Hypoxia-inducible factor-1alpha: A promising therapeutic target in endometriosis

Hypoxia-induced Semaphorin 3A promotes the development of endometriosis through regulating macrophage polarization

BACKGROUND

Semaphorin 3A (Sema3A) is a member of neural guidance factor family well-known for inducing the collapse of nerve cell growth cone and regulating nerve redistribution. It also has been characterized as an immunoregulatory and tumor promoting factor. Our previous study showed that Sema3A was involved in the regulation of sympathetic innervation and neuropathic pain of endometriosis. Nevertheless, the role of Sema3A in the development of endometriosis and its potential upstreaming factor are still not clear.

METHODS

Histology experiments were carried to detect the expression of Sema3A, hypoxia -inducible factor 1α (HIF-1α) and the distribution of macrophages. Cell experiments were used to explore the effect of Sema3A on the proliferation and migration of endometrial stromal cells (ESCs) and to confirm the regulatory action of HIF-1α on Sema3A. In vivo experiments were carried out to explore the role of Sema3A on the development of endometriosis.

RESULTS

Sema3A was highly expressed in endometriotic lesions and could enhanced the proliferation and migration abilities of ESCs. Aberrant macrophage distribution was found in endometriotic lesions. Sema3A also promoted the differentiation of monocytes into anti-inflammatory macrophages, so indirectly mediating the proliferation and migration of ESCs. Hypoxic microenvironment induced Sema3A mRNA and protein expression in ESCs via HIF-1α. Administration of Sema3A promoted the development of endometriosis in a mouse model.

CONCLUSIONS

Sema3A, which is regulated by HIF-1α, is a promoting factor for the development of endometriosis. Targeting Sema3A may be a potential treatment strategy to control endometriotic lesions.

Cannabidiol as a possible treatment for endometriosis through suppression of inflammation and angiogenesis

BACKGROUND

Endometriosis is associated with a wide variety of signs and symptoms and can lead to infertility, embryo death, and even miscarriage. Although the exact pathogenesis and etiology of endometriosis is still unclear, it has been shown that it has a chronic inflammatory nature and angiogenesis is also involved in it.

OBJECTIVE

This review aims to explore the role of inflammation and angiogenesis in endometriosis and suggest a potential treatment targeting these pathways.

FINDINGS

Among the pro-inflammatory cytokines, studies have shown solid roles for interleukin 1β (IL-β), IL-6, and tumor necrosis factor α (TNF-α) in the pathogenesis of this condition. Other than inflammation, angiogenesis, the formation of new blood vessels from pre-existing capillaries, is also involved in the pathogenesis of endometriosis. Among angiogenic factors, vascular endothelial growth factor (VEGF), hypoxia-inducible factor 1α (HIF-1α), transforming growth factor β1 (TGF-β1), and matrix metalloproteinases (MMPs) are more essential in the pathogenesis of endometriosis. Interestingly, it has been shown that inflammation and angiogenesis share some similar pathways with each other that could be potentially targeted for treatment of diseases caused by these two processes. Cannabidiol (CBD) is a non-psychoactive member of cannabinoids which has well-known and notable anti-inflammatory and antiangiogenic properties. This agent has been shown to decrease IL-1β, IL-6, TNF-α, VEGF, TGFβ, and MMPs in different animal models of diseases.

CONCLUSION

It seems that CBD could be a possible treatment for endometriosis due to its anti-inflammatory and antiangiogenic activity, however, further studies are needed.

Potential mechanism of Luoshi Neiyi prescription in endometriosis based on serum pharmacochemistry and network pharmacology

Introduction

Endometriosis (EMs) is characterized by ectopic growth of active endometrial tissue outside the uterus. The Luoshi Neiyi prescription (LSNYP) has been extensively used for treating EMs in China. However, data on the active chemical components of LSNYP are insufficient, and its pharmacological mechanism in EMs treatment remains unclear. This study aimed to explore the potential mechanism of LSNYP for EMs through network pharmacology based on the components absorbed into the blood.

Methods

Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry was used to analyze blood components, and a series of network pharmacology strategies were utilized to predict targets of these components and EMs. Protein-protein interaction (PPI) network analysis, component-target-disease network construction, gene ontology (GO) functional enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed. Additionally, molecular docking, molecular dynamics simulations, and in vitro and in vivo experiments were conducted to validate the HIF1A/EZH2/ANTXR2 pathway associated with hypoxic pathology in EMs.

