Effect of controlled ovarian hyperstimulation in IVF on endometrial gene expression profiles

Detrimental effects of high-dose gonadotropin on outcome of IVF: making a case for gentle ovarian stimulation strategies

OBJECTIVE

Limited data identify detrimental influences of aggressive use of gonadotropins (G) for controlled ovarian hyperstimulation (COH); the underlying mechanisms however remain unclear. We report on the relationship between G dose and in vitro fertilization (IVF) cycle parameters (ovarian response, endometrial thickness [EMT]) and cycle outcome (implantation rate [IR] and clinical pregnancy [CP] rate) in a cohort of women undergoing IVF.

METHODS

Retrospective analysis of fresh embryo transfer (ET) cycles. Univariate and multivariable regression analyses assessed relationship between G dose and outcomes of interest.

RESULTS

Higher G dose related positively with advancing age (P < .001) and inversely with EMT (P < .001). The overall CP rate was 30%. Significantly lower IR (.003) and CP rate (.002) were observed across increasing tertiles of G dose. Increasing G dose was identified as an independent negative predictor of EMT after adjusting for age, COH protocol and duration, infertility diagnosis, and ovarian response (P = .016). Adjusting for age, suppression protocol (gonadotropin-releasing hormone agonist vs antagonist), infertility diagnoses, EMT, quality, and cleavage of ET, lower G dose was an independent positive predictor of CP rate (odds ratio for CP rate was 1.57 for G dose in middle compared to the highest G dose quartile (95% confidence interval 1.09-2.24). Stratified analyses identified detrimental associations of higher G dose with CP rate to be relevant in women aged 35 years and younger.

CONCLUSIONS

Our analyses suggest detrimental influences of higher G dose on the endometrium and confirm the previously reported adverse association between higher G dose and IVF outcome. Gentler COH regimens may be of particular benefit in women aged ≤35 years.

Ovarian stimulation and low birth weight in newborns conceived through in vitro fertilization

OBJECTIVE

Singleton neonates born after in vitro fertilization (IVF) are at increased risk for low birth weight, preterm delivery, or both. We sought to assess whether the alteration of the peri-implantation maternal environment resulting from ovarian stimulation may contribute to increased risk of low birth weight in IVF births.

METHODS

The Society for Assisted Reproductive Technologies database was used to identify IVF-conceived neonates born in the United States between 2004 and 2006. Associations were assessed in neonates born after fresh compared with frozen and thawed embryo transfer in women of similar ovarian responsiveness, in paired analysis of neonates born to the same woman after both types of embryo transfer, and in neonates born after oocyte donation.

RESULTS

Of 56,792 neonates identified, 38,626 and 18,166 were conceived after transfer of fresh and frozen embryos, respectively. In singletons, there was no difference in preterm delivery. However, the odds of overall low birth weight (10% compared with 7.2%; adjusted odds ratio [OR] 1.35; 95% confidence interval [CI] 1.20-1.51), low birth weight at term (2.5% compared with 1.2%, adjusted OR 1.73, 95% CI 1.31-2.29), and preterm low birth weight (34.1% compared with 23.8%, adjusted OR 1.49, 95% CI 1.24-1.78) were all significantly higher after fresh embryo transfer. In singletons, after either fresh or frozen embryo transfer in the same patient, this association was even stronger (low birth weight: 11.5% compared with 5.6%, adjusted OR 4.66, 95% CI 1.18-18.38). In oocyte donor recipients who do not undergo any ovarian hormonal stimulation for either a fresh or a frozen embryo transfer, no difference in low birth weight was demonstrated (11.5% compared with 11.3% adjusted OR 0.99, 95% CI 0.82-1.18).

CONCLUSION

The ovarian stimulation-induced maternal environment appears to represent an independent mediator contributing to the risk of low birth weight, but not preterm delivery, in neonates conceived after IVF.

LEVEL OF EVIDENCE

II.

Increased endometrial placenta growth factor (PLGF) gene expression in women with successful implantation

OBJECTIVE

To analyze the vascularization of the endometrium via hysteroscopy and to assess its correlation with angiogenic factor gene expression and embryo implantation rate.

DESIGN

Cross-sectional study.

SETTING

Public university hospital.

PATIENT(S)

Patients undergoing hysteroscopy for supposed infertility.

INTERVENTION(S)

Endometrial quality assessment according to Sakumoto-Masamoto, performed in the early secretory phase of the cycle. Collection of an endometrial tissue biopsy.

MAIN OUTCOME MEASURE(S)

RNA extraction, reverse transcription, and determination of gene expression of angiogenesis- and implantation-relevant factors using quantitative polymerase chain reaction. Retrieval of pregnancy information from the medical records.

RESULT(S)

Good quantity/quality RNA with infertility history was obtained from 63 participating women. Those with a "good" endometrium and subsequent pregnancy showed increased gene expression for placenta growth factor when compared with patients with a "bad" endometrium and who did not succeed with pregnancy to date. Nonpregnant women with a "good" endometrium presented an intermediate result. No significant differences were observed for several other genes tested, but trends in the same direction were observed.

CONCLUSION(S)

This study demonstrates for the first time that endometrial PLGF expression corresponds to the hysteroscopic appearance of the endometrium, and therefore has potential as a clinically relevant prognosticator for infertility treatment success.

Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfers in high responders

Clinical pregnancy rates of 80% and 65% were observed in cycles using thawed and fresh embryos, respectively, although embryo quality indicators revealed morphologically and numerically inferior embryo cohorts after cryopreservation. Subsequent logistic regression analysis controlled for differences in embryo quality and revealed significantly greater probability of clinical pregnancy with thawed embryos when compared with fresh, suggesting a negative effect of ovarian stimulation on endometrial receptivity.

Differential effects of urinary and recombinant chorionic gonadotropin on oxidative stress responses in decidualizing human endometrial stromal cells

Human chorionic gonadotropin (hCG) is one of the earliest signals secreted by the implanting embryo. In addition to its well-known luteotropic function in early pregnancy, hCG also acts directly on decidualizing endometrium. Recently, we demonstrated that recombinant hCG (rhCG) prevented apoptosis in decidualizing human endometrial stromal cells (HESCs) exposed to oxidative stress. Two hCG preparations are widely used clinically: rhCG, produced by recombinant DNA technology, and urinay hCG (uhCG), extracted from urine of post-menopausal women. However, an analysis of the direct effects of rhCG and uhCG on the decidual phenotype of HESCs has not yet been done. In this study, we investigated the effects of uhCG and rhCG on the morphological and functional profiles of decidualizing HESCs. We demonstrate that neither rhCG nor uhCG alter the morphological appearance of the decidual HESC cultures, although rhCG but not uhCG attenuated prolactin expression, a major decidual marker protein. Moreover, rhCG, but not uhCG, protected decidualizing HESCs from oxidative cell death, mediated at least in part by two major mechanisms. First, rhCG, but not uhCG, enhances the expression of manganese superoxide dismutase, a cardinal enzyme in the cellular defense against oxidative damage. Second, rhCG signaling selectively limits activation of the apoptotic machinery in decidualizing HESCs by enhancing Bcl-2 expression whereas uhCG induces the expression of Fas ligand. Our results suggest that rhCG might be a preferable agent to protect the maternal decidua against oxidative damage in pregnancy, especially at the time of implantation and beyond.

Ovarian stimulation affects the levels of regulatory endometrial NK cells and angiogenic cytokine VEGF

PROBLEM

Endometrial NK cells play a critical role in uterine vascularization producing angiogenic factors. Impact of ovarian stimulation on endometrial expression of NK cells and VEGF in normal fertile oocyte donors and the effect of endometrial injury treatment on these parameters have been investigated.

METHOD OF STUDY

Endometrial tissue was obtained from oocyte donors during natural and stimulated cycles. NK cell subsets were measured by flow cytometry. VEGF was determined by ELISA and flow cytometry. Endometrial angiogenic parameters were determined by ultrasound Doppler. Local injury was induced by scratching endometrial tissue previous to implantation window.

RESULTS

Ovarian stimulation decreased endometrial levels of NK cells and vascularization index but increased VEGF levels. Local injury normalized only the CD56(+) NK cell count.

CONCLUSION

Hormonal therapy for ovarian stimulation may be associated with poor endometrial vascularization. Local injury before the implantation window seems not to influence endometrial angiogenic parameters altered by ovarian stimulation.

Endometrial gene expression in the window of implantation is altered in obese women especially in association with polycystic ovary syndrome

OBJECTIVE

To determine whether luteal phase endometrial transcriptome is altered in obese women during the window of implantation (WOI), considering the presence of infertility, fat distribution and association with polycystic ovary syndrome (PCOS).

DESIGN

Prospective study.

SETTING

University-affiliated infertility clinic, between May 2007 and March 2009.

PATIENT(S)

One control group of women with normal weight (n=4), and four study groups of obese women (n=6 each one) according to the association with infertility, PCOS, and ovarian stimulation.

INTERVENTION(S)

The endometrium was biopsied 7 days after LH surge or hCG administration in 28 women.

MAIN OUTCOME MEASURE(S)

Endometrial gene expression during the WOI.

RESULT(S)

One hundred and fifty-one genes were dysregulated in obese groups compared with controls. This dysregulation was more pronounced when infertility was associated. The biologic processes of these genes belonged mainly to development and regulation of different biological functions such as transcription and biosynthesis. The molecular functions overrepresented were transcription and peptide receptor activity. The endometrium of obese women with PCOS showed dysregulated genes related to biologic processes such as development, morphogenesis, and the immune system, as well as different molecular functions such as protein binding, binding, growth factor activity, and carboxylic acid transmembrane transporter activity. Some of these genes have been previously related to implantation and unexplained infertility.

CONCLUSION(S)

Obese women present a different endometrial gene expression than controls during the WOI, which is more pronounced when infertility or polycystic ovary syndrome are associated.

Endometrial morphology and modulation of hormone receptors during ovarian stimulation for assisted reproductive technology cycles

OBJECTIVE

To study the biochemical and morphologic implications of different hormonal levels on endometrial development during assisted reproductive technology (ART) cycles.

DESIGN

Prospective, controlled study.

SETTING

University center.

PATIENT(S)

Eleven women during a natural cycle (controls) and 11 oocyte donors during an ART cycle (treated).

INTERVENTION(S)

At the time consistent with day-3 ET, a transvaginal ultrasound, an endometrial biopsy, and blood sampling were performed. Morphology and thickness of the endometrial stripe were recorded. Real-time reverse transcriptase-polymerase chain reaction was used to measure messenger RNA (mRNA) levels for estrogen receptor (ER)-α, ER-β, P receptor (PR)-A, and PR-B in the endometrial tissue.

