CD55 is upregulated by cAMP/PKA/AKT and modulates human decidualization via Src and ERK pathway and decidualization-related genes

Decidualization is an essential process for embryo implantation and maintenance of pregnancy, and abnormal decidualization contributed to several pregnancy disorders like a miscarriage. The objective of this study was to explore the regulation and function of CD55 in human decidualization. By immunohistochemical staining, it was found that CD55 expression was higher in first-trimester decidua than in the endometrium. In both primary endometrial stromal cells and immortalized cell line T-hESCs, CD55 was upregulated by induction of in vitro decidualization with medroxyprogesterone acetate (MPA) and 8-Br-cAMP. During decidualization in vitro, CD55 was stimulated by 8-Br-cAMP in a time- and concentration-dependent manner, which was reversed by a PKA inhibitor H89 and partially by an AKT activator SC79. Knocking down CD55 expression diminished the expression of decidualization markers prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP1), accompanied by inhibition of Src, aberrant activation of ERK and decreased expression of several decidualization-related genes, including FOXO1, EGFR, and STAT3. Furthermore, the decidua of unexplained miscarriage women and the endometrium of unexplained infertile women both exhibited decreased CD55 expression. Collectively, these findings revealed that 8-Br-cAMP promotes CD55 expression via PKA activation and AKT dephosphorylation, and decreased CD55 impairs decidualization by inactivation of Src, aberrant activation of ERK pathway, and compromised expression of decidualization-related genes, indicating that CD55 deficiency may contribute to the pathogenesis of spontaneous miscarriage and infertility.

Cyanidin-3-O-glucoside ameliorates cadmium induced uterine epithelium proliferation in mice

Cadmium (Cd) is an environmental pollutant and endocrine disrupter, abundantly present in water, food, and soil. Accumulation of Cd in the body can negatively affect female reproduction; especially the uterus is exceptionally sensitive to the toxic actions of Cd. The anthocyanin cyanidin-3-O-glucoside (C3G) is a naturally occurring phenolic compound in fruits and plants that can antagonize the toxic effects of Cd. This capacity makes C3G a possible candidate to prevent Cd-induced female infertility. The present study aimed to investigate: 1) whether C3G intake could prevent Cd-induced female reproductive toxicity, and 2) the underlying mechanisms responsible for this protective effect. The results of our study indicated that Cd exposure did not affect ovarian function, but induced hypertrophy of the uterine endometrium. Oral intake of C3G markedly reduced the effects of Cd exposure on the thickness of the uterine epithelium cells. Transcriptomic analysis of the endometrium revealed that C3G intake had anti-estrogenic effects, attenuating Cd-induced endometrial epithelial cell proliferation by inhibiting estrogen-responsive genes, enhancing epithelial progesterone receptor expression, and regulating Klf4 expression. The current findings implicate that C3G has the potential to be used as a dietary supplement based on its capacity to intervene in Cd-induced female reproductive toxicity.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

Implantation failure in rats with subclinical hypothyroidism is associated with LIF/STAT3 signaling

BACKGROUND

Pregnant women with subclinical hypothyroidism are associated with an increased risk of spontaneous abortion. This study aims to investigate the mechanisms underlying the effects of maternal subclinical hypothyroidism during early pregnancy on abortion in the uterus, focusing upon the LIF/STAT3 signaling pathway.

METHODS

One hundred five Wistar rats were randomly divided into three groups (35 rats in each group): control (CON) group, subclinical hypothyroidism (SCH) group and overt hypothyroidism (OH) group. We examined the weight of rat uteri, rat placenta and embryos. We also determined the number of implantation sites and the embryo absorption rates. The protein and mRNA expressions of TSHR, TR-α, TR-β, LIFR, gp130, JAK1, p-STAT3 and STAT3 were measured by immunohistochemical staining, real-time PCR and Western blotting.

RESULTS

The weights of rat uteri, rat placenta and embryos were significantly reduced in the SCH and OH groups. The number of implantation sites was significantly decreased in the SCH and OH groups, while embryo absorption rates were significantly increased. The mRNA and protein expressions of TSHR were upregulated in the SCH and OH groups, while TR-α and TR-β showed no difference when compared between the three groups. The expression levels of LIFR, gp130, JAK1 and p-STAT3 were significantly higher in the SCH and OH groups.

CONCLUSIONS

Clinical and subclinical hypothyroidism during early pregnancy might cause adverse pregnancy outcomes. Implantation failure in rats with subclinical hypothyroidism was associated with abnormal LIF/STAT3 signaling.

