MicroRNAs and angiogenesis in endometriosis

The Regulation of MicroRNA-21 by Interleukin-6 and Its Role in the Development of Fibrosis in Endometriotic Lesions

Endometriosis is one of the most common causes of chronic pelvic pain and infertility that affects 10% of women of reproductive age. It is currently defined as the presence of endometrial epithelial and stromal cells at ectopic sites; however, advances in endometriosis research have some authors believing that endometriosis should be re-defined as "a fibrotic condition in which endometrial stroma and epithelium can be identified". microRNAs (miRNAs) are regulatory molecules that potentially play a role in endometriotic lesion development. There is evidence that suggests that miRNAs, including microRNA-21 (miR-21), participate in fibrotic processes in different organs, including the heart, kidney, liver and lungs. The objective of this study was to understand the role of miR-21 and the mechanisms that can contribute to the development of fibrosis by determining how IL-6 regulates miR-21 expression and how this miRNA regulates the transforming growth factor beta (TGF-β) signaling pathway to promote fibrosis. We investigated the expression of miR-21 in the baboon and mouse model of endometriosis and its correlation with fibrosis. We demonstrated that inflammation and fibrosis are present at a very early stage of endometriosis and that the inflammatory environment in the peritoneal cavity, which includes interleukin 6 (IL-6), can regulate the expression of miR-21 in vitro and in vivo.

Comprehensive analysis of circRNA-miRNA-mRNA network related to angiogenesis in recurrent implantation failure

BACKGROUND

Abnormal endometrial blood flow causes a decrease in endometrial receptivity and is considered a relatively independent risk factor for recurrent implantation failure (RIF). This study aimed to explore the potentially functional circRNA-miRNA-mRNA network in RIF, and further explore its mechanism.

METHODS

Datasets were downloaded from the GEO database to identify differentially expressed circRNAs, miRNAs and mRNAs. The circRNA-miRNA-mRNA and PPI networks were constructed using Cytoscape 3.6.0 and the STRING database, the hub genes were identified with the cytoHubba plug-in, and a circRNA-miRNA-hub mRNA regulatory sub-network was constructed. Then, GO and KEGG pathway enrichment analyses of the hub genes were performed to comprehensively analyze the mechanism of hub mRNAs in RIF. Due to the results of circRNAs-miRNAs-hub mRNAs regulatory network, we verified the expression of circRNA_0001721, circRNA_0000714, miR-17-5p, miR-29b-3p, HIF1A and VEGFA in the RIF mouse model by qRT‒PCR and western blotting.

RESULTS

We initially identified 175 DEmRNAs, 48 DEmiRNAs and 56 DEcircRNAs in RIF associated with angiogenesis and constructed a circRNA-miRNA‒mRNA network and PPI network. We further identified six hub genes in the acquired network. Based on these genes, functional enrichment analysis revealed that the HIF-1 signaling pathway plays a vital role in endometrial angiogenesis in RIF. In addition, the interaction networks of circRNA_0001721/miR-17-5p/HIF1A and the circRNA_0000714/miR-29b-3p/VEGFA axis were predicted. In the RIF mouse model, circRNA_0001721, circRNA_0000714, HIF1A and VEGFA were down-regulated, whereas miR-17-5p and miR-29b-3p were up-regulated according to qRT‒PCR and western blotting.

CONCLUSION

This study revealed that the HIF-1 signaling pathway plays a vital role in endometrial angiogenesis in RIF. The circRNA_0001721/miR-17-5p/HIF1A and circRNA_0000714/miR-29b-3p/VEGFA axes might play a role in the pathogenesis of endometrial angiogenesis in RIF.

Kallikrein-Related Peptidase 4 Promotes Proliferation, Migration, Invasion, and Pro-Angiogenesis of Endometrial Stromal Cells via Regulation of Brain-Derived Neurotrophic Factor Production in Endometriosis

Endometriosis is a common benign gynecologic condition. Endometriosis lesions are associated with endometrial cell proliferation, migration, invasion, and neovascularization, while the specific molecular mechanisms are still elusive. Transcriptome sequencing has been used for the identification of diagnostic markers in endometriosis. Here, transcriptome profiling revealed that kallikrein-related peptidase 4 (KLK4) expression was up-regulated in ectopic endometrium (EC) tissues of patients with endometriosis. KLK4 mediates the degradation of extracellular matrix proteins, and its proteolytic activity activates many tumorigenic and metastatic pathways via tumor invasion and migration. Nevertheless, whether KLK4 serves as an important regulatory factor in endometriosis remains unclear. This study confirmed that KLK4 was highly expressed in ectopic endometrial stromal cells (EC-ESCs). KLK4 overexpression promoted proliferation and suppressed apoptosis of EC-ESCs, induced cell migration and invasion, and enhanced angiogenesis in vivo. Mechanistically, KLK4 overexpression mediated the protein cleavage of pro-brain-derived neurotrophic factor in EC-ESCs. Finally, brain-derived neurotrophic factor was a vital downstream substrate of KLK4 maintained the proliferation, metastasis, and pro-angiogenesis abilities and inhibited apoptosis of ESCs through a rescue study. Together, these findings demonstrate the promotive role of KLK4 in endometriosis development. In addition, the study provides a new insight that KLK4 might be a potential therapeutic target and prognostic marker for patients with endometriosis.

