Expression of clusterin in Crohn's disease of the terminal ileum

Crohn's disease (CD) is a chronic inflammatory intestinal disorder with disturbance and injury of the intestinal mucosal barrier, in which various proinflammatory molecules as well as molecules with antiinflammatory activity and cytoprotective function are found to be expressed. We investigated whether clusterin, a multifunctional cytoprotective protein, is upregulated in Crohn's disease, because augmented expression of clusterin is seen in many organs following various forms of tissue injury. Human actively and inactively inflamed ileal tissues from CD patients as well as normal intestinal specimens from control patients (normal ileum) were investigated by Western blot analysis, immunohistochemisty and in situ hybridization. As compared with controls, a strongly enhanced expression of clusterin was found in CD tissues, correlating with disease activity. Immunohistochemistry and in situ hybridization analysis revealed foci of crypts almost completely lined by clusterin expressing enterocytes in CD, a feature that was never seen in controls. Such crypts appeared especially within the morphologically intact mucosa apart from erosive or ulcerative lesions. Besides epithelia, clusterin was also expressed by inflammatory mononuclear cells. Enhanced expression of clusterin by crypt epithelia might reflect a cytoprotective function of the protein in order to prevent further injury of the intestinal mucosal barrier in CD.