Results

Thirty-four absorbed components suitable for network pharmacology analysis were identified, and core targets, such as interleukin 6, EGFR, HIF1A, and EZH2, were founded. Enrichment results indicated that treatment of EMs with LSNYP may involve the regulation of hypoxia and inflammatory-related signaling pathways and response to oxidative stress and transcription factor activity. Experimental results demonstrated that LSNYP could decrease the expression of HIF1A, ANTXR2, YAP1, CD44, and β-catenin, and increased EZH2 expression in ectopic endometrial stromal cells and endometriotic tissues. Molecular docking and molecular dynamics simulations manifested that there was stable combinatorial activity between core components and key targets of the HIF1A/EZH2/ANTXR2 pathway.

Conclusion

LSNYP may exert pharmacological effects on EMs via the HIF1A/EZH2/ANTXR2 pathway; hence, it is a natural herb-related therapy for EMs.

The "Road" to Malignant Transformation from Endometriosis to Endometriosis-Associated Ovarian Cancers (EAOCs): An mTOR-Centred Review

Ovarian cancer is an umbrella term covering a number of distinct subtypes. Endometrioid and clear-cell ovarian carcinoma are endometriosis-associated ovarian cancers (EAOCs) frequently arising from ectopic endometrium in the ovary. The mechanistic target of rapamycin (mTOR) is a crucial regulator of cellular homeostasis and is dysregulated in both endometriosis and endometriosis-associated ovarian cancer, potentially favouring carcinogenesis across a spectrum from benign disease with cancer-like characteristics, through an atypical phase, to frank malignancy. In this review, we focus on mTOR dysregulation in endometriosis and EAOCs, investigating cancer driver gene mutations and their potential interaction with the mTOR pathway. Additionally, we explore the complex pathogenesis of transformation, considering environmental, hormonal, and epigenetic factors. We then discuss postmenopausal endometriosis pathogenesis and propensity for malignant transformation. Finally, we summarize the current advancements in mTOR-targeted therapeutics for endometriosis and EAOCs.

HIF-1α regulates DcR3 to promote the development of endometriosis

OBJECTIVE

The aim of this study was to investigate the expression and clinical significance of HIF-1α and DcR3 in endometriosis by analysing clinical case data. Tissue samples were collected for tissue chip analysis and staining, and human endometrial stromal cells were isolated and cultured for cell experiments. Additionally, experiments were conducted on collected peritoneal fluid to explore the association and role of HIF-1α and DcR3 in endometriosis.

STUDY DESIGN

Patients who visited the Department of Obstetrics and Gynaecology at Central Hospital in Fengxian District, Shanghai, from January 2018 to December 2021 were recruited for this controlled study. Clinical data and tissue chip staining results were collected for multiple regression analysis on the clinical significance of HIF-1α and DcR3. Endometrial tissue, ovarian cysts, and pelvic fluid were collected, and human endometrial stromal cells were cultured. The impact of HIF-1α on DcR3 in different oxygen environments and its role in endometriosis were investigated through PCR, Western blotting, enzyme-linked immunosorbent assay, as well as adhesion and migration assays.

RESULTS

In patients with endometriosis, the expression of DcR3 and HIF-1α was found to be upregulated and correlated in ectopic endometrium. The expression of DcR3 served as an indicator of the severity of endometriosis. Hypoxia induced the expression of DcR3, which was regulated by HIF-1α and promoted migration and adhesion.

CONCLUSION

DcR3 can be used as a clinical indicator to assess the severity of endometriosis. The hypoxic environment in endometriosis enhances disease progression by regulating DcR3 through HIF-1α.

Pathways of Hypoxia-Inducible Factor (HIF) in the Orchestration of Uterine Fibroids Development

Uterine fibroids (UF) are common benign tumors in women. The course of UF is associated with troubling symptoms and the development of infertility and pregnancy pathology. Surgical treatment even implies hysterectomy, while pharmacological interventions are modestly effective. Classically, hypoxic metabolism is considered a hallmark of malignant tumor. However, the role of hypoxia-induced factor (HIF) is significant in benign tumors as well. Herein, we briefly review the basic biology of HIF-family proteins, outlining their possible roles in UF. Apart from theoretical justifications, we summarized 15 studies reporting increased expression of HIFs and downstream factors in UF samples. Altogether, data suggest that increased expression of the HIF-protein and altered expression of its dependent genes are presumed to be the factors leading to UF development. Thus, even without being a malignant tumor, UF is characterized by the strong involvement of HIF. This novel insight may give rise to further research in the direction of finding new prognostic markers and effective medicines against UF.