Functional genomic analysis of the human receptive endometrium transcriptome upon administration of mifepristone at the time of follicle rupture

The aim of this study was to analyze the effects of progesterone withdrawal on gene transcription in receptive endometrium by the administration of a single dose of 50 mg of the anti-progesterone receptor mifepristone (MFP) at the time of follicle rupture (FR). Six volunteer ovulatory women were studied, taking endometrial biopsies of three control and three MFP-treated women on days LH+2 (C-LH+2) and LH+7 (T-MFP), respectively. The biopsies were prepared for RNA isolation or histological and immunohistochemistry studies. The genomic data from 14 women (C-LH+7) were included as a historical control. The functional genomic analysis of the differentially expressed genes showed that MFP interfered negatively with the bio-functions decidualization of uterus and implantation of blastocyst and embryo. The results of this study confirm but also give new information on how MFP affects endometrial gene expression when administered at the time of FR and the dose used in emergency contraception.

Decay-accelerating factor promotes endometrial cells proliferation and motility under ovarian hormone stimulation

The intent of the study was to explore the elevating expression of decay-accelerating factor(DAF) exerts influence on biological behaviors of endometrial stromal cells except in classical immunology on the basis of bioinformatic statistics and clinical miscarriages findings suggesting its potential role in the establishment of endometrial receptivity. We confirmed that DAF locates on the cellular surface of endometrial epithelium and stroma. By using plasmid transfection to down-regulate DAF expression in primary endometrial stromal cells(ESCs), we discovered that DAF expression in ESCs increases in response to estradiol and progesterone stimulation in dose- and time-dependent manners; moreover, tamoxifen and RU486 stimulations to block estrogen receptors(ERs) and progesterone receptors(PRs) respectively result in reduced DAF mRNA and protein, and it is more obvious to block PRs. Meanwhile, knocked-down DAF in ESCs weakens the proliferation, migration and invasion of endometrial cells. Cell cycle analysis showed knocked-down DAF accumulates cells in S phase and diminishes cells in G0/G1 phase, which substantiates DAF mediates endometrial cells proliferation. In conclusion, DAF is a potential molecule involving in endometrial cellular proliferation and motility to verify up-expressed DAF during the WOI may facilitate endometrial physiobiological behavior changes, which shed light on DAF function and potential role in the endometrial receptivity establishment.

Role of osteopontin in decidualization and pregnancy success

OPN is essential for blastocyst implantation and placentation. Previous study found that miR181a was increased while miR181b was downregulated in endometrium during decidualization. However, the information regarding their effects on decidualization in human endometrium is still limited. Here, we report a novel role of OPN and miR181b in uterine decidualization and pregnancy success in humans. The expression of OPN was high in endometrium in secretory phase and in vitro decidualized hESC, whereas miR181b expression was low in identical conditions. Further analysis confirmed that OPN expression was upregulated by cAMP and C/EBPβ signal pathway, while downregulated by miR181b. Increased OPN expression could promote the expression of decidualization-related and angiogenesis-related genes. Conversely, the processes of decidualization and angiogenesis in hESC were compromised by inhibiting OPN expression in vitro OPN expression was repressed in implantation failure group when compared with successful pregnancy group in IVF/ICSI-ET cycles. These findings add a new line of evidence supporting the fact that OPN is involved in decidualization and pregnancy success.

Meta-signature of human endometrial receptivity: a meta-analysis and validation study of transcriptomic biomarkers

Previous transcriptome studies of the human endometrium have revealed hundreds of simultaneously up- and down-regulated genes that are involved in endometrial receptivity. However, the overlap between the studies is relatively small, and we are still searching for potential diagnostic biomarkers. Here we perform a meta-analysis of endometrial-receptivity associated genes on 164 endometrial samples (76 from 'pre-receptive' and 88 from mid-secretory, 'receptive' phase endometria) using a robust rank aggregation (RRA) method, followed by enrichment analysis, and regulatory microRNA prediction. We identify a meta-signature of endometrial receptivity involving 57 mRNA genes as putative receptivity markers, where 39 of these we confirm experimentally using RNA-sequencing method in two separate datasets. The meta-signature genes highlight the importance of immune responses, the complement cascade pathway and the involvement of exosomes in mid-secretory endometrial functions. Bioinformatic prediction identifies 348 microRNAs that could regulate 30 endometrial-receptivity associated genes, and we confirm experimentally the decreased expression of 19 microRNAs with 11 corresponding up-regulated meta-signature genes in our validation experiments. The 57 identified meta-signature genes and involved pathways, together with their regulatory microRNAs could serve as promising and sought-after biomarkers of endometrial receptivity, fertility and infertility.

Uterosome-like vesicles prompt human sperm fertilizing capability

STUDY QUESTION

Does the rapid transit through the uterine environment modulate the sperm physiological state?

SUMMARY ANSWER

The uterosome-like vesicles (ULVs) secreted by endometrial epithelial cells (EECs) in vitro are able to fuse with human spermatozoa, prompting their fertilizing capacity.

WHAT IS KNOWN ALREADY

Early studies suggest that sperm capacitation begins in the uterus and ends in the oviduct, and that a synergistic effect of both female organs may accelerate this process. Although it has been reported that co-incubation of human spermatozoa with endometrial cell-conditioned medium (CM) stimulates sperm capacitation, the mechanism mediating this communication is unknown.

