Endometriosis : involvement of stem cells and clinical impact

Introduction: Endometriosis is a common gynaecological disease affecting up to 10% of \nwomen of reproductive age. The women suffer from severe abdominal pain and infertility as \na consequence of the chronic inflammation. The disease has also been associated with an \nincreased risk of cancer, in particular endometrial and ovarian cancer. Endometriosis \nrepresents an important socioeconomic burden as the condition is associated with \nproductivity loss, medical and surgical treatments including assisted reproduction, and a \ncompromised quality of life. The pathophysiology of endometriosis is not fully understood, \nand as of today we are unable to identify women at risk for cancer development and offer \nthem a tailor-made prophylactic treatment. \n \n \n \nAims: The overall aim of this thesis is to explore some of the mechanisms that have an \nimportant influence on clinical impact, in particular infertility and the risk of developing \nendometriosis-associated cancer. The mechanisms enabling endometriotic lesion \nestablishment are explored in an in vitro experimental model and the methylation profile of \nthe fertility-regulating gene HOXA10 is investigated in eutopic and ectopic endometrium. \nThis study also attempts to identify the molecular link between endometriotic stem cells and \nthe development of ovarian cancer by exploring CSC-specific markers and their molecular \nsignatures, and gene expression profile of cancer-correlated molecules in different \nendometrial compartments. \n \n \n \nResults: Significant changes were found in the endometrium of women with endometriosis \ncompared to healthy controls. The first study demonstrated the expression of ApoE, ITGB2, \nITGB7, LAMC1, CD24, and JAM-1 in women with and without endometriosis. Also, some \nof the molecules showed a significant altered expression upon comparing endometrium from \nwomen with and without endometriosis, as well as eutopic and ectopic endometrium of \nwomen with endometriosis. ApoE and JAM-1 were decreased in both proliferative and \nsecretory phase in endometrium from women with endometriosis, and mRNA expression of \nLAMC1 was reduced in endometrium from endometriosis patients compared with controls in \nthe proliferative phase. CD24 expression was significantly expressed in eutopic and ectopic \nendometrium in women with endometriosis. In the second study, we found a significant \nhypermethylation of the HOXA10 gene in eutopic secretory endometrium in women with \nendometriosis compared with controls. When comparing the methylation profile in patients \nsuffering from ovarian endometriosis with patients presenting extra-ovarian disease, we could \nnot demonstrate any significant correlation between methylation status and stage of disease. \nThe third study demonstrated that mesenchymal endometrial stem cells from women with \nendometriosis showed an active S-phase as well as an up-regulation of PTEN, VEGF-α, and \ndecreased BCL2 gene-expression compared to controls. A subset of potentially ‘high-risk’ \npatients could be identified showing a significant up-regulation of genes involved in \nreprogramming SOX2, NANOG; cancer metabolism TP53, K-ras; and epithelial- \nmesenchymal transition genes TGF-α and SNAI1. TP53 turned out to play the role of a \nmaster regulator. When comparing monolayer to 3D spheroid cultures, an increased coexpression \nof CSC surface markers CD44 and CD133 was seen, and the chemo-sensitivity \nassay performed in a 3D-tumour microenvironment revealed increased tumour invasion in the \n‘high-risk’ group. In the fourth study, we found a significant difference in the expression of \ngenes that correlated with endometrial malignant transformation in both endometrial stromal \nand glandular compartments in endometriosis patients compared with controls. \n \n \n \nConclusions: Our results shed light on the molecular linkage to the etiology of endometriosis \nand malignant transformation of endometriosis, as well as providing useful information \nrelevant to endometriosis-associated infertility and pathogenesis.