The molecular basis for implantation failure in endometriosis: on the road to discovery

Long noncoding RNA BMPR1B-AS1 stability regulated by IGF2BP2 affects the decidualization in endometriosis patients through the SMAD1/5/9 pathway

Endometriosis (EMs)-related infertility commonly has decreased endometrial receptivity and normal decidualization is the basis for establishing and maintaining endometrial receptivity. However, the potential molecular regulatory mechanisms of impaired endometrial decidualization in patients with EMs have not been fully clarified. We confirmed the existence of reduced endometrial receptivity in patients with EMs by scanning electron microscopy and quantitative real-time PCR. Here we identified an lncRNA, named BMPR1B-AS1, which is significantly downregulated in eutopic endometrium in EMs patients and plays an essential role in decidual formation. Furthermore, RNA pull-down, mass spectrometry, RNA immunoprecipitation, and rescue analyses revealed that BMPR1B-AS1 positively regulates decidual formation through interaction with the RNA-binding protein insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). Downregulation of IGF2BP2 led to a decreased stability of BMPR1B-AS1 and inhibition of activation of the SMAD1/5/9 pathway, an inhibitory effect which diminished decidualization in human endometrial stromal cells (hESCs) decidualization. In conclusion, our identified a novel regulatory mechanism in which the IGF2BP2-BMPR1B-AS1-SMAD1/5/9 axis plays a key role in the regulation of decidualization, providing insights into the potential link between abnormal decidualization and infertility in patients with EMs, which will be of clinical significance for the management and treatment of infertility in patients with EMs.

[Fertility, endometriosis and pregnancy planning]

Endometriosis does not always mean infertility, and treatment depends on the couple's prognosis and their wishes. Spontaneous pregnancy remains possible, all the more so if endometriosis treatment is initiated early in the patient's life. Surgery and assisted reproduction are available to couples who wish to have a child.

Fertility Outcomes after Surgical Management of Colorectal Endometriosis: A Single-center Retrospective Study

STUDY OBJECTIVE

To assess the pregnancy rate after surgery for colorectal endometriosis.

DESIGN

A retrospective, single-center study performed from January 2014 to December 2019.

SETTING

A university tertiary referral center.

PATIENTS

Patients with the intention to get pregnant younger than the age of 43 years, with or without a history of infertility and who were surgically managed for colorectal endometriosis.

INTERVENTIONS

Complete excision of deeply infiltrating endometriosis.

MEASUREMENTS AND MAIN RESULTS

The postoperative pregnancy rate was assessed. Seventy-seven patients had surgery; their mean age was 32.5 ± 4.4 years. Preoperative documented infertility was present in 77.9% of patients (n = 60). The mean length of history of infertility was 36.2 ± 24.9 months. The procedure was performed by laparoscopic surgery in 92.2% of patients (n = 71). Nonconservative, conservative, and mixed treatment were performed in 66.2% (n = 51), 29.9% (n = 23), and 3.9% of patients (n = 3), respectively. According to the Clavien-Dindo classification, the 3B complication rate was 6.5% (n = 5). The mean follow-up was 46.7 ± 20.6 months. Clinical pregnancies were defined by the presence of intrauterine pregnancy with an embryo with cardiac activity. The postoperative pregnancy rate was 62.3% (n = 48), and 54.2% (n = 26) were spontaneous. The mean number of pregnancies was 1.2 ± 0.4 per patient. In addition, 18.7% of patients (n = 9) got pregnant twice. The mean time from surgery to pregnancy was 13.8 ± 13.1 months. The live birth rate was 89.1% (n = 41). There were no significant differences concerning the prognostic criteria reported in the literature (antimüllerian hormone level, age, presence of adenomyosis). There were no predictive criteria for live births.

CONCLUSION

According to this study, surgery for colorectal endometriosis results in a high postoperative pregnancy rate. Studies with a high level of evidence are needed to determine good candidates for this type of surgery.

The mid-secretory endometrial transcriptomic landscape in endometriosis: a meta-analysis

STUDY QUESTION

Do women with endometriosis have a different endometrial gene expression profile at the time of embryo implantation than women without endometriosis?

SUMMARY ANSWER

The endometrial gene expression profile of women with endometriosis differs from that of women without endometriosis at the mid-secretory phase, although the differences are small.

WHAT IS KNOWN ALREADY

About 50% of women with endometriosis suffer infertility. Several molecular studies have suggested impaired endometrial receptivity in women with endometriosis, while others have detected no dysregulation of endometrial receptivity. Nevertheless, the previous endometrial transcriptome studies comparing women with and without endometriosis have been performed in small sample size with limited statistical power. We set out to systematically search and compile data of endometrial gene expression signatures at the receptive phase in women with endometriosis versus control women. Based on the obtained data, we conducted a meta-analysis of differentially expressed genes in order to raise the power of the analysis for identifying the molecular profiles of receptive phase endometria in endometriosis.

STUDY DESIGN, SIZE, DURATION

A systematic literature search was conducted up to February 2022 following PRISMA criteria and included PubMed, Cochrane and Web of Science databases. For the systematic search, the term ‘endometriosis’ was paired with the terms ‘transcriptomics’, ‘transcriptome’, ‘gene expression’, ‘RNA-seq’, ‘sequencing’ and ‘array’, by using the Boolean operator ‘AND’ to connect them. Articles written in English were screened and interrogated for data extraction.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A meta-analysis was performed on the selected studies to extract the differentially expressed genes described at the mid-secretory phase in women with endometriosis versus women without endometriosis in natural cycles, using the robust rank aggregation method. In total, transcriptome data of 125 women (78 patients and 47 controls) were meta-analysed, with a special focus on endometrial receptivity-specific genes based on commercial endometrial receptivity tests.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 8 studies were eligible for the quantitative meta-analysis, gathering transcriptome data from the mid-secretory phase endometria of 125 women. A total of 7779 differentially expressed transcripts between the study groups were retrieved (3496 up-regulated and 4283 down-regulated) and were meta-analysed. After stringent multiple correction, there was no differential expression of any single molecule in the endometrium of women with endometriosis versus controls, while enrichment analysis detected that the pathways of chemotaxis and locomotion are dysregulated in endometriosis. Further analysis of endometrial receptivity-specific genes highlighted dysregulation of C4BPA, MAOA and PAEP and enrichment of immune and defence pathways in women with endometriosis.

LIMITATIONS, REASONS FOR CAUTION

Most of the studies included into the meta-analysis were relatively small and had different study designs, which might have contributed to a bias.

WIDER IMPLICATIONS OF THE FINDINGS

The current meta-analysis supports the hypothesis that endometrial receptivity is altered in women with endometriosis, although the changes are small. The molecules and pathways identified could serve as future biomarkers and therapeutical targets in detecting and treating endometriosis-associated infertility.

STUDY FUNDING/COMPETING INTEREST(S)

The authors declare no competing interests. This work was supported by the Spanish Ministry of Education, Culture and Sport [grant FPU15/01193] and the Margarita Salas program for the Requalification of the Spanish University system [grant UJAR01MS]; Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and European Regional Development Fund (FEDER): grants RYC-2016-21199 and ENDORE SAF2017-87526-R; Programa Operativo FEDER Andalucía (B-CTS-500-UGR18; A-CTS-614-UGR20); the Junta de Andalucía [BIO-302; and PAIDI P20_00158]; the University of Jaén [PAIUJA-EI_CTS02_2017]; the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES), and by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades and European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR; the Estonian Research Council (grant PRG1076); Horizon 2020 innovation (ERIN, grant no. EU952516) of the European Commission and Enterprise Estonia (grant EU48695).

TRIAL REGISTRATION NUMBER

The systematic review was registered at PROSPERO (identifier: CRD42020122054).