STUDY DESIGN, SIZE, DURATION

Human ULVs secreted by EECs were characterized and their effect on human sperm physiology was analysed. Spermatozoa were incubated with EEC-derived CM or ULV, after which sperm capacitation was evaluated at different time points. In addition, the interaction of spermatozoa with ULV was analysed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ULVs were isolated by ultracentrifugation and identified using electron microscopy and Western blotting to assess the presence of specific protein markers. Following seminal plasma removal, human spermatozoa were incubated CM or ULV, after which sperm capacitation was evaluated as the ability of the sperm to undergo the induced acrosome reaction and the level of protein tyrosine phosphorylation (PY) determined by Western blot and immunocytochemistry. The interaction of spermatozoa with labelled ULV was analysed by fluorescence microscopy. In all cases, at least three biological replicates from different sperm donors were performed for each set of experiments. Significant differences between mean values were determined by one-way ANOVA followed by Tukey's post hoc test. Differences between treatments were considered statistically significant at P ≤ 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

The level of capacitated spermatozoa and those recruited by chemotaxis increased 3- to 4-fold when spermatozoa were incubated in the presence of CM for 4 h. Even a 15 min incubation of spermatozoa with CM was also enough to increase the level of capacitated cells 3- to 4-fold (P < 0.05). Furthermore, a short co-incubation of spermatozoa with ULV stimulates sperm capacitation, as determined by the increase in the level of induced acrosome reaction and the induction of PY. In addition, after the co-incubation of spermatozoa with fluorescent labelled ULV, the sperm cells acquired the fluorescent staining which indicates that ULV might be transferred to the sperm surface by a fusion mechanism.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study performed with human biological material, spermatozoa and endometrial derived cells; the latter being a cell line originally isolated from a uterine adenocarcinoma.

WIDER IMPLICATIONS OF THE FINDINGS

The capability of spermatozoa to briefly interact with ULVs supports the hypothesis that any step of sperm transport may have physiological consequences, despite the interaction lasting for only a limited period of time. This way of communication of spermatozoa with cell products of uterine origin opens new frontiers of investigation (e.g. the signalling molecules involved), shedding light on the sperm processes that prepare the male gamete for fertilization, which might have implications for human infertility treatment.

LARGE SCALE DATA

N/A.

STUDY FUNDING AND COMPETING INTERESTS

The project was financially supported by SECyT-UNC. The authors declare no conflict of interest.

Osteopontin and Integrin αvβ3 Expression during the Implantation Window in IVF Patients with Elevated Serum Progesterone and Oestradiol Level

Background: To explore whether endometrial receptivity is determined by osteopontin (OPN) and integrin αvβ3 expression in women with elevated serum progesterone (P) and/or oestradiol (E₂) who are undergoing in vitro fertilisation (IVF). Methods: According to serum hormone levels on the day of HCG administration, 33 infertile women were divided into 3 groups: the high E₂, high P, and high E₂ and P groups. The control group included 11 fertile, healthy women. Endometrial biopsy was performed on ovulation day + 7 to + 8 for all study participants, and the mRNA and protein expression levels of OPN and integrin αvβ3 were analyzed. Result: No statistically significant differences regarding OPN and integrin αvβ3 expression were found between infertile patients in the high P, high E₂, high E₂ and P and control groups. There was no significant correlation between OPN and integrin αvβ3 staining intensity during the implantation window biopsy in any of the groups studied. Conclusion: Endometrial OPN and integrant αvβ3 expression/co-expression is not impaired during the window of implantation in patients with high P, high E₂, or high E₂ and P levels. The clinical value of assessing endometrial receptivity with OPN and integrin αvβ3 seems to be uncertain.

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.

Osteopontin is expressed in the mouse uterus during early pregnancy and promotes mouse blastocyst attachment and invasion in vitro

Embryo implantation into the maternal uterus is a decisive step for successful mammalian pregnancy. Osteopontin (OPN) is a member of the small integrin-binding ligand N-linked glycoprotein family and participates in cell adhesion and invasion. In this study, we showed that Opn mRNA levels are up-regulated in the mouse uterus on day 4 and at the implantation sites on days 5 and 8 of pregnancy. Immunohistochemistry localized the OPN protein to the glandular epithelium on day 4 and to the decidual zone on day 8 of pregnancy. OPN mRNA and proteins are induced by in vivo and in vitro decidualization. OPN expression in the endometrial stromal cells is regulated by progesterone, a key regulator during decidualization. As a secreted protein, the protein level of OPN in the uterine cavity is enriched on day 4, and in vitro embryo culturing has indicated that OPN can facilitate blastocyst hatching and adhesion. Knockdown of OPN attenuates the adhesion and invasion of blastocysts in mouse endometrial stromal cells by suppressing the expression and enzymatic activity of matrix metalloproteinase-9 in the trophoblast. Our data indicated that OPN expression in the mouse uterus during early pregnancy is essential for blastocyst hatching and adhesion and that the knockdown of OPN in mouse endometrial stroma cells could lead to a restrained in vitro trophoblast invasion.