miRNAs and lncRNAs: Potential Non-Invasive Biomarkers for Endometriosis

Many studies have tried to understand the mechanism of endometriosis and its manner of manifestation. However, the only method of diagnosis considered as the gold standard in endometriosis is an invasive method called exploratory laparoscopy. Hence, there is a need to identify non-invasive or minimally invasive methods to minimize patients' suffering, thus increasing their addressability at the earliest possible staging of the disease, and to diagnose this condition as soon as possible. miRNAs (microRNAs) and lncRNAs (long-noncoding RNAs) are potential non-invasive diagnostic methods for endometriosis. Multiple clinical trials indicate that miRNA can be used as a non-invasive method in the diagnosis and differentiation of endometriosis stages.

Circulating miRNAs Related to Epithelial-Mesenchymal Transitions (EMT) as the New Molecular Markers in Endometriosis

Endometriosis is a chronic gynecological disease defined by the presence of endometrial-like tissue found outside the uterus, most commonly in the peritoneal cavity. Endometriosis lesions are heterogenous but usually contain endometrial stromal cells and epithelial glands, immune cell infiltrates and are vascularized and innervated by nerves. The complex etiopathogenesis and heterogenity of the clinical symptoms, as well as the lack of a specific non-invasive diagnostic biomarkers, underline the need for more advanced diagnostic tools. Unfortunately, the contribution of environmental, hormonal and immunological factors in the disease etiology is insufficient, and the contribution of genetic/epigenetic factors is still fragmentary. Therefore, there is a need for more focused study on the molecular mechanisms of endometriosis and non-invasive diagnostic monitoring systems. MicroRNAs (miRNAs) demonstrate high stability and tissue specificity and play a significant role in modulating a range of molecular pathways, and hence may be suitable diagnostic biomarkers for the origin and development of endometriosis. Of these, the most frequently studied are those related to endometriosis, including those involved in epithelial–mesenchymal transition (EMT), whose expression is altered in plasma or endometriotic lesion biopsies; however, the results are ambiguous. Specific miRNAs expressed in endometriosis may serve as diagnostics markers with prognostic value, and they have been proposed as molecular targets for treatment. The aim of this review is to present selected miRNAs associated with EMT known to have experimentally confirmed significance, and discuss their utility as biomarkers in endometriosis.

miRNAs in the Era of Personalized Medicine: From Biomarkers to Therapeutics

In recent years, interest in personalized medicine has considerably increased [...].

Variations in the Profiles of Vascular-Related Factors Among Different Sub-Types of Polycystic Ovarian Syndrome in Northern China

Recently, a growing body of evidence has suggested that abnormal ovarian angiogenesis, secondary to the imbalance between various angiogenic markers, is involved in the pathogenesis of PCOS, and this has led to the use of various interventions (such as Diane-35) to restore the normal ovarian angiogenesis. Therefore, we conducted the current investigation to determine the role of such markers (endothelial growth factor (VEGF), endostatin (ES), and thrombospondin-1 (TSP-1)) in the pathogenesis of PCOS along with the associated changes in ovarian blood flow in patients with PCOS compared to healthy controls, both before and after a course of oral contraception. A total of 381 patients with PCOS and 98 healthy females of childbearing age were recruited from July 2014 to June 2017 at the Reproductive Center of the Second Affiliated Hospital of Harbin Medical University. The serum levels of VEGF, ES, and TSP-1 were determined by enzyme-linked immunosorbent assay, while ovarian perfusion was measured by the pulsatility index (PI) and resistance index (RI) by using transvaginal color Doppler ultrasound. Repeated analyses were carried out after 3 months of Diane-35 treatment. Post-treatment serum levels of luteinizing hormone (LH)/follicle stimulating hormone (FSH) ratio of patients with PCOS decreased significantly (P <0.05). The RI values of most PCOS patients increased after treatment (P<0.05), while PI was significantly increased in all patients (P<0.05). However, variable changes in the serum levels of TSP-1, VEGF, and ES after treatment were observed. Serum VEGF levels showed a negative correlation with serum LH/FSH ratio, T concentration, and ES (P <0.05), while ES levels were negatively correlated with serum T concentrations only (P<0.05). The markers of angiogenesis (VEGF, ES, and TSP-1) were expressed differently among PCOS patients, who also responded differently to the same course of Diane-35 treatment. This field still warrants further investigation to reach a more definitive conclusion.

