Localization of ZO-1 and E-cadherin in the nasal polyp epithelium

The tight junction and adherens junction complex of epithelial cells, which show disturbed localization in some inflammatory conditions, serve as an important paracellular barrier in polarized epithelial cells. However, very little information is available about the expression of the tight-junction protein, ZO-1, and the adherens-junction protein, E-cadherin, in nasal polyp epithelium. The aim of this study was to investigate the localization of ZO-1 and E-cadherin in nasal polyp epithelia by means of immunohistochemistry. We classified nasal polyp epithelia from 20 patients into pseudostratified ciliated columnar epithelia, basal and mucous cell hyperplasia and squamous metaplasia according to their dominant cell type. The expression of ZO-1 and E-cadherin in each epithelial cell type was analyzed and compared with normal ethmoidal mucosa, which was taken as a control. In pseudostratified ciliated columnar epithelia, as in the normal control epithelia, ZO-1 showed a spot-like distribution on the apicolateral junction of the adjoining cells. E-cadherin labeling was seen as a distinct basolateral staining on the mid-portion of the lateral walls. In basal and mucosal cell hyperplasia-dominant epithelia, the localization of ZO-1 positivity was similar to that in the normal mucosa, whereas the E-cadherin on the lateral walls showed a more intense distribution along the lateral cell-to-cell junction. In the nasal polyp epithelia showing squamous metaplasia, ZO-1 was rarely expressed; by contrast, E-cadherin exhibited stronger expression on the periphery of the cells in a circumferential fashion. In conclusion, in nasal polyp epithelia, ZO-1 showed down-regulation as in the worsening of epithelial dedifferentiation, whereas E-cadherin exhibited up-regulation with the increasing severity of epithelial remodeling.