Molecular basis of thyrotropin and thyroid hormone action during implantation and early development

BACKGROUND

Implantation and early embryo development are finely regulated processes in which several molecules are involved. Evidence that thyroid hormones (TH: T4 and T3) might be part of this machinery is emerging. An increased demand for TH occurs during gestation, and any alteration in maternal thyroid physiology has significant implications for both maternal and fetal health. Not only overt but also subclinical hypothyroidism is associated with infertility as well as with obstetric complications, including disruptions and disorders of pregnancy, labor, delivery, and troubles in early neonatal life.

METHODS

We searched the PubMed and Google Scholar databases for articles related to TH action on ovary, endometrium, trophoblast maturation and embryo implantation. In addition, articles on the regulation of TH activity at cellular level have been reviewed. The findings are hereby summarized and critically discussed.

RESULTS

TH have been shown to influence endometrial, ovarian and placental physiology. TH receptors (TR) and thyrotropin (thyroid-stimulating hormone: TSH) receptors (TSHR) are widely expressed in the feto-maternal unit during implantation, and both the endometrium and the trophoblast might be influenced by TH either directly or through TH effects on the synthesis and activity of implantation-mediating molecules. Interestingly, due to the multiplicity of mechanisms involved in TH action (e.g. differential expression of TR isoforms, heterodimeric receptor partners, interacting cellular proteins, and regulating enzymes), the TH concentration in blood is not always predictive of their cellular availability and activity at both genomic and nongenomic level.

CONCLUSIONS

In addition to the known role of TH on the hormonal milieu of the ovarian follicle cycle, which is essential for a woman's fertility, evidence is emerging on the importance of TH signaling during implantation and early pregnancy. Based on recent observations, a local action of TH on female reproductive organs and the embryo during implantation appears to be crucial for a successful pregnancy. Furthermore, an imbalance in the spatio-temporal expression of factors involved in TH activity might induce early arrest of pregnancy in women considered as euthyroid, based on their hormonal blood concentration. In conclusion, alterations of the highly regulated local activity of TH may play a crucial, previously underestimated, role in early pregnancy and pregnancy loss. Further studies elucidating this topic should be encouraged.

The transcriptomic and proteomic effects of ectopic overexpression of miR-30d in human endometrial epithelial cells

miR-30d is known to be up-regulated during the acquisition of receptivity in the endometrium. In order to determine the transcriptomic and proteomic changes which occur after transient overexpression of miR-30d in primary endometrial epithelial cells, in vitro cultured human endometrial epithelial cells (hEECs) were studied experimentally. Two different miRNAs (scramble versus mimic; n = 15) were transiently transfected into primary hEECs from four different patients and were evaluated for mRNA and protein expression using Agilent's gene expression microarray and iTRAQ analysis techniques, respectively. A set of differentially expressed mRNAs were validated by qPCR and several differentially expressed proteins were validated by western blot. Finally, methylation differential immunoprecipitation (MeDIP) was used to validate the epigenetic changes in the H19 gene. The results showed that transient transfection with miR-30d miRNA induced the differential mRNA-expression of 176 genes (75 up-regulated and 101 down-regulated). Several of them have been associated with reproductive and endocrine system disorders, tissue development, and are implicated in epithelial cell proliferation. Also, the down-regulation of some genes such as H19 and N-methyltransferase (NNMT) may suggest that epigenetic alterations are induced. Furthermore, upstream effects of genes regulated by the estrogen receptor alpha 1 (ESR1) transcription factor have been predicted. Proteomic analysis identified 2290 proteins, of which 108 were differentially expressed (47 up-regulated and 61 down-regulated). Among these differentially expressed proteins DNA methyl transferase (DNMT)1 was found to be up-regulated; this protein participates in the maintenance of DNA methylation, supporting an epigenetic role for miR-30d. Finally MeDIP showed an increase in methylation in the H19 DMR region. In conclusion transient in vitro overexpression of the receptivity-up-regulated miRNA miR-30d in hEECs seems to activate genes which are associated with hormonal response and the epigenetic status of these cells.

Uterine micro-environment and estrogen-dependent regulation of osteopontin expression in mouse blastocyst

Embryo implantation is a highly synchronized bioprocess between an activated blastocyst and a receptive uterus. In mice, successful implantation relies on the dynamic interplay of estrogen and progesterone; however, the key mediators downstream of these hormones that act on blastocyst competency and endometrium receptivity acquisition are largely unknown. In this study, we showed that the expression of osteopontin (OPN) in mouse blastocysts is regulated by ovarian estrogen and uterine micro-environment. OPN mRNA is up-regulated in mouse blastocyst on day 4 of pregnancy, which is associated with ovarian estrogen secretion peak. Hormone treatment in vivo demonstrated that OPN expression in a blastocyst is regulated by estrogen through an estrogen receptor (ER). Our results of the delayed and activated implantation model showed that OPN expression is induced after estrogen injection. While estrogen treatment during embryo culture in vitro showed less effect on OPN expression, the tubal ligation model on day 3 of pregnancy confirmed that the regulation of estrogen on OPN expression in blastocyst might, through some specific cytokines, have existed in a uterine micro-environment. Collectively, our study presents that estrogen regulates OPN expression and it may play an important role during embryo implantation by activating blastocyst competence and facilitating the endometrium acceptable for active blastocyst.

