Physiological and pathological expression of intermediate filaments in the equine endometrium

The aim of this study was to investigate the expression of the intermediate filaments cytokeratin, vimentin and desmin in the equine endometrium by immunohistological techniques. For this purpose, endometrial biopsies of 151 mares were examined to determine physiological cycle patterns and changes resulting from endometriosis. During the physiological cycle epithelial cells and mesenchymal cells express cytokeratin and vimentin, respectively, whilst desmin and vimentin were coexpressed by the smooth muscle cells. Epithelial coexpression of cytokeratin and vimentin was seen in numerous fibrotic glands and in the uterine glands of three mares with pathologically inactive endometria. Three different staining patterns (basal, perinuclear, diffuse) of vimentin were associated with typical morphological alterations of the affected epithelia. In addition, in 14 cases a stromal coexpression of vimentin and desmin was found, indicating an atypical stromal differentiation in inactive endometria of older mares, barren for several years.