Coelomic metaplasia theory of endometriosis: Evidence from in vivo studiesand an in vitro experimental model

Ultrastructure studies of pelvic peritoneal tissue from women undergoing la parotomy suggest that before endometriosis has become established in the pe ritoneum, there might be a metaplastic change by peritoneal mesothelial cel ls into endometrial glandular cells. A new in vitro experimental model of e ndometriosis using human ovarian surface epithelium cells has shown evidenc e that endometriotic lesions can arise by a process of metaplasia from the ovarian surface epithelium. In this model, when both ovarian surface epithe lium and ovarian stromal cells were cocultured with 17 beta estradiol in a three-dimensional collagen gel lattice, the ovarian surface epithelium cell s formed a lumen structure, surrounded by endometrial stromal cells with an epithelial mesenchymal structure. Immunoreactivity for epithelial membrane antigen and cytokeratin was shown in the glandular cells and cilia, as wel l as in the microvilli, Electron microscopy showed evidence of tight juncti ons on cell surfaces. These findings suggest that endometriosis may manifes t as a serial change from the adjacent mesothelial cells.