Complement C3 and decay-accelerating factor expression levels are modulated by human chorionic gonadotropin in endometrial compartments during the implantation window

The control of complement activation in the embryo-maternal environment has been demonstrated to be critical for embryo survival. Complement proteins are expressed in the human endometrium; however, the modulation of this expression by embryo signals has not been explored. To assess the expression of complement proteins in response to human chorionic gonadotropin (hCG), we designed an experimental study using in vivo and in vitro models. Twelve fertile women were treated with hCG or left untreated during the mid-luteal phase, and an endometrial biopsy was performed 24 hours later. The localizations of C3, membrane cofactor protein (MCP; CD46), decay-accelerating factor (DAF; CD55), and protectin (CD59) were assessed by immunohistochemistry, and the messenger RNA (mRNA) levels of these proteins were quantified by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in cells harvested from endometrial compartments using laser capture microdissection. Endometrial explants were cultured with or without hCG for 24 hours, and the C3 and DAF protein levels were measured by Western blotting. Elevated C3 mRNA levels in stromal cells and elevated DAF levels in epithelial luminal cells were detected after hCG treatment. In the endometrial explant model, the progesterone receptor antagonist RU486 inhibited the increases in the levels of C3 and DAF in response to hCG. The findings of this study indicate that hCG plays a role in embryo-endometrium communication and affects the expression of complement proteins in endometrial compartments during the implantation window.

Consequences of nongenomic actions of estradiol on pathogenic genital tract response

Estradiol is a steroid hormone that regulates the structure and function of the female reproductive system. In addition to its genomic effects, which are mediated by activated nuclear receptors, estradiol elicits a variety of rapid signaling events independently of transcriptional or genomic regulation. These nongenomic actions influence the milieu of the genital tract, which changes the ability of pathogens to infect the genital tract. This review discusses our current knowledge regarding the mechanisms and relevance of nongenomic estradiol signaling in the genital tract that could change the ability of pathogens to invade epithelial cells. PubMed was searched through January 1980 for papers related to estradiol actions in the ovary, fallopian tube, uterus and cervix. The mechanisms conveying these rapid effects consist of a multitude of signaling molecules and include cross-talk with slower transcriptional actions. The nongenomic actions of estradiol that influence the infectious abilities of pathogens occur either directly on the genital tract cells or indirectly by modulating the local and systemic immune systems. Additional in-depth characterization of the response is required before the normal and pathological reproductive functions of the nongenomic estradiol pathway can be targeted for pharmacological intervention.

Modulation of the expression of the transcription factors T-bet and GATA-3 in immortalized human endometrial stromal cells (HESCs) by sex steroid hormones and cAMP

T-bet and GATA-3 are known to regulate cytokine expression in T lymphocytes, and cytokines have been implicated in endometrial regulation and implantation. Previous work showed that female steroid hormones modulate the expression of T-bet in endometrial epithelial cells, suggesting a mechanism for local immune regulation in the human endometrium. We hypothesized that stromal cells are involved in immune regulation, as they have been shown to exert paracrine effects on other endometrial cells and compartments and also secrete cytokines. The objective of this study was to examine the modulation of the gene expression of T-bet and GATA-3, and of the cytokines interferon γ (IFN-γ) and interleukin 4 (IL-4), by female steroid hormones, in human endometrial stromal cells (HESC) in long-term cultures (30 days) mimicking the normal menstrual cycle. T-bet and GATA-3 messenger RNA (mRNA) expression was detected by real-time polymerase chain reaction, and intracellular protein production was demonstrated by immunoblotting. In addition, secretion of IL-4 and IL-15 was measured by enzyme-linked immunosorbent assay. T-bet and IL-4 mRNA expression increased and GATA-3 decreased under decidualization conditions; IFN-γ was not detected. Secretion of IL-15 increased during decidualization, and IL-15 upregulated T-bet gene expression. In conclusion, gene expression of T-bet and GATA-3 by endometrial stromal cells is under hormonal conditions mimicking decidualization, and the results are consistent with an autocrine regulatory mechanism of IL-15 secretion and T-bet expression.

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.

The endocrine and paracrine control of menstruation

During the reproductive life, the human endometrium undergoes cycles of substantial remodeling including, at menstruation, a massive but delimited tissue breakdown immediately followed by scarless repair. The present review aims at summarizing the current knowledge on the endocrine and paracrine control of menstruation in the light of recent observations that undermine obsolete dogmas. Menstruation can be globally considered as a response to falling progesterone concentration. However, tissue breakdown is heterogeneous and tightly controlled in space and time by a complex network of regulators and effectors, including cytokines, chemokines, proteases and various components of an inflammatory response. Moreover, menstruation must be regarded as part of a complex and integrated mechanism of tissue remodeling including features that precede and follow tissue lysis, i.e. decidualization and immediate post-menstrual regeneration. The understanding of the regulation of menstruation is of major basic and clinical interest. Indeed, these mechanisms largely overlap with those controlling other histopathological occurrences of tissue remodeling, such as development and cancer, and inappropriate control of menstrual features is a major potential cause of two frequent endometrial pathologies (i.e. abnormal uterine bleeding and endometriosis).

