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Endometriosis is a chronic inflammatory disease distinguished by ectopic endometrium and fibrosis. NLRP3 inflammasome and pyroptosis are present in endometriosis. Aberrant increase of Long noncoding (Lnc)-metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays a vital role in endometriosis. However, the relationship between lnc-MALAT1, pyroptosis, and fibrosis is not completely known. In the present study, we found that the pyroptosis levels in ectopic endometrium of patients with endometriosis were significantly increased, consistent with fibrosis levels. Lipopolysaccharide (LPS) + ATP could induce pyroptosis of primary endometrial stromal cells (ESCs), thereby releasing interleukin (IL)-1β and stimulating transforming growth factor (TGF)-β1-mediated fibrosis. NLRP3 inhibitor MCC950 had the same effect as TGF-β1 inhibitor SB-431542 in suppressing the fibrosis-inducing effect of LPS + ATP in vivo and in vitro. The abnormal increase of lnc-MALAT1 in ectopic endometrium was connected with NLRP3-mediated pyroptosis and fibrosis. Leveraging bioinformatic prediction and luciferase assays combined with western blotting (WB) and quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), we validated that lnc-MALAT1 sponges miR-141-3p to promote NLRP3 expression. Silencing lnc-MALAT1 in HESCs ameliorated NLRP3-mediated pyroptosis and IL-1β release, thereby relieving TGF-β1-mediated fibrosis. Consequently, our findings suggest that lnc-MALAT1 is critical for NLRP3-induced pyroptosis and fibrosis in endometriosis through sponging miR-141-3p, which may indicate a new therapeutic target of endometriosis treatment.

Owing to lacking protective effect of estrogen, OVX mice have higher risk of non-alcoholic fatty liver disease compared with normal female mice, when fed with high fat diet. Our study was to explore how estrogen protect against nonalcoholic steatohepatitis in female mice. We found that, lacking estrogen, M1 macrphages was activated and promoted steatohepatitis in obese OVX mice. And, ERα was responsible for estrogen to inhibit M1 macrphages activation and steatohepatitis. ERα knockdown aggravated M1 macrophages infiltration by transcriptionally upregulated its CCR2 expression. CCR2 antagonist effectively improved nonalcoholic steatohepatitis, ER stress and insulin resistance in ERα knockdown obese female mice. These results demonstrated ERα mediated M1 macrophages activation played a key role in nonalcoholic steatohepatitis.

Research question: What are the protein levels and localization of oestrogen receptors (including ERa, ERb and G protein-coupled oestrogen receptor [GPER]) and hypoxia-inducible factor-1alpha (HIF-1a) in normal control endometrium (COEM) and ectopic endometrium from abdominal wall endometriosis (AWE). Design: AWE (n = 20) were obtained during surgery; COEM (n = 40) were collected by curettage. All tissues were obtained during the proliferative or secretory phase. Formalin-fixed paraffin-embedded tissues were used for immunohistochemical study for oestrogen receptors and HIF-1a proteins. Result(s): The expression of oestrogen receptors and HIF-1a in AWE differed from that in the corresponding menstrual cycle phase of COEM. Compared with COEM, ERa and HIF-1a were decreased whereas ERb and GPER were increased in AWE. The greatest difference was in GPER, with increased protein expression in both the cytoplasm and nucleus of endometrial epithelial and stromal cells, as well as a distinct change in localization from cytoplasmic expression to nuclear and cytoplasmic expression, compared with COEM. Conclusions: Our data suggest that the expression changes of oestrogen receptors and HIF-1a, especially GPER, are associated with AWE, which may provide new clues to understanding the cause of endometriosis.