Circulating and Endometrial Regulatory T Cell and Related Populations in Endometriosis and Infertility: Endometriosis Is Associated with Blunting of Endometrial Cyclical Effects and Reduced Proportions in Moderate-Severe Disease

Evidence to date supports regulatory T cell (Treg) alterations in endometriosis; however, the relationship remains unclear, and Tregs have not previously been investigated with respect to infertility in endometriosis. This prospective cross-sectional cohort study details circulating and endometrial tissue-specific disturbances in Tregs and broader gated populations in women of reproductive age with and without endometriosis (n = 57 and 29, respectively) using flow cytometry and immunohistochemistry. Participants were characterised by menstrual cycle phase, r-ASRM endometriosis disease stage and fertility status.In the endometrium of women with endometriosis, endometrial Tregs and CD4+ lymphocyte proportions did not change between the proliferative and secretory phases, while in women without the disease, they significantly decreased (p = 0.045 and p = 0.039, respectively). In women with endometriosis, endometrial Tregs were lower than in women without endometriosis overall (p = 0.050 as a proportion of all CD45+ immune cells). We have shown for the first time that proportions of CD4+ lymphocytes (p = 0.021), overall lymphocytes (p = 0.034) and non-granulocytes (p = 0.027) were significantly decreased in the endometrium of women with moderate-severe (r-ASRM stages III and IV) compared to minimal-mild (r-ASRM stages I and II) endometriosis. During the secretory phase, circulating Treg proportions were significantly increased in infertile compared to fertile women (p = 0.049). This study confirms differences in endometrial Tregs in women with endometriosis, with blunting of normal menstrual cyclical variations, reduced proportions during the proliferative phase and disease stage-specific relationships.

Screening of Variants in the Transcript Profile of Eutopic Endometrium from Infertile Women with Endometriosis during the Implantation Window

OBJECTIVE

 Abnormalities in the eutopic endometrium of women with endometriosis may be related to disease-associated infertility. Although previous RNA-sequencing analysis did not show differential expression in endometrial transcripts of endometriosis patients, other molecular alterations could impact protein synthesis and endometrial receptivity. Our aim was to screen for functional mutations in the transcripts of eutopic endometria of infertile women with endometriosis and controls during the implantation window.

METHODS

 Data from RNA-Sequencing of endometrial biopsies collected during the implantation window from 17 patients (6 infertile women with endometriosis, 6 infertile controls, 5 fertile controls) were analyzed for variant discovery and identification of functional mutations. A targeted study of the alterations found was performed to understand the data into disease's context.

RESULTS

 None of the variants identified was common to other samples within the same group, and no mutation was repeated among patients with endometriosis, infertile and fertile controls. In the endometriosis group, nine predicted deleterious mutations were identified, but only one was previously associated to a clinical condition with no endometrial impact. When crossing the mutated genes with the descriptors endometriosis and/or endometrium, the gene CMKLR1 was associated either with inflammatory response in endometriosis or with endometrial processes for pregnancy establishment.

CONCLUSION

 Despite no pattern of mutation having been found, we ponder the small sample size and the analysis on RNA-sequencing data. Considering the purpose of the study of screening and the importance of the CMKLR1 gene on endometrial modulation, it could be a candidate gene for powered further studies evaluating mutations in eutopic endometria from endometriosis patients.

The modulating effects of vitamin D on the activity of β-catenin in the endometrium of women with endometriosis: a randomized exploratory trial

AIMS

The aim of this prospective study was to investigate the effects of vitamin D on the expression and activity of β-catenin, as the key molecule of the Wnt/β-catenin signaling pathway, in endometriosis women.

MATERIALS AND METHODS

Thirty four infertile women with stage III or IV endometriosis were randomly divided to two groups. The control group received the routine treatment and the treatment group, beside the routine protocol, received 50000 IU vitamin D weekly for 12-14 weeks. Blood and endometrial tissue were collected from both groups before and after the intervention. Protein and Gene expression levels of β-catenin were assessed by Western blotting and Real-Time PCR, respectively.

RESULTS

Compared to before intervention, the expression of active form of β-catenin reduced significantly within treatment group (p = .000), in addition, the difference between control and treatment groups (p = .012) was significant after intervention, too. Also, the ratio of active/total form of β-catenin protein expression was significantly decreased within the treatment group at the end of intervention period (p = .000).

CONCLUSIONS

It seems vitamin D can change the activity of β-catenin protein in the endometrial cells of endometriosis patients. Further studies on the therapeutic potential of vitamin D in modifying the β-catenin activity in endometriosis patients are warranted.

CLINICAL TRIAL REGISTRATION NUMBER

IRCT2015081823678N1.

TRIAL REGISTRATION DATE

29 September 2015.

Comprehensive analysis utilizing flow cytometry and immunohistochemistry reveals inflammatory changes in local endometrial and systemic dendritic cell populations in endometriosis

STUDY QUESTION

What are the detailed endometrial tissue specific and systemic dendritic cell (DC) subset disturbances in endometriosis?

SUMMARY ANSWER

This study confirms myeloid DC (mDC) and plasmacytoid DC subsets are readily identified in endometrial tissue and shows both endometrial and circulating differences in DC populations in women with endometriosis, with disease stage-specific relationships evident locally in the endometrium.

WHAT IS KNOWN ALREADY

Immune factors in the uterus, the peritoneal environment and systemically are implicated in the pathogenesis and progression of both endometriosis and infertility. While there is some evidence that endometrial DC populations are altered in endometriosis, DC subset involvement in both the endometrium and peripheral blood have not been comprehensively investigated so the functional consequences have been unknown.

STUDY DESIGN, SIZE, DURATION

This prospective cross-sectional cohort study compares circulating and endometrial DC populations in women of reproductive age with and without endometriosis (n = 55 and 30, respectively), wherein each participant donated samples at a single time point. Study participants were surveyed for menstrual cycle phase, American Society for Reproductive Medicine (ASRM) endometriosis disease stage and fertility status (where possible).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Peripheral blood samples were processed into mononuclear cells for analysis by flow cytometry, and endometrial samples were analysed by immunohistochemistry and dissociated into single-cell suspension for flow cytometry.

MAIN RESULTS AND THE ROLE OF CHANCE

In the endometrium of women with endometriosis, IRF-8+ cells were increased during the proliferative phase (P = 0.014), total DC proportions increased in the secretory phase (P = 0.038) and normal menstrual cyclical fluctuations in CD1c+ and IRF-8+ cells blunted; indicative of a consistently inflammatory tissue environment. The inflammatory changes in CD141+ and IRF-8+ populations in the endometrium of women with endometriosis were particularly evident in more advanced ASRM stages of the disease (respective P-values 0.032 and 0.045). There was also evidence of systemic inflammation in women with endometriosis, with increased circulating CD141+ mDC proportions (overall P = 0.040, secretory phase P = 0.021).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

As is common in this type of study, one of the main limitations was small sample numbers, particularly during the menstrual phase of the cycle.

WIDER IMPLICATIONS OF THE FINDINGS

Further phenotyping of local and circulating immune cell subtypes is critical to improving understanding of endometriosis pathogenesis and immune contributions to infertility associated with the disease.

STUDY FUNDING/COMPETING INTEREST(S)

This research was financially supported by a Sydney Medical School and Balnaves Foundation Kick Start Grant and the Department of Obstetrics, Gynaecology and Neonatology at The University of Sydney. The authors have no conflicts of interest to declare.

Is the profile of transcripts altered in the eutopic endometrium of infertile women with endometriosis during the implantation window?

STUDY QUESTION

Compared to healthy women, is the profile of transcripts altered in the eutopic endometrium of infertile women with endometriosis during the implantation window (IW)?

SUMMARY ANSWER

The eutopic endometrium of infertile women with endometriosis seems to be transcriptionally similar to the endometrium of infertile and fertile controls (FC) during the IW.

WHAT IS KNOWN ALREADY

Endometriosis is a disease related to infertility; nevertheless, little is known regarding the ethiopathogenic mechanisms underlying this association. Some studies evaluating the eutopic endometrium of endometriosis patients suggest there is an endometrial factor involved in the disease-related infertility. However, no study to date has evaluated the endometrial transcriptome (mRNA and miRNA) by next generation sequencing (NGS), comparing patients with endometriosis as the exclusive infertility factor (END) to infertile controls (IC; male and/or tubal factor) and FC.

