Wide genomic analysis of human endometrial receptivity: new times, new opportunities

Diverse endometrial mRNA signatures during the window of implantation in patients with repeated implantation failure

High endometrial receptivity in the window of implantation (WOI) is essential for successful implantation. However, a diagnostic tool with high specificity for impaired endometrial receptivity remains to be developed. We collected endometrium specimens during the WOI from patients with RIF and women who conceived after one IVF/ICSI attempt. We conducted mRNA microarray on the samples followed by relevant comparative and functional analysis. Microarray analysis revealed 357 dysregulated mRNAs between the two groups. The majority of these mRNAs were found to encode membrane proteins by Gene Ontology (GO) analysis. The major functional biological pathways associated with the down-regulated mRNAs were cytokine-cytokine receptor interaction, the p53 signalling pathway and the complement and coagulation cascades. Up-regulated mRNAs were found mainly to participate in pathways such as PPAR signalling, hematopoietic cell lineage, phosphatidylinositol signalling system, ECM-receptor interaction and notch signalling. AQP3, DPP4 and TIMP3 whose expression patterns were down-regulated in RIF patients both by microarray and real-time PCR had a high correspondence with previous studies demonstrating that these genes may contribute to the defects in endometrial receptivity in RIF patients. Overall, these RIF-associated mRNAs may help devise new diagnostic tools for endometrial receptivity.

An integrative transcriptomic analysis reveals bisphenol A exposure-induced dysregulation of microRNA expression in human endometrial cells

Bisphenol A (BPA) are commonly used in the manufacture of polycarbonate plastics. Higher BPA exposure levels have been found in patients with endometrial hyperplasia that is one of risk factors of endometrial cancer (EC). Aberrant microRNAs (miRNAs) regulation has been observed in the development of cancer. Thus, this study investigated whether BPA exposure can disrupt miRNA regulation and its gene expression regarding to EC carcinogenic progress. Microarray experiments of miRNA and mRNA were performed in human endometrial cancer RL95-2 cells with treatment of low-to-moderate (10, 10³ and 10⁵nM) BPA to explore the aberrant genes corresponding to human EC progression. According to the analysis of KEGG pathway and Cytoscape gene network, this study identified that BPA exposure reduced miR-149 expression to down-regulate DNA repair gene ARF6 (ADP-ribosylation factor 6) and tumor protein p53 (TP53), and up-regulate CCNE2 (cyclin E2) potentially to interrupt cell cycle. BPA also increased miR-107 to suppress hedgehog signaling factors, suppressor of fused homolog (SUFU) and GLI family zinc finger 3 (GLI3) to activate hedgehog signaling for cell proliferation underlying carcinogenesis. Furthermore, the BPA-induced cell proliferation was attenuated by transfection with miR-149 mimic and miR-107 inhibitor. These findings provided an insight into potential epigenetic mechanism of BPA exposure on the risk of endometrial carcinogenesis.

Transcription profile analysis of the endometrium revealed molecular markers of the personalized 'window of implantation' during in vitro fertilization

To determine the most informative markers for assessing the functional state of endometrium during the 'window of implantation' and creating a model for assessment of the readiness of endometrium for embryo implantation. Forty-seven women with tubal infertility and a successful IVF pregnancy participated in the study. Pipelle endometrial sample was performed during the supposed 'window of implantation' in natural cycle with subsequent histological study, and transcriptional profile of genes GPX3, PAEP, DPP4, TAGLN, HABP2, IMPA2, AQP3, HLA-DOB, MSX1, POSTN determined by real-time quantitative polymerase chain reaction (qRT-PCR). Differences in the level of mRNA expression of all the studied genes in the receptive endometrium were found in comparison to the prereceptive one, which allowed us to classify two functional states of the endometrium. The results of histological examination responded to the stage of maturation of the endometrium in 78.7% of cases. Receptive endometrial status can be determined based on the integral evaluation of mRNA expression level of 4 PAEP, DPP4, MSX1, and HLA-DOB genes. The model for determining a personalized `window implantation' is offered for practical application in ART.

Integrative Analyses of Uterine Transcriptome and MicroRNAome Reveal Compromised LIF-STAT3 Signaling and Progesterone Response in the Endometrium of Patients with Recurrent/Repeated Implantation Failure (RIF)

Intimate two-way interactions between the implantation-competent blastocyst and receptive uterus are prerequisite for successful embryo implantation. In humans, recurrent/repeated implantation failure (RIF) may occur due to altered uterine receptivity with aberrant gene expression in the endometrium as well as genetic defects in embryos. Several studies have been performed to understand dynamic changes of uterine transcriptome during menstrual cycles in humans. However, uterine transcriptome of the patients with RIF has not been clearly investigated yet. Here we show that several signaling pathways as well as many genes and microRNAs are dysregulated in the endometrium of patients with RIF (RIFE). Whereas unsupervised hierarchical clustering showed that overall mRNA and microRNA profiles of RIFE were similar to those of endometria of healthy women, many genes were significantly dysregulated in RIFE (cut off at 1.5 fold change). The majority (~75%) of differentially expressed genes in RIFE including S100 calcium binding protein P (S100P), Chemokine (C-X-C motif) ligand 13 (CXCL13) and SIX homeobox 1 (SIX1) were down-regulated, suggesting that reduced uterine expression of these genes is associated with RIF. Gene Set Enrichment analyses (GSEA) for mRNA microarrays revealed that various signaling pathways including Leukemia inhibitory factor (LIF) signaling and a P4 response were dysregulated in RIFE although expression levels of Estrogen receptor α (ERα) and Progesterone receptor (PR) were not significantly altered in RIFE. Furthermore, expression and phosphorylation of Signal transducer and activator of transcription 3 (STAT3) are reduced and a gene set associated with Janus kinase (JAK)-STAT signaling pathway is systemically down-regulated in these patients. Pairwise analyses of microRNA arrays with prediction of dysregulated microRNAs based on mRNA expression datasets demonstrated that 6 microRNAs are aberrantly regulated in RIFE. Collectively, we here suggest that dysregulation of several major signaling pathways and genes critical for uterine biology and embryo implantation may lead to uterine abnormalities in patients with RIF.