Endometriosis is an oestrogen-dependent disease, and epithelial-mesenchymal transition (EMT) is involved in the process of endometriosis. Whether oestrogen could induce EMT in endometriosis remains largely unknown. Here, we reported that up-regulated expression of EMT markers in ovarian chocolate cyst is accompanied by high expression 17β-hydroxysteroid dehydrogenase 1 (17β-HSD1), and exposure of primary human endometrial epithelial cells to oestradiol conditions could promote EMT occurrence and activate both β-catenin and Snail signalling. Furthermore, we found nuclear β-catenin and Snail expression was closely linked in ovarian endometriosis, and β-catenin knockdown abrogated oestrogen-induced Snail mediated EMT in vitro. This is due to that β-catenin/ TCF-3 could bind to Snail promoter and activate its transcription. These results suggested that β-catenin signalling functions as the Snail activator and plays a critical role in oestradiol-induced EMT in endometriosis.

The Hippo pathway is an evolutionarily conserved regulator of organ size and tumorigenesis that negatively regulates cell growth and survival. Whether the Hippo pathway regulates cell metabolism is unknown. Here, we report that in the nucleus of hepatocytes, Yes‐associated protein(YAP)—the terminal effector of the Hippo pathway—directly interacts with sterol regulatory element binding proteins (SREBP‐1c and SREBP‐2) on the promoters of the fatty acid synthase (FAS) and 30‐hydroxylmethyl glutaryl coenzyme A reductase (HMGCR), thereby stimulating their transcription and promoting hepatocyte lipogenesis and cholesterol synthesis. In diet‐induced diabetic mice, either Lats1 overexpression or YAP knockdown protects against hepatic steatosis and hyperlipidaemia through suppression of the interaction between YAP and SREBP‐1c/SREBP‐2. These results suggest that YAP is a nuclear co‐factor of SREBPs and that the Hippo pathway negatively affects hepatocyte lipogenesis by inhibiting the function of YAP‐SREBP complexes.

Endometriosis is an estrogen-dependent benign gynecological disease that shares some common features of malignancy. Epithelial–mesenchymal transition (EMT) has been recognized as a core mechanism of endometriosis. MALAT1 is widely known as EMT promoter, while miR200 family members (miR200s) are considered as EMT inhibitors. Previous studies have reported that MALAT1 upregulation and miR200s downregulation are observed in endometriosis. MiR200c has been regarded as the strongest member of miR200s to interact with MALAT1. However, whether MALAT1/miR200c regulates EMT remains largely unclear. In this study, the roles of miR200s and MALAT1 in ectopic endometrium were investigated. Additionally, the effects of E2 on EMT and MALAT1/miR200s were examined in both EECs and Ishikawa cells. Notably, E2 could upregulate MALAT1 and downregulate miR200s expression levels and induce EMT in EECs and Ishikawa cells. PHTPP, an ERβ antagonist, could reverse the effect of E2. Overexpression of miR200c and knockdown of MALAT1 significantly inhibited E2-mediated EMT, suggesting that both miR200c and MALAT1 are involved in the E2-induced EMT process in endometriosis. In addition, a reciprocal inhibition was found between miR200s and MALAT1. Therefore, the role of MALAT1/miR200c in EMT is influenced by the presence of estrogen during endometriosis development.

Background Polycystic ovary syndrome (PCOS) is the most common endocrine disorder with complex pathophysiological mechanism. It is reported that even a modest weight loss of 5-10% substantially may improve the reproductive and metabolic profile. This study aims to assess the efficacy of the low dose of liraglutide (0.6mg QD) combined with metformin (0.85g BID) in weight loss in Chinese Han women with Polycystic ovary syndrome.Methods We included clinical data of 102 obese/overweight (≥18 years, body mass index ≥28 kg/m2 or ≥24 kg/m2) women who were diagnosed with PCOS from October 2016 to March 2018 in Wuhan Union Hospital initially. They were treated with Diane-35, low dose of liraglutide (0.6mg QD) and metformin (0.85g BID) for 12 weeks. The demographic and clinical data were retrieved retrospectively, and weight loss was the main outcome measure. Student’s paired t-test and Wilcoxon rank sum test were used to compare the differences before and after therapy, p