Inflammatory Cytokine-Induced HIF-1 Activation Promotes Epithelial-Mesenchymal Transition in Endometrial Epithelial Cells

The endometrium undergoes repeated proliferation and shedding during the menstrual cycle. Significant changes to this environment include fluctuations in the partial pressure of oxygen, exposure to a high-cytokine environment associated with intrauterine infection, and inflammation. Chronic endometritis is a condition wherein mild inflammation persists in the endometrium and is one of the causes of implantation failure and miscarriage in early pregnancy. It is thought that the invasion of embryos into the endometrium requires epithelial-mesenchymal transition (EMT)-associated changes in the endometrial epithelium. However, the effects of inflammation on the endometrium remain poorly understood. In this study, we investigated the effects of the intrauterine oxygen environment, hypoxia-inducible factor (HIF), and inflammation on the differentiation and function of endometrial epithelial cells. We elucidated the ways in which inflammatory cytokines affect HIF activity and EMT in an immortalized cell line (EM-E6/E7/TERT) derived from endometrial epithelium. Pro-inflammatory cytokines caused significant accumulation of HIF-1α protein, increased HIF-1α mRNA levels, and enhanced hypoxia-induced accumulation of HIF-1α protein. The combined effect of inflammatory cytokines and hypoxia increased the expression of EMT-inducing factors and upregulated cell migration. Our findings indicate that pro-inflammatory factors, including cytokines and LPS, work synergistically with hypoxia to activate HIF-1 and promote EMT in endometrial epithelial cells.

Down-regulating HK2 inhibits proliferation of endometrial stromal cells through a noncanonical pathway involving phosphorylation of STAT1 in endometriosis

BACKGROUND

Endometriosis is a benign gynecologic disease that causes chronic pelvic pain, dysmenorrhea and infertility and shares several characteristics with malignant tumors, afflicting women of reproductive age. Hexokinase 2 (HK2) plays an essential role as the first rate-limiting enzyme in the metabolic glycolysis pathway, and its abnormal elevation in tumors is associated with tumor genesis and metastasis. However, the expression and role of HK2 in endometriosis remain unclear.

METHODS

We sequenced the primary endometrial stromal cells from patients with endometrioma and utilized immunohistochemistry, quantitative real-time PCR and western blot to determine the expression of HK2. Then wound healing assays, cell invasion assays, cell proliferation assays were performed to explore the functions of HK2 in endometrial stromal cells. Furthermore, mice models of endometriosis were used to observe the effects of HK2 inhibitors in vivo. Lastly, glycolysis metabolism detection and transcriptome sequencing were carried out in HK2-knockdown endometrial stromal cells to analyze the mechanism of HK2 affecting cell function.

RESULTS

Endometrial stromal cells of endometrioma displayed active glycolysis metabolism and elevated expression of HK2. Downregulating HK2 reduced the migration, invasion and proliferation capacity of endometrial stromal cells. Knockdown of HK2 induced upregulation of signal transducer and activator of transcription 1 (STAT1) and their phosphorylation to attenuate the proliferation of endometrial stromal cells.

CONCLUSIONS

HK2 is associated with the migration, invasion and proliferation of endometrial stromal cells, which might provide new insights into the pathogenesis and treatment of endometriosis.

Therapeutic Strategies Focused on Cancer-Associated Hypercoagulation for Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC) is associated with chemotherapy resistance and poor prognosis, especially in advanced cases. Although comprehensive genomic analyses have clarified the significance of genomic alterations such as ARID1A and PIK3CA mutations in OCCC, therapeutic strategies based on genomic alterations have not been confirmed. On the other hand, OCCC is clinically characterized by a high incidence of thromboembolism. Moreover, OCCC specifically shows high expression of tissue factor and interleukin-6, which play a critical role in cancer-associated hypercoagulation and may be induced by OCCC-specific genetic alterations or the endometriosis-related tumor microenvironment. In this review, we focused on the association between cancer-associated hypercoagulation and molecular biology in OCCC. Moreover, we reviewed the effectiveness of candidate drugs targeting hypercoagulation, such as tissue factor- or interleukin-6-targeting drugs, anti-inflammatory drugs, anti-hypoxia signaling drugs, anticoagulants, and combined immunotherapy with these drugs for OCCC. This review is expected to contribute to novel basic research and clinical trials for the prevention, early detection, and treatment of OCCC focused on hypercoagulation.

Immunology and Immunotherapy of Endometriosis

Endometriosis is one of the most common gynecological and systemic diseases, with a remarkable immune background. Patients suffer from pain and fertility reduction. Due to the distinct immune component, an immunotherapeutic approach may gain importance in the future. In endometriosis, shifts in the cell fractions of the immune system are well known. Moreover, hypoxia concomitant with inflammation causes a disturbed immune response. The removal of endometriosis has a therapeutic effect, normalizes the immune disorders, and remains the most effective causative treatment in terms of pain and infertility. A key issue is whether a similar effect can be achieved for fertility with non-invasive immunotherapy where surgery is inadvisable or cannot be performed for various reasons. Numerous immunotherapy trials, including vaccines, were conducted on animals only, although the research is encouraging. Among the promising methods of non-specific immunotherapy is the administration of an ethiodized oil contrast. Moreover, due to the significant successes of immunotherapy in oncology, the possibility of immunotherapy affecting NK cells has been postulated. NK cells are responsible for the surveillance and apoptosis of ectopic cells. Expanding the arsenal of endometriosis treatment by immunotherapy is promising due to the significant contribution of immunological factors and the limitations of current treatment methods.