Establishment of an immortalized stromal cell line derived from human Endometriotic lesion

BACKGROUND

Endometriosis is a benign gynecological disease with obviously feature of estrogen-dependence and inflammatory response. The applications of primary endometriotic stromal cells in research of endometriosis are restricted for short life span, dedifferentiation of hormone and cytokine responsiveness. The objective of this study was to establish and characterize immortalized human endometriotic stromal cells (ihESCs).

METHODS

The endometriotic samples were from a patient with ovarian endometriosis and the primary endometriotic stromal cells were isolated from the endometriotic tissues. The primary cells were infected by lentivirus to establish telomerase reverse transcriptase (hTERT)-induced immortalized cells. Quantification of mRNA and proteins was examined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western Blot. CCK-8 assay and EdU labeling assay were assigned to assess the growth of ihESCs. Karyotype assay was performed to detect the chromosomes of ihESCs. Colony formation assay and nude mouse tumorigenicity assay were used to evaluate colony-formation and tumorigenesis abilities.

RESULTS

ihESCs continuously overexpressed hTERT via infection of lentivirus and significant extended the life span reaching 31 passages. The morphology, proliferation and karyotype of ihESCs remained unchanged. The expression of epithelial-mesenchymal transition (EMT) markers, estrogen-metabolizing proteins and estrogen/progesterone receptors (ERs and PRs) were unaltered. Furthermore, the treatment of estrogen increased the proliferation and EMT of ihESCs. Lipopolysaccharides (LPS) and IL-1β remarkably induced inflammatory response. The clonogenesis ability of ihESCs was consistent with primary cells, which were much lower than Ishikawa cells. In addition, nude mouse tumorigenicity assay demonstrated that ihESCs were unable to trigger tumor formation.

CONCLUSION

This study established and characterized an immortalized endometriotic stromal cell line that exhibited longer life span and kept the cellular morphology and physiological function as the primary cells. The immortalized cells remained normal feedback to estrogen and inflammatory response. Moreover, the immortalized cells were not available with tumorigenic ability. Therefore, ihESCs would be serviceable as in vitro cell tool to investigate the pathogenesis of endometriosis.

TSP1-CD47-SIRPα signaling facilitates the development of endometriosis by mediating the survival of ectopic endometrium

PROBLEM

To explore whether the thrombospondin-1(TSP1)-CD47-signal regulatory protein alpha (SIRPα) signaling pathway has impacts on the development of endometriosis.

METHOD OF STUDY

Endometrial stromal cells (ESCs) originated from ectopic and eutopic endometrial tissues with or without endometriosis. Monocytes (Macrophages) were isolated from peripheral blood and peritoneal fluids with or without endometriosis. The expression levels of molecules were investigated by flow cytometry (FCM), immunohistochemistry (IHC), and RT-qPCR. The concentration of TSP1 was assessed via ELISA. The capacities of angiogenesis and phagocytosis were measured via tube formation assay and phagocytic assay, respectively.

RESULTS

We confirmed the up-regulation of critical molecules within the pathway in endometriosis patients. TSP1 can encourage normal ESCs (NESCs) growth and fibrosis. It simultaneously promotes the secretion of inflammatory factors and inhibits the phagocytic abilities of macrophages. Moreover, the proliferation of vascular endothelial cells (VECs) may be improved by TSP1. These effects may be offset by CD47 blocking antibodies. In addition, ectopic ESCs (EESCs) directly improve SIRPα expression on macrophages, which may further exhaust their phagocytic ability. Phagocytosis efficiency of macrophages on EESCs significantly improves by blocking CD47-SIRPα pathway.

CONCLUSION

TSP1-CD47-SIRPα signaling pathway not only improves the viability of NESCs per se but also promotes their survival circumstances by affecting the function of macrophages and VECs, which are mutually reinforcing and jointly promote the development of endometriosis.