Endometriosis is a common gynecological disease characterized by diminished apoptosis, sustained ectopic survival of dysfunctional endometrial cells. Hypoxia has been implicated as a crucial microenvironmental factor that contributes to endometriosis. It has been reported that long non‐coding RNA MALAT1 (lncRNA‐MALAT1) highly expressed in endometriosis and up‐regulated by hypoxia. Hypoxia may also induce autophagy, which might act as cell protective mechanism. However, the relationship between lncRNA‐MALAT1 and autophagy under hypoxia conditions in endometriosis remains unknown. In the present study, we found that both lncRNA‐MALAT1 and autophagy level were up‐regulated in ectopic endometrium from patients with endometriosis, and its expression level correlates positively with that of hypoxia‐inducible factor‐1α (HIF‐1α). In cultured human endometrial stromal cells, both lncRNA‐MALAT1 and autophagy were induced by hypoxia in a time‐dependent manner and lncRNA‐MALAT1 up‐regulation was dependent on HIF‐1α signalling. Our analyses also show that knockdown of lncRNA‐MALAT1 suppressed hypoxia induced autophagy. Furthermore, inhibiting autophagy with specific inhibitor 3‐Methyladenine (3‐MA) and Beclin1 siRNA enhanced apoptosis of human endometrial stromal cells under hypoxia condition. Collectively, our findings identify that lncRNA‐MALAT1 mediates hypoxia‐induced pro‐survival autophagy of endometrial stromal cells in endometriosis.

Endometriosis is a benign gynecologic disorder, and presents with malignant characteristics, such as migration and invasion. Hypoxia has been implicated in triggering epithelial–mesenchymal transition (EMT). Hypoxia is also known to induce autophagy. However, the relationship between autophagy and EMT under hypoxia conditions in endometriosis remains unknown. In the present study, we found that the expression of hypoxia-inducible factor-1α (HIF-1α), microtubule associated protein light chain 3 (LC3), and mesenchymal cell marker vimentin was significantly higher in ectopic endometrium from patients with endometriosis, along with decreased expression of epithelial cell marker E-cadherin. After hypoxia treatment, endometrial epithelial cells exhibited enhanced migration and invasion abilities, as well as promoted autophagy and the EMT phenotype. Our analyses also show that HIF-1α was responsible for induction of autophagy. Moreover, inhibition of autophagy by chemical or genetic approaches suppressed hypoxia triggered EMT and reduced cell migration and invasion. Collectively, our findings identify that autophagy is critical for the migration and invasion of endometrial cells through the induction of EMT and indicate that inhibition of autophagy may be a novel useful strategy in the treatment of endometriosis.

Background: Endometriosis is a benign gynecological disorder which shares certain characteristics with malignant tumor like migration, invasion and proliferation. Glioma-associated oncogene homolog 1 (GLI1) has been implicated in some cancers including endometrial cancer, however, its role in endometriosis remains unknown. Methods: The aim of this study was to explore the expression pattern of GLI1 in endometriosis, and further investigate the effect of GLI1 regulation on human endometrial stromal cells. The expression of GLI1 in normal endometrium and ectopic tissues was analyzed by immunohistochemistry, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. The Short hairpin RNA (ShRNA) intervention technique and GLI1 inhibitor GANT-61 were used to silence GLI1. The expression levels of GLI1, MMP2 and MMP9 was detected by qRT-PCR and western blot. The migration and invasion ability of human endometrial stromal cells was determined by wound healing assay and transwell migration/invasion assay. The viability and proliferation potentiality of cells was detected by MTT assays and colony formation assay, respectively. Results: We found that the expression of GLI1 mRNA and protein were significantly higher in ectopic endometrium from patients with endometriosis. Our analyses also show that GLI1 downregulation attenuated cells migration, invasion and proliferation abilities. What’s more, reduced expression of GLI1 inhibited the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9). Conclusions: Our findings suggest that high levels of GLI1 may contribute to the development of endometriosis by promoting cell migration, invasion and proliferation involving regulation of MMP2 and MMP9 expression. Therefore, inhibition of GLI1 might be a novel potential therapeutic approach to the treatment of endometriosis, which sheds new light on our understanding of the pathogenesis of endometriosis.

