Co-expression of cytokeratin and vimentin filaments in mesothelial, granulosa and rete ovarii cells of the human ovary

Abstract

The intermediate filament (IF) system of the various cells of human, pig and rat ovaries was studied by electron microscopy, by immunolocalization using antibodies to cytokeratins, vimentin, desmin and desmoplakin, and by two-dimensional gel electrophoresis of cytoskeletal proteins from microdissected tissue samples. In human ovaries, surface epithelial cells (mesothelium) were stained by antibodies against cytokeratins, desmoplakins and vimentin. Biochemical analysis revealed cytokeratins Nos. 8, 18 and 19, together with variable amounts of No. 7. Granulosa cells of follicles of all stages were also positive for cytokeratins, desmoplakins and vimentin, in agreement with the electron microscopic finding of desmosomes in these cells. As the follicle matured, the cytokeratin content usually appeared to decrease, whereas vimentin remained unchanged. On gel electrophoresis, granulosa cells presented cytokeratins Nos. 8 and 18 and vimentin. Rete ovarii cells were also positive for both cytokeratins, desmoplakins and vimentin, and the electron microscopy revealed numerous desmosome-tonofilament complexes. Oocytes appeared to be devoid of IFs. Corpus luteum cells were rich in vimentin but biochemical analysis also revealed small amounts of cytokeratins Nos. 8 and 18. In contrast, cells of the ovarian stroma and luteinized stromal nodules were positive for vimentin only. A certain type of scattered stromal cells, especially around tertiary follicles and corpora lutea, and also desmin-positive. Pig and rat ovaries differed from human ones in that vimentin was not detected in ovarian mesothelium and cytokeratins were not seen in granulosa cells. The latter, however, contained significant amounts of vimentin. These results indicate that three cell types of human ovary, i.e. surface epithelial, granulosa and rete ovarii cells, can be regarded as true epithelial cells which, however, simultaneously express vimentin, a phenomenon frequently seen in cultured epithelial cells but uncommon in epithelial tissues. The presence of cytokeratins in granulosa cells in all types of human follicles is discussed with regard to the development of these cells. In contrast, granulosa cells of the other two mammalian species only display vimentin IF. Such differences between different mammalian species in IF composition of ovarian components present an example which precludes extrapolation of data from one species to another. The results are discussed in relation to current views of the histogenesis of various ovarian tumors.