Diagnosis of Endometrial-Factor Infertility: Current Approaches and New Avenues for Research

Over the last decade, research to improve success rates in reproductive medicine has focused predominantly on the understanding and optimization of embryo quality. However, the emergence of personalized medicine in ovulation induction and embryology has shifted the focus to assessing the individual status of the endometrium. The endometrium is considered receptive during an individually defined period, the window of implantation (WOI), when the mother permits a blastocyst to attach and implant. This individual receptivity status can now be objectively diagnosed using the endometrial receptivity array (ERA) developed in 2011. The ERA, together with a computational algorithm, detects the unique transcriptomic signature of endometrial receptivity by analyzing 238 differentially expressed genes and reliably predicting the WOI. We and others have illustrated the utility of this personalized diagnostic approach to discriminate between individual physiological variation in endometrial receptivity and unknown endometrial pathology, deemed as causal in recurrent implantation failure (RIF). An international randomized controlled trial ("The ERA as a diagnostic guide for personalized embryo transfer." ClinicalTrials.gov Identifier: NCT01954758) is underway to determine the clinical value of this endometrial diagnostic intervention in the work-up for reproductive care. In this review, we analyse the current clinical practice in the diagnosis of the endometrial factor together with new avenues of research.

Endometrial transcriptome analysis indicates superiority of natural over artificial cycles in recurrent implantation failure patients undergoing frozen embryo transfer

Little consensus has been reached on the best protocol for endometrial preparation for frozen embryo transfer (FET). It is not known how, and to what extent, hormone supplementation in artificial cycles influences endometrial preparation for embryo implantation at a molecular level, especially in patients who have experienced recurrent implantation failure. Transcriptome analysis of 15 endometrial biopsy samples at the time of embryo implantation was used to compare two different endometrial preparation protocols, natural versus artificial cycles, for FET in women who have experienced recurrent implantation failure compared with fertile women. IPA and DAVID were used for functional analyses of differentially expressed genes. The TRANSFAC database was used to identify oestrogen and progesterone response elements upstream of differentially expressed genes. Cluster analysis demonstrated that natural cycles are associated with a better endometrial receptivity transcriptome than artificial cycles. Artificial cycles seemed to have a stronger negative effect on expression of genes and pathways crucial for endometrial receptivity, including ESR2, FSHR, LEP, and several interleukins and matrix metalloproteinases. Significant overrepresentation of oestrogen response elements among the genes with deteriorated expression in artificial cycles (P < 0.001) was found; progesterone response elements predominated in genes with amended expression with artificial cycles (P = 0.0052).

Uterine and arcuate arteries blood flow for predicting of ongoing pregnancy in in vitro fertilization

BACKGROUND

In this study, we aimed to investigate the ability of transvaginal Doppler ultrasonography in predicting in vitro fertilization (IVF) outcome in women undergoing this procedure.

MATERIALS AND METHODS

In this prospective observational study, 65 infertile women underwent IVF procedure in Isfahan, during 2013-2014, were studied. The pulsatility index (PI), resistive index (RI) and peak systolic velocity (PSV) of the uterine arteries and arcuate arteries were measured in all selected women using transvaginal color and pulsed Doppler measurements on the day of human chorionic gonadotrophin injection. The women followed up for the primary endpoint which was a successful pregnancy. The mean of PI, RI, and PSV were compared in groups of women who had successful IVF and not. The receiver operating characteristic (ROC) curve was used to determine the predictive value of studied indices.

RESULTS

In this study, from 65 women, 32 (49.2%) and 33 (50.8%) have successful and unsuccessful IVF outcome, respectively. The mean of PI and RI of both uterine and arcuate arteries were significantly lower in pregnant women than non-pregnant ones (P < 0.001). The area under the ROC curve of PI (84.7%) and RI (84.4%) for uterine arteries was higher than other indices. The most accurate indices for predicting the outcome of IVF was RI of uterine arteries with an accuracy of 81.5%.

CONCLUSION

The findings of this study indicated that PI and RI assessments of uterine arteries could be used as a routine non-invasive factor, before hCG stimulation, for predicting the outcome of IVF.

Potential causes of subfertility in patients with intramural fibroids

BACKGROUND

Intramural leiomyomas have been long debated as a potential cause of infertility and pregnancy loss.

FINDINGS

Previous research has linked intramural fibroids to defective implantation, as well as to abnormal peristaltic events of the uterine smooth muscle. Previous reports describe the effects of intramural fibroids on normal human fertility and early pregnancy loss, specifically in regards to implantation failure.

CONCLUSION

A thorough understanding of prior research may direct new research focus, leading to better understanding of leiomyoma-associated infertility.

MicroRNA-regulated molecular mechanism underlying bovine subclinical endometritis

An impaired uterine environment triggered by the incidence of subclinical endometritis often compromises fertility in the bovine. The uterus is a dynamic organ with tight regulation of specific genes at the transcriptional and translational levels. Herein, we hypothesised that subclinical endometritis alters the expression of uterine microRNAs (miRNAs), which may result in the dysregulation of corresponding target genes and biological pathways. To test this hypothesis, we used a genome-wide RT(2) (Exiqon, Vedbaek, Denmark) miRNA PCR array consisting of 354 miRNA primers and analysed miRNA expression in uterine cytobrush samples taken from cows with and without subclinical endometritis. The results revealed aberrant expression of 23 miRNAs in cows with subclinical endometritis compared with healthy cows. Furthermore, we designed an in vitro endometrial cell culture model challenged by lipopolysaccharide (LPS) to validate the differential regulation of miRNAs in cytobrush samples. Interestingly, we observed similar expression miRNA patterns in cytobrush samples taken from cows with or without subclinical endometritis and in vitro cultured endometrial cells challenged by LPS. To trace signalling pathways and biological functions potentially controlled by the aberrantly expressed miRNAs, we filtered high-ranking target genes from miRBase and analysed them using ingenuity pathway analysis. The gene networks, canonical pathways and biological functions strikingly converged to signalling pathways that mediate inflammatory responses, cellular proliferation, cell movement, the cell cycle and apoptosis in the bovine endometrium. In addition, expression analysis of key genes from the gene networks confirmed their presence and the potential regulation of these genes by uterine miRNAs. Furthermore, luciferase assay data substantiated the primary information from bioinformatic prediction that generated potential target genes for the dysregulated miRNAs in subclinical endometritis. Together, these data suggest the potential regulatory role of uterine miRNAs in the development and progression of bovine subclinical endometritis.