Endometriosis is an oestrogen‐dependent disease, and epithelial‐mesenchymal transition (EMT) is involved in the process of endometriosis. Whether oestrogen could induce EMT in endometriosis remains largely unknown. Here, we reported that up‐regulated expression of EMT markers in ovarian chocolate cyst is accompanied by high expression 17β‐hydroxysteroid dehydrogenase 1 (17β‐HSD1), and exposure of primary human endometrial epithelial cells to oestradiol conditions could promote EMT occurrence and activate both β‐catenin and Snail signalling. Furthermore, we found nuclear β‐catenin and Snail expression was closely linked in ovarian endometriosis, and β‐catenin knockdown abrogated oestrogen‐induced Snail mediated EMT in vitro. This is due to that β‐catenin/ TCF‐3 could bind to Snail promoter and activate its transcription. These results suggested that β‐catenin signalling functions as the Snail activator and plays a critical role in oestradiol‐induced EMT in endometriosis.

Background Endometriosis is a debilitating gynecological condition that manifests many common malignant features, including migration and invasion. Hypoxia is a hallmark of endometriosis, characterized by endometrial cell metastasis via epithelial-mesenchymal transition (EMT). The long noncoding RNA (lncRNA) UBOX antisense RNA 1 (UBOX5-AS1) has been shown to be upregulated in ovarian endometriosis. However, the molecular mechanisms and biological functions of lncRNA UBOX5-AS1 in hypoxia-induced endometriosis EMT remain to be explored. Methods Normal, eutopic, and ectopic endometrium from ovarian endometriosis tissues were collected, and the expressions of hypoxia inducible factor (HIF)-1α, lncRNA UBOX5-AS1, E-cadherin, and vimentin were analyzed by quantitative real time polymerase chain reaction (qRT-PCR) and western blotting analysis. Primary human endometrial epithelial cells and human endometrial epithelial adenocarcinoma Ishikawa cell lines were cultured under hypoxic conditions, and western blotting analysis and immunocytochemistry were performed to investigate hypoxia-induced EMT. Moreover, HIF-1α and lncRNA UBOX5-AS1 were overexpressed and knocked down in endometrial epithelial cells to explore the role and mechanisms of lncRNA UBOX5-AS1 in hypoxia-triggered EMT. The migration and invasion potential of human endometrial epithelial cells was detected by Transwell migration/invasion assays. Results In ovarian endometriosis, the expression of hypoxia-inducible factor-1α (HIF-1α) and lncRNA UBOX5-AS1 were significantly increased, and this was accompanied by EMT. Furthermore, endometrial epithelial cells cultured under hypoxic conditions exhibited elevated lncRNA UBOX5-AS1 expression, as well as migration, invasion, and an EMT-like phenotype. This data indicated that HIF-1α signaling was crucial for hypoxia-induced lncRNA UBOX5-AS1 upregulation and the EMT process. Moreover, downregulation of lncRNA UBOX5-AS1 inhibited the hypoxia-induced EMT and attenuated cell migration and invasion. Conclusions The present research demonstrated that hypoxia upregulated the expression of lncRNA UBOX5-AS1 via HIF-1α-dependent signaling. The increased expression of lncRNA UBOX5-AS1 plays a vital role in mediating the hypoxia-regulated EMT and invasiveness of endometriosis, suggesting that lncRNA UBOX5-AS1 may be an important potential therapeutic target for endometriosis.