MAIN OUTCOME MEASURE(S)

To evaluate morphologic and biochemical endometrial development.

RESULT(S)

Endometrium was mostly trilaminar (proliferative-like pattern) and thicker in the treated group, as opposed to homogeneous and thinner in the controls. The PR-B mRNA expression increased 41% in treated patients; PR-A mRNA expression, instead, was unchanged. Serum E(2) and P were higher in the treated group than in controls. In contrast, FSH and LH levels were lower in the treated group.

CONCLUSION(S)

When compared with natural cycles, exposure of the endometrium to high hormone levels during ovarian stimulation significantly increased PR-B receptor expression at the time of ET. Concurrently, a proliferative-like endometrial pattern persisted. These findings reflect a delayed endometrial development in ART.

Variation in hyaluronan-binding protein 2 (HABP2) promoter region is associated with unexplained female infertility

We set up to analyze polymorphisms in hyaluronan-binding protein 2 (HABP2) gene in healthy fertile women (n = 158) and in women with unexplained infertility (n = 116) and to investigate the potential role of HABP2 in receptive endometrium. Minor rs1157916 A and the major rs2240879 A alleles together with AA genotypes were significantly less frequent in infertile women than in controls. Immunohistochemistry analysis of endometrial HABP2 expression at the time of implantation identified significantly lower HABP2 protein level in infertile women in stroma and vessels than in fertile women. Migration assay analysis of cultured trophoblast and endothelial cells toward HABP2 protein referred to the function of HABP2 in endometrial endothelial cells. In conclusion, our results indicate that polymorphisms in the regulatory region of HABP2 gene could influence gene expression levels in the receptive endometrium and could thereby be one reason for infertility complications in women with unexplained infertility. Additionally, HABP2 protein involvement in endometrial angiogenesis is proposed.

Ovarian stimulation for in vitro fertilization alters the intrauterine cytokine, chemokine, and growth factor milieu encountered by the embryo

OBJECTIVE

To elucidate the impact of ovarian stimulation on the intrauterine milieu represented by the cytokine, chemokine, and growth factor profile in endometrial secretions aspirated before embryo transfer.

DESIGN

Prospective cohort study.

SETTING

Fertility center in tertiary referral university hospital.

PATIENT(S)

Forty-two patients undergoing ovarian stimulation with GnRH analogues were recruited. They participated in both a natural and an ovarian-stimulated cycle for within patient comparisons.

INTERVENTION(S)

Endometrial secretion aspiration was performed immediately before embryo transfer.

MAIN OUTCOME MEASURE(S)

The concentrations of 17 mediators known to be involved in human embryo implantation were assessed by multiplex immunoassay.

RESULT(S)

After correction for multiple testing, significantly higher concentrations of interleukin (IL)-1β, IL-5, IL-10, IL-12, IL-17, tumor necrosis factor (TNF)-α, heparin-binding epidermal growth factor (HbEGF), eotaxin, and dickkopf homologue-1 were present in endometrial secretions obtained in stimulated compared with natural cycles.

CONCLUSION(S)

Endometrial secretion analysis provides a novel means of investigating the effect of ovarian stimulation on the intrauterine milieu. The in vivo milieu encountered by the embryo after transfer is significantly altered by ovarian stimulation.

Excessive ovarian stimulation up-regulates the Wnt-signaling molecule DKK1 in human endometrium and may affect implantation: an in vitro co-culture study

BACKGROUND

High serum estradiol (E2) levels following ovarian stimulation lead to reduced implantation and pregnancy rates, yet the underlying mechanisms remain unknown. We investigated if aberrant expression of genes in the Wnt-signaling pathway may be involved.

METHODS

Microarray and real-time PCR analysis were performed to analyze gene expression profiles of endometrial samples taken at day hCG + 7 in stimulated cycles, and days LH + 7 and LH + 10 in natural cycles. Expression of several Wnt-signaling transcripts, including Dickkopf homolog 1 (DKK1), DKK2 and secreted frizzled-related protein 4 (sFRP4), was analyzed throughout the menstrual cycle. JAr spheroid/Ishikawa endometrial cell co-culture experiments were established to study effects of DKK1 on spheroid attachment in vitro.

RESULTS

We identified 351 differentially expressed genes. Endometrial samples taken at hCG + 7 had similar expression profiles to those at LH + 10. DKK1 transcripts were up-regulated and DKK2 and sFRP4 were down-regulated in the stimulated compared with LH + 7 group (all P < 0.05). DKK1 transcripts were low in proliferative phase (PS) and increased in late-secretory phase (LS, P < 0.05), although DKK2 peaked in mid-secretory phase (P < 0.05). sFRP4 transcripts were high in PS. Treatment of spheroid with recombinant human DKK-1 protein dose-dependently suppressed (P < 0.05 versus control) spheroids attachment onto endometrial cells (associated with decreased beta-catenin protein): this suppression was nullified by anti-DKK1 antibody.

CONCLUSION

Gene expression patterns in stimulated cycles resembled those of LS in natural cycles, when the implantation window is about to close, suggesting high serum E2 and/or progesterone concentrations may advance endometrial development, altering the implantation window and possibly decreasing pregnancy rate. Aberrant expression of DKK1 might impair embryo attachment and implantation in vivo.

Gene expression profile of human endometrial receptivity: comparison between natural and stimulated cycles for the same patients

BACKGROUND

The adjunction of exogenous hormones for controlled ovarian stimulation (COS) may alter endometrial receptiveness. In order to identify the genes misregulated under COS, we compared the endometrium gene expression profiles, from the same patients, in a natural cycle and in a subsequent COS cycle.

