals, as far as verifiable due to\nthe existing tissue damage. Comparison of the expression pattern of Ki-67, a protein that acts as a cellular marker for\nproliferation, and survivin demonstrated a coincidental localization of the two proteins in the small intestinal and\nascending colonic tissue.\nConclusions: Survivin was expressed strongly in epithelial cells of small intestinal as well as ascending colonic tissue. Its\nexpression was located in cells with a high proliferation rate and regenerative capacity. This further supports the decisive\nrole of survivin in cell division. Surprisingly, the ischemically damaged small intestinal and ascending colonic tissue\nshowed a comparably high expression level. These results suggest that there is already a maximal survivin expression\nunder normal conditions. However, the intestine is able to maintain the regenerative capacity even in spite of an\nischemic injury. These findings reflect the important relevance of an intact intestinal barrier.
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