The Role of Long Non-Coding RNAs in Endometriosis

Endometriosis is a chronic gynecological disorder affecting the quality of life and fertility of many women around the world. Heterogeneous and non-specific symptoms may lead to a delay in diagnosis, with treatment options limited to surgery and hormonal therapy. Hence, there is a need to better understand the pathogenesis of the disease to improve diagnosis and treatment. Long non-coding RNAs (lncRNAs) have been increasingly shown to be involved in gene regulation but remain relatively under investigated in endometriosis. Mutational and transcriptomic studies have implicated lncRNAs in the pathogenesis of endometriosis. Single-nucleotide polymorphisms (SNPs) in lncRNAs or their regulatory regions have been associated with endometriosis. Genome-wide transcriptomic studies have identified lncRNAs that show deregulated expression in endometriosis, some of which have been subjected to further experiments, which support a role in endometriosis. Mechanistic studies indicate that lncRNAs may regulate genes involved in endometriosis by acting as a molecular sponge for miRNAs, by directly targeting regulatory elements via interactions with chromatin or transcription factors or by affecting signaling pathways. Future studies should concentrate on determining the role of uncharacterized lncRNAs revealed by endometriosis transcriptome studies and the relevance of lncRNAs implicated in the disease by in vitro and animal model studies.

Hypoxia‑induced lactate dehydrogenase A protects cells from apoptosis in endometriosis

The pathological expression and function of lactate dehydrogenase A (LDHA), a key enzyme that converts pyruvate into lactic acid during glycolysis, remains unknown in endometriosis. In the present study, LDHA expression in tissue samples was determined by immunohistochemistry. To examine whether LDHA was induced by hypoxia, primary cultured endometrial stromal cells (ESCs) and glandular epithelial Ishikawa cells were exposed to 1% O₂ (hypoxia) or 21% O₂ (normoxia). Cellular functions were assessed by flow cytometry, Transwell and Cell Counting Kit-8 assays in LDHA-silenced ESCs and Ishikawa cells. Mitochondrial functions were evaluated using mitochondrial membrane potential JC-1 staining, reactive oxygen species flow cytometric analysis and ATP detection. Additionally, lactic acid production was examined and western blotting was used to evaluate the expression levels of proteins associated with apoptosis, cell cycle and glycolysis, as well as regulatory proteins involved in epithelial-mesenchymal transformation and glycolytic pathways. LDHA was localized to endometrial glandular cells and stromal cells. However, LDHA protein expression was higher in endometriotic lesions compared with that in normal and eutopic endometria. LDHA expression levels in ectopic glandular cells were higher during the proliferative stage compared with during the secretory stage. Hypoxia treatment of Ishikawa cells and ESCs markedly induced the mRNA and protein expression of LDHA. Silencing of LDHA expression in Ishikawa cells and THESC cells significantly promoted impaired mitochondrial function and apoptosis while inhibiting migration and glycolysis. However, it had no obvious effect on proliferation. In conclusion, the present study revealed that LDHA was highly expressed in endometriotic tissues, where it may serve a notable role in the occurrence and development of endometriosis.

Upregulation of the long noncoding RNA UBOX5 antisense RNA 1 (UBOX5-AS1) under hypoxic conditions promotes epithelial-mesenchymal transition 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.

miR‑143‑3p inhibits endometriotic stromal cell proliferation and invasion by inactivating autophagy in endometriosis

Endometriosis (EM) is a multifactorial and debilitating chronic benign gynecological disease, but the pathogenesis of the disease is not completely understood. Dysregulated expression of microRNAs (miRNA/miR) is associated with the etiology of EM due to their role in regulating endometrial stromal cell proliferation and invasion. The present study aimed to identify the functions and mechanisms underlying miR-143-3p in EM. To explore the role of miR-143-3p in EM, functional miRNAs were analyzed via bioinformatics analysis. miR-143-3p expression levels in endometriotic stromal cells (ESCs) and normal endometrial stromal cells (NESCs) were measured via reverse transcription-quantitative PCR. The role of miR-143-3p in regulating ESC proliferation and invasion was assessed by performing Cell Counting Kit-8 and Transwell assays, respectively. miR-143-3p expression was significantly upregulated in ESCs compared with NESCs. Functionally, miR-143-3p overexpression inhibited ESC proliferation and invasion, whereas miR-143-3p knockdown promoted ESC proliferation and invasion. Moreover, miR-143-3p inhibited autophagy activation in ESCs, as indicated by decreased green puncta, which represented autophagic vacuoles, decreased microtubule associated protein 1 light chain 3α expression and increased p62 expression in the miR-143-4p mimic group compared with the control group. Moreover, compared with the control group, miR-143-3p overexpression significantly decreased the expression levels of autophagy-related 2B (ATG2B), a newly identified target gene of miR-143-3p, in ESCs. ATG2B overexpression reversed miR-143-3p overexpression-mediated inhibition of ESC proliferation and invasion. Collectively, the results of the present study suggested that miR-143-3p inhibited EM progression, thus providing a novel target for the development of therapeutic agents against EM.