Milk fat globule epidermal growth factor 8 (MFG-E8): a novel protein in the mammalian endometrium with putative roles in implantation and placentation

OBJECTIVES

MFG-E8 is a novel endometrial protein with conserved functions in tissue remodeling and angiogenesis in non-uterine tissues. Our aims were: 1. To examine the presence of MFG-E8 protein in the human endometrium during the window of implantation, in human endometrial cell lines, in human placental tissue at different gestational ages, and in murine implantation sites during early gestation; and 2. To study the regulation of MFG-E8 mRNA expression in mice implantation sites.

STUDY DESIGN

MFG-E8 protein and its receptor integrin αvβ3 were detected by immunostaining in human endometrial biopsies obtained from normal volunteers, in human endometrial cell lines (epithelial: Ishikawa and HEC-1A, stromal: HESC, and endothelial: HEEC), in human products of conception from all trimesters of gestation, and in murine implantation and inter-implantation sites dissected on days 5 and 8 post-coitus. MFG-E8 gene expression was assessed by RT-PCR.

MAIN OUTCOME MEASURES

Immunohistochemical determination of MFG-E8 in endometrium and products of conception as well as relative MFG-E8 mRNA expression in mice implantation sites.

RESULTS

MFG-E8 protein was present almost exclusively in the epithelial compartment of human endometrium. It was also expressed in the cytotrophoblasts and syncytiotrophoblasts outlining chorionic villi of the human placenta at all trimesters of gestation, and in murine implantation sites. MFG-E8 mRNA was significantly up-regulated in murine implantation sites and with increased gestational age.

CONCLUSIONS

MFG-E8 expression in the endometrial epithelium as well as in chorionic villi suggests its possible role in endometrial reorganization during the receptive phase and in events related to normal pregnancy in mammals.

The genomics of the human endometrium

The endometrium is a complex tissue that lines the inside of the endometrial cavity. The gene expression of the different endometrial cell types is regulated by ovarian steroids and paracrine-secreted molecules from neighbouring cells. Due to this regulation, the endometrium goes through cyclic modifications which can be divided simply into the proliferative phase, the secretory phase and the menstrual phase. Successful embryo implantation depends on three factors: embryo quality, the endometrium's state of receptivity, and a synchronised dialogue between the maternal tissue and the blastocyst. There is a need to characterise the endometrium's state of receptivity in order to prevent reproductive failure. No single molecular or histological marker for this status has yet been found. Here, we review the global transcriptomic analyses performed in the last decade on a normal human endometrium. These studies provide us with a clue about what global gene expression can be expected for a non-pathological endometrium. These studies have shown endometrial phase-specific transcriptomic profiles and common temporal gene expression patterns. We summarise the biological processes and genes regulated in the different phases of natural cycles and present other works on different conditions as well as a receptivity diagnostic tool based on a specific gene set profile. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Gene and protein expression signature of endometrial glandular and stromal compartments during the window of implantation

OBJECTIVE

To map the changes in messenger RNA (mRNA) and protein abundance during the window of implantation in specifically endometrial stromal and glandular epithelial cells obtained using laser microdissection microscopy (LDM).

DESIGN

Endometrial samples were collected from two menstrual cycles at 2 and 7 days after first significant rise in blood LH, and separate cell populations were obtained using LDM. A new generation linear polymerase chain reaction (PCR) amplified the mRNA, which were hybridized to both Affymetrix U133 Plus2 and Agilent 4x44K microarrays followed by gene set analysis. Immunohistochemistry assessed protein expression between the two collection times.

SETTING

In vitro fertilization clinic.

PATIENT(S)

Nine Caucasian, fertile, cycling women.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Cycle dating using blood markers; microarrays on laser microdissected glands and stroma; dual platform microarray confirmation; immunohistochemical analysis of cell cycle proteins.

RESULT(S)

The two microarray platforms showed concordance. During the window of implantation, a statistically significant network of 22 mRNA associated with the cell cycle was down-regulated. Immunohistochemistry identified altered localization in stroma.

CONCLUSION(S)

Microarrays demonstrated glands and stroma have distinct mRNA signatures, each dependent on the day of the cycle. We characterized two compartments of the receptive endometrium with a transcriptomic signature identifying regulation of only the cell cycle. Immunohistochemical analysis of cell cycle proteins identified a signature staining pattern of nuclear relocalization of a group of cyclins of stromal cells, which may be clinically applicable.