Endometriosis is a common benign gynecological disease defined as the presence of endometrial tissue outside the uterine cavity. The aim of this study was to identify the molecular mechanism underlying hypoxia-induced increases in invasive ability of human endometrial stromal cells (HESCs). Herein, we show that the expression levels of hypoxia-inducible factor lα (HIF-1α) and β-catenin were greater in ectopic endometriotic tissue compared with eutopic tissue from controls. Exposure of eutopic endometrial stromal cells under hypoxic conditions or treated with desferrioxamine (DFO, chemical hypoxia) resulted in a time-dependent increase in β-catenin expression and its dephosphorylation. Hypoxia/HIF-1α also activated the β-catenin/T-cell factor (TCF) signaling pathway and the expression of target genes, vascular endothelial growth factor and matrix metalloproteinase 9, and knockdown of HIF-1α or β-catenin abrogated hypoxia-induced increases in HESC invasiveness. These results suggest that HIF-1α interacting with β-catenin/TCF signaling pathway, which is activated by hypoxia, may provide new insights into the etiology of endometriosis.

Study hypothesis Do estrogen and Wnt/β-catenin signaling promote vascular endothelial growth factor (VEGF) expression in endometriosis and how? Study finding 17β-Estradiol (E2)-drives β-catenin triggered up-regulation of VEGF in effector human primary endometrial stromal cells (ESCs) and thus enhances their ability to establish a new blood supply to the human exfoliated endometrium. What is known already Implantation and survival of exfoliated endometrium is crucially dependent on neovascularization and Wnt/β-catenin signaling plays an important role in stimulating angiogenesis. Study design, samples/materials, methods Expression levels of VEGF mRNA, estrogen receptor α (ERα) and β-catenin protein were measured in ovarian endometriosis, eutopic endometrium of endometriosis patients and normal endometrium with real-time RT-PCR and western blot. ESCs were treated with 10 nM E2 for different times in order to evaluate the effect of E2 on ERα, β-catenin and VEGF expression in these cells. Human endometrial stromal cells (T HESCs) were cultured for transfection with expression vectors and siRNA constructs and used in chromatin immunoprecipitation (ChIP) and luciferase assays, which were conducted to clarify the regulation mechanism of E2 on VEGF. Main results and the role of chance VEGF, ERα and β-catenin expression was increased in endometriotic lesions compared with normal endometrium. E2 could promote ERα, β-catenin and VEGF expression in ESCs. ChIP and luciferase assays revealed that E2 up-regulated β-catenin expression by binding to the estrogen response element site on the β-catenin promoter. β-Catenin stabilization could activate Wnt/β-catenin signaling, which has a direct transcriptional effect on VEGF gene expression. Limitations, reasons for caution Endometriotic lesions were all from ovarian endometriosis and may differ from other type of endometriosis. Wider implications of the findings These promising results improve the body of knowledge on endometriosis pathogenesis and could open up new therapeutic strategies for the treatment of endometriosis. Study funding and competing interests This project was supported by the National Natural Science Foundation of China (grant no. 81170545 Y.L. and 81471439 Y.L.). None of the authors has any conflicting interests to declare.

Oestrogen has been reported to control the invasiveness of endometrial stromal cells in endometriosis. Notch signalling, a master regulator of cell invasion in tumours, is regulated by oestrogen in other diseases and hyperactivated in endometriotic stromal cells. Therefore, we hypothesized that an interaction between Notch signalling and oestrogen may exist in the regulation of endometrial stromal cell invasion, which is essential for the development of endometriosis. Western blot analysis of tissues showed that the expression levels of Notch components (JAG1 and NOTCH1) and Notch activity were markedly higher in ectopic endometria than in their eutopic and normal counterparts. Primary stromal cells obtained from normal endometria cultured with oestrogen presented significant increases in the expression of Notch components and Notch activity, the cytoplasmic and nuclear accumulation of NOTCH1 intracellular domain, the expression of matrix metallopeptidase 9 and vascular endothelial growth factor and cell invasiveness. Knockdown ofNOTCH1markedly alleviated oestrogen-induced matrix metallopeptidase 9 and vascular endothelial growth factor expression and cell invasion. ICI (an oestrogen receptor α antagonist) also blocked these oestrogenic effects. Oestrogen-responsive elements were found in the promoters ofNOTCH1andJAG1. A luciferase reporter analysis revealed that oestrogen regulated the expression of Notch components via oestrogen receptor alpha, which is bound to oestrogen-responsive elements in theJAG1andNOTCH1promoters. Collectively, our findings indicate that oestrogen engages in crosstalk with Notch signalling to regulate cell invasion in endometriosis via the activation of oestrogen receptor alpha and the enhancement of Notch activity. Notch signalling blockade may therefore be a novel therapeutic target for endometriosis.