STUDY DESIGN, SIZE, DURATION

From November 2011 to November 2015 we performed a case-control study, where 17 endometrial samples (six END, six IC, five FC) were collected during the IW.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All endometrial samples had the RNA extracted. Two libraries were prepared for each one (mRNA and miRNA), which were sequenced, respectively, at HISEQ 2500 (RNA-Seq) and MiSeq System (miRNA-Seq), Illumina. The normalization and differential expression were conducted in statistical R environment using DESeq2 package. qPCR was used for data validation, which were analyzed by Kruskal–Wallis test and Dunn posttest (P < 0.05).

MAIN RESULTS AND THE ROLE OF CHANCE

RNA-Seq revealed no differentially expressed genes (DEG) among END, IC and FC groups. miRNA-Seq revealed three differentially expressed miRNAs (has-27a-5p, has-miR-150-5p, has-miR-504-5p) in END group compared to FC group. However, none of the miRNAs identified in the sequencing was validated by qPCR.

LIMITATIONS, REASONS FOR CAUTION

The main limitation of this study was the small sample size evaluated as a result of the restrictive eligibility criteria adopted, limiting the generalization of the results obtained here. On the other hand, strict eligibility criteria, which eliminated factors potentially related to impaired endometrial receptivity, were required to increase the study’s internal validity.

WIDER IMPLICATIONS OF THE FINDINGS

This study brings new perspectives on the mechanisms involved in endometriosis-related infertility. The present findings suggest the eutopic endometrium of infertile women with endometriosis, without considering the disease’s stage, is transcriptionally similar to controls during the IW, possibly not affecting receptivity. Further studies are needed to evaluate endometrial alterations related to endometriosis’ stages.

STUDY FUNDING/COMPETING INTEREST(S)

This study received financial support from the Sao Paulo Research Foundation (FAPESP—Fundação de Amparo à Pesquisa do Estado de São Paulo; fellowship 2011/17614–6, MGB) and from the National Council for Scientific and Technological Development (CNPq—Conselho Nacional de Desenvolvimento Científico e Tecnológico; INCT—National Institutes of Hormones and Woman’s Health, grant 471 943/2012-6, 309 397/2016-2, PAN; fellowship 140 137/2015-7, MGB). The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Ethiopathogenic mechanisms of endometriosis-related infertility

Endometriosis is a highly prevalent disease among women of reproductive age and is frequently associated to infertility. However, the mechanisms underlying endometriosis-related infertility are still not completely known. Several studies have been conducted in order to elucidate this question. Besides anatomical changes that may impair gametes and embryo transport along the tubes; a smaller ovarian reserve due to advanced endometriosis and endometriomas; and a dysregulated hypothalamic-pituitary-ovarian axis, there are pieces of evidence suggesting that the peritoneal ectopic endometrial foci may induce a local inflammatory response, with the recruitment of macrophages, cytokine release, and reactive oxygen species generation, leading to a pro-oxidant peritoneal microenvironment. These alterations may be systemically reflected and also affect the follicular microenvironment. A harmful follicular fluid may disrupt cumulus cells functions and, consequently, compromise oocyte competence. There is also evidence suggesting that the peritoneal fluid of women with endometriosis may alter sperm function. Reduced endometrial receptivity is also pointed as a possible mechanism involved in endometriosis-related infertility, which needs further investigation.

Molecular and Cellular Pathogenesis of Endometriosis

BACKGROUND

A substantial body of studies supports the view that molecular and cellular features of endometriotic lesions differ from those of eutopic endometrium. Apart from that, evidence exists that the eutopic endometrium from pa-tients with endometriosis differs from that of females without endometriosis.

OBJECTIVE

Aberrant expression profiles include a number of non-steroid signaling pathways that exert their putative influ-ence on the pathogenesis of endometriosis at least in part via crosstalk(s) with estrogen-mediated mechanisms. A rational to focus research on non-steroid signal pathways is that they might be remunerative targets for the development and selection of novel therapeutics to treat endometriosis possibly without affecting estrogen levels.

RESULTS AND CONCLUSION

In this article, we describe molecular and cellular features of endometriotic lesions and focus on the canonical WNT/β-signaling pathway, a key regulatory system in biology (including stem cell homeostasis) and often in pathophysiological conditions such as endometriosis. Recently emerged novel biological concepts in signal transduction and gene regulation like exosomes and microRNAs are discussed in their putative role in the pathogenesis of endometriosis.

Physiological and pathological implications of retinoid action in the endometrium

Retinol (vitamin A) and its derivatives, collectively known as retinoids, are required for maintaining vision, immunity, barrier function, reproduction, embryogenesis and cell proliferation and differentiation. Despite the fact that most events in the endometrium are predominantly regulated by steroid hormones (estrogens and progesterone), accumulating evidence shows that retinoid signaling is also involved in the development and maintenance of the endometrium, stromal decidualization and blastocyst implantation. Moreover, aberrant retinoid metabolism seems to be a critical factor in the development of endometriosis, a common gynecological disease, which affects up to 10% of reproductive age women and is characterized by the ectopic localization of endometrial-like tissue in the pelvic cavity. This review summarizes recent advances in research on the mechanisms and molecular actions of retinoids in normal endometrial development and physiological function. The potential roles of abnormal retinoid signaling in endometriosis are also discussed. The objectives are to identify limitations in current knowledge regarding the molecular actions of retinoids in endometrial biology and to stimulate new investigations toward the development potential therapeutics to ameliorate or prevent endometriosis symptoms.

Calpain7 impairs embryo implantation by downregulating β3-integrin expression via degradation of HOXA10

Endometriosis (ENDO) is a common gynecological disease that causes infertility in many women. Previous studies noted that the dysregulation of Homeo box A10 (HOXA10) in the endometrium of women with ENDO was involved in the failure of embryo implantation. However, the mechanism by which HOXA10 expression is reduced in women with ENDO is still poorly understood. Here we found that a member of the calcium (Ca²⁺)-dependent cysteine protease family calpain7 (CAPN7), negatively correlated with HOXA10, was highly expressed in the endometrium of infertile women with ENDO and was significantly downregulated during the window of embryo implantation in mice. Overexpression of CAPN7 in Ishikawa cells or in the uterus of mice inhibited embryo implantation in vitro and in vivo. In the current study, we identified a sequence rich in proline, glutamic acid, serine, and threonine (PEST sequence) that enhanced the Ca²⁺-dependent degradation of HOXA10 by CAPN7. Furthermore, the interaction between HOXA10 and CAPN7 repressed the transcriptional activity and protein stability of HOXA10. In contrast, the administration of the calpain inhibitor ALLN reversed the CAPN7-induced HOXA10 degradation. Moreover, truncation of the PEST motif in HOXA10 abolished its CAPN7-dependent proteolysis. These studies reveal a novel pattern of HOXA10 regulation via PEST sequence-mediated calpain proteolysis that was demonstrated to be reversed by a calpain inhibitor. Thus, the inhibition of CAPN7-induced HOXA10 degradation may represent a novel potential therapeutic method to improve impaired embryo implantation in women with ENDO.

The Wnt/β-catenin signaling in endometriosis, the expression of total and active forms of β-catenin, total and inactive forms of glycogen synthase kinase-3β, WNT7a and DICKKOPF-1

OBJECTIVES

The cyclical changes in proliferation and differentiation of endometrial cells are regulated by estrogen and progesterone via modulating Wnt/β-catenin signaling. Imbalance in the expression of estrogen and progesterone receptors causes progesterone resistance in endometriosis patients. The aim of this study was to investigate the expression of some main components of Wnt/β-catenin signaling including WNT7a, DKK-1, β-catenin, and GSK-3β in eutopic endometrium and peritoneal endometriotic lesions of endometriosis patients compared to healthy endometrium in the mid-secretory phase of menstrual cycle.

STUDY DESIGN

This prospective study was performed, during a 12 months period from December 2015 to November 2016, on healthy women as the control group (n=14) and endometriosis patients (n=34). We used real-time polymerase chain reaction and Western blot techniques.

