Tracing cellular and molecular mechanisms involved in endometriosis.

The aetiology and pathogenesis of endometriosis, defined as the presence of endometrium-like tissue outside the uterine cavity, is largely unknown. In this paper we present and discuss possibilities to study the putative pathogenic properties of endometriotic cells in vitro. The current focus of our investigations is on the invasive phenotype of the disease, assuming that this might contribute to the pathogenesis of endometriosis. So far, we have shown that: (i) cytokeratin-positive and E-cadherin-negative endometriotic cells have an invasive phenotype in a collagen invasion assay in vitro similar to metastatic carcinoma cells; (ii) the invasiveness of endometriotic but not of eutopic endometrial cells can be stimulated by a heat-stable protein present in peritoneal fluid; and (iii) the endometriotic cell line EEC145T, which we established, may be a useful tool for the identification of gene products which are, positively or negatively, invasion-related. Finally, our studies suggest that the invasive phenotype in endometriosis shares aspects with tumour metastasis, but might also have unique mechanisms.