METHODS

For the same normal-responder patients (n = 21), endometrial biopsies (n = 84) were collected during the pre-receptive (LH + 2) and receptive stages (LH + 7) of a natural cycle and, subsequently, on oocyte retrieval day (hCG + 2) and on transfer day (hCG + 5) of a stimulated cycle. Samples were analyzed using DNA microarrays. Gene expression profiles and biological pathways involved in endometrial receptivity were analyzed.

RESULTS

Although endometrium transition profiles from pre-receptive to receptive phases are similar between patients, COS regimens alter endometrial receptivity in comparison with natural cycle. Under COS conditions, two endometrial profiles were identified and were associated either with a moderately altered receptivity profile for the majority of the patients or a strongly altered profile for a sub-category of patients. The receptive endometrium transcription profile under COS was defective for biological functions such as TGFbeta signaling, leukocyte transendothelial migration and the cell cycle.

CONCLUSIONS

Gonadotrophin treatments in COS cycles led to disruptions of the transcriptional activation of genes involved in normal endometrial receptivity. We propose that when the receptiveness of the endometrium is seriously compromised by the COS protocol, fresh embryo replacement should be cancelled, the embryo frozen and thawed embryo replacement should be performed under natural cycles.

Effect of estradiol on oocyte development

OBJECTIVE

To determine whether elevated serum estradiol (E(2)) concentrations in oocyte donors affect assisted reproduction outcome.

METHOD

In a retrospective cohort study of 58 consecutive oocyte donation cycles, donors were stratified into 2 groups according to E(2) concentration, group 1 (n=32; E(2)<or=2000 pg/mL [range 456-2000 pg/mL]) and group 2 (n=27; E(2)>2000 pg/mL [range, 2062-6957 pg/mL]). Data were analyzed using the t test and chi(2) test.

RESULTS

Donors in group 1 produced significantly less oocytes than donors in group 2 (19.3+/-1.7 vs 12.0+/-1.4; P<0.001), and recipients of oocytes from group 1 had significantly fewer numbers of embryos available for transfer (10.4+/-1.1 vs 6.4+/-0.8; P=0.003). However, the mean number (3.3) of embryos transferred and the pregnancy rate were the same in both groups.

CONCLUSION

Elevated estradiol concentration in oocyte donors did not affect pregnancy outcome, suggesting that estradiol levels in donors do not affect oocyte development.

Controlled ovarian stimulation induces a functional genomic delay of the endometrium with potential clinical implications

CONTEXT

Controlled ovarian stimulation induces morphological, biochemical, and functional genomic modifications of the human endometrium during the window of implantation.

OBJECTIVE

Our objective was to compare the gene expression profile of the human endometrium in natural vs. controlled ovarian stimulation cycles throughout the early-mid secretory transition using microarray technology.

METHOD

Microarray data from 49 endometrial biopsies obtained from LH+1 to LH+9 (n=25) in natural cycles and from human chorionic gonadotropin (hCG) +1 to hCG+9 in controlled ovarian stimulation cycles (n=24) were analyzed using different methods, such as clustering, profiling of biological processes, and selection of differentially expressed genes, as implemented in Gene Expression Pattern Analysis Suite and Babelomics programs.

RESULTS

Endometria from natural cycles followed different genomic patterns compared with controlled ovarian stimulation cycles in the transition from the pre-receptive (days LH/hCG+1 until LH/hCG+5) to the receptive phase (day LH+7/hCG+7). Specifically, we have demonstrated the existence of a 2-d delay in the activation/repression of two clusters composed by 218 and 133 genes, respectively, on day hCG+7 vs. LH+7. Many of these delayed genes belong to the class window of implantation genes affecting basic biological processes in the receptive endometrium.

CONCLUSIONS

These results demonstrate that gene expression profiling of the endometrium is different between natural and controlled ovarian stimulation cycles in the receptive phase. Identification of these differentially regulated genes can be used to understand the different developmental profiles of receptive endometrium during controlled ovarian stimulation and to search for the best controlled ovarian stimulation treatment in terms of minimal endometrial impact.

Endometrial receptivity and implantation are not affected by the presence of uterine intramural leiomyomas: a clinical and functional genomics analysis

CONTEXT

Uterine leiomyomas are the most frequent benign tumors during reproductive age. Whether intramural leiomyomas cause infertility and should be removed is controversial because no study has addressed the underlying mechanism of infertility.

OBJECTIVE

The objective of the study was to test the effect of intramural leiomyomas on endometrial function by comparing gene during the window of implantation and implantation in an oocyte donation program, in which the quality of the embryos replaced is similar and the endocrine environment of the endometrium is standardized by exogenous steroids.

DESIGN

Human endometria of women with single intramural leiomyomas (group A, <5 cm and group B, > or =5 cm) and controls (group C) were collected on day LH+7 and processed for histology and gene expression analysis, using different methods and validated by quantitative RT-PCR. To compare in vitro fertilization outcome, a total of 1035 cases from our oocyte donation database were included, comprising patients with one fibroid less than 5 cm (A1, n = 532); two leiomyomas less than 5 cm (A2, n = 128); three or more leiomyomas less than 5 cm (A3, n = 125); one fibroid 5 cm or greater (B, n = 22); and two control groups: C1 (n = 93), women with previous myomectomy; and C2 (n = 135), women without uterine pathology treated on the same dates as C1.