Apoptotic functions of microRNAs in pathogenesis, diagnosis, and treatment of endometriosis

MicroRNAs or miRNAs are a component of the non-coding RNAs family which is engaged in many cellular functions such as cell proliferation, apoptosis, gene expression, signaling pathways, angiogenesis, and etc. Endometriosis is a malignant gynecologic disorder occurring in women before menopausal age. Pathogenesis of this illness is still a discussion subject between the scientists but in our knowledge, microRNAs can be one of the possible involved factors. The purpose of this paper is to investigate the role of apoptotic activities of miRNAs in endometriosis. Accumulative evidence has demonstrated the role of cell proliferation, apoptosis, and invasion in the progression of these diseases. In this review, we looked into the specific role of apoptosis and its related genes and pathways in endometriosis and tied to present an explanation of how miRNAs can affect endometriosis by their apoptotic activities. What we found is that a great extent of miRNAs is involved in this illness and they are responsible for repressing apoptosis and progression of the disease. As a result, miRNAs have two different usages in endometriosis: biomarkers and potential therapeutic targets. In this review we gathered a great amount of evidence to inquire into the role of micro RNAs in inducing apoptosis and how this mechanism can be exerted for therapeutic purposes for endometriosis.

Reduced microRNA-451 expression in eutopic endometrium contributes to the pathogenesis of endometriosis

BACKGROUND

Endometriosis (EMs) is a chronic and recurrent, but benign, disease in women of reproductive age, and EMs patients have a high risk of developing gynecological tumors and autoimmune disorders. The etiology of EMs is not clear. Certain genetic markers in the eutopic endometrium are key in the pathogenesis of EMs. MicroRNAs (miRNAs) are implicated in several biological processes, such as cell proliferation, differentiation, and apoptosis. MiR-451 is interesting, as it acts as a tumor suppressor and is relevant to the poor prognosis of cancers.

AIM

To evaluate the expression levels and role of miR-451 in the eutopic endometrium and predict possible targets of miR-451 and related signaling pathways.

METHODS

Quantitative real-time polymerase chain reaction was used to evaluate miR-451 expression in cultured cell lines as well as in pathologic tissues from 40 patients with EMs and 20 donors with no history of the disease (controls). Cell Counting Kit-8 and flow cytometric assays were performed to determine cell proliferation and survival rates after transfection with miR-451 mimics and siRNAs. MiR-451 targets were predicted using miRDB and miRcode target-predicting databases.

RESULTS

We observed lower miR-451 levels in eutopic endometrial tissues from patients with EMs than in control tissues, and this difference was not related to the American Society for Reproductive Medicine stage. Ectopic overexpression of miR-451 in eutopic cells induced apoptosis and inhibited cell proliferation. SiRNA-mediated miR-451 knockdown reversed these effects. Using miRDB and miRcode, we identified 12 potential miR-451 target genes. We hypothesize that the expression of YWHAZ, OSR1, TTN, and CDKN2D may be regulated by miR-451 and be involved in disease pathogenesis.

CONCLUSION

Reduced miR-451 expression in the eutopic endometrium contributes to the pathogenesis of EMs by promoting cell proliferation and reducing apoptosis. Thus, miR-451 is a novel biomarker for EMs. YWHAZ, OSR1, TTN, and CDKN2D are potential target genes of miR-451 and may have key roles in this disease.

Anti-inflammatory cytokines in endometriosis

Although the pathogenesis of endometriosis is not fully understood, it is often considered to be an inflammatory disease. An increasing number of studies suggest that differential expression of anti-inflammatory cytokines (e.g., interleukin-4 and -10, and transforming growth factor-β1) occurs in women with endometriosis, including in serum, peritoneal fluid and ectopic lesions. These anti-inflammatory cytokines also have indispensable roles in the progression of endometriosis, including by promoting survival, growth, invasion, differentiation, angiogenesis, and immune escape of the endometriotic lesions. In this review, we provide an overview of the expression, origin, function and regulation of anti-inflammatory cytokines in endometriosis, with brief discussion and perspectives on their future clinical implications in the diagnosis and therapy of the disease.

Circulating miRNAs as Biomarkers for Endometriosis and Endometriosis-Related Ovarian Cancer-An Overview

Early detection and accurate diagnosis are pivotal in the management of endometriosis and endometriosis-related ovarian neoplasms (ERONs), yet there is no clear common ground regarding their pathogenesis. Endometriosis is a debilitating pathology that profoundly impairs the quality of life. Although the spontaneous resolution of endometriosis is possible, studies suggest that it can be a progressive condition, and ERONs can develop. The gold standard for diagnosis remains as the invasive method of laparoscopy followed by histological confirmation. In recent years, novel biomarkers have been discovered. MicroRNAs (miRNA) represent important epigenetic modulators of gene expression and are very attractive as biomarkers due to their lower complexity, tissue specificity, and stability in bodily fluids. Several studies have advanced the possibility of miRNAs becoming potential biomarkers in endometriosis and ERONs. Our aim is to bring these studies together in order to have a better understanding of whether, how, and when miRNAs might be used as biomarkers for these pathologies.

