Epithelial and mesenchymal characteristics of the ovarian surface epithelium in two and three dimensional culture

The ovarian surface epithelium (OSE) is thought to give rise to 85% of ovarian cancers, predominantly in invaginating clefts and cysts in the ovarian stroma. The cells of the ovarian neoplasms express more complex epithelial characteristics than the cuboidal OSE on the surface. As well, ovarian cancer cells when cultured retain their epithelial characteristics whereas OSE expresses a dual epithelial-mesenchymal phenotype and gradually loses its epithelial characteristics. These observations raised several questions: 1) could cyst-like structures be developed in culture; 2) could improving culture conditions avoid the loss of epithelial characteristics by OSE; and 3) were variations in expression of epithelial and mesenchymal characteristics clinically significant. This study used a rat OSE line (ROSE 199) to explore the use of two collagenous 3-D culture systems for the development of cysts: seeding cells in sponges and gels. The impact of collagen on the morphology of these cells was also assessed using collagen coats and seeding on gels. It became apparent that two sublines of ROSE 199 had developed that differed in the amount of matrix deposited and in the ability to migrate into the extracellular matrix (ECM); one subline exhibiting a predominantly epithelial response whereas the other showed characteristics of an epithelial-mesenchymal conversion response. The collagen sponge supported the formation of cyst-like structures and affected the organization, but not the types, of basic E CM components produced by the ROSE 199 High ECM subline. Therefore the sponge system is useful for developing cyst and cleftlike structures in culture, while the two sublines may be useful for determining the signals that trigger the mesenchymal response in OSE. Co-culturing ROSE 199 with human OSE was used in an attempt to improve culture conditions that would maintain the original characteristics of the latter. ROSE 199, like human OSE in culture, produces both epithelial and mesenchymal E CM components. However, unlike human OSE, it forms a cuboidal epithelium on a thick autologous matrix with underlying cellular layers. It was hoped that ROSE 199 could provide the signals that human OSE needed to maintain their epithelial characteristics. This did not occur. Instead, the human OSE cells migrated into the ROSE matrix assuming a mesenchymal morphology even when able to maintain epithelial colonies when grown alone. Therefore this system does not improve the retention of epithelial characteristics by human OSE. Thirdly, the study examined whether neoplastic progression or genetic changes associated with a family history of ovarian cancer affected the expression of epithelial and mesenchymal characteristics. Normal OSE from women with (FH-OSE) and without (NFH-OSE) a family history of ovarian cancer, SV40 immortalized lines of each, and ovarian cancer lines were compared. The parameters examined were keratin and collagen III expression as cytodifferentiation markers, and three-dimensional morphogenesis. The results indicate there is a decrease in expression of mesenchymal characteristics with neoplastic progression while epithelial characteristics are maintained, and that FH-OSE cells are phenotypically different from NFH-OSE and are less prone to undergo epithelialmesenchymal conversion in culture. This suggests that an increase in commitment to an epithelial phenotype and/or reduced responsiveness to signals in culture may be one of the earliest changes in the process of ovarian carcinogenesis.Medicine, Faculty ofGraduat