RESULTS

There was a strong positive and negative correlation in the expression profile of 69 genes according to the leiomyomas's size, but only three of the 25 genes related to the window of implantation were dysregulated. Term pregnancy rates after oocyte donation were 36.9, 34.1, 39.0, 36.4, 39.2, and 42.6% (P = 0.769) among the established groups. Similarly, no correlation between implantation and miscarriage with leiomyoma number and size was found.

CONCLUSIONS

This study provides evidence that intramural leiomyomas not affecting the endometrial cavity alters the expression pattern of some endometrial genes, but the genes involved in implantation are not affected. This is confirmed by leiomyomas having no effect on oocyte donation outcome when the size and number of leiomyomas are analyzed.

The impact of ovarian stimulation with recombinant FSH in combination with GnRH antagonist on the endometrial transcriptome in the window of implantation

The aim of this prospective paired cohort study is to elucidate the impact of ovarian stimulation with recombinant follicle-stimulating hormone in combination with gonadotropin-releasing hormone antagonist on the endometrial transcriptome. Oocyte donors underwent endometrial biopsy during the implantation window of the nonstimulated cycle and following ovarian stimulation with recombinant follicle-stimulating hormone and gonadotropin-releasing hormone antagonist but no luteal progesterone supplementation (n = 4). Microarray analysis showed 142 genes to be significantly upregulated and 98 significantly downregulated. Significantly upregulated genes included those sequencing for the chemokine ligand CXCL 13, the Dickkopf homolog, steroidogenic acute regulatory protein, and homeobox C6. Also upregulated were genes inhibited by progesterone, such as insulin-like growth factor binding protein 5. In conclusion, ovarian stimulation with follicle-stimulating hormone and gonadotropin-releasing hormone antagonist dysregulates the expression of many genes involved in cell adhesion, T-cell receptor signaling, and regulation of signal transduction. These data suggest that dysregulation of the endometrial transcriptome in the stimulated cycle is not fully attributable to supraphysiological sex steroid levels at the folliculo-luteal transition.

Gene expression profiling of human peri-implantation endometria between natural and stimulated cycles

OBJECTIVE

To investigate the effect of high serum E(2) levels in gonadotropin-stimulated cycles (hCG+7) on the gene expression patterns of human endometrium compared with natural cycles on the seventh day of LH surge (LH+7) and elucidate the underlying molecular changes that may be related to endometrial receptivity.

DESIGN

Observational study.

SETTING

University Hospital.

PATIENTS(S)

Infertile patients with normal menstrual cycles undergoing IVF treatment.

INTERVENTION(S)

Gonadotropin stimulation and endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Gene expression by microarray and quantitative polymerase chain reaction (qPCR).

RESULT(S)

Endometrial samples from natural (n = 5) and stimulated (n = 8) cycles were collected. Patients in the stimulated cycles were classified as moderate (n = 4) or excessive (n = 4) responders if their serum E(2) levels on the day of administration of hCG were <or=20,000 pmol/L or >20,000 pmol/L, respectively. The RNA transcripts were profiled by Affymetrix HG-U133A microarray. Clustering and principal component analysis demonstrated a significant difference (>or=2-fold) in the expression patterns of 411 genes among the three groups. Putative estrogen response elements or progesterone response elements were identified in the promoter regions of 49 differentially expressed genes of diverse biologic functions. The qPCR confirmed the microarray result in 47 endometrial samples.

CONCLUSION(S)

High serum E(2) and/or progesterone modulate the gene expression profiles of human endometrium and may affect endometrial receptivity.

En fécondation in vitro (FIV): pourquoi je ne stimule pas?

In vitro fertilization without stimulation, in natural or semi-natural cycles ("FIV-NAT") offers an interesting alternative to controlled ovarian hyperstimulation (COH) for some patients. This protocol may be proposed to patients suffering from altered ovarian status (AOS) with encouraging results. The second indication might be patients presenting repeated implantation failure (IMF). FIV-NAT allows avoiding possible adverse effects of HOC on the endometrium. Results are respectively 15.4 and 16.6% clinical pregnancy rate per oocyte retrieval for AOS and IMF, and 25.5 and 26.3% over 3 cumulative cycles. This treatment is less expensive and patient friendly.

The role of the endometrium and embryo in human implantation

Despite many advances in assisted reproductive technologies (ART), implantation rates are still low. The process of implantation requires a reciprocal interaction between blastocyst and endometrium, culminating in a small window of opportunity during which implantation can occur. This interaction involves the embryo, with its inherent molecular programme of cell growth and differentiation, and the temporal differentiation of endometrial cells to attain uterine receptivity. Implantation itself is governed by an array of endocrine, paracrine and autocrine modulators, of embryonic and maternal origin. Implantation failure is thought to occur as a consequence of impairment of embryo developmental potential and/or impairment of uterine receptivity and the embryo-uterine dialogue. Therefore a better comprehension of implantation, and the relative importance of the factors involved, is warranted. New techniques for monitoring changes in the endometrium and/or the embryo at the level of gene regulation and protein expression may lead to the identification of better markers for implantation. Moreover, the use of predictive sets of markers may prove to be more reliable than a single marker. Continuing refinements to ART protocols, such as optimizing ovarian stimulation regimens, the timing of human chorionic gonadotrophin injection, or the timing of embryo transfer, should help to increase implantation rates further.