RESULTS

Protein and mRNA expression of DKK-1 were significantly down-regulated in both endometriotic lesions and eutopic endometrium of endometriosis group. We also demonstrated that the expression of non-phosphorylated β-catenin (active form) and phosphorylated GSK-3β (inactive form) were up-regulated in endometriosis patients. The mRNA levels of β-catenin, GSK-3β, and WNT7a, as well as the protein levels of total β-catenin, total GSK-3β, and WNT7a in endometriosis group, were not significantly different with those in control group. The patterns of mRNA and protein expression of all interested factors in the lesions were similar to those in the eutopic endometrium of same patients.

CONCLUSIONS

It seems that the aberrant activation of Wnt/β-catenin signaling in the secretory phase of the menstrual cycle in endometriosis has two essential elements: excessive inactivation of GSK-3β and suppression of the expression of Wnt signaling inhibitor DKK-1. Interventions in this signaling pathway may allow for the exploration of potential new targets for the control of development and progression of endometriosis.

[Bowel endometriosis and infertility: Do we need to operate?]

Endometriosis is a benign chronic inflammatory disease, whose pathogenesis is still unclear. Endometriosis is responsible for infertility and/or pelvic pain. One of the most important features of the disease is the heterogeneity (clinical and anatomical: superficial peritoneal, ovarian and/or deep infiltrating lesions). Bowel involvement constitutes one particularly severe form of the disease, affecting 8-12% of women with deep endometriosis. In case of associated infertility, bowel endometriosis constitutes a real therapeutic challenge for gynecologists. Indeed, while complete resection of the lesions alleviates pain and seems to improve spontaneous fertility, surgery remains technically challenging and may cause severe complications. Reverting to assisted Reproductive Technology (ART) is another valuable therapeutic option regarding pregnancy rates. Thus, the choice between surgical management or ART is still debated. Benefits and risks of these two options should be considered and discussed before planning treatment. In the present study, we aimed to answer the question: Bowel endometriosis and infertility: do we need to operate?

Altered retinoid signaling compromises decidualization in human endometriotic stromal cells

Decidualization alters multiple molecular pathways in endometrium to permit successful embryo implantation. We have reported that paracrine factors, including retinoids, secreted from progesterone-treated endometrial stromal cells, act on nearby epithelial cells to induce the estradiol metabolizing enzyme HSD17B2. This same induction is not seen in endometriotic stromal cells. We have also shown significant differences in retinoid uptake, metabolism and action in endometriotic tissue and stromal cells compared to normal endometrium. Here, we characterize retinoid signaling during decidualization in these cells. Endometrial and endometriotic cells were isolated, cultured and incubated and decidualized. Genes involved in retinoid metabolism and trafficking were examined using RT-PCR and Western blotting. Prolactin, a decidualization marker, was also examined. We found that both endometrial and endometriotic stromal cells express all intracellular proteins involved in retinoid uptake and metabolism. Decidualization significantly reduced the expression of the genes responsible for retinoid uptake and shuttling to the nucleus. However, expression of CRBP1, an intracellular carrier protein for retinol, increased, as did RBP4, a carrier protein for retinol in the blood, which can function in a paracrine manner. Secreted RBP4 was detected in the media from decidualized endometrial cells but not from endometriotic cells. We believe that retinoid trafficking in endometrial stromal cells during decidualization may shift to favor paracrine rather than intracrine signaling, which may enhance signaling to the adjacent epithelium. There is blunting of this signaling in endometriotic cells. These alterations in retinoid signaling may help explain the decidualization defects and deficient estradiol inactivation (via HSD17B2) seen in endometriosis.

miR-196a overexpression activates the MEK/ERK signal and represses the progesterone receptor and decidualization in eutopic endometrium from women with endometriosis

STUDY QUESTION

Do microRNAs (miRNAs) contribute to aberrant progesterone receptor (PGR) expression in the eutopic endometrium of women with endometriosis? SUMMARY ANSWER: miR-196a upregulates MEK/ERK signalling, mediating a downregulation of PGR expression in the eutopic endometrium of women with minimal or mild endometriosis.

WHAT IS KNOWN ALREADY

Implantation failure is strongly suggested as an underlying cause for the observed infertility in minimal or mild endometriosis. Progesterone resistance, which is mainly caused by aberrantly expressed progesterone receptor in the eutopic endometrium, is considered as a key factor of decreased endometrial receptivity; thus far, epigenetics, but not miRNA, has been shown to affect PGR expression in the endometrium.

STUDY DESIGN SIZE, DURATION

Microarray analysis was used to analyse the eutopic endometrium. The differential expression of miR-196a was validated. Bioinformatics analysis predicted that miR-196a targets the 3'-untranslated region (UTR) of the PGR. The relationship between the miR-196a level and PGR expression was studied and the role of the MEK/ERK signal pathway was investigated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Total RNA was extracted from eutopic endometrium samples in three infertile women with mild/minimal endometriosis and three disease-free control subjects. The miRNA and mRNA expression levels were analysed by microarray analysis. The miR-196a expression was validated by qRT-PCR [endometriosis (n = 22) and control (n = 20)], while functional analysis utilised in vitro transfection of endometrial stromal cells (ESCs), induction of decidualization of ESCs, and luciferase reporter assays in 293 T cell lines.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 66 dysregulated miRNAs and 357 dysregulated mRNAs were screened by microarray analysis. miR-196a and P-MEK/P-ERK were both found to be significantly upregulated in the eutopic endometrium in patients with mild/minimal endometriosis. PGR and PGR-B mRNA were inhibited by miR-196a overexpression and upregulated by miR-196a inhibition. Luciferase reporter failed to confirm the target regulation of miR-196a on PGR. Transfection of ESCs with a miR-196a mimic led to an increase in the P-MEK/P-ERK protein levels, decrease in the PGR protein levels, and atypical decidualization. Following miR-196a inhibition, the P-MEK/P-ERK protein was downregulated and the PGR protein was upregulated. Inhibition of P-MEK/P-ERK also increased PGR expression.

LARGE SCALE DATA

Data are presented in Supplementary Tables SI and SII.

LIMITATIONS REASONS FOR CAUTION

This study focused on the role of miR-196a, and therefore does not involve other miRNAs; hence, it is possible that other miRNAs may also be responsible for progestin resistance in endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our data revealed altered miRNA expression and activated MEK/ERK signalling in the eutopic endometrium in minimal or mild endometriosis. We showed that the miR-196a level is associated with reduced expression of PGR isoforms through MEK/ERK, suggesting that miR-196a and MEK/ERK are both potential biomarkers of endometriosis. These results provide a novel approach to target the mechanisms behind progesterone resistance in endometriosis.

STUDY FUNDING/COMPETING INTERESTS

This research was supported by the National Natural Science Foundation of China (No. 81370693). The authors have no conflicts of interest.

Oocyte competence in in vitro fertilization and intracytoplasmic sperm injection patients suffering from endometriosis and its possible association with subsequent treatment outcome: a matched case-control study

INTRODUCTION

Endometriosis affects up to 15% of women of reproductive age. There is an obvious lack of studies dealing with morphological parameters of oocyte morphology in endometriosis patients in assisted reproduction. One aim of the study is to describe oocyte morphology in patients undergoing intracytoplasmic sperm injection suffering from endometriosis. In addition, the impact of endometriosis on in vitro fertilization results is analyzed. Both in vitro fertilization and intracytoplasmic sperm injection patients are then matched with an endometriosis-free control group for highlighting the possible association of endometriosis with pregnancy outcome.

MATERIAL AND METHODS

Oocyte morphology of endometriosis patients was assessed in two groups. Both study group and control group consisted of 129 in vitro fertilization/intracytoplasmic sperm injection cycles each. Patients were matched according to anti-Müllerian hormone, female age, previous treatment cycles, and method of fertilization. Endometriosis was graded according to the revised American Society for Reproductive Medicine guidelines of 1997.

RESULTS

Patients with endometriosis had a significantly lower rate of mature oocytes (p < 0.03) and morphologically normal oocytes (p < 0.001). In particular, brownish oocytes (p < 0.009; stage I-IV) and the presence of refractile bodies (p < 0.001; stage IV) were found to be increased. Endometriosis stage IV was associated with significantly worse-quality oocytes than stages I-III (p < 0.01). Fertilization was significantly reduced in conventional in vitro fertilization but not in intracytoplasmic sperm injection (p < 0.03). This was due to lower fertilization rates in stage III-IV endometriosis compared with stage I-II (p < 0.04). No difference was observed with respect to rates of implantation, clinical pregnancy, miscarriage, live birth, and malformation.