Cigarette Smoke Extract Activates Hypoxia-Inducible Factors in a Reactive Oxygen Species-Dependent Manner in Stroma Cells from Human Endometrium

Cigarette smoking (CS) is a major contributing factor in the development of a large number of fatal and debilitating disorders, including degenerative diseases and cancers. Smoking and passive smoking also affect the establishment and maintenance of pregnancy. However, to the best of our knowledge, the effects of smoking on the human endometrium remain poorly understood. In this study, we investigated the regulatory mechanism underlying CS-induced hypoxia-inducible factor (HIF)-1α activation using primary human endometrial stromal cells and an immortalized cell line (KC02-44D). We found that the CS extract (CSE) increased reactive oxygen species levels and stimulated HIF-1α protein stabilization in endometrial stromal cells, and that CS-induced HIF-1α-dependent gene expression under non-hypoxic conditions in a concentration- and time-dependent manner. Additionally, we revealed the upregulated expression of a hypoxia-induced gene set following the CSE treatment, even under normoxic conditions. These results indicated that HIF-1α might play an important role in CS-exposure-induced cellular stress, inflammation, and endometrial remodeling.

Circ_0007331 knock-down suppresses the progression of endometriosis via miR-200c-3p/HiF-1α axis

Endometriosis is considered a benign gynaecological disease with cancer-like characterizations, which has a high incidence among women of reproductive age. However, this disease has so far lacked timely diagnosis and effective treatment owing to its unclear aetiology. In this study, we identified aberrant high expression of circ_0007331 in ectopic endometrial cells by comparing the endometrial samples from patients with and without endometriosis. Further functional experiments revealed that circ_0007331 knock-down effectively suppressed the viability, proliferation and invasive capacity of ectopic endometrial cells. Additionally, we attempted to define the molecular mechanism of circ_0007331 in the initiation and progression of endometriosis. Circ_0007331 acted as a miRNA sponge for miR-200c-3p to indirectly regulate the function of HIF-1α, which plays a key role in the local angiogenesis and hypoxic mechanisms of ectopic endometrium. A final in vivo experiment confirmed that circ_0007331 knock-down could suppress the development of endometriosis through down-regulating the expression of HIF-1α. Collectively, we preliminarily characterized the role and possible insights of circ_0007331/miR-200c-3p/HIF-1α axis in the proliferation and invasion of ectopic endometrial cells. We hope that by exploring the potential function and molecular mechanism of circ_0007331, we can increase our biological insight into the pathogenesis of endometriosis, which will bring the new ways for the diagnosis and therapy of this disease.

Identification of differentially expressed genes and signaling pathways involved in endometriosis by integrated bioinformatics analysis

Endometriosis is a common gynecological disease characterized by the presence and growth of endometrial tissue outside the uterus, including the pelvis and abdominal cavity. This condition causes various clinical symptoms, such as non-menstrual pelvic pain, dysmenorrhea and infertility, seriously affecting the health and quality of life of women. To date, the specific mechanism and the key molecules of endometriosis remain uncertain. The purpose of the present study was to elucidate the mechanisms involved in the development and persistence of the disease. A number of mRNA expression profile datasets (namely GSE11691, GSE23339, GSE25628 and GSE78851) were downloaded from the Gene Expression Omnibus (GEO) database. These gene expression profiles were normalized, and the differentially expressed genes (DEGs) were identified by integrated bioinformatics analysis. A total of 103 DEGs were screened upon excluding the genes that exhibited inconsistency of expression (P<0.05). Furthermore, the Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, and construction of protein-protein interaction networks of DEGs were performed using online software. The results revealed that the DEGs were closely associated with cell migration, adherens junction and hypoxia-inducible factor signaling. In addition, immunohistochemical assay results were found to be consistent with the bioinformatics results. The present study may help us understand underlying molecular mechanisms and the development of endometriosis, which has a great clinical significance for early diagnosis of the disease.