Systematic Analysis of the Molecular Mechanism Underlying Decidualization Using a Text Mining Approach

Decidualization is a crucial process for successful embryo implantation and pregnancy in humans. Defects in decidualization during early pregnancy are associated with several pregnancy complications, such as pre-eclampsia, intrauterine growth restriction and recurrent pregnancy loss. However, the mechanism underlying decidualization remains poorly understood. In the present study, we performed a systematic analysis of decidualization-related genes using text mining. We identified 286 genes for humans and 287 genes for mice respectively, with an overlap of 111 genes shared by both species. Through enrichment test, we demonstrated that although divergence was observed, the majority of enriched gene ontology terms and pathways were shared by both species, suggesting that functional categories were more conserved than individual genes. We further constructed a decidualization-related protein-protein interaction network consisted of 344 nodes connected via 1,541 edges. We prioritized genes in this network and identified 12 genes that may be key regulators of decidualization. These findings would provide some clues for further research on the mechanism underlying decidualization.

Endometrial receptivity array: Clinical application

Human implantation is a complex process requiring synchrony between a healthy embryo and a functionally competent or receptive endometrium. Diagnosis of endometrial receptivity (ER) has posed a challenge and so far most available tests have been subjective and lack accuracy and a predictive value. Microarray technology has allowed identification of the transcriptomic signature of the window of receptivity window of implantation (WOI). This technology has led to the development of a molecular diagnostic tool, the ER array (ERA) for diagnosis of ER. Use of this test in patients with recurrent implantation failure (RIF) has shown that the WOI is displaced in a quarter of these patients and use of a personalized embryo transfer (pET) on the day designated by ERA improves reproductive performance. Our results in the Indian population revealed an endometrial factor in 27.5% RIF patients, which was significantly greater than the non-RIF group 15% (P = 0.04). After pET, the overall ongoing pregnancy rate was 42.4% and implantation rate was 33%, which was at par with our in-vitro fertilization results over 1-year. We also performed ERA in patients with persistently thin endometrium, and it was reassuring to find that the endometrium in 75% of these patients was receptive despite being 6 mm or less. A pregnancy rate of 66.7% was achieved in this group. Though larger studies are required to validate these results ERA has become a useful tool in our diagnostic armamentarium for ER.

Transcriptome of early embryonic invasion at implantation sites in a murine model

Successful implantation relies on the interaction between a competent embryo and a receptive endometrium. The aim of the present study was to investigate genes differentially expressed in early invasive embryonic tissue versus decidual tissue in mice. Samples were obtained from the ectoplacental cone, the immediately surrounding deciduas and from deciduas from interimplantation sites. Microarray analysis showed that 817 genes were differentially expressed between extra-embryonic tissue and the surrounding decidua and that 360 genes were differentially expressed between the different deciduas, with a high representation of developmental processes. Genes differentially expressed in the maternal compartment included chemokines, lipoproteins, growth factors and transcription factors, whereas the embryonic invasive tissue expressed genes commonly observed in invasive tumour-like processes. These results provide information about genes involved in early embryonic invasion and the control exerted by the surrounding decidua. This information may be useful to find targets involved in pathologies associated with implantation failure and early pregnancy loss.

Application of gel-based proteomic technique in female reproductive investigations

Recently, gel-based proteomics has been increasingly applied to investigate proteins involved in female reproductive tract in healthy and disease states. Gel-based proteomics coupled by mass spectrometry (MS) facilitate the identification of new proteins playing roles in cellular and molecular interactions underlying female reproductive biology and it is a useful method to identify novel biomarkers of diseases by studying thousands of proteins simultaneously involved in female reproductive tract in healthy state compared to disease state. This review will discuss the best studies areas contributed to female reproductive biology in which gel-based proteomics coupled by MS has been applied to generate proteome of female reproductive tract in a healthy state.

Human Endometrial Transcriptomics: Implications for Embryonic Implantation

Human endometrium has been extensively investigated in the search for markers capable of predicting its receptive status. The completion of the Human Genome Project has triggered a rapid development of new fields in molecular biology, the "transcriptomics" being a major turning point in the knowledge acquisition of endometrial receptivity. Based on this, a customized Endometrial Receptivity Array (ERA) has been developed, which is capable of identifying the genomic signature of receptivity. This diagnostic tool showed that the window of implantation (WOI) is displaced in one out of four patients with implantation failure, allowing the identification of their personalized WOI. This strategy allows performing a personalized embryo transfer (pET) on the day in which the endometrium is receptive. The combination of a systems biology approach and next-generation sequencing will overcome the limitations of microarrays, and will, in the future, allow elucidation of the mechanisms involved in embryo implantation.

Live birth rates using conventional in vitro fertilization compared to intracytoplasmic sperm injection in Bologna poor responders with a single oocyte retrieved

PURPOSE

To compare reproductive outcomes following conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in poor responders fulfilling the Bologna criteria, with a single oocyte retrieved.

METHODS

The present retrospective study included 243 Bologna poor responders with a single oocyte retrieved, who were categorized into three groups, depending on the fertilization method and semen quality (IVF non-male factor-IVF/NMF n = 101; ICSI non-male factor ICSI/NMF n = 50; ICSI male factor-ICSI/MF n = 92).

RESULTS

In IVF/NMF, ICSI/NMF and ICSI/MF similar fertilization rates [65.3, 66, 58.7%, respectively], proportions of embryo formation [63.4, 60, 53.3%, respectively], proportions of good quality embryos [54.7, 56.7, 57.1%, respectively], implantation rates [8.9, 10, 8.2% respectively] and live birth rates per oocyte retrieval [5.0, 4.0, 3.3%, respectively] were observed. Degeneration rate of oocytes due to mechanical damage was significantly higher after ICSI in the ICSI/NMF and ICSI/MF groups (8 and 6.5%, respectively) compared to IVF/NMF (0%) (p = 0.02).

CONCLUSIONS

Conventional IVF and ICSI are associated with similar reproductive outcomes in poor responder patients with a single oocyte retrieved. Therefore, the choice of fertilization method should be based primarily on semen quality, in combination with the patient's previous history. A randomized controlled trial should be performed to confirm this study's findings that conventional IVF and ICSI have similar reproductive outcomes in poor responders.

Role of Mucin 1 and Glycodelin A in recurrent implantation failure

OBJECTIVE

To evaluate and compare the levels of Mucin 1 (MUC-1) and Glycodelin A (GdA) in precisely timed endometrial biopsies and blood samples taken from women with recurrent implantation failure, and women with proven fertility, in a control group.

DESIGN

Molecular studies in human blood and tissue.

SETTING

University hospital.

PATIENT(S)

Women with recurrent implantation failure and women with proven fertility.

INTERVENTION(S)

Primary endometrial cells and blood samples during the implantation "window" (between day 7 and day 9 after the surge in luteinizing hormone).