Expression pattern of osteopontin and αvβ3 integrin during the implantation window in infertile patients with early stages of endometriosis

BACKGROUND

To study endometrial receptivity in terms of osteopontin (OPN) and αvβ3 integrin expression and co-expression in infertile women with early stages of endometriosis.

METHODS

We investigated the immunohistochemical expression and co-expression of OPN and αvβ3 integrin in the endometrium of 20 infertile patients with Stage I or II endometriosis as the only detectable cause of infertility, 20 infertile patients with unexplained infertility and 20 fertile women undergoing tubal sterilization. Two endometrial biopsies were performed during a single menstrual cycle (postovulatory Day +7 to +8 and 4 days later) in each subject.

RESULTS

No statistically significant differences regarding OPN and αvβ3 integrin expression were found between infertile patients with endometriosis and the two control groups. There was no significant correlation between OPN and αvβ3 integrin staining intensity in the mid-luteal phase biopsies in any of the groups studied.

CONCLUSIONS

Endometrial OPN and αvβ3 integrin expression or co-expression is not impaired during the window of implantation in patients with Stage I-II endometriosis. Further studies are needed to determine whether these results imply normal endometrial receptivity in such patients or add to the increasing uncertainty about the clinical value of assessing the endometrium with these markers of implantation.

A novel model of human implantation: 3D endometrium-like culture system to study attachment of human trophoblast (Jar) cell spheroids

There is an urgent need to develop optimized experimental models to examine human implantation. These studies aimed to (i) establish a human endometrium-like three-dimensional (3D) culture system, and (ii) examine the attachment of trophoblast-like Jar spheroids to the culture. In the present work, 3D endometrial cultures were constructed with fibrin-agarose as matrix scaffold, and using epithelial and stromal cells from both human primary cultures and established cell lines. An attachment assay between trophoblast cells and the 3D culture was developed. Epithelial cells (cytokeratin(+)) concentrated on top of the matrix forming a monolayer, and stromal cells (vimentin(+)) resided within the matrix, resembling the normal endometrial structure. The capability of primary epithelial cells to form glands spontaneously was observed. Human trophoblast cells (Jar cells) were hCG(+) by immunostaining, allowed to form spheroids, and confirmed to secrete hCG into the medium. Time-dependent experiments demonstrated a high rate of attachment of Jar spheroids to the epithelium, and adhesion was strongly related to the various cell types present in the 3D culture. An architecturally and functionally competent 3D endometrial culture system was established, that coupled with Jar spheroids mimicking trophoblast cells, provides a unique in vitro model for the study of certain aspects of human implantation.

Bioinformatic detection of E47, E2F1 and SREBP1 transcription factors as potential regulators of genes associated to acquisition of endometrial receptivity

BACKGROUND

The endometrium is a dynamic tissue whose changes are driven by the ovarian steroidal hormones. Its main function is to provide an adequate substrate for embryo implantation. Using microarray technology, several reports have provided the gene expression patterns of human endometrial tissue during the window of implantation. However it is required that biological connections be made across these genomic datasets to take full advantage of them. The objective of this work was to perform a research synthesis of available gene expression profiles related to acquisition of endometrial receptivity for embryo implantation, in order to gain insights into its molecular basis and regulation.

METHODS

Gene expression datasets were intersected to determine a consensus endometrial receptivity transcript list (CERTL). For this cluster of genes we determined their functional annotations using available web-based databases. In addition, promoter sequences were analyzed to identify putative transcription factor binding sites using bioinformatics tools and determined over-represented features.

RESULTS

We found 40 up- and 21 down-regulated transcripts in the CERTL. Those more consistently increased were C4BPA, SPP1, APOD, CD55, CFD, CLDN4, DKK1, ID4, IL15 and MAP3K5 whereas the more consistently decreased were OLFM1, CCNB1, CRABP2, EDN3, FGFR1, MSX1 and MSX2. Functional annotation of CERTL showed it was enriched with transcripts related to the immune response, complement activation and cell cycle regulation. Promoter sequence analysis of genes revealed that DNA binding sites for E47, E2F1 and SREBP1 transcription factors were the most consistently over-represented and in both up- and down-regulated genes during the window of implantation.

CONCLUSIONS

Our research synthesis allowed organizing and mining high throughput data to explore endometrial receptivity and focus future research efforts on specific genes and pathways. The discovery of possible new transcription factors orchestrating the CERTL opens new alternatives for understanding gene expression regulation in uterine function.

Laboratory methods in the study of endometrial Claudin-4

Immunohistochemistry is a suitable method for the detection of proteins from the Claudin family and several antibodies are commercially available for the detection of Claudin congeners. Immunodetection of Caludin-4 in the paraffin-embedded specimens might be a useful tool for studying the role of these proteins in the cyclic transformation of the endometrium and its role in the endometrial receptivity; furthermore, other components of the junctional zone involved in the transformational process of the endometrium can be detected by means of immunohistochemistry/immunofluorescence with several polyclonal or monoclonal antibodies. The aim of this chapter is to comprehensively overview the materials and methods to perform the endometrial biopsy and to detect Claudin-4 in paraffin-embedded samples of endometrium. Additionally, the interpretation of the results is addressed.