METHODS

We selected the reviewed papers from Google Academic, PubMed, and CrossRef. A total of eight studies met the inclusion criteria.

RESULTS

MiR-200 family, miR-143, 145, miR-20a, and miR199a were the most commonly dysregulated miRNAs in endometriosis, and miR-200 family was found to be dysregulated in both ERONs and endometriosis.

CONCLUSIONS

No single miRNA was considered as a sole biomarker for this pathology. However, since the prognostic value of biomarkers is generally enhanced if more are assessed at the same time, a panel of miRNAs could be a better indicator of the disease.

Galectin-3 plays an important role in endometriosis development and is a target to endometriosis treatment

This study aimed to analyze galectin-3 importance in endometriotic lesions development and the effect of recombinant Gal-3 carbohydrate recognition domain (Gal3C) in experimental endometriosis treatment. Experimental endometriosis was induced in WT and Gal-3-/- mice. Initially developed lesions were macroscopically and histologically analyzed, including immunohistochemical analysis. Then, WT mice were treated with Gal3C for 15 days. Gal-3 deficiency and Gal3C treatment significantly impaired endometriosis development. A significant decrease in lesions implantation and size, VEGF and VEGFR-2 expression, vascular density and macrophage distribution were observed in Gal-3 absence or inhibition. A greater presence of iNOS positive cells was observed in knockout mice lesions, while the presence of Arginase positive cells was higher in the WT animal lesions. In addition, COX-2 and TGFb1 were reduced by Gal3C treatment. Data showed here indicate a relevant role of Gal-3 in endometriosis development and highlight a target of endometriosis treatment using Gal-3 inhibitor.

The Exosomal Long Noncoding RNA aHIF is Upregulated in Serum From Patients With Endometriosis and Promotes Angiogenesis in Endometriosis

OBJECTIVE

The transfer of long noncoding RNAs (lncRNAs) via exosomes to modulate recipient cells represents an important mechanism for disease progression. Antisense hypoxia-inducible factor (aHIF) is a well-known angiogenesis-related lncRNA. Here, we aimed to investigate the clinical implications of aHIF and exosomal aHIF in endometriosis and the involvement of exosome-shuttled aHIF in endometriosis angiogenesis.

STUDY DESIGN

The distribution and expression of aHIF in ectopic, eutopic, and normal endometria was evaluated. Serum exosomal aHIF levels in patients with endometriosis were tested. The correlation between serum exosomal aHIF and aHIF expression in ectopic endometria was analyzed. Endometriotic cyst stromal cells (ECSCs)-derived exosomes were characterized. The internalization of exosomes by human umbilical vein endothelial cells (HUVECs) was observed. A series of in vitro assays were conducted to investigate the roles and mechanisms of exosomal aHIF in endometriosis angiogenesis.

RESULTS

Clinically, aHIF was highly expressed in ectopic endometria and serum exosomes in patients with endometriosis. Serum exosomal aHIF was significantly correlated to aHIF expression in matched ectopic endometria. In vitro, PKH67-labeled exosomes derived from aHIF high expression ECSCs were effectively internalized by recipient HUVECs. Notably, exosome-shuttled aHIF was transferred from ECSCs to HUVECs, which in turn elicited proangiogenic behavior in HUVECs by activating vascular endothelial growth factor (VEGF)-A, VEGF-D, and basic fibroblast growth factor, thereby facilitating endometriosis angiogenesis.

CONCLUSION

Our study illustrates a potential cell-cell communication between ECSCs and HUVECs in an ectopic environment, provides a novel mechanistic model explaining how ECSCs induce angiogenesis from the perspective of the "exosomal transfer of aHIF," and highlights the clinical value of circulating exosomal aHIF in 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.

Clotrimazole is effective for the regression of endometriotic implants in a Wistar rat experimental model of endometriosis

The present work aimed to evaluate molecular, angiogenic and inflammatory changes induced by clotrimazole (CTZ) on endometriosis lesions. For this, thirty female Wistar rats with surgically implanted autologous endometrium were treated with CTZ or vehicle (200 mg/kg) via esophageal gavage for 15 consecutive days. CTZ treatment significantly decreased the growth and the size of the implants, and histological examination indicated regression and atrophy, with no toxicity to the animals. The levels of the angiogenic markers VEGF and VEGFR-2 were significantly decreased in CTZ group. The treatment also promotes a reduction on PGE₂ and TNF-α levels. All these effects involve the amelioration of ERK1/2, Akt, AMPK and PERK signaling upon CTZ treatment. In conclusion, CTZ promoted an overall amelioration of endometriosis in a rat model due to the anti-angiogenic properties of the drug. Therefore, our results support the proposal of a clinical trial using CTZ for the treatment of endometriosis.