Endometriosis is an estrogen-dependent disease that involves the adhesion, invasion, and angiogenesis of endometrial tissues outside of the uterine cavity. We hypothesized that a link exists between estrogen and beta-catenin (β-catenin) signaling in the pathogenesis of endometriosis. Human endometrial stromal cells (HESCs) were separated from eutopic endometrial tissues that were obtained from patients with endometriosis. β-catenin expression and cells invasiveness ability were up-regulated by 17β-estradiol (E2) in an estrogen receptor (ESR)-dependent manner, whereas β-catenin siRNA abrogated this phenomenon. Moreover, co-immunoprecipitation and dual immunofluorescence studies confirmed ESR1, β-catenin, and lymphoid enhancer factor 1/T cell factor 3 co-localization in the nucleus in HESCs after E2 treatment. To determine the role of β-catenin signaling in the implantation of ectopic endometrium, we xenotransplanted eutopic endometrium from endometriosis patients into ovariectomized severe combined immunodeficiency mice. The implantation of the endometrium was suppressed by β-catenin siRNA. Collectively, studies regarding β-catenin signaling are critical for improving our understanding of the pathogenesis of estrogen-induced endometriosis, which can translate into the development of treatments and therapeutic strategies for endometriosis.

Endometriosis is a benign gynecological disease that shares some characteristics with malignancy like migration and invasion. It has been reported that both hypoxia-inducible factor-1α (HIF-1α) and autophagy were upregulated in ectopic endometrium of patients with ovarian endometriosis. However, the crosstalk between HIF-1α and autophagy in the pathogenesis of endometriosis remains to be clarified. Accordingly, we investigated whether autophagy was regulated by HIF-1α, as well as whether the effect of HIF-1α on cell migration and invasion is mediated through autophagy upregulation. Here, we found that ectopic endometrium from patients with endometriosis highly expressed HIF-1α and autophagy-related protein LC3. In cultured human endometrial stromal cells (HESCs), autophagy was induced by hypoxia in a time-dependent manner and autophagy activation was dependent on HIF-1α. In addition, migration and invasion ability of HESCs were enhanced by hypoxia treatment, whereas knockdown of HIF-1α attenuated this effect. Furthermore, inhibiting autophagy with specific inhibitors and Beclin1 siRNA attenuated hypoxia triggered migration and invasion of HESCs. Taken together, these results suggest that HIF-1α promotes HESCs invasion and metastasis by upregulating autophagy. Thus, autophagy may be involved in the pathogenesis of endometriosis and inhibition of autophagy might be a novel therapeutic approach to the treatment of endometriosis.

Extracellular matrix remodeling is necessary for ectopic endometrium implantation. Many studies have shown an increased expression of matrix metalloproteinase 9 (MMP9) in the ectopic endometrium of endometriosis. However, the signaling pathways and cellular effects related to this process remain incompletely elucidated. The objective of our study was to investigate the association between MMP9 and the Wnt signaling pathway under the regulation of 17beta-estradiol (E2) in endometrial stromal cells. We found that MMP9 was elevated in tissues from women with endometriosis compared with normal women. Furthermore, MMP9 and beta-catenin increased concurrently in a time- and dose-dependent manner after E2 treatment. To clarify the relationship between MMP9 and beta-catenin, we performed luciferase promoter reporter and chromatin immunoprecipitation assays. A beta-catenin/TCF3/LEF1 complex bound to a specific site on the MMP9 promoter that promoted MMP9 gene and protein expression. The promotion of MMP9 by the Wnt signaling pathway under the regulation of E2 may contribute to the pathophysiology of this disease.