Is ovarian stimulation detrimental to the endometrium?

Ovarian stimulation in assisted reproduction technology produces lower implantation rates per embryo transferred than natural and ovum donation cycles, suggesting suboptimal endometrial development due to the abnormal concentrations of hormones used to recruit more oocytes. After the publication of several studies on the gene expression profile of endometrial receptivity in the natural cycle using microarray technology, researchers have investigated the impact of ovarian stimulation on the gene expression pattern of the endometrium. Ovarian stimulation cycles that use gonadotrophin-releasing hormone (GnRH) agonists and antagonists have been analysed in detail during the window of implantation to establish differences compared with the natural cycle. This paper reviews results obtained in different studies to elucidate the changes induced by the different protocols used in clinics. At the morphological level, no relevant alteration was observed in endometrial development in the early and mid-luteal phases in women undergoing ovarian stimulation following GnRH antagonist treatments. However, the gene expression pattern of the endometrium showed some differences. In addition, the endometrial development after GnRH antagonist mimics the natural endometrium more closely than after GnRH agonist at both the morphological (no relevant differences) and molecular level (only 23 genes dysregulated at high dose). Clinical implications of these differences should be analysed in more detail.

Towards a more physiological approach to IVF

The International Society for Mild Approaches in Assisted Reproduction (ISMAAR) is founded to promote a more physiological, less drug-oriented, lower risk, less expensive and more patient friendly approach to Assisted Reproduction embracing not only natural cycle treatment but also gentle stimulation protocols and in-vitro maturation of oocytes. Recent research suggests that IVF in modified natural cycle/mild stimulation with antagonist is likely to replace the current conventional approach in down-regulated cycles. The Society will focus both on the basic science and clinical aspects of assisted reproduction. It will be committed to promoting international multi-centre scientific research, regular practical workshops for training and also seminars for educating assisted reproduction technology professionals. ISMAAR aims to establish a direct dialogue with the voluntary sector and politicians to campaign for IVF to be a safer, softer and affordable treatment globally.

Effects of urinary and recombinant gonadotrophins on gene expression profiles during the murine peri-implantation period

BACKGROUND

Controlled ovarian stimulation (COS) with urinary gonadotrophins but not recombinant gonadotrophins, adversely affect the implantation process. In this study, we investigated the effects of urinary and recombinant gonadotrophins on gene expression profiles at implantation sites during the mouse peri-implantation period and the possible molecular mechanisms involved in the detrimental effects of urinary gonadotrophins using microarray technology.

METHODS

Adult female CD1 mice were treated with (i) urinary human FSH (hFSH) and urinary HCG, (ii) recombinant hFSH and recombinant human LH or (iii) saline. Gene expression profiling with GeneChip mouse genome 430 2.0 arrays, containing 45 101 probe sets, was performed using implantation sites on embryonic day 5. Data were statistically analysed using Significance Analysis of Microarrays. Ten genes from the microarray analysis were selected for validation using quantitative RT-PCR (qRT-PCR). A parallel group of pregnant mice was allowed to give birth to study the effect of gonadotrophins on resorption.

RESULTS

Urinary gonadotrophins differentially up-regulated the expression of 30 genes, increased resorption and reduced litter size, whereas recombinant gonadotrophins did not. Nine of the 10 genes were confirmed by qRT-PCR.

CONCLUSIONS

Urinary gonadotrophins, but not recombinant gonadotrophins, exerted differential effects on gene expression during the murine peri-implantation period. These findings might contribute to improve protocols for COS, leading to higher successful pregnancy rates.

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

Microarray technology has broadened the insight into many research fields allowing scientists to analyse the expression of many genes in quick and efficient experiments aimed at translating these findings into clinical applications. In reproductive medicine, researchers have exploited microarrays to increase understanding of the molecular mechanisms involved in endometrial receptivity and how a possible therapeutic translation can be feasible. In the last 4 years, several studies have focused on the genomics of the human endometrium in different physiological and pathological conditions, and these studies have generated a large amount of information about the regulation and dysregulation of the window of implantation (WOI) genes in fertile, subfertile and refractory conditions. However, the key molecules/mechanisms in endometrial receptivity remain to be elucidated. In this comprehensive review, we have analysed the available results obtained in our own and other laboratories, defining the genomic profile of the receptive endometrium in different situations and its possible clinical application.

Downregulation of Human Endometrial IL-18 by Exogenous Ovarian Steroids

PROBLEM

To evaluate the influence of ovarian steroids on IL-18, IL-15 and angiopoietin-2 mRNA expression in the endometrium in the mid luteal phase.

METHOD OF STUDY

We quantified IL-18/GAPDH, IL-18 BP/GAPDH, IL-15/GAPDH and angiopoietin-2/GAPDH in the endometrium by quantitative polymerase chain reaction on day 21 of the cycle. We first compared cytokines expression over two natural cycles (n = 15) then between natural and oestrogen-progestin replacement treatment (n = 18).

RESULTS

Endometrial IL-18, IL-18 BP, IL-15 and angiopoietin-2 mRNA expression did not change over two natural cycles. Addition of exogenous hormones significantly decreased IL-18 and IL-18 BP mRNA expression but not influence IL-15 or angiopoietin-2 ratios. This was also observed with immunohistochemistry.

CONCLUSION

Exogenous oestro-progestative hormones influence endometrial IL-18 system expression involved in angiogenesis and in the uterine natural killer (uNK) cell activation pathway during the implantation process.