Basic mechanisms of vascularization in endometriosis and their clinical implications

BACKGROUND

Vascularization is a major hallmark in the pathogenesis of endometriosis. An increasing number of studies suggests that multiple mechanisms contribute to the vascularization of endometriotic lesions, including angiogenesis, vasculogenesis and inosculation.

OBJECTIVE AND RATIONALE

In this review, we provide an overview of the basic mechanisms of vascularization in endometriosis and give special emphasis on their future clinical implications in the diagnosis and therapy of the disease.

SEARCH METHODS

Literature searches were performed in PubMed for English articles with the key words 'endometriosis', 'endometriotic lesions', 'angiogenesis', 'vascularization', 'vasculogenesis', 'endothelial progenitor cells' and 'inosculation'. The searches included both animal and human studies. No restriction was set for the publication date.

OUTCOMES

The engraftment of endometriotic lesions is typically associated with angiogenesis, i.e. the formation of new blood vessels from pre-existing ones. This angiogenic process underlies the complex regulation by angiogenic growth factors and hormones, which activate intracellular pathways and associated signaling molecules. In addition, circulating endothelial progenitor cells (EPCs) are mobilized from the bone marrow and recruited into endometriotic lesions, where they are incorporated into the endothelium of newly developing microvessels, referred to as vasculogenesis. Finally, preformed microvessels in shed endometrial fragments inosculate with the surrounding host microvasculature, resulting in a rapid blood supply to the ectopic tissue. These vascularization modes offer different possibilities for the establishment of novel diagnostic and therapeutic approaches. Angiogenic growth factors and EPCs may serve as biomarkers for the diagnosis and classification of endometriosis. Blood vessel formation and mature microvessels in endometriotic lesions may be targeted by means of anti-angiogenic compounds and vascular-disrupting agents.

WIDER IMPLICATIONS

The establishment of vascularization-based approaches in the management of endometriosis still represents a major challenge. For diagnostic purposes, reliable angiogenic and vasculogenic biomarker panels exhibiting a high sensitivity and specificity must be identified. For therapeutic purposes, novel compounds selectively targeting the vascularization of endometriotic lesions without inducing severe side effects are required. Recent progress in the field of endometriosis research indicates that these goals may be achieved in the near future.

Redox regulation of microRNAs in endometriosis-associated pain

Endometriosis is a chronic, painful condition with unknown etiology. A differential expression of microRNAs in the endometriotic tissues from women with endometriosis with pain compared to those without suggested a plausible role for miRNA or epigenetic mechanisms in the etiology of endometriotic pain. The peritoneal milieu is involved in maintenance of endometriotic lesion and nociception. We recently showed the mechanistic role for oxidized-lipoproteins (ox-LDLs) present in peritoneal fluid (PF) in endometriosis and pain. We explored the possibility of ox-LDLs modulating the expression of miRNAs in a manner similar to PF from women with endometriosis. Expression levels of miRNAs and their predicted nociceptive and inflammatory targets were determined in PF and ox-LDL treated human endometrial cell-lines. Samples from IRB-approved and consented patients with and without endometriosis or pain were used. These were compared to endometrial cell-lines treated with various forms of oxidized-lipoproteins. RNA (including miRNAs) were isolated from treated endometrial cells and expression levels were determined using commercial miRNome arrays. Cell lysates were used in immunoblotting for inflammatory proteins using a protein array. Twenty miRNAs including isoforms of miR-29, miR-181 and let-7 were mutually differentially expressed in cells treated with PF from endometriosis patients with pain and those treated with ox-LDL components. The ox-LDLs and endo-PF treatment also produced significant overexpression of microRNA predicted target genes nerve growth factor, interleukin-6 and prostaglandin E synthase and overexpression of their downstream protein targets Mip1α and MCP1. This study showed similarities between miRNA regulation in PF from endometriotic women and ox-LDLs present in abundance in the PF of these women. Key miRNAs responsible for targeting nociceptive and inflammatory molecules were downregulated in the presence of ox-LDLs and endo-PF, thus playing a role in the etiology of endometriotic pain. These redox-sensitive miRNAs can be of potential use as targets in the treatment of endometriosis-associated pain.

