Epithelial-Mesenchymal Transition (EMT), a cellular process in which epithelial cells lose epithelial characteristics while acquire mesenchymal features, is believed to contribute to migration and invasion abilities of the endometriotic cells. Studies on gene expression of the transcription factor ZEB1, a crucial transcription factor of EMT, show that there is probably a modified expression in the endometriotic lesions. The aim of the study was to compare the expression levels of ZEB1 in types of endometriotic lesions with different biological behavior such as endometriomas and deep infiltrating endometriotic nodules.
We have studied 19 patients with endometriosis and 8 patients with benign gynecological lesions without endometriosis. The endometriosis patient group included 9 women with only endometriotic cysts without deep infiltrating endometriotic lesion (DIE) and 10 women with DIE who had developed concurrent endometriotic cysts. The technique applied to investigate ZEB1 expression levels is Real-Time PCR. The results of the reaction were normalized by simultaneously investigating the expression of the house-keeping gene G6PD.
Analysis of the samples showed underexpression of ZEB1 in the eutopic endometrium of women with only endometriotic cysts when compared to normal endometrium. A tendency of higher ZEB1 expression, without reaching significant difference, was found between the endometriotic cysts and their paired eutopic endometrium. In women with DIE, no significant difference was found between their eutopic and normal endometrium. No significant difference was found between the endometriomas and DIE lesions. ZEB1 shows different expression profile in the endometriotic cysts of women with and without DIE when the cyst is compared to their paired eutopic endometrium.
It therefore appears that ZEB1 expression differs between different types of endometriosis. The expression levels of ZEB1 in the eutopic endometrium could affect the development of infiltrating lesions or not. However, the most important observation is the different ZEB1 expression profile of endometriomas between women with and without DIE. Although, they both share the same histologic characteristics, they show different ZEB1 expression indicating different pathogenetic mechanisms of endometriomas in cases with and without DIE. Therefore, future research on endometriosis should consider DIE and ovarian endometriosis as different diseases.

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