Oestrogen and progesterone regulation of inflammatory processes in the human endometrium

The human endometrium is a unique tissue that has to undergo cycles of proliferation, differentiation, destruction and repair. This ensures that the endometrium is optimally prepared for potential embryo implantation but in the absence of an embryo, menstruation occurs to allow endometrial regeneration. These cycles of tissue remodelling occur under the sequential influence of the sex steroid hormones, oestrogen and progesterone. The physiological events of implantation and menstruation display features of inflammation, tightly regulated by oestrogen and progesterone. After menstruation cellular proliferation and blood vessel growth is modulated by oestrogen while after ovulation progesterone is the dominant hormone. In preparation for implantation, progesterone regulates decidualization of the endometrium, uterine natural killer cell numbers within the endometrium and chemokine and cytokine expression. Menstruation, in contrast, is preceded by progesterone withdrawal, which results in an influx of leukocytes into the endometrium and increased production of chemokines and matrix metalloproteinases allowing tissue degradation. The aim of this article is to review the current knowledge on the regulation of inflammatory events within the endometrium by oestrogen and progesterone, in relation to two pivotal events for human reproduction, implantation and menstruation.

Implication of expression of osteopontin and its receptor integrin alphanubeta3 in the placenta in the development of preeclampsia

To investigate the expression of osteopontin (OPN) and its receptor integrin alphanubeta3 in the placental tissue from pregnant women complicated with preeclampsia, the expression of OPN and alphanubeta3 in the placenta of the pregnant women with preeclampsia and healthy pregnant women was detected by immunohistochemistry, Western blotting and RT-PCR. Our results showed that OPN and alphanubeta3 protein were expressed in the placenta from normal pregnant woman and those with preeclampsia. OPN was located in the placental syncytiotrophoblasts and the cytoplasm of capillary endothelial cells and integrin alphanubeta3 was mainly expressed on the surface of trophoblast cells. Expression of OPN and integrin alphanubeta3 in the placental tissue from preeclampsia subjects was significantly lower than that from the control group (P<0.05). Compared with the control group, expression of OPN in the placental tissue from preeclampsia group was significantly lower (P<0.05) but there was no significant difference in the expression of alphanu and beta3 between the preeclampsia group and the controls. It is concluded that OPN and its receptor integrin alphanubeta3 may be involved in the pathogenesis of preeclampsia.

Cancer and pregnancy: parallels in growth, invasion, and immune modulation and implications for cancer therapeutic agents

Many proliferative, invasive, and immune tolerance mechanisms that support normal human pregnancy are also exploited by malignancies to establish a nutrient supply and evade or edit the host immune response. In addition to the shared capacity for invading through normal tissues, both cancer cells and cells of the developing placenta create a microenvironment supportive of both immunologic privilege and angiogenesis. Systemic alterations in immunity are also detectable, particularly with respect to a helper T cell type 2 polarization evident in advanced cancers and midtrimester pregnancy. This review summarizes the similarities between growth and immune privilege in cancer and pregnancy and identifies areas for further investigation. Our PubMed search strategy included combinations of terms such as immune tolerance, pregnancy, cancer, cytokines, angiogenesis, and invasion. We did not place any restrictions on publication dates. The knowledge gained from analyzing similarities and differences between the physiologic state of pregnancy and the pathologic state of cancer could lead to identification of new potential targets for cancer therapeutic agents.

Spatiotemporal coupling of focal extracellular matrix degradation and reconstruction in the menstrual human endometrium

Coupling of focal degradation and renewal of the functional layer of menstrual endometrium is a key event of the female reproductive biology. The precise mechanisms by which the various endometrial cell populations control extracellular matrix (ECM) degradation in the functionalis while preserving the basalis and the respective contribution of basalis and functionalis in endometrium regeneration are still unclear. We therefore compared the transcriptome of stromal and glandular cells isolated by laser capture microdissection from the basalis as well as degraded and preserved areas of the functionalis in menstrual endometria. Data were validated by in situ hybridization. Expression profile of selected genes was further analyzed throughout the menstrual cycle, and their response to ovarian steroids withdrawal was studied in a mouse xenograft model. Immunohistochemistry confirmed the results at the protein level. Algorithms for sample clustering segregated biological samples according to cell type and tissue depth, indicating distinct gene expression profiles. Pairwise comparisons identified the greatest numbers of differentially expressed genes in the lysed functionalis when compared with the basalis. Strikingly, in addition to genes products associated with tissue degradation (matrix metalloproteinase and plasmin systems) and apoptosis, superficial lysed stroma was enriched in gene products associated with ECM biosynthesis (collagens and their processing enzymes). These results support the hypothesis that fragments of the functionalis participate in endometrial regeneration during late menstruation. Moreover, menstrual reflux of lysed fragments overexpressing ECM components and adhesion molecules could easily facilitate implantation of endometriotic lesions.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.