MicroRNAs: Impaired vasculogenesis in metal induced teratogenicity

Certain metals have been known for their toxic effects on embryos and fetal development. The vasculature in early pregnancy is extremely dynamic and plays an important role in organogenesis. Nascent blood vessels in early embryonic life are considered to be a primary and delicate target for many teratogens since the nascent blood islands follow a tightly controlled program to form vascular plexus around and inside the embryo for resourcing optimal ingredients for its development. The state of the distribution of toxic metals, their transport mechanisms and the molecular events by which they notch extra-embryonic and embryonic vasculatures are illustrated. In addition, pharmacological aspects of toxic metal induced teratogenicity have also been portrayed. The work reviewed state of the current knowledge of specific role of microRNAs (miRNAs) that are differentially expressed in response to toxic metals, and how they interfere with the vasculogenesis that manifests into embryonic anomalies.

MicroRNA expression profiling in endometriosis-associated infertility and its relationship with endometrial receptivity evaluated by ultrasound

OBJECTIVE

To investigate the microRNA expression profiling in endometriosis-associate infertility, and relationship between the microRNA expression and endometrial receptivity evaluated by ultrasound.

METHODS

First, miRNA expression profiling difference of ectopic endometrium between 8 endometriosis patients and 6 endometriosis-free patients were compared. Bioinformatics analyses detected 61 differentially expressed (DE) known miRNAs and 57 DE novel miRNAs. Next, other 24 patients were selected for checking the microRNAs in differential expression by RT-PCR. Among them, case and control groups include 14 endometriosis and 10 endometriosis-free infertility patients, respectively. Last, endometrial receptivity of other 20 endometriosis patients was evaluated by ultrasound. In this group of patients, 12 had high endometrial receptivity, in which infertility is caused by fallopian tube occlusion, and 8 had low endometrial receptivity. The study compared endometrial miRNAs expression between two groups, and also evaluated the relationship between the endometrial miRNAs expression and the endometrial receptivity.

RESULTS

First, study indicated that "proteinaceous extracellular matrix," "laminin binding" and "extracellular matrix binding" were enriched in 6 up-regulated miRNA targets, while "cell proliferation" was enriched in the 4 down-regulated miRNA targets. Second, 10 miRNAs in different expression (miR-1304- 3p, miR-544b, miR-3684, miR-494-5p, miR-4683, miR-6747-3p; miR-3935, miR-4427, miR-652-5p, miR-205-5p) were detected by RT-PCR, and the results showed statistically significant differences between 2 groups in all 10 miRNAs. Third, the expression levels of miR-1304-3p, miR-494-5p, and miR-4427 were different between the two groups with different endometrial receptivity. But for the miR-544b, there was no statistically significant difference between two groups.

CONCLUSIONS

The study provided a comprehensive understanding to the current knowledge in the field of miRNAs in endometriosis and the relationship between them and the endometrial receptivity. miRNAs could be used as diagnostic biomarkers and therapeutic agents for this disease. The combination of ultrasound and miRNAs detection could be a better choice for the diagnosis of infertility in the future.

Comprehensive study of angiogenic factors in women with endometriosis compared to women without endometriosis

OBJECTIVE

Endometriosis is a benign gynaecological disease, affecting women during their reproductive years. Angiogenesis represents a crucial step in the pathogenesis of endometriosis, because endometriotic lesions require neovascularization. In this study several angiogenesis-related genes have been studied in the context of endometriosis. Some of the analyzed angiogenic factors as well as their interactions were studied the first time regarding a possible association with endometriosis.

STUDY DESIGN

This case-control study consisted of 205 biopsies of 114 patients comprising 61 endometriosis patients and 53 control patients. Among them in 29 cases paired samples were obtained. VEGFA, VEGFR2, HIF1A, HGF, NRP1, PDGFB, FGF18, TNFα, TGFB2, EPHB4, EPO and ANG mRNA expression was analyzed by qRT-PCR in ectopic tissue samples, in eutopic endometrium of women with and without endometriosis, and in unaffected peritoneum of women with and without endometriosis.

RESULTS

VEGFR2, HIF1A, HGF, PDGFB, NRP1 and EPHB4 are overexpressed in ectopic lesions compared to eutopic tissues. VEGFR2, HGF, PDGFB, NRP1, and EPHB4 showed highest mRNA levels in peritoneal implants, in contrast HIF1A showed the highest expression in ovarian endometriomas. Correlation analyses of angiogenic factors in ectopic lesions revealed the strongest associations between VEGFR2, PDGFB, and EPHB4. We further showed a significant upregulation of VEGFR2, HIF1A and EPHB4 in eutopic endometrium of women with endometriosis compared to that of controls and a trend towards upregulation of HGF. Additionally, a significant downregulation for HIF1A, HGF and EPHB4 was observed in unaffected peritoneal tissues of women with endometriosis compared to controls.