Extracellular matrix remodeling is necessary for ectopic endometrium implantation. Many studies have shown an increased expression of matrix metalloproteinase 9 (MMP9) in the ectopic endometrium of endometriosis. However, the signaling pathways and cellular effects related to this process remain incompletely elucidated. The objective of our study was to investigate the association between MMP9 and the Wnt signaling pathway under the regulation of 17beta-estradiol (E2) in endometrial stromal cells. We found that MMP9 was elevated in tissues from women with endometriosis compared with normal women. Furthermore, MMP9 and beta-catenin increased concurrently in a time- and dose-dependent manner after E2 treatment. To clarify the relationship between MMP9 and beta-catenin, we performed luciferase promoter reporter and chromatin immunoprecipitation assays. A beta-catenin/TCF3/LEF1 complex bound to a specific site on the MMP9 promoter that promoted MMP9 gene and protein expression. The promotion of MMP9 by the Wnt signaling pathway under the regulation of E2 may contribute to the pathophysiology of this disease.

Study question How does hypoxia promote growth of lesions in the development of endometriosis? Summary answer Hypoxia induces the epithelial-mesenchymal transition (EMT) of endometrial cells, resulting in changes in cellular characteristics, which may be a prerequisite for the establishment of endometriotic lesions. What is known already Up-regulated hypoxia-inducible factor 1α (HIF-1α) has recently been found in ectopic endometrial lesions. There is increasing evidence that EMT, in which epithelial cells acquire mesenchymal and migratory properties, may also play a role in the establishment of the disease. EMT induced by HIF-1α has been reported to play a role in the development of many tumor types. Study design, size, duration We investigated expression changes of N-cadherin, E-cadherin, β-catenin, HIF-1α and vimentin using immunohistochemistry in normal, eutopic and ectopic endometria. Endometrial tissues from 96 additional females without related pathology were collected, and these tissues were subjected to subsequent primary cell culture for further experiments. Participants/materials, setting, methods 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. Human primary endometrial epithelial cells were isolated from 96 normal endometrial tissues. Times for hypoxia treatment for western blot analysis were 1, 2, 4 and 8 h, for transwell experiments was 48 h. Ishikawa cells were used instead of primary endometrial epithelial cells for transfection and part of the transwell experiments. The impact of hypoxia on invasion was evaluated by transwell assays. Overexpression and inhibition of HIF-1α were achieved by transfection of pG/CMV/HIF-1α/IRES/EGFP and MCS-shHIF-1α-EGFP-IRES plasmids separately. 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 reverse transcriptase polymerase chain reaction (RT-PCR). Main results and the role of chance Overexpression of HIF-1α and changes associated with EMT were observed in normal, eutopic and ectopic endometrial tissues. Primary cultured human endometrial epithelial cells responded to hypoxia with classic EMT changes (fibroblastoid phenotype, increased expression of snail family zinc finger 1, β-catenin and mesenchymal markers, and decreased expression of E-cadherin) and increased invasiveness. The decreased invasiveness of Ishikawa cells by knockdown of HIF-1α was observed under hypoxic conditions. While up-regulation of HIF-1α induced changes characteristic of EMT, down-regulation of HIF-1α had the opposite effect. Statistical significance was defined as P Limitations, reasons for caution A weakness of this study is the relatively small sample size for immunohistochemistry. Ishikawa cells were used instead of primary endometrial epithelial cells for transfection and part of the transwell experiments. Wider implications of the findings Hypoxia-stabilized HIF-1α may play an important role in the invasion of endometrial cells in ectopic endometrial lesions, and it may induce EMT in the development of endometriosis. HIF-1α may be a new and important target for the endometriosis treatment. Study funding/competing interests This study was funded by the National Nature Science Foundation of China (grant number 81170545 and 81471439). The authors declare no competing interests.