Genomic Function of Estrogen Receptor β in Endometriosis

Estrogen receptor (ER) β plays a critical role in endometriosis progression because cytoplasmic ERβ stimulates proinflammatory signaling in ectopic lesions and prevents apoptosis to promote their survival. However, the role of "nuclear ERβ" in endometriosis progression is not known. This critical knowledge gap obscures our understanding of the full molecular etiology of ERβ-mediated endometriosis progression. To fill this void, we generated an ERβ-regulated transcriptome and ERβ cistrome in ectopic lesions and the eutopic endometrium of mice with endometriosis by using a new endometrium-specific FLAG-tagged human ERβ overexpression mouse model. The integration of these omics data sets revealed that ERβ stimulated the proliferation activities of ectopic lesions and the eutopic endometrium by directly upregulating MYC and E2 transcription factor target genes and genes associated with the G2/M transition. Additionally, ERβ stimulated gene expression associated with TNFα/nuclear factor κB (NF-κB) signaling, epithelial-mesenchymal transition, reactive oxygen species signaling, IL-6/Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling, and hypoxia signaling and suppressed IFNα signaling in ectopic lesions to enhance endometriosis progression. ERβ also stimulated gene expression associated with the unfolded protein response and IL-6/JAK/STAT3 inhibitory signaling and suppressed TNFα/NF-κB signaling in the eutopic endometrium to cause endometriosis-associated endometrial dysfunction. Therefore, nuclear ERβ-regulated gene networks provide critical clues to understand the molecular etiology and complexity of endometriosis and endometriosis-associated endometrial dysfunction.

MiR-210-3p protects endometriotic cells from oxidative stress-induced cell cycle arrest by targeting BARD1

Endometriosis is associated with benign but adversely developed cysts in the extrauterine environment. The oxidative imbalanced environment induces DNA damage and affects cell cycle progression of endometrial stromal cells (ESCs) and endometrial epithelial cells, but how endometriotic cells maintain proliferation in the presence of oxidative stress is not clear. Growing evidence has indicated that the ectopic hypoxic microenvironment and oxidative stress can stimulate the growth of endometriotic cells, which is mainly due to the increase of HIF-1α. We found that the master hypoxia-associated miRNA miR-210-3p was increased in stromal and glandular cells of ectopic lesions compared with that of eutopic and normal endometria and was consistent with the expression of HIF-1α and the local oxidative stress-induced DNA damage predictor 8-OHdG. Moreover, miR-210-3p was upregulated in ESCs and Ishikawa cells under hypoxic conditions but not in normoxic culture. Knockdown of miR-210-3p induced a G2/M arrest of ESCs and Ishikawa cells under hypoxia, while no effect was found under normoxia. BARD1 was identified as a target of miR-210-3p. BARD1 expression was decreased in endometriotic tissues compared with eutopic and normal endometria and negatively correlated with the expression of miR-210-3p. Multivariate regression analysis showed that BARD1 downregulation could serve as an indicator for endometriotic severity. Our results suggest that miR-210-3p attenuates the G2/M cell cycle checkpoint by inactivating BRCA1 complex function in response to DNA damage under hypoxia via targeting the 3′ untranslated region of BARD1 mRNA. Endometriotic mouse model experiments showed that intraperitoneal injection of the miR-210-3p inhibitor or vitamin C suppressed the growth of endometriotic lesions. Together, our results demonstrate that endometriotic cells inhibit BARD1/BRCA1 function by upregulating miR-210-3p, which might be the underlying mechanism for endometriotic cell maintenance of growth in oxidative stress. Furthermore, inhibition of miR-210-3p and administration of vitamin C are promising approaches for the treatment of endometriosis.

Pathogenesis of endometriosis: the genetic/epigenetic theory

OBJECTIVE

To study the pathophysiology of endometriosis.

DESIGN

Overview of observations on endometriosis.

SETTING

Not applicable.

PATIENT(S)

None.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

The hypothesis is compatible with all observations.

RESULT(S)

Endometriosis, endometrium-like tissue outside the uterus, has a variable macroscopic appearance and a poorly understood natural history. It is a hereditary and heterogeneous disease with many biochemical changes in the lesions, which are clonal in origin. It is associated with pain, infertility, adenomyosis, and changes in the junctional zone, placentation, immunology, plasma, peritoneal fluid, and chronic inflammation of the peritoneal cavity. The Sampson hypothesis of implanted endometrial cells following retrograde menstruation, angiogenic spread, lymphogenic spread, or the metaplasia theory cannot explain all observations if metaplasia is defined as cells with reversible changes and an abnormal behavior/morphology due to the abnormal environment. We propose a polygenetic/polyepigenetic mechanism. The set of genetic and epigenetic incidents transmitted at birth could explain the hereditary aspects, the predisposition, and the endometriosis-associated changes in the endometrium, immunology, and placentation. To develop typical, cystic ovarian or deep endometriosis lesions, a variable series of additional transmissible genetic and epigenetic incidents are required to occur in a cell which may vary from endometrial to stem cells. Subtle lesions are viewed as endometrium in a different environment until additional incidents occur. Typical cystic ovarian or deep endometriosis lesions are heterogeneous and represent three different diseases.