The human endometrium as a fertility-determining factor

Intensive research work has been performed to better understand the regulation of the endometrium and its clinical implications to improve implantation. Although many proteins and molecules may influence endometrial development, their co-ordinated contribution to the implantation process is still poorly understood and a translation into clinical use has not sufficiently been performed. Clinical evaluation of the endometrium by ultrasound and other techniques, like endometrial biopsy and analysis of uterine secretions, has been intensively studied and therapeutic options to improve endometrial function have been suggested and tested. Systemic treatment with heparin, aspirin or corticosteroids did not result in improved implantation rates. Gene therapy and cervical treatment, e.g. with seminal plasma, are still in the phase of clinical research. Therefore, this review focuses on different aspects of endometrial research, which all contribute to the diagnosis, evaluation and therapy of endometrial function and dysfunction. First, the endometrial development towards a receptive milieu is described. Second, the actual clinical evaluation of endometrial receptivity, possible therapeutic strategies and in particular, the evaluation of endometrial function in the non-natural situation of hormonal stimulation is critically evaluated. In conclusion, the endometrium shall be considered as an important fertility-determining factor and therapeutic options should be developed in near future.

Ovarian stimulation with GnRH agonist, but not GnRH antagonist, partially restores the expression of endometrial integrin 3 and leukaemia-inhibitory factor and improves uterine receptivity in mice

BACKGROUND

The impact of different ovarian stimulation (OS) protocols on endometrial receptivity remains controversial. In this study, the effects of different OS on the expression of endometrial integrin beta3 subunit and leukaemia-inhibitory factor (LIF) during the implantation window and the implantation rate in mice were investigated.

METHODS

Three OS protocols were used, involving either pregnant mare's serum gonadotrophin (PMSG) alone, PMSG plus GnRH agonist or PMSG plus GnRH antagonist. Uterus samples were collected at 48 h after OS or ovulation and were detected with immunohistochemistry, Western blot and RT-PCR analyses. Normal embryos at gestation day 4 were transferred into the uteri of mice in the control and OS groups.

RESULTS

All OS groups showed a significant decrease in the expression of both the endometrial integrin beta3 subunit and LIF during the implantation window and the implantation rate. Among the three OS groups, GnRH agonist-treated mice showed a higher endometrial integrin beta3 subunit and LIF expression and a higher implantation rate. No significant difference was found in the measured indices between the GnRH antagonist and PMSG groups.

CONCLUSIONS

OS may inhibit the expression of endometrial integrin beta3 subunit and LIF and impair endometrial receptivity in mice. OS with GnRH agonist, but not GnRH antagonist, may partially restore the endometrial physiological secretion and improve uterine receptivity.

The science behind 25 years of ovarian stimulation for in vitro fertilization

To allow selection of embryos for transfer after in vitro fertilization, ovarian stimulation is usually carried out with exogenous gonadotropins. To compensate for changes induced by stimulation, GnRH analog cotreatment, oral contraceptive pretreatment, late follicular phase human chorionic gonadotropin, and luteal phase progesterone supplementation are usually added. These approaches render ovarian stimulation complex and costly. The stimulation of multiple follicular development disrupts the physiology of follicular development, with consequences for the oocyte, embryo, and endometrium. In recent years, recombinant gonadotropin preparations have become available, and novel stimulation protocols with less detrimental effects have been developed. In this article, the scientific background to current approaches to ovarian stimulation for in vitro fertilization is reviewed. After a brief discussion of the relevant aspect of ovarian physiology, the development, application, and consequences of ovarian stimulation strategies are reviewed in detail.

Molecular phenotyping of human endometrium distinguishes menstrual cycle phases and underlying biological processes in normo-ovulatory women

Histological evaluation of endometrium has been the gold standard for clinical diagnosis and management of women with endometrial disorders. However, several recent studies have questioned the accuracy and utility of such evaluation, mainly because of significant intra- and interobserver variations in histological interpretation. To examine the possibility that biochemical or molecular signatures of endometrium may prove to be more useful, we have investigated whole-genome molecular phenotyping (54,600 genes and expressed sequence tags) of this tissue sampled across the cycle in 28 normo-ovulatory women, using high-density oligonucleotide microarrays. Unsupervised principal component analysis of all samples revealed that samples self-cluster into four groups consistent with histological phenotypes of proliferative (PE), early-secretory (ESE), mid-secretory (MSE), and late-secretory (LSE) endometrium. Independent hierarchical clustering analysis revealed equivalent results, with two major dendrogram branches corresponding to PE/ESE and MSE/LSE and sub-branching into the four respective phases with heterogeneity among samples within each sub-branch. K-means clustering of genes revealed four major patterns of gene expression (high in PE, high in ESE, high in MSE, and high in LSE), and gene ontology analysis of these clusters demonstrated cycle-phase-specific biological processes and molecular functions. Six samples with ambiguous histology were identically assignable to a cycle phase by both principal component analysis and hierarchical clustering. Additionally, pairwise comparisons of relative gene expression across the cycle revealed genes/families that clearly distinguish the transitions of PE-->ESE, ESE-->MSE, and MSE-->LSE, including receptomes and signaling pathways. Select genes were validated by quantitative RT-PCR. Overall, the results demonstrate that endometrial samples obtained by two different sampling techniques (biopsy and curetting hysterectomy specimens) from subjects who are as normal as possible in a human study and including those with unknown histology, can be classified by their molecular signatures and correspond to known phases of the menstrual cycle with identical results using two independent analytical methods. Also, the results enable global identification of biological processes and molecular mechanisms that occur dynamically in the endometrium in the changing steroid hormone milieu across the menstrual cycle in normo-ovulatory women. The results underscore the potential of gene expression profiling for developing molecular diagnostics of endometrial normalcy and abnormalities and identifying molecular targets for therapeutic purposes in endometrial disorders.

