HIF-1α-induced Epithelial–mesenchymal Transition Of Endometrial Epithelial Cells May Contribute To The Development Of Endometriosis

Objective: Whether hypoxia induced EMT promote growth of lesions in the development of endometriosis or not.Methods: 1)The expression of N-cadherin, E-cadherin, β-catenin, HIF-1α and vimentin in 20 normal, 21 eutopic and 21 ectopic endometrial samples was assessed by immunohistochemistry. All eutopic samples from women with or without endometriosis were taken during the early proliferative phase of the menstrual cycle. The endometriosis were in stage Ⅲ~Ⅳ. All normal endometria were collected from women who simply because of fallopian tubal infertility. 2)Human primary endometrial epithelial cells were isolated. Times for hypoxia treatment for Western blot and reverse transcriptase polymerase chain reaction(RT-PCR) were 1 hour, 2 hours, 4 hours and 8 hours, for transwell was 48 hours. Then detect the expression of HIF-1α, β-catenin, snail,E-cadherin, N-cadherin, vimentin. 3)Ishikawa cells were used instead of primary endometrial epithelial cells for transfection and part of transwell experiments.Overexpression and inhibition of HIF-1α were achieved by transfection of differnet plasmids. The effect of hypoxia, overexpression and knockdown of HIF-1α on hypoxia-induced changes of EMT markers and β-catenin were analyzed by Western blot and RT-PCR. 4) The impact of hypoxia on invasion was evaluated in endometrial epithelial cells and Ishikawa cells by transwell assays. Detect the invasive ability of Ishikawa cells which is knockdown of HIF-1α under hypoxia.Results: 1) The positive expression rate of HIF-1 in normal, eutopic and ectopic endometrial samples were 35%、33.3% and 85.7%,for β-catenin were 15%、19.0%and 57.1%,for E-cadherin were 95%、90.5 and 57.1%,for N-cadherin were 5%、9.5% and 38.1%,for vimentin were 10%、23.8% were 61.9%. 2) Primary cultured human endometrial epithelial cells responded to hypoxia with classic EMT changes(fibroblastoid phenotype, increased expression of snail, β-catenin and mesenchymal markers, and decreased expression of E-cadherin) and increased invasiveness. 3)Whilst upregulation of HIF-1α induced changes characteristic of EMT,downregulation of HIF-1α had the opposite effect. 4) The increased invasiveness of epithelial cells and Ishikawa cells were observed under hypoxia.The decreased invasiveness of Ishikawa cells by knockdown of HIF-1α was observed under hypoxic conditions.Conclusion: Hypoxia induces the epithelial–mesenchymal transition(EMT) of endometrial cells, resulting in changes of cellular characteristics, which may be a prerequisite for the establishment of endometriotic lesions...