CONCLUSIONS

Endometriosis patients, in particular those with severe endometriosis, present lower-quality oocytes. Once fertilized, no impairment of further preimplantation embryo development and pregnancy outcome right up to healthy live birth rate has to be expected.

Fenretinide: A Potential Treatment for Endometriosis

OBJECTIVE

Fenretinide is a synthetic retinoid analogue that promotes apoptosis but has decreased toxicity when compared to other retinoids. We have previously shown that retinoic acid (RA) production in endometriotic tissue is decreased, resulting in reduced estrogen metabolism and apoptotic resistance. We hypothesize fenretinide may induce apoptosis in endometriotic cells and tissues, thereby reducing disease burden.

MATERIALS AND METHODS

Primary endometriotic stromal cells were collected, isolated, cultured, and treated with fenretinide in doses from 0 to 20 µmol/L. Cell count, viability, and immunoblots were performed to examine apoptosis. Quantitative reverse transcription-polymerase chain reaction from endometriotic cells treated with fenretinide was used to examine expression of genes involved in RA signaling including stimulated by RA 6 (STRA6), cellular RA binding protein 2 (CRABP2), and fatty acid binding protein 5 (FABP5). Endometriotic tissue was xenografted subcutaneously into the flanks of mice which were treated with fenretinide for 2 weeks, after which the mice were killed and lesion volumes calculated. Statistical analysis was performed using t test and analysis of variance.

RESULTS

Treatment with fenretinide significantly decreased total cell count (doses 5-20 µL) and viability (doses 10-20 µmol/L). Fenretinide increased protein levels of the apoptotic marker poly (ADP ribose) polymerase (starting at 10 µmol/L) and decreased proliferation marker proliferating cell nuclear antigen (10 µmol/L, starting at 8-day treatment). Examination of genes involved in retinoid uptake and action showed that treatment induced STRA6 expression while expression of CRABP2 and FABP5 remained unchanged. Fenretinide also significantly decreased the endometriotic lesion xenograft volume.

CONCLUSIONS

Fenretinide increases STRA6 expression thereby potentially reversing the pathological loss of retinoid availability. Treatment with this compound induces apoptosis. In vivo treatments decrease lesion volume. Targeting the RA signaling pathway may be a promising novel treatment for women with endometriosis.

Laparoscopic endometrioma resection increases peri-implantation endometrial HOXA-10 and HOXA-11 mRNA expression

OBJECTIVE

To determine whether laparoscopic endometrioma resection alters peri-implantation endometrial HOXA-10, HOXA-11, LIF, ITGB3 and ITGAV mRNA expression.

DESIGN

Case-control study.

SETTING

Medical school.

PATIENT(S)

Twenty infertile patients with uni- or bilateral endometrioma, five infertile patients having nonendometriotic benign ovarian cyst, and five fertile control subjects.

INTERVENTION(S)

Mid-luteal-phase endometrial sampling was performed at the time of surgery. Second endometrial biopsies were obtained 3 months after laparoscopic endometrioma resection during the mid-luteal phase of the cycle.

MAIN OUTCOME MEASURE(S)

Endometrial HOXA-10, HOXA-11, LIF, ITGAV, and ITGB3 mRNA expressions were evaluated with the use of reverse-transcription polymerase chain reaction.

RESULT(S)

Significantly decreased endometrial ITGAV mRNA expression was noted in biopsies obtained from endometrioma and nonendometriotic cyst groups before surgery. Trends toward decreased endometrial HOXA-10, HOXA-11, LIF, and ITGB3 mRNA expressions were noted in the endometrioma and nonendometriotic cyst groups before surgery compared with the fertile subjects. However, the differences failed to show statistical significance. Compared with preoperative values, significantly increased HOXA-10 (12.1-fold change) and HOXA-11 (17.2-fold change) mRNA expressions were noted in endometrial biopsies obtained from subjects who were undergoing endometrioma surgery. Fold change in endometrial ITGAV mRNA after endometrioma surgery was found to be 30.1 and indicated a positive regulation. However, this fold increase was statistically insignificant. Expressions of these endometrial receptivity markers did not change significantly after surgical removal of nonendometriotic benign ovarian cysts.

CONCLUSION(S)

Laparoscopic endometrioma resection increases peri-implantation endometrial HOXA-10 and HOXA-11 mRNA expression, suggesting an improvement in endometrial receptivity.

Decreased Notch pathway signaling in the endometrium of women with endometriosis impairs decidualization

CONTEXT

Endometriosis is a common gynecological disease affecting one in 10 women of reproductive age and is a major cause of pelvic pain and impaired fertility. Endometrial stromal cells of women with endometriosis exhibit a reduced response to in vitro decidualization. NOTCH1 is critical for decidualization of both mouse and human uterine stromal cells.

OBJECTIVE

This study aimed to determine whether decidualization failure in women with endometriosis is a consequence of impaired Notch signaling.

SETTING AND DESIGN

We investigated expression levels of Notch signaling components in the endometrium of women and baboons with or without endometriosis. We identified NOTCH1-regulated genes during decidualization of human uterine fibroblast (HuF) cells by microarray and quantified their expression levels in in vitro-decidualized endometrial stromal cells isolated from women with or without endometriosis.

RESULTS

Notch signaling receptors NOTCH1 and NOTCH4, ligands JAGGED2 and DLL4, as well as direct target genes HES5 and HEY1 were decreased in the eutopic endometrium of women and baboons with endometriosis. Notch signaling was decreased in stromal cells isolated from women with endometriosis, which was associated with impaired in vitro decidualization. Genes that were down-regulated by NOTCH1 silencing in decidualized HuF cells were also decreased in decidualized endometrial stromal cells of women with endometriosis. FOXO1 acts as a downstream target of Notch signaling and endometriosis is associated with decreased expression of NOTCH1-regulated, FOXO1-responsive genes during decidualization.

CONCLUSIONS

Decreased Notch signaling is associated with endometriosis and contributes to impaired decidualization through the down-regulation of FOXO1.

Potential influence of the microbiome on infertility and assisted reproductive technology

Although an altered vaginal microbiota has been demonstrated to affect parturition, its role in assisted reproductive technologies is uncertain. Nevertheless, the effect of known pathogens such as Mycoplasma tuberculosis, Chlamydia trachomatis, and Neisseria gonorrhoeae is clear, causing subclinical changes thought to be risk factors in subfertility. The Human Microbiome Project (HMP) has allowed for metagenomic studies to aid in characterizing normal vaginal flora. Recent findings from the HMP demonstrate that many different species of Lactobacillus are present in the vaginal tract, with a few that predominate. Studies that characterize the vaginal microbiome in assisted reproductive technology support the hypothesis that colonizing the transfer-catheter tip with Lactobacillus crispatus at the time of embryo transfer may increase the rates of implantation and live birth rate while decreasing the rate of infection. In addition, there is some evidence that a progesterone-resistant endometrium might increase the risk of an abnormal vaginal microbiome.

Tissue and circulating microRNA influence reproductive function in endometrial disease

microRNA (miRNA) have emerged as important epigenetic modulators of gene expression in diverse pathological and physiological processes. In the endometrium, miRNA appear to have a role in the dynamic changes associated with the menstrual cycle, in implantation and in the pathophysiology associated with reproductive disorders such as recurrent miscarriage and endometriosis. This review explores the role of miRNA in endometrial physiology and endometrial disorders of reproduction and also raises the prospect that circulating miRNA may modulate endometrial function or reflect disordered endometrial activity. The clinical potential to use miRNA in diagnostic tests of endometrial function or in the treatment of endometrial disorders will also be discussed.