Application of functional genomics to primate endometrium: insights into biological processes

Endometrium is a dynamic tissue that responds on a cyclic basis to circulating levels of the ovarian-derived steroid hormones, estradiol and progesterone. Functional genomics has enabled a global approach to understanding gene regulation in whole endometrial tissue in the setting of a changing hormonal milieu. The proliferative phase of the cycle, under the influence of estradiol, has a preponderance of genes involved in DNA synthesis and cell cycle regulation. Interestingly, genes encoding ion channels and cell adhesion, as well as angiogenic factors, are also highly regulated in this phase of the cycle. After the LH surge, different gene expression profiles are uniquely observed in the early secretory, mid-secretory (window of implantation), and late secretory phases. The early secretory phase is notable for up-regulation of multiple genes and gene families involved in cellular metabolism, steroid hormone metabolism, as well as some secreted glycoproteins. The mid-secretory phase is characterized by multiple biological processes, including up-regulation of genes encoding secreted glycoproteins, immune response genes with a focus on innate immunity, and genes involved in detoxification mechanisms. In the late secretory phase, as the tissue prepares for desquamation, there is a marked up-regulation of an inflammatory response, along with matrix degrading enzymes, and genes involved in hemostasis, among others. This monograph reviews hormonal regulation of gene expression in this tissue and the molecular events occurring therein throughout the cycle derived from functional genomics analysis. It also highlights challenges encountered in using human endometrial tissue in translational research in this context.

Obesity and assisted reproductive technology outcomes

Obesity is a rising health problem in Western societies. It has been related to increased morbidity and mortality rates due to several pathologies. In the field of gynaecology and reproduction, obesity is associated with menstrual disorders, hirsutism, infertility, miscarriage and obstetric complications. It is known to impair human reproduction through different mechanisms such as insulin resistance, hyperandrogenism and elevated leptin levels. Weight management and dietary intervention can reverse this situation and improve reproductive function. Obesity can also impair the outcome of assisted reproductive technologies. The lower probability of a healthy live birth described in obese women seems to be the result of a combination of lower implantation and pregnancy rates, higher preclinical and clinical miscarriage rates and increased complications during pregnancy for both mother and fetus. Studies performed in infertile women undergoing assisted reproduction technologies indicate that the ovary plays a leading, but not exclusive, role in the fertility prognosis of these patients. The endocrine and metabolic environment may affect oocyte quality and, therefore, embryo development, implantation and pregnancy outcome. The endometrium seems to play a subtle role in the more negative reproductive outcome of obese women, according to recent studies based on the ovum donation model.

Similar endometrial development in oocyte donors treated with either high- or standard-dose GnRH antagonist compared to treatment with a GnRH agonist or in natural cycles

BACKGROUND

This descriptive study evaluates the impact on endometrial development of standard and high doses of a GnRH antagonist in stimulated cycles compared with GnRH agonist and natural cycles.

METHODS

Thirty-one oocyte donors were treated with a combination of rFSH and 0.25 mg/day ganirelix (standard dose), 2 mg/day ganirelix (high dose) or 0.6 mg/day buserelin (long protocol). Vaginal progesterone (200 mg/day) was administered in the luteal phase. Endometrial biopsies were performed 2 and 7 days after HCG administration. Additional biopsies were carried out in a subset of 12 subjects, 2 and 7 days following the LH peak of their previous natural cycle. Biopsies were evaluated histologically and by scanning electron microscopy. Gene expression profiles were also studied.

RESULTS

At HCG +2, all the parameters studied were similar in all the groups and comparable to those observed in the natural cycle. At HCG +7, endometrial dating, steroid receptors and the presence of pinopodes were comparable in both GnRH antagonist groups and in the natural cycle. In buserelin group, endometrial dating and pinopode expression suggested an arrested endometrial development. For window of implantation genes, expression patterns were closer to those in the natural cycle following standard- or high-dose ganirelix than after buserelin administration.

CONCLUSION

No relevant alteration was observed in the endometrial development in the early and mid-luteal phases in women undergoing controlled ovarian stimulation for oocyte donation following daily treatment with a standard- or high-dose GnRH antagonist. In addition, the endometrial development after GnRH antagonist mimics the natural endometrium more closely than after GnRH agonist.

A guide to issues in microarray analysis: application to endometrial biology

Within the last decade, the development of DNA microarray technology has enabled the simultaneous measurement of thousands of gene transcripts in a biological sample. Conducting a microarray study is a multi-step process; starting with a well-defined biological question, moving through experimental design, target RNA preparation, microarray hybridisation, image acquisition and data analysis – finishing with a biological interpretation requiring further study. Advances continue to be made in microarray quality and methods of statistical analysis, improving the reliability and therefore appeal of microarray analysis for a wide range of biological questions. The purpose of this review is to provide both an introduction to microarray methodology, as well as a practical guide to the use of microarrays for gene expression analysis, using endometrial biology as an example of the applications of this technology. While recommendations are based on previous experience in our laboratory, this review also summarises the methods currently considered to be best practice in the field.