Morphological and functional characteristics of cells cultured from the endolymphatic sac

The endolymphatic sac is a part of the homeostasis-regulating system of the membranous labyrinth of the inner ear. Disturbances in the function of the endolymphatic sac are believed to be involved in the genesis of different inner ear disorders, such as endolymphatic hydrops and Meniere's disease. T o make studies of the ion- and fluid-regulating mechanisms of the sac possi ble, a method to culture the tissue in vitro was developed. Epithelial cell s and fibroblasts were morphologically characterised in the cell cultures w ith light and electron microscopy as well as immunohistochemically using an tibodies against cytokeratin and vimentin. Since mesenchymal cells have bee n shown to express vimentin and epithelial cells cytokeratin, the antibodie s against these two intermediate filament proteins were used to further con firm the morphological identification. In addition, some functional charact eristics of the cultured cells from the endolymphatic sac were studied. ATP and K+ were added to the cell cultures and changes in cytoplasmic free Ca2 + concentration ([Ca2+](i)) were determined with the fura-2 method. A rapid and transient increase in [Ca2+](i), could be seen in both epithelial cell s and fibroblasts after applying ATP (200 muM) extracellularly. However, wh en K+ was added in concentrations of 50 mM and 100 mM, no changes in [Ca2+] (i) could be seen in either the epithelial cells or the fibroblasts. The re sults show that the cultured endolymphatic sac cells preserve their morphol ogical characteristics and maintain a high viability. Accordingly, this met hod provides a tool for further studies of ion transport mechanisms and flu id homeostasis in the endolymphatic sac. (C) 2001 Elsevier Science B.V. All rights reserved.