CONCLUSION

We identified new genes (EPHB4 and NRP1) that may contribute to angiogenesis in endometriosis beside known factors (VEGFA, VEGFR2, HIF1A, HGF, and PDGFB). Correlation studies revealed the putative importance of EBHB4 in association with endometriosis. Our analyses support preliminary reports that angiogenic factors seem to be differently expressed in peritoneal implants, ovarian endometriomas and deep infiltrating endometriosis. Our observation that angiogenic factors are differently expressed in the unaffected peritoneum of women with endometriosis compared to women without endometriosis underlines the importance of the peritoneum in the establishment of endometriosis.

miRNAs Regulation and Its Role as Biomarkers in Endometriosis

MicroRNAs (miRNAs) are small non-coding RNAs (18-22 nt) that function as modulators of gene expression. Since their discovery in 1993 in C. elegans, our knowledge about their biogenesis, function, and mechanism of action has increased enormously, especially in recent years, with the development of deep-sequencing technologies. New biogenesis pathways and sources of miRNAs are changing our concept about these molecules. The study of the miRNA contribution to pathological states is a field of great interest in research. Different groups have reported the implication of miRNAs in pathologies such as cancer, diabetes, cardiovascular, and gynecological diseases. It is also well-known that miRNAs are present in biofluids (plasma, serum, urine, semen, and menstrual blood) and have been proposed as ideal candidates as disease biomarkers. The goal of this review is to highlight the current knowledge in the field of miRNAs with a special emphasis to their role in endometriosis and the newest investigations addressing the use of miRNAs as biomarkers for this gynecological disease.

Altered expression of microRNA-451 in eutopic endometrium of baboons (Papio anubis) with endometriosis

STUDY QUESTION

Are microRNAs (miRs) altered in the eutopic endometrium (EuE) of baboons following the induction of endometriosis?

SUMMARY ANSWER

Induction of endometriosis causes significant changes in the expression of eight miRs, including miR-451, in the baboon endometrium as early as 3 months following induction of the disease.

WHAT IS KNOWN ALREADY

Endometriosis is one of the most common gynecological disorders and causes chronic pelvic pain and infertility in women of reproductive age. Altered expression of miRs has been reported in women and has been suggested to play an important role in the pathophysiology of several gynecological disorders including endometriosis.

STUDY DESIGN, SIZE, DURATION

EuE was obtained from the same group of baboons before and 3 months after the induction of endometriosis. The altered expression of miR-451 was validated in the eutopic and ectopic endometrium of additional baboons between 3 and 15 months following disease induction. Timed endometrial biopsies from women with and without endometriosis were also used to validate the expression of miR-451.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Total RNA was extracted from EuE samples before and after the induction of endometriosis, and miRNA expression was analyzed using a 8 × 15 K miR microarray. Microarray signal data were preprocessed by AgiMiRna software, and an empirical Bayes model was used to estimate the changes. The present study focused on quantitative RT-PCR validation of the microarray data, specifically on miR-451 and its target genes in both baboons (n = 3) and women [control (n = 7) and endometriosis (n = 19)]. Descriptive and correlative analysis of miR-451 and target gene expression was conducted using in situ hybridization and immunohistochemistry, while functional analysis utilized an in vitro 3' untranslated region (UTR) luciferase assay and overexpression of miR-451 in human endometrial and endometriotic cell lines.

MAIN RESULTS AND THE ROLE OF CHANCE

Induction of endometriosis results in the altered expression of miR-451, -141, -29c, -21, -424, -19b, -200a and -181a in the baboon endometrium. In the baboon, induction of endometriosis significantly decreased the expression of miR-451 at 3 months (P < 0.001), which was also associated with increased expression of its target gene YWHAZ (14.3.3ζ). A similar significant (P < 0.0001) decrease in miR-451 expression was observed in women with endometriosis. The 3' UTR luciferase assay confirmed the regulation of YWHAZ expression by miR-451. Furthermore, overexpression of miR-451 in 12Z cells (immortalized human endometriotic epithelial cell line) led to the decreased expression of its target YWHAZ and this was correlated with decreased cell proliferation.

LIMITATIONS, REASONS FOR CAUTION

The study focused only on miR-451 and one of its targets, namely YWHAZ. A single miR could target number of genes and a single gene could also be regulated by number of miRs; hence, it is possible that other miRs and their regulated genes may contribute to the pathophysiology of endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that the presence of ectopic lesions in baboon causes changes in EuE miR expression as early as 3 months postinduction of the disease, and some of these changes may persist throughout the course of the disease. We propose that the marked down-regulation of miR-451 in both baboons and women with endometriosis increases the expression of multiple target genes. Increased expression of one of the target genes, YWHAZ, increases proliferation, likely contributing to the pathophysiology of the disease.