MAIN OUTCOME MEASURE(S)

Expression of MUC-1 and GdA in the human endometrium and in blood during the implantation window were analyzed by enzyme-linked immunosorbent assay. Additionally, MUC-1 and GdA levels in tissue were analyzed by western blot during the same period.

RESULT(S)

Both blood and tissue measurements of MUC-1 and GdA were significantly lower in women with recurrent implantation failure than in fertile women during the implantation window. In addition, we found a highly significant correlation between blood vs. tissue measurements of both MUC-1 and GdA.

CONCLUSION(S)

The present study reveals that blood and tissue levels of MUC-1 and GdA are much lower in women with RIF, compared with those in fertile women. Receptivity can be evaluated with noninvasive blood sampling, rather than more-invasive endometrium sampling, as the blood and tissue measurements of MUC-1 and GdA are correlated.

Activation of Toll-like receptor 3 reduces actin polymerization and adhesion molecule expression in endometrial cells, a potential mechanism for viral-induced implantation failure

STUDY QUESTION

Does activation of endometrial Toll-like receptor 3 (TLR 3) affect cell receptivity to trophoblast adhesion?

SUMMARY ANSWER

TLR 3 activation in vitro reduces the attachment of trophoblast cells to endometrial cells by altering the cell cytoskeleton and reducing the expression of adhesion molecules in human endometrial cells.

WHAT IS KNOWN ALREADY

It is well documented that the presence of an infection at the time of implantation can lead to implantation failure. The female reproductive tract recognizes invading micro-organisms through the innate pathogen recognition receptors such as the TLRs.

STUDY DESIGN, SIZE, DURATION

Poly I:C was used as a TLR 3-specific ligand and endometrial cells were either treated or not with Poly I:C (treated versus control) in vitro. The experiments were performed in three replicates on three separate days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An in vitro assay was developed using RL95-2 (a human endometrial cell line) and JAr (a human trophoblast cell line) cells. Initially, the percentage of attached JAr spheroids to RL95-2 was measured in response to TLR 3 activation. Next, actin polymerization in RL95-2 cells was assessed in response to TLR 2/6, 3 and 5 activation. Phalloidin was used to assess the mean fluorescence intensity of F-actin by flow cytometry or confocal microscopy. Secondly, the influence of TLR 2/6, 3 and 5 activation on the expression of cluster of differentiation 98 (CD98) and β3 integrin was determined. To further understand through which pathways the TLR 3-induced alterations occur, inhibitors were applied for Toll/interleukin-1 receptor domain-containing adaptor inducing interferon-beta (TRIF), myeloid differentiation primary response 88 (MYD88), mitogen-activated protein kinases (MAPK) and nuclear factor pathways.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed that stimulation of TLR 3 in endometrial cells with different concentrations of Poly I:C led to a reduction in the percentage of trophoblasts attached to the endometrial cells in a dose-dependent manner (P < 0.05). This decrease was consistent in the Poly I:C treated group regardless of the co-incubation time (P < 0.05). In addition, our results demonstrated that actin polymerization and CD98 expression significantly decreased only in response to TLR 3 activation (P < 0.05). Activation of endometrial cells with TLR 2/6, 3 and 5 significantly reduced β3 integrin expression (P < 0.05). These alterations were shown to work via MYD88-MAPK pathways (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study has been performed in vitro. Future in vivo studies will be required in order to confirm our data.

WIDER IMPLICATIONS OF THE FINDINGS

This is a novel discovery which extends our current knowledge concerning diagnosis and treatment of viral-induced infertility cases.

STUDY FUNDING/COMPETING INTERESTS

This research was supported by the COST Action FA1201 (GEMINI) by granting a Short Term Scientific Mission and the Instituto de Salud Carlos III by granting Grant PI11/01645. The authors have no conflict of interest to declare.

Implantation and Establishment of Pregnancy in Human and Nonhuman Primates

Implantation and the establishment of pregnancy are critical for the propagation of the species, but yet remain the limiting steps in human and primate reproduction. Successful implantation requires a competent blastocyst and a receptive endometrium during a specific window of time during the menstrual cycle to initiate the bilateral communication required for the establishment of a successful pregnancy. This chapter provides an overview of these processes and discusses the molecular mechanisms associated with implantation of the blastocyst and decidualization of the uterus in primates.

No evidence for mutations in NLRP7, NLRP2 or KHDC3L in women with unexplained recurrent pregnancy loss or infertility

STUDY QUESTION

Are mutations in NLRP2/7 (NACHT, LRR and PYD domains-containing protein 2/7) or KHDC3L (KH Domain Containing 3 Like) associated with recurrent pregnancy loss (RPL) or infertility?

SUMMARY ANSWER

We found no evidence for mutations in NLRP2/7 or KHDC3L in unexplained RPL or infertility.

WHAT IS KNOWN ALREADY

Mutations in NLRP7 and KHDC3L are known to cause biparental hydatidiform moles (BiHMs), a rare form of pregnancy loss. NLRP2, while not associated with the BiHM pathology, is known to cause recurrent Beckwith Weidemann Syndrome (BWS).

STUDY DESIGN, SIZE, AND DURATION

Ninety-four patients with well characterized, unexplained infertility were recruited over a 9-year period from three IVF clinics in Sweden. Blood samples from 24 patients with 3 or more consecutive miscarriages of unknown etiology were provided by the Recurrent Miscarriage Clinic at St Mary's Hospital, London, UK.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients were recruited into both cohorts following extensive clinical studies. Genomic DNA was isolated from peripheral blood and subject to Sanger sequencing of NLRP2, NLRP7 and KHDC3L. Sequence electropherograms were analyzed by Sequencher v5.0 software and variants compared with those observed in the 1000 Genomes, single nucleotide polymorphism database (dbSNP) and HapMap databases. Functional effects of non-synonymous variants were predicted using Polyphen-2 and sorting intolerant from tolerant (SIFT).

MAIN RESULTS AND THE ROLE OF CHANCE

No disease-causing mutations were identified in NLRP2, NLRP7 and KHDC3L in our cohorts of unexplained infertility and RPL.

LIMITATIONS, REASONS FOR CAUTION

Due to the limited patient size, it is difficult to conclude if the low frequency single nucleotide polymorphisms observed in the present study are causative of the phenotype. The design of the present study therefore is only capable of detecting highly penetrant mutations.