Pilot study on molecular quantitation and sequencing of endometrial cytokines gene expression and their effect on the outcome of in vitro fertilization (IVF) cycle

Human trophoblast invasion and differentiation are essential for successful pregnancy outcome. The molecular mechanisms, however, are poorly understood. Interleukin (IL)-11, a cytokine, regulates endometrial epithelial cell adhesion. Leukemia inhibitory factor (LIF) is one of the key cytokines in the embryo implantation regulation. The present study aimed to assess the levels of LIF, IL-11, and IL-11 α receptor gene expression in the endometrium of women undergoing IVF and correlate their levels with the IVF pregnancy outcome. Also, the study aimed to detect any mutation in these three genes among IVF pregnant and non-pregnant women versus control menstrual blood of fertile women. Endometrial tissue biopsies were taken from 15 women undergoing IVF on the day of oocyte retrieval. The quantitative expression of IL-11, IL-11Rα, and LIF genes was assessed by real-time PCR and PCR products were sequenced. Menstrual blood from 10 fertile women was used as control to compare the DNA sequence versus DNA sequence of the studied genes in endometrial biopsies. LH, FSH, and E2 were assessed for enrolled patients by ELISA. Endometrial thickness was also assessed by pelvic ultrasonography. No significant difference was detected between quantitative expression of the three studied genes and pregnancy IVF outcome. Although DNA sequence changes were found in IL-11 and LIF genes of women with negative pregnancy IVF outcome compared to women with positive pregnancy IVF outcome, no DNA sequence changes were detected for IL-11Rα. Other studied parameters (e.g., age, LH, FSH, E2, and endometrial thickness) showed no significant differences or correlation of quantitative expression of the three studied involved genes. Data suggested that there were no significant differences between quantitative expression of IL-11, IL-11Rα, and LIF genes and the IVF pregnancy outcome. The present study may reveal that changes in IL-11 and LIF genes sequence may contribute in pregnancy IVF outcome.

Cellular and molecular basis for endometriosis-associated infertility

Endometriosis is a gynecological disease characterized by the presence of endometrial glandular epithelial and stromal cells growing in the extra-uterine environment. The disease afflicts 10%–15% of menstruating women causing debilitating pain and infertility. Endometriosis appears to affect every part of a woman’s reproductive system including ovarian function, oocyte quality, embryo development and implantation, uterine function and the endocrine system choreographing the reproductive process and results in infertility or spontaneous pregnancy loss. Current treatments are laden with menopausal-like side effects and many cause cessation or chemical alteration of the reproductive cycle, neither of which is conducive to achieving a pregnancy. However, despite the prevalence, physical and psychological tolls and health care costs, a cure for endometriosis has not yet been found. We hypothesize that endometriosis causes infertility via multifaceted mechanisms that are intricately interwoven thereby contributing to our lack of understanding of this disease process. Identifying and understanding the cellular and molecular mechanisms responsible for endometriosis-associated infertility might help unravel the confounding multiplicities of infertility and provide insights into novel therapeutic approaches and potentially curative treatments for endometriosis.

Regulation of human endometrial stromal proliferation and differentiation by C/EBPβ involves cyclin E-cdk2 and STAT3

During each menstrual cycle, the human uterus undergoes a unique transformation, known as decidualization, which involves endometrial stromal proliferation and differentiation. During this process, the stromal cells are transformed into decidual cells, which produce factors that prepare the uterus for potential embryo implantation. We previously identified the transcription factor CCAAT/enhancer-binding protein (C/EBP)β as a regulator of endometrial stromal proliferation and differentiation in mice. In this study, we addressed the role of C/EBPβ in human endometrial decidualization. Using small interfering RNA targeted to C/EBPβ mRNA, we demonstrated that C/EBPβ controls the proliferation of primary human endometrial stromal cells (HESCs) by regulating the expression of several key cell cycle-regulatory factors during the G(1)-S phase transition. Additionally, loss of C/EBPβ expression blocked the differentiation of HESCs in response to estrogen, progesterone, and cyclic AMP. Gene expression profiling of normal and C/EBPβ-deficient HESCs revealed that the receptor for the cytokine IL-11 and its downstream signal transducer signal transducer and activator of transcription 3 (STAT3) are targets of regulation by C/EBPβ. Chromatin immunoprecipitation analysis indicated that C/EBPβ controls the expression of STAT3 gene by directly interacting with a distinct regulatory sequence in its 5'-flanking region. Attenuation of STAT3 mRNA expression in HESCs resulted in markedly reduced differentiation of these cells, indicating an important role for STAT3 in decidualization. Gene expression profiling, using STAT3-deficient HESCs, showed an extensive overlap of pathways downstream of STAT3 and C/EBPβ during stromal cell differentiation. Collectively, these findings revealed a novel functional link between C/EBPβ and STAT3 that is a critical regulator of endometrial differentiation in women.

Is abnormal eutopic endometrium the cause of endometriosis? The role of eutopic endometrium in pathogenesis of endometriosis

Endometriosis (EM) is one of the most common diseases which severely affect the health and reproductive function of women of childbearing age. There are fundamental abnormal changes within the eutopic endometrium of women with endometriosis compared to normal endometrium of women without endometriosis. Eutopic endometrium shows enhanced ability of proliferation, implantation and angiogenesis, and greater probability of escaping the unfavorable conditions of the ectopic environment. Therefore, the character of eutopic endometrium determines the fate of the backward-flowing endometrial tissue – to live or to die. The abnormal endometrial tissue in EM patients flows backward to the pelvic cavity, completing a 3-step procedure of pathogenesis (attachment-aggression-angiogenesis), and ultimately develops into EM. Abnormal eutopic endometrium may also play important roles in endometriosis-associated infertility. This recognition regarding the pathogenesis of endometriosis ultimately will help to discover new methods for diagnosis and treatment. Endometrial markers for micro-invasive diagnosis and direct treatment of eutopic endometrium as the origin of the disease should be further investigated.

MicroRNA array and microarray evaluation of endometrial receptivity in patients with high serum progesterone levels on the day of hCG administration

BACKGROUND

To determine the effect of higher progesterone (P) level on endometrial receptivity.

METHODS

This was a prospective analysis conducted in the Reproductive Medical Center of Peking University Third Hospital. All patients received IVF treatment and canceled embryo transfer in the same cycle and were divided into group 1 (normal P; 7 patients) and group 2 (elevated P; 12 patients). Endometrial biopsies were performed 6 days after oocyte retrieval. The global miRNA and mRNA gene expressions in endometrial biopsies were investigated with a V4.0 miRNA probe and 22 K Human Genome Array. Fold ratios were derived to compare gene regulation between the groups. Spp1 and Ang gene expression was selected to verify the array results by RT-PCR and the protein expression of osteopontin and VEGF was determined using an immunohistochemical method.

RESULTS

There were 4 miRNA (all down-regulated) and 22 mRNA (13 up-regulated and 9 down-regulated) exhibiting differential expression between the groups on the microRNA and microarray chips. miRNA-451, Spp1, and Ang expression in RT-PCR verified the array results. Osteopontin and VEGF were also shown to have positive expression in the endometrium.

CONCLUSIONS

Data from microRNA and microarray analysis suggests dissimilar endometrial receptivity in patients with high P levels on the day of hCG, and elevated osteopontin and decreased VEGF had poor pregnancy rates.

Bovine pretransfer endometrium and embryo transcriptome fingerprints as predictors of pregnancy success after embryo transfer

Aberrant gene expression in the uterine endometrium and embryo has been the major causes of pregnancy failure in cattle. However, selecting cows having adequate endometrial receptivity and embryos of better developmental competence based on the gene expression pattern has been a greater challenge. To investigate whether pretransfer endometrial and embryo gene expression pattern has a direct relation with upcoming pregnancy success, we performed a global endometrial and embryo transcriptome analysis using endometrial and embryo biopsy technology and the pregnancy outcome information. For this, endometrial samples were collected from Simmental heifers at day 7 and 14 of the estrous cycle, one cycle prior to embryo transfer. In the next cycle, blastocyst stage embryos were transferred to recipients at day 7 of the estrous cycle after taking 30-40% of the blastocyst as a biopsy for transcriptome analysis. The results revealed that at day 7 of the estrous cycle, the endometrial gene expression pattern of heifers whose pregnancy resulting in calf delivery was significantly different compared with those resulting in no pregnancy. These differences were accompanied by qualitative and quantitative alteration of major biological process and molecular pathways. However, the transcriptome difference was minimal between the two groups of animals at day 14 of the estrous cycle. Similarly, the transcriptome analysis between embryos biopsies that resulted in calf delivery and those resulted in no pregnancy revealed a total of 70 differentially expressed genes. Among these, the transcript levels of 32 genes including SPAG17, PF6, UBE2D3P, DFNB31, AMD1, DTNBP1, and ARL8B were higher in embryo biopsies resulting in calf delivery. Therefore, the present study highlights the potential of pretransfer endometrial and embryo gene expression patterns as predictors of pregnancy success in cattle.