CONCLUSION(S)

The genetic epigenetic theory is compatible with all observations on endometriosis. Implications for treatment and prevention are discussed.

Autophagy contributes to hypoxia-induced epithelial to mesenchymal transition of endometrial epithelial 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.

Long non-coding RNA MALAT1 mediates hypoxia-induced pro-survival autophagy of endometrial stromal cells in endometriosis

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.

The Endometriotic Tumor Microenvironment in Ovarian Cancer

Women with endometriosis are at increased risk of developing ovarian cancer, specifically ovarian endometrioid, low-grade serous, and clear-cell adenocarcinoma. An important clinical caveat to the association of endometriosis with ovarian cancer is the improved prognosis for women with endometriosis at time of ovarian cancer staging. Whether endometriosis-associated ovarian cancers develop from the molecular transformation of endometriosis or develop because of the endometriotic tumor microenvironment remain unknown. Additionally, how the presence of endometriosis improves prognosis is also undefined, but likely relies on the endometriotic microenvironment. The unique tumor microenvironment of endometriosis is composed of epithelial, stromal, and immune cells, which adapt to survive in hypoxic conditions with high levels of iron, estrogen, and inflammatory cytokines and chemokines. Understanding the unique molecular features of the endometriotic tumor microenvironment may lead to impactful precision therapies and/or modalities for prevention. A challenge to this important study is the rarity of well-characterized clinical samples and the limited model systems. In this review, we will describe the unique molecular features of endometriosis-associated ovarian cancers, the endometriotic tumor microenvironment, and available model systems for endometriosis-associated ovarian cancers. Continued research on these unique ovarian cancers may lead to improved prevention and treatment options.

Hypoxia Promotes Ectopic Adhesion Ability of Endometrial Stromal Cells via TGF-β1/Smad Signaling in Endometriosis

Hypoxia plays a vital role in the progression of endometriosis. Additionally, integrin-mediated aberrant adhesion is also essential for establishment of endometriotic lesions. In this study, we sought to determine the function of hypoxia in integrin-mediated adhesion of endometrial stromal cells (ESCs) in endometriosis. The expressions of adhesion molecule integrins (integrin α5, integrin αV, integrin β3, and integrin β5) were determined in 15 normal endometria and 15 paired eutopic and ectopic endometria by immunohistochemistry. Thirteen primary ESCs from patients with peritoneal endometriosis in the proliferative phase were cultured under a hypoxic (1% O2) or normoxic (21% O2) environment, and the expression levels of hypoxia-inducible factor (HIF)-1α, transforming growth factor (TGF)-β1, and integrins were detected by quantitative reverse transcription polymerase chain reaction and western blot. The alteration of integrins in endometriotic mouse models were also explored. Our results demonstrated that HIF-1α and integrins were highly expressed in ESCs of endometriotic lesions compared with ESCs of eutopic and normal endometrium. Hypoxia treatment significantly increased ESC adhesion abilities and integrin expression, which were positively correlated with TGF-β1 expression. Both TGF-β1 and hypoxia enhanced ESC adhesion properties, whereas hypoxia combined with TGF-β1 receptor inhibitor inhibited ESC adhesion. Knockdown of HIF-1α attenuated TGF-β1/Smad signaling activation and integrin expression and reduced ESC adhesion. Higher expression levels of HIF-1α, TGF-β1, and integrins were detected in endometriotic cysts from mice models. Our findings provide a novel insight of endometriosis that the hypoxic microenvironment stimulates ESCs to produce excessive TGF-β1 and activates the TGF-β1/Smad signaling pathway, thus enhancing integrin expression and the adhesion ability of ESCs.

Autophagy in endometriosis: Friend or foe?

Endometriosis is a chronic, estrogen-dependent disease and characterized by the implantation of endometrial glands and stroma deep and haphazardly into the outside the uterine cavity. It affects an estimated 10% of the female population of reproductive age and results in obvious reduction in health-related quality of life. Unfortunately, there is no a consistent theory for the etiology of endometriosis. Furthermore, the endometriosis is hard to diagnose in early stage and the treatment methods are limited. Importantly, emerging evidence has investigated that there is a close relationship between endometriosis and autophagy. However, autophagy is a friend or foe in endometriosis is puzzling, the precise mechanism underlying autophagy in endometriosis has not been fully elucidated yet. Here, we provide an integrated view on the acquired findings of the connections between endometriosis and autophagy. We also discuss which may contribute to the abnormal level of autophagy in endometriosis.