WIDER IMPLICATIONS OF THE FINDINGS

The present study supports the hypothesis that mutations in NLRP7 and KHDC3L are specific for the BiHM phenotype and do not play a role in other adverse reproductive outcomes. Furthermore, to date, mutations in NLRP2 have only been associated with the imprinting disorder BWS in offspring and there is no evidence for a role in molar pregnancies, RPL or unexplained infertility.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by the following sources: Estonian Ministry of Education and Research (Grant SF0180044s09), Enterprise Estonia (Grant EU30020); Mentored Resident research project (Department of Obstetrics and Gynecology, Baylor College of Medicine); Imperial NIHR Biomedical Research Centre; Grant Number C06RR029965 from the National Center for Research Resources (NCCR; NIH). No competing interests declared.

Biopsy-induced inflammatory conditions improve endometrial receptivity: the mechanism of action

A decade ago, we first reported that endometrial biopsy significantly improves the success of pregnancy in IVF patients with recurrent implantation failure, an observation that was later confirmed by others. Recently, we have demonstrated that this treatment elevated the levels of endometrial pro-inflammatory cytokines and increased the abundance of macrophages (Mac) and dendritic cells (DCs). We therefore hypothesised that the biopsy-related successful pregnancy is secondary to an inflammatory response, and aimed at deciphering its mechanism of action. Supporting our hypothesis, we found that the pro-inflammatory TNFα stimulated primary endometrial stromal cells to express cytokines that attracted monocytes and induced their differentiation into DCs. These monocyte-derived DCs stimulated endometrial epithelial cells to express the adhesive molecule SPP1 (osteopontin (OPN)) and its receptors ITGB3 and CD44, whereas MUC16, which interferes with adhesion, was downregulated. Other implantation-associated genes, such as CHST2, CCL4 (MIP1B) and GROA, were upregulated by monocyte-derived Mac. These findings suggest that uterine receptivity is mediated by the expression of molecules associated with inflammation. Such an inflammatory milieu is not generated in some IVF patients with recurrent implantation failure in the absence of local injury provoked by the biopsy treatment.

Leptin down-regulates γ-ENaC expression: a novel mechanism involved in low endometrial receptivity

OBJECTIVE

To examine epithelial Na(+) channel (ENaC) expression in endometrium of overweight/obese women with polycystic ovary syndrome (PCOS) during the window of implantation, and to explore the mechanism linking leptin-mediated reduction of γ-ENaC to low endometrial receptivity.

DESIGN

Controlled, prospective, clinical, experimental study.

SETTING

University-based infertility center.

PATIENT(S)

Blood and endometrium samples were collected from 12 control women and 12 overweight/obese PCOS patients. Pregnancy outcomes were obtained from 245 women with male-factor infertility (533 cycles) and 57 infertile women with PCOS (120 cycles) who underwent intrauterine insemination.

INTERVENTION(S)

Human endometrial biopsies.

MAIN OUTCOME MEASURE(S)

Expression of ENaC mRNA and protein in endometrium.

RESULT(S)

The expression of γ-ENaC decreased in the secretory phase endometrium of PCOS patients who showed increased serum leptin levels. In cultured endometrial cells (Ishikawa cells), leptin dose-dependently down-regulated the expression of γ-ENaC and reduced the JAr spheroid attachment rate, which could be blocked by knockdown of STAT3, a signal in the pathway of leptin receptor activation. The overweight/obese PCOS patients with increased serum leptin levels showed a significantly increased biochemical pregnancy rate, suggesting that high leptin might attenuate endometrial receptivity and increase very early pregnancy loss.

CONCLUSION(S)

High serum leptin may reduce endometrial receptivity by activating the STAT3 signal pathway and down-regulating γ-ENaC expression in the endometrium. These results provide valuable new insights into the molecular mechanisms linking abnormal ENaC gene expression to early pregnancy loss in overweight/obese PCOS patients.

Associations between Individual and Combined Polymorphisms of the TNF and VEGF Genes and the Embryo Implantation Rate in Patients Undergoing In Vitro Fertilization (IVF) Programs

BACKGROUND

A multiple pregnancy is now considered to be the most common adverse outcome associated with in vitro fertilization (IVF). As a consequence, the identification of women with the best chances of embryo implantation is a challenge in IVF program, in which the objective is to offer elective single-embryo transfer (eSET) without decreasing the pregnancy rate. To date, a range of hormonal and clinical parameters have been used to optimize eSET but none have significant predictive value. This variability could be due to genetic predispositions related to single-nucleotide polymorphisms (SNPs). Here, we assessed the individual and combined impacts of thirteen SNPs that reportedly influence the outcome of in vitro fertilisation (IVF) on the embryo implantation rate for patients undergoing intracytoplasmic sperm injection program (ICSI).

MATERIALS AND METHODS

A 13 gene polymorphisms: FSHR(Asn680Ser), p53(Arg72Pro), AMH(Ile49Ser), ESR2(+1730G>A), ESR1(-397T>C), BMP15(-9C>G), MTHFR1(677C>T), MTHFR2(1298A>C), HLA-G(-725C>G), VEGF(+405G>C), TNFα(-308A>G), AMHR(-482A>G), PAI-1(4G/5G), multiplex PCR assay was designed to genotype women undergoing ICSI program. We analyzed the total patients population (n = 428) and a subgroup with homogeneous characteristics (n = 112).

RESULTS

Only the VEGF(+405G>C) and TNFα(-308A>G) polymorphisms impacted fertilization, embryo implantation and pregnancy rates. Moreover, the combined VEGF+405.GG and TNFα-308.AG or AA genotype occurred significantly more frequently in women with high implantation potential. In contrast, the VEGF+405.CC and TNFα-308.GG combination was associated with a low implantation rate.

CONCLUSION

We identified associations between VEGF(+405G>C) and TNFα(-308A>G) polymorphisms (when considered singly or as combinations) and the embryo implantation rate. These associations may be predictive of embryo implantation and could help to define populations in which elective single-embryo transfer should be recommended (or, conversely, ruled out). However, the mechanism underlying the function of these polymorphisms in embryo implantation remains to be determined and the associations observed here must be confirmed in a larger, more heterogeneous cohort.

Endometrial gene expression reveals compromised progesterone signaling in women refractory to embryo implantation

BACKGROUND

Endometrial function is essential for embryo implantation. The aim of this study was to analyze gene expression profiles from individual endometrial samples obtained from women with repeated implantation failure after IVF in oocyte donation programs.

METHODS

Seventeen volunteers were recruited: women who had previously participated as recipients in oocyte donation cycles and repeatedly exhibited implantation failure (Group A, study group, n = 5) or had at least one successful cycle (Group B, control group, n = 6) and spontaneously fertile women (Group C, normal fertility group, n = 6). An endometrial cycle was induced with exogenous estradiol (E2) and progesterone (P) and an endometrial sample was collected on the seventh day of P treatment.