The protein kinase A pathway-regulated transcriptome of endometrial stromal fibroblasts reveals compromised differentiation and persistent proliferative potential in endometriosis

Intrinsic abnormalities in transplanted eutopic endometrium are believed to contribute to the pathogenesis of pelvic endometriosis. Herein we investigated transcriptomic differences in human endometrial stromal fibroblasts (hESFs) from women with (hESF(endo)) vs. without (hESF(nonendo)) endometriosis, in response to activation of the protein kinase A (PKA) pathway with 8-bromoadenosine-cAMP (8-Br-cAMP). hESF(nonendo) (n = 4) and hESF(endo) (n = 4) were isolated from eutopic endometrium and treated +/- 0.5 mm 8-Br-cAMP for 96 h. Purified total RNA was subjected to microarray analysis using the whole-genome Gene 1.0 ST Affymetrix platform. A total of 691 genes were regulated in cAMP-treated hESF(nonendo) vs. 158 genes in hESF(endo), suggesting a blunted response to cAMP/PKA pathway activation in women with disease. Real-time PCR and ELISA validated the decreased expression of decidualization markers in hESF(endo) compared with hESF(nonendo). In the absence of disease, 8-Br-cAMP down-regulated progression through the cell cycle via a decrease in cyclin D1, cyclin-dependent kinase 6, and cell division cycle 2 and an increase in cyclin-dependent kinase inhibitor 1A. However, cell cycle components in hESF(endo) were not responsive to 8-Br-cAMP, resulting in persistence of a proliferative phenotype. hESF(endo) treated with 8-Br-cAMP exhibited altered expression of immune response, extracellular matrix, cytoskeleton, and apoptosis genes. Changes in phosphodiesterase expression and activity were not different among experimental groups. These data support that eutopic hESF(endo) with increased proliferative potential can seed the pelvic cavity via retrograde menstruation and promote establishment, survival, and proliferation of endometriosis lesions, independent of hydrolysis of cAMP and likely due to an inherent abnormality in the PKA pathway.

Endometrial decidualization: of mice and men

In murine and human pregnancies, embryos implant by attaching to the luminal epithelium and invading into the stroma of the endometrium. Under the influence of the steroid hormones estrogen and progesterone, the stromal cells surrounding the implanting embryo undergo a remarkable transformation event. This process, known as decidualization, is an essential prerequisite for implantation. It comprises morphogenetic, biochemical, and vascular changes driven by the estrogen and progesterone receptors. The development of mutant mouse models lacking these receptors has firmly established the necessity of steroid signaling for decidualization. Genomic profiling of mouse and human endometrium has uncovered a complex yet highly conserved network of steroid-regulated genes that supports decidualization. To advance our understanding of the mechanisms regulating implantation and better address the clinical challenges of infertility and endometrial diseases such as endometriosis, it is important to integrate the information gained from the mouse and human models.

Calcium-binding protein S100P is highly expressed during the implantation window in human endometrium

OBJECTIVE

To investigate S100P expression and localization in human endometrium throughout the menstrual cycle.

DESIGN

Experimental study.

SETTING

University hospital.

PATIENT(S)

Eighty-four women.

INTERVENTION(S)

Complementary DNA (cDNA) microarray analysis was performed on human endometrium from days LH+4, LH+7, and hCG+7. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis were used to detect the expression of S100P and of additional S100 family members, S100A4, S100A13, and S100A6. Immunofluorescence was used to detect the localization of S100P protein in LH+7 and LH+4 endometrium.

MAIN OUTCOME MEASURE(S)

Differential gene expression, levels of S100P messenger RNA (mRNA), and protein expression and immunofluorescent localization of S100P.

RESULT(S)

A statistical method, based on hierarchical clustering, identified genes whose expression varied at LH+7 compared with LH+4. We found that S100P was the fourth most up-regulated gene at LH+7. The S100P mRNA and protein levels were quite low during the proliferative phase and LH+4, but were elevated significantly at LH+7. The S100P expression at hCG+7 was lower than that at LH+7. However, the expression of S100A4, S100A13, and S100A6 did not vary throughout the menstrual cycle.

CONCLUSION(S)

S100P was specifically up-regulated during the implantation window. The underlying biological effects of S100P need further exploration.

HOXA-10 expression in the mid-secretory endometrium of infertile patients with either endometriosis, uterine fibromas or unexplained infertility

BACKGROUND

The aim of this study was to investigate HOXA-10 expression in endometrium from infertile patients with different forms of endometriosis; with uterine fibromas, or with unexplained infertility and from normal fertile women.

METHODS

Expression levels of HOXA-10 mRNA and protein in endometrium were measured during the mid-secretory phase. This study utilized laser capture microdissection, real-time RT-PCR and immunohistochemistry.

RESULTS

HOXA-10 mRNA and protein expression levels in endometrial stromal cells were significantly lower in infertile patients with different types of endometriosis (deep infiltrating endometriosis, ovarian endometriosis and superficial peritoneal endometriosis), with uterine myoma, and unexplained infertility patients as compared with healthy fertile controls. HOXA-10 mRNA expression levels of microdissected glandular epithelial cells were significantly lower than those of microdissected stromal cells, without significant differences among the different groups. No protein expression was detected in glandular epithelial cells. The percentage of patients with altered protein expression of HOXA-10 in stromal cells were significantly higher in patients with only superficial peritoneal endometriosis (100%, 20/20, P < 0.05) compared with the other infertile groups (deep infiltrating endometriosis: 72.7%, 16/22; ovarian endometriosis: 70.0%, 14/20; uterine myoma: 68.8%, 11/16; unexplained infertility: 55.6%, 5/9).

CONCLUSION

The present findings suggested that altered expression of HOXA-10 in endometrial stromal cells during the window of implantation may be one of the potential molecular mechanisms of infertility in infertile patients, particularly in patients with only superficial peritoneal endometriosis. One of the underlying causes of infertility in patients with only superficial endometriosis may be altered expression of HOXA-10 in endometrial stromal cells.

Connexin expression pattern in the endometrium of baboons is influenced by hormonal changes and the presence of endometriotic lesions

Experimentally induced endometriosis in baboons serves as an elegant model to discriminate between endometrial genes which are primarily associated with normal endometrial function and those that are changed by the presence of endometriotic lesions. Since connexin genes are characteristic of the hormonally regulated differentiation of the endometrium, we have examined connexin expression in baboon endometrium to delineate if they are altered in response to the presence of endometriotic lesions. Connexin expression in the endometrium of cycling baboons is similar to that of the human endometrium with Connexin(Cx)43 being primarily seen in the stromal compartment and Cx26 and Cx32 being present predominantly in the epithelium. Although Cx32 is up-regulated during the secretory phase, Cx26 and Cx43 are down-regulated. In the baboon model of induced endometriosis a change in connexin pattern was evident in the presence of endometriotic lesions. In the secretory phase, Cx26 and Cx32 are no longer present in the epithelium but Cx26 is now observed primarily in the stromal cells. Infusion of chorionic gonadotrophin in a manner that mimics blastocyst transit in utero failed to rescue the aberrant stromal expression of Cx26 that is associated with the presence of endometriotic lesions suggesting an impairment of the implantation process. The altered connexin pattern coupled with a loss of the channel protein in the epithelium and a gain of Cx26 in the stromal compartment suggests that the presence of lesions changes the uterine environment and thereby the differentiation programme. This aberrant expression of connexins may be an additional factor that contributes to endometriosis-associated infertility.