Overexpression of Four Joint Box-1 Protein (FJX1) in Eutopic Endometrium From Women With Endometriosis

The four jointed box 1 (FJX1) is a regulator of angiogenesis, and the levels of FJX1 are increased in several types of cancer. Angiogenesis plays a critical role in endometrial growth as well as in several gynecologic disorders including endometriosis. However, the function of FJX1 has not been studied in endometriosis. Therefore, we examined the levels of FJX1 in eutopic endometrium from women with or without endometriosis. The levels of FJX1 protein did not change in endometrial cells during the menstrual cycle in endometrium from women without endometriosis. However, its levels were significantly higher in the secretory phase of the eutopic endometrium from women with endometriosis when compared to women without endometriosis. Hypoxia-inducible factor-1α (HIF1α) is known as a key mediator of endometriosis by regulating genes essential to estrogen production, angiogenesis, proliferation, inflammation, and extracellular invasion. It has been reported that FJX1 induces an increase in HIF1α through posttranslational stabilization. The results of our Western blot analysis reveal a significant positive correlation between FJX1 and HIF1α proteins in endometrium of women with and without endometriosis. This overexpression of FJX1 was confirmed by sequential analysis of the eutopic endometrium during endometriosis progression, using an induced model of endometriosis in the baboon. Therefore, our results suggest that high levels of FJX1 proteins may play an important role in the pathogenesis of endometriosis.

Hypoxia-inducible factor-1α promotes endometrial stromal cells migration and invasion by upregulating autophagy in 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.

Estrogen stabilizes hypoxia-inducible factor 1α through G protein-coupled estrogen receptor 1 in eutopic endometrium of endometriosis

OBJECTIVE

To investigate whether G protein-coupled estrogen receptor (GPER, also known as GPR30 and GPER1) stabilizes hypoxia-inducible factor 1α (HIF-1α) in eutopic endometrium (EuEM) of endometriosis.

DESIGN

Immunohistochemical analysis and experimental in vitro study.

SETTING

University hospital.

PATIENT(S)

Patients with or without endometriosis.

INTERVENTION(S)

The EuEM and normal control endometrium (CoEM) were obtained by curettage. Primary cultured endometrial stromal cells (ESCs) were treated with 17β-E₂, G1, or G15.

MAIN OUTCOME MEASURE(S)

The EuEM and CoEM were collected for immunohistochemistry. Western blot, polymerase chain reaction, ELISA, and dual luciferase experiments were used to detect expression of GPER, HIF-1α, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 9 (MMP9) in ESCs. Estradiol and G1 were used as agonists of GPER, G15 as an antagonist. Migration of ESCs and endothelial tube formation of human umbilical vein endothelial cells cultured in medium collected from ESCs were measured.

RESULT(S)

Protein levels of GPER and HIF-1α were higher in EuEM than in CoEM. Protein levels of HIF-1α but not HIF-1α mRNA levels increased concurrently with GPER after E₂ and G1 treatment. Furthermore, expression and activity of VEGF and MMP9 increased under E₂ and G1 stimulation. However, these effects disappeared when GPER was blocked.

CONCLUSION(S)

G protein-coupled estrogen receptor stabilizes HIF-1α and thus promotes HIF-1α-induced VEGF and MMP9 in ESCs, which play critical roles in endometriosis.

Effect of rapamycin on endometriosis in mice

The aims of the present study were to investigate the impact of rapamycin (RAPA) on the endometriosis (EMS) lesions in severe combined immunodeficiency (SCID) mice, and to examine the possible mechanism involved in a novel therapy in EMS. Following the successful establishment of an EMS-SCID mouse model, the mice were randomly assigned into the RAPA, control and saline treatment groups. Subsequent to treatment for 2 weeks, the serum hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) were detected using ELISA. The levels of HIF-1α and VEGF, as well as the size of EMS lesions, were compared among the three groups. In addition, the HIF-1α, VEGF and CD34 protein expression levels, and the microvessel density (MVD) of the lesions were determined by immunohistochemical analysis. Compared with the control and saline groups, the volume of EMS lesions in the RAPA-treated SCID mice was significantly reduced. Furthermore, the serum level and protein expression of VEGF, and the MVD in the lesions of the RAPA-treated group were significantly reduced when compared with the other two groups. These parameters were comparable in the control and saline groups. In conclusion, RAPA may inhibit the growth of endometriotic lesions, most possibly through the inhibition of the expression of VEGF in lesions, thereby inhibiting angiogenesis.