RESULTS

Transcriptome analysis showed 82 genes with consistent differential gene expression when comparing A vs. B and A vs. C. One hundred transcripts differentially expressed in group A vs. B have been shown to be regulated by P, suggesting compromised P signaling in the endometrium. The P receptor (PR) mutation PROGINS was not detected in women from group A. Semi-quantitation of immunoreactive PRA/B, PRB and Sp1 (a transcription factor related to P signaling) in paraffin-embedded endometrial sections, did not show statistically significant differences amongst groups. However immunostaining glycodelin was significantly decreased in endometrial samples from group A.

CONCLUSIONS

We conclude that some cases of repeated implantation failure could be associated with an aberrant gene expression profile. Compromised P signaling might be the underlying mechanism for such endometrial gene expression deregulation in women with repeated implantation failure.

ART and uterine pathology: how relevant is the maternal side for implantation?

BACKGROUND

Assisted reproduction technology (ART) has become a standard treatment for infertile couples. Increased success rates obtained over the years have resulted primarily from improved embryo quality, but implantation rates still remain lower than expected. The uterus, an important player in implantation, has been frequently neglected. While a number of uterine pathologies have been associated with decreased natural fertility, less information exists regarding the impact of these pathologies in ART. This report reviews the evidence to help clinicians advise ART patients.

METHODS

An electronic search of PubMed and EMBASE was performed to identify articles in the English, French or Spanish language published until May 2014 which addressed uterine pathology and ART. Data from natural conception were used only in the absence of data from ART. Studies were classified in decreasing categories: RCTs, prospective controlled trials, prospective non-controlled trials, retrospective studies and experimental studies. Studies included in lower categories were only used if insufficient evidence was available. Pooled data were obtained from systematic reviews with meta-analyses when available. The summary of the evidence for the different outcomes and the degree of the recommendation for interventions were based on the GRADE (Grading of Recommendations Assessment, Development and Evaluation) statement recommendations.

RESULTS

There is strong evidence that surrogacy is effective for uterine agenesia. For the remaining pathologies, however, there is very little evidence that the established treatments improve outcomes, or that these pathologies have a negative effect on ART. In the presence of an apparently normal uterus, assessing endometrial receptivity (ER) is the goal; however diagnostic tests are still under development.

CONCLUSIONS

The real effect of different uterine/endometrial integrity pathologies on ART is not known. Moreover, currently proposed treatments are not based on solid evidence, and little can be done to assess ER in normal or abnormal conditions. No strong recommendations can be given based on the published experience, bringing an urgent need for well-designed studies. In this context, we propose algorithms to study the uterus in ART.

Ovarian stimulation using human chorionic gonadotrophin impairs blastocyst implantation and decidualization by altering ovarian hormone levels and downstream signaling in mice

Ovarian stimulation induced by follicle-stimulating hormone and human chorionic gonadotrophin (hCG) is commonly used in assisted reproductive technology to increase embryo production. However, recent clinical and animal studies have shown that ovarian stimulation disrupts endometrial function and embryo development and adversely affects pregnancy outcomes. How ovarian stimulation impairs pregnancy establishment and the precise mechanisms by which this stimulation reduces the chances of conception remain unclear. In this study, we first demonstrated that ovarian stimulation using hCG alone impairs implantation, decidualization and fetal development of mice by generating abnormal ovarian hormone levels. We also showed that ovarian hormone levels were altered because of changes in the levels of the enzymes involved in their synthesis in the follicles and corpora lutea. Furthermore, we determined that anomalous ovarian hormone secretion induced by ovarian stimulation alters the spatiotemporal expression of progesterone receptors and their downstream genes, especially in the uterine epithelium. Epithelial estrogenic signaling and cell proliferation were promoted on the day of implantation in stimulated mice and these changes led to the failure of uterine transition from the prereceptive to the receptive state. Collectively, our findings indicate that ovarian stimulation using hCG induces an imbalance in steroid hormone secretion, which causes a failure of the development of uterine receptivity and subsequent implantation and decidualization by altering the expression of steroid receptors and their downstream signaling associated with embryo implantation.

MicroRNA and implantation

We provide a review of microRNA (miRNA) related to human implantation which shows the potential diagnostic role of miRNAs in impaired endometrial receptivity, altered embryo development, implantation failure after assisted reproduction technology, and in ectopic pregnancy and pregnancies of unknown location. MicroRNAs may be emerging diagnostic markers and potential therapeutic tools for understanding implantation disorders. However, further research is needed before miRNAs can be used in clinical practice for identifying and treating implantation failure.

Endometrial receptivity profile in patients with premature progesterone elevation on the day of HCG administration

The impact of a premature elevation of serum progesterone level, the day of hCG administration in patients under controlled ovarian stimulation during IVF procedure, on human endometrial receptivity is still debated. In the present study, we investigated the endometrial gene expression profile shifts during the prereceptive and receptive secretory stage in patients with normal and elevated serum progesterone level on the day of hCG administration in fifteen patients under stimulated cycles. Then, specific biomarkers of endometrial receptivity in these two groups of patients were tested. Endometrial biopsies were performed on oocyte retrieval day and on day 3 of embryo transfer, respectively, for each patient. Samples were analysed using DNA microarrays and qRT-PCR. The endometrial gene expression shift from the prereceptive to the receptive stage was altered in patients with high serum progesterone level (>1.5 ng/mL) on hCG day, suggesting accelerated endometrial maturation during the periovulation period. This was confirmed by the functional annotation of the differentially expressed genes as it showed downregulation of cell cycle-related genes. Conversely, the profile of endometrial receptivity was comparable in both groups. Premature progesterone rise alters the endometrial gene expression shift between the prereceptive and the receptive stage but does not affect endometrial receptivity.

Recent advances in understanding endometrial receptivity: molecular basis and clinical applications

Advancement in the field of ART has lead to the possibility of achieving good quality embryos. However, the success rate in ART needs further improvement. This is largely dependent on identifying the receptive endometrium for the successful implantation of embryos as well as modulating the endometrium to the receptive stage. In the last half-a-decade, focus has been shifting toward identifying the receptive endometrium. Here, we summarize different tools explored to identify receptive endometrium from the literature, mainly focusing on the past decade, with the help of PubMed. The quest to identify endometrial receptivity markers has lead to the exploration of morphological features at micro and macro scale levels. A large number of studies at molecular levels have focused on genomic, proteomic and lipidomic targets. Recent development of endometrial receptivity array is a promising diagnostic instrument. However, a noninvasive possibility for the diagnosis of endometrial receptivity would be an ideal tool, which could be used in the clinic to improve the success rate of ART. Improved knowledge on endometrial receptivity will not only help to improve the diagnosis and treatment of infertility but will also give possibilities to develop new contraceptive methods targeting the endometrium.