The non-human primate model of endometriosis: research and implications for fecundity

The development of an animal model of endometriosis is crucial for the investigation of disease pathogenesis and therapeutic intervention. These models will enhance our ability to evaluate the causes for the subfertility associated with disease and provide a first-line validation of treatment modulators. Currently rodents and non-human primate models have been developed, but each model has their limitations. The aim of this manuscript is to summarize the current findings and theories on the development of endometriosis and disease progression and the effectiveness of therapeutic targets using the experimental induced model of endometriosis in the baboon (Papio anubis).

Reduced expression of biomarkers associated with the implantation window in women with endometriosis

OBJECTIVE

To evaluate the expression of biomarkers of implantation, glycodelin A (GdA), osteopontin (OPN), lysophosphatidic acid receptor 3 (LPA3), and HOXA10, in eutopic endometrium of women with and without endometriosis.

DESIGN

Prospective observational study.

SETTING

Clinical research center.

PATIENT(S)

Twenty-four women with endometriosis and 23 healthy volunteers of similar age.

INTERVENTION(S)

Secretory phase endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Expression of immunohistochemical staining intensity and localization of GdA, OPN, LPA3, and HOXA10 in eutopic endometrium.

RESULT(S)

Endometrial GdA expression was significantly reduced in patients after cycle day 22. The endometrium from women with endometriosis also showed decreased expression of OPN in the late secretory phase and LPA3 and HOXA10 expression in the midsecretory and late secretory phases.

CONCLUSION(S)

The decreased expression of these four biomarkers of implantation may indicate impaired endometrial receptivity in patients with endometriosis, providing one explanation for the subfertility observed even in women with few pelvic implants. Because many of these markers are P dependent, these findings suggest the possibility of reduced endometrial P action in this population.

Microarray evaluation of endometrial receptivity in Chinese women with polycystic ovary syndrome

Patients with polycystic ovary syndrome (PCOS) have lower pregnancy and higher miscarriage rates, possibly due to decreased endometrial receptivity. In this study, endometrium was processed for RNA extraction and hybridization of chemically fragmented, biotinylated, complementary RNA on high-density oligonucleotide microarrays, and screened for 21,571 genes. Real-time polymerase chain reaction (PCR) was used to verify the result. Genes found to be down-regulated in the endometrium during the implantation window in PCOS patients included those whose activity was integral to membrane function, adhesion, invasive growth and the cytoskeleton. Among these genes, some have previously been associated with endometrial receptivity (by microarray research or other methods) and some have never previously been associated with endometrial receptivity. Using real-time PCR, expression of transmembrane 4 superfamily member 4 (TM4SF4) and matrix metalloproteinase 26 (MMP26) was found to be significantly decreased during the implantation window in patients with PCOS (P= 0.003). TM4SF4 has been demonstrated to be associated with adhesion; MMP26 has been shown to be related to degradation of extracellular matrix. It is suggested the down-regulated gene expression during the implantation window in patients with PCOS indicates differential gene expression in the endometrium between PCOS and normal women during the implantation window. This might affect endometrial receptivity.

Decreased expression of angiogenin in the eutopic endometrium from women with advanced stage endometriosis

Angiogenin, a potent inducer of angiogenesis, is expressed in human endometrium. This study was performed to compare the expression of angiogenin mRNA level in the eutopic endometrium from women with and without endometriosis. Thirty-two women with advanced stage endometriosis and 29 control women were recruited. Following isolation of total RNA from endometrial tissue and reverse transcription, cDNA samples were amplified by real time polymerase chain reaction to quantify the expression of angiogenin genes. In selected patients, immunohistochemical staining was utilized to localize the area of angiogenin expression. Angiogenin mRNA level was significantly lower in the endometriosis group than in the control group during the secretory phase, especially the mid-secretory phase, and the decline was observed mainly in the women who presented with infertility. Within the endometriosis group, angiogenin mRNA levels did not differ between the proliferative and secretory phases, but, in the control group, the level in the secretory phase was higher than that during the proliferative phase. Immunohistochemistry showed that the glandular epithelial cell layer was decorated positively in both groups. These findings suggest that the relative deficiency of angiogenin expression in the secretory endometrium could impair implantation in women with advanced stage endometriosis.

In vitro fertilization in normoresponder patients with endometriomas: comparison with basal simple ovarian cysts

OBJECTIVE

To investigate whether the space-occupying effect of an endometrioma, rather than endometriosis itself, affects results in in vitro fertilization (IVF) using women with simple ovarian cysts as the control group.

METHODS

85 normoresponder patients with endometriomas of 10-50 mm who underwent IVF treatment directly without initial removal were compared with 83 normoresponder patients with simple ovarian cysts of 10-35 mm detected at the beginning of stimulation and initiated treatment without aspiration.

RESULTS

Gonadotropin consumption was higher in the endometrioma group (3,013 vs. 2,451 IU; p = 0.001), although significantly fewer numbers of oocytes were retrieved (13.9 vs. 16.4; p = 0.03). However, oocyte maturation rates were similar. The transferred grade I embryos ratio was evaluated and found to be better in the cyst group (79.7 vs. 70.7%; p = 0.03). Consequently, the implantation rate was found to be significantly higher in the cyst group (28 vs. 19%; p = 0.02), although pregnancy and ongoing pregnancy rates were similar.

CONCLUSION

The presence of an endometriotic cyst during the IVF cycle was demonstrated to be associated with a lower embryo quality and implantation rate, although pregnancy success was unaffected. This adverse effect is suggested to be the result of the disease itself, not the presence of a cystic mass.

The altered distribution of the steroid hormone receptors and the chaperone immunophilin FKBP52 in a baboon model of endometriosis is associated with progesterone resistance during the window of uterine receptivity

This study examines the distribution of estrogen receptors (ESR), progesterone receptors (Pgr), and the chaperone immunophilin FKBP52 in the eutopic endometrium in a baboon model of endometriosis during the window of receptivity to determine if their aberrant distribution contributes to reduced fecundity. Endometriosis was induced by inoculation of menstrual endometrium into the peritoneal cavity. Eutopic endometrium was collected at 3, 6, 9, 12, and 15 months postinoculation. Western blot (WB) and immunohistochemical analyses were performed. Isolated endometrial stromal cells were cultured in the presence or absence of steroid hormones. In animals with endometriosis, ESR-1 (ER-alpha) decreased in endometrial stromal cells, while ESR-2 (ER-beta) was reduced in both glandular epithelial (GE) and stromal cells. Immunoreactive total Pgr was markedly diminished in the GE, which was confirmed by WB analysis. Furthermore, treatment of isolated stromal cells from baboons with endometriosis with hormones did not increase levels of PRA or PRB as in control baboons. FKBP52 was also reduced in the eutopic endometrium of baboons with endometriosis. Endometriosis results in an aberrant distribution of ESR-1, ESR-2, Pgr, and FKBP52 in the eutopic endometrium. The authors propose that a dysregulation in the paracrine signaling between the endometrial stromal and GE cells reduces the responsiveness of Pgr, creating an endometrial environment that is unsuitable for implantation.

Expression of epidermal growth factor, fibroblast growth factor-2, and platelet-derived growth factor-A in the eutopic endometrium of women with endometriosis

AIM

The objective of the present study was to compare the levels of expression of epidermal growth factor (EGF), fibroblast growth factor-2 (FGF-2), and platelet-derived growth factor-A (PDGF-A) mRNA in the eutopic endometrium of women with and without endometriosis.

METHODS

Thirty-five women with advanced stage endometriosis and 31 control women were recruited. Following isolation of total RNA from endometrial tissue and reverse transcription, cDNA samples were amplified to quantify the level of expression of EGF, FGF-2, PDGF-A.

RESULTS

While the levels of mRNA of EGF and FGF-2 were not different between the two groups, the PDGF-A mRNA level was significantly lower in the endometriosis group than in the control group during the secretory phase (6.12 +/- 0.51 vs 12.50 +/- 0.99, mean +/- SEM, P < 0.05).

CONCLUSION

The expression level of PDGF-A, but not EGF and FGF-2, might be decreased during the secretory phase in the eutopic endometrium of women with advanced stage endometriosis.