Guidelines for the design, analysis and interpretation of 'omics' data: focus on human endometrium

BACKGROUND

'Omics' high-throughput analyses, including genomics, epigenomics, transcriptomics, proteomics and metabolomics, are widely applied in human endometrial studies. Analysis of endometrial transcriptome patterns in physiological and pathophysiological conditions has been to date the most commonly applied 'omics' technique in human endometrium. As the technologies improve, proteomics holds the next big promise for this field. The 'omics' technologies have undoubtedly advanced our knowledge of human endometrium in relation to fertility and different diseases. Nevertheless, the challenges arising from the vast amount of data generated and the broad variation of 'omics' profiling according to different environments and stimuli make it difficult to assess the validity, reproducibility and interpretation of such 'omics' data. With the expansion of 'omics' analyses in the study of the endometrium, there is a growing need to develop guidelines for the design of studies, and the analysis and interpretation of 'omics' data.

METHODS

Systematic review of the literature in PubMed, and references from relevant articles were investigated up to March 2013.

RESULTS

The current review aims to provide guidelines for future 'omics' studies on human endometrium, together with a summary of the status and trends, promise and shortcomings in the high-throughput technologies. In addition, the approaches presented here can be adapted to other areas of high-throughput 'omics' studies.

CONCLUSION

A highly rigorous approach to future studies, based on the guidelines provided here, is a prerequisite for obtaining data on biological systems which can be shared among researchers worldwide and will ultimately be of clinical benefit.

The association of trefoil factor 3 gene polymorphisms and haplotypes with unexplained female infertility: molecular insights into TFF3 regulation in receptive phase endometrium

Abstract This study examined the genetic variation within the gene trefoil factor 3 (TFF3) in relation to unexplained female infertility in a group of women where aberrant endometrial maturation was suspected. The study consisted of 113 women with a diagnosis of unexplained infertility and 289 healthy fertile volunteers. Five single nucleotide polymorphisms rs225439, rs533093, rs225361, rs11701143, and rs77436142 within TFF3 gene were analyzed using real-time PCR. The formed haplotype pattern within the TFF3 gene in relation to infertility was also assessed. TFF3 protein localization and expression in receptive stage endometrium at the time of implantation was measured in a subset of fertile (n = 7) and infertile (n = 12) women. Allele and genotype frequencies did not differ significantly between fertile and infertile women, nor did the formed haplotypes. TFF3 protein was expressed in all cell types in receptive stage endometria in fertile and infertile women. No significant association was observed between protein expression and analyzed genotypes. A significantly higher TFF3 expression in luminal epithelial cells was detected in women with unexplained infertility (p = 0.003).

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.

Effects of fertility on gene expression and function of the bovine endometrium

Infertility and subfertility are important and pervasive reproductive problems in both domestic animals and humans. The majority of embryonic loss occurs during the first three weeks of pregnancy in cattle and women due, in part, to inadequate endometrial receptivity for support of embryo implantation. To identify heifers of contrasting fertility, serial rounds of artificial insemination (AI) were conducted in 201 synchronized crossbred beef heifers. The heifers were then fertility classified based on number of pregnancies detected on day 35 in four AI opportunities. Heifers, classified as having high fertility, subfertility or infertility, were selected for further study. The fertility-classified heifers were superovulated and flushed, and the recovered embryos were graded and then transferred to synchronized recipients. Quantity of embryos recovered per flush, embryo quality, and subsequent recipient pregnancy rates did not differ by fertility classification. Two in vivo-produced bovine embryos (stage 4 or 5, grade 1 or 2) were then transferred into each heifer on day 7 post-estrus. Pregnancy rates were greater in high fertility than lower fertility heifers when heifers were used as embryo recipients. The reproductive tracts of the classified heifers were obtained on day 14 of the estrous cycle. No obvious morphological differences in reproductive tract structures and histology of the uterus were observed in the heifers. Microarray analysis revealed differences in the endometrial transcriptome based on fertility classification. A genome-wide association study, based on SNP genotyping, detected 7 moderate associations with fertility across 6 different chromosomes. Collectively, these studies support the idea that innate differences in uterine function underlie fertility and early pregnancy loss in ruminants. Cattle with defined early pregnancy success or loss is useful to elucidate the complex biological and genetic mechanisms governing endometrial receptivity and uterine competency for pregnancy.

Discovery of biomarkers of endometrial receptivity through a minimally invasive approach: a validation study with implications for assisted reproduction

OBJECTIVE

To determine whether a minimally invasive approach to sampling endometrial cells that can be applied during an active conception cycle can generate robust biomarker candidates for endometrial receptivity by genomewide gene expression profiling.

DESIGN

Longitudinal study comparing gene expression profiles of cells isolated from uterine aspirates collected during the prereceptive and receptive phases of a natural cycle.

SETTING

University-affiliated hospital.

PATIENT(S)

Healthy volunteers, ≤40 years of age, with regular menstrual cycles and no history of infertility.

INTERVENTION(S)

One menstrual cycle monitored with urinary kits to identify the luteinizing hormone (LH) surge; uterine aspirations collected at LH + 2 days (LH + 2) and at LH + 7; endometrial biopsy obtained on LH + 7; RNA extraction from the cellular material for gene expression profiling, and differential gene expression validated by NanoString assay and cross-validated against a publically available data set.

MAIN OUTCOME MEASURE(S)

Differentially expressed genes between LH + 2 and LH + 7 samples.

RESULT(S)

NanoString assay validated 96% of the 245 genes found differentially expressed at LH + 7. Unsupervised hierarchical clustering of aspiration and biopsy samples demonstrated the concordance of the sampling methods. A predictor gene cassette derived by a shrunken centroid class prediction technique correctly classified the receptive phase within an external data set.

CONCLUSION(S)

Uterine aspiration, which can be performed during an active conception cycle, identified robust candidate biomarkers of endometrial receptivity, and will enable their validation by direct correlation with clinical outcomes.

MicroRNAs miR-30b, miR-30d, and miR-494 regulate human endometrial receptivity

MicroRNAs (miRNAs) act as important epigenetic posttranscriptional regulators of gene expression. We aimed to gain more understanding of the complex gene expression regulation of endometrial receptivity by analyzing miRNA signatures of fertile human endometria. We set up to analyze miRNA signatures of receptive (LH + 7, n = 4) versus prereceptive (LH + 2, n = 5) endometrium from healthy fertile women. We found hsa-miR-30b and hsa-miR-30d to be significantly upregulated, and hsa-miR-494 and hsa-miR-923 to be downregulated in receptive endometrium. Three algorithms (miRanda, PicTar, and TargetScan) were used for target gene prediction. Functional analyses of the targets using Ingenuity Pathways Analysis and The Database for Annotation, Visualization and Integrated Discovery indicated roles in transcription, cell proliferation and apoptosis, and significant involvement in several relevant pathways, such as axon guidance, Wnt/β-catenin, ERK/MAPK, transforming growth factor β (TGF-β), p53 and leukocyte extravasation. Comparison of predicted miRNA target genes and our previous messenger RNA microarray data resulted in a list of 12 genes, including CAST, CFTR, FGFR2, and LIF that could serve as a panel of genes important for endometrial receptivity. In conclusion, we suggest that a subset of miRNAs and their target genes may play important roles in endometrial receptivity.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Factor seven activating protease (FSAP) expression in human placenta and its role in trophoblast migration

OBJECTIVES

Factor seven activating protease (FSAP) is a plasma serine protease known to play a critical role in hemostasis and remodeling processes: FSAP levels increase markedly during normal pregnancy. In order to define the role of FSAP in vascular pathophysiology in pregnant women and particularly in the placenta, we performed this study (i) to evaluate the FSAP expression in human placenta and (ii) to identify the role of FSAP in human trophoblast migration.

STUDY DESIGN

FSAP expression in placental tissues was analyzed by using immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). To determine whether FSAP plays any role in trophoblast migration, we used human trophoblast cells in transwell migration assays.

RESULTS

Immunohistochemistry showed that FSAP protein was expressed by syncytiotrophoblast and in the cytoplasma of invasive extravillous trophoblasts (EVT) within the maternal decidua (DC) in implantation sites of human first trimester placenta. Furthermore, FSAP mRNA and protein decreased with gestational age (p<0.05, 1st vs 3rd trimester). FSAP (10μg/ml) had a significant stimulatory effect on the migration of human trophoblast cells. This effect was abolished by addition of aprotinin to block the enzymatic activity of FSAP.

CONCLUSIONS

The high expression level of FSAP in the placenta supports a relevant role of this protease in trophoblast migration and vascular remodeling, identifies a new concept of coagulation/fibrinolysis at the feto-maternal interface and may be essential for the maintenance of pregnancy.

Gene expression and DNA-methylation of bovine pretransfer endometrium depending on its receptivity after in vitro-produced embryo transfer

Embryonic implantation to establish a pregnancy is a complex process that requires appropriate communication between the embryo and the maternal endometrium. Inadequate uterine receptivity may contribute to the majority of implantation failures. To provide a comprehensive inventory of genes and functional networks that represent the maternal input of the embryo-maternal cross-talk, a longitudinal, holistic study of the endometrial transcriptome in relation to the days of estrous and to the receptivity of the endometrium was performed in bovine. At day 3 of estrous, genes related to cell communication and mitochondrial energy metabolism were differentially expressed among high- and low-receptive endometria (HR, LR); at day 7, transcripts functioning in immune and inflammatory pathways, oxidative stress, and angiogenesis had different abundances. Additionally, temporal transcriptional changes between days 3 and 7 differed considerably among HR and LR. Further, several transcription factors were predicted as relevant for receptivity because they were either differentially expressed among HR and LR animals or are known to be associated with genes we detected to have differential expression. Finally, global DNA methylation varied according to the interaction of receptivity group and day of estrous, and a divergent trend, which correlated with abundance of DNMT1 transcript, was observed in LR and HR along the estrous cycle days. The study revealed that, even in early estrous, transcripts related to cell communication and response to exogenous stimuli, vascularization, and energy supply show divergent expression and longitudinal temporal regulation in HR and LR. Key components of these molecular pathways are known to be dependent on ovarian hormones that promote uterine receptivity.

Endometrial expression of selected genes in patients achieving pregnancy spontaneously or after ICSI and patients failing at least two ICSI cycles

The objective of this study was to identify the endometrial gene expression profile in receptive phase, which could represent a useful prognostic tool for selecting IVF patients. Endometrial expression of 47 selected genes biopsied during the window of implantation in natural cycles was compared between patients who achieved a successful pregnancy spontaneously or after subsequent intracytoplasmic sperm injection (ICSI) cycles and patients who did not achieve a pregnancy after at least two failed ICSI cycles. The comparative analysis showed significantly different levels of expression in 19 genes, five implicated in apoptosis (CASP8, FADD, CASP10, APAF1, ANXA4), three in immunity (LIF, SPP1, C4BPA), five in transcriptional activity (MSX1, HOXA10, MSX2, HOXA11, GATA2), two in lipid metabolism (LEPR, APOD) and four in oxidative metabolism (AOX1, ALDH1A3, GPX3, NNMT). The evidence for these genes being differently expressed could represent the starting point of identifying the ideal receptive endometrial gene expression profile, which could be used in the future as a prognostic tool for IVF patients. Gene expression analysis technology has opened new important perspectives on the study of the physiological processes of different tissues and organs. Specifically for the endometrium, it would be really interesting to find out an endometrial gene expression profile of receptive phase, which could be used in future as a useful prognostic tool for selecting IVF patients. To achieve this aim, the objective of the present paper was the comparison of endometrial expression in natural cycles of 47 selected genes between the biopsies of patients who achieved a successful pregnancy, either spontaneously or after subsequent ICSI cycles, and those of patients who did not achieve a pregnancy after at least two failed ICSI cycles. The comparative analysis showed a significant different expression in 19 genes: five implicated in programmed cell death, known as apoptosis (CASP8, FADD, CASP10, APAF1, ANXA4), three in immunity (LIF, SPP1, C4BPA), five in transcriptional activity (MSX1, HOXA10, MSX2, HOXA11, GATA2), two in lipid metabolism (LEPR, APOD) and four in oxidative metabolism (AOX1, ALDH1A3, GPX3, NNMT). The evidence of these genes being differently expressed could represent the starting point of identifying the ideal receptive endometrial gene expression profile which could be used in the future as a prognostic tool for IVF patients.