Embryo effects in human implantation: embryonic regulation of endometrial molecules in human implantation

Embryonic implantation requires coordinated development of the blastocyst and the maternal endometrium. Considerable advances have been made in the understanding of the cell biology of human embryo and maternal endometrium as separate entities. Nevertheless, communication between them and their reciprocal effects on each other constitute an exciting and as-yet unsolved problem in reproductive medicine. Cross-talk among the embryo, endometrium, and the corpus luteum are known to occur in ruminants and primates; more specifically, endometrial-embryonic interactions have been reported in rodents and primates. Here, we present updated information in humans on the embryonic regulation of endometrial epithelial molecules such as chemokines, adhesion molecules, antiadhesion molecules, and leptin during the apposition and adhesion phases of human implantation. Also the embryonic induction of apoptosis in endometrial epithelial cells as a mechanism for crossing the epithelial barrier will be described.

Endometrial quality in infertile women with endometriosis

Several analyses in our infertility (IVF) and oocyte donation programs were carried out to gain clinical knowledge of the factors involved in the etiology of endometriosis-associated infertility. We first compared the IVF outcomes in women with tubal infertility and endometriosis. The results indicated that patients with endometriosis had a poorer IVF outcome in terms of reduced pregnancy rate per cycle, per transfer, and reduced implantation rate per embryo replaced. We then evaluated embryo development in vitro in women with and without endometriosis who underwent IVF and embryo replacement 72 hours after oocyte retrieval. We observed that compared to controls, patients with endometriosis had a significantly reduced number of blastomeres per embryo as well as an increased incidence of arrested embryos in vitro. In subsequent studies we compared fertility parameters in patients receiving donor oocytes. We noted that when donor oocytes came from patients without known endometriosis, embryo development and implantation rates were similar in patients with and without endometriosis. However, when the results of oocyte donation were classified according to the nature of the oocytes donated, patients who received embryos derived from oocytes from women with endometriotic ovaries showed a significantly reduced implantation rate compared to the controls. Taken together, these observations suggest that IVF in patients with endometriosis may be related to alterations within the oocyte, which, in turn, result in embryos of lower quality with a reduced ability to implant.

Expression, production, and secretion of vascular endothelial growth factor and interleukin-6 by granulosa cells is comparable in women with and without endometriosis

OBJECTIVE

To investigate the production and secretion of interleukin (IL)-6 and vascular endothelial growth factor (VEGF) mRNA and protein by granulosa luteal cells (GCs) in vivo and in vitro in women with and without endometriosis.

DESIGN

Prospective study.

SETTING

A private, university-affiliated assisted reproduction unit and a university center.

PATIENT(S)

Women with severe endometriosis (n = 6) or without the disease (n = 14) after laparoscopy, undergoing in vitro fertilization/intracytoplasmic sperm injection and embryo transfer.

INTERVENTION(S)

GCs were obtained from each aspirate.

MAIN OUTCOME MEASURE(S)

Intracellular and secreted protein, as well as mRNA for both VEGF and IL-6 in GCs.

RESULT(S)

The expression of VEGF and IL-6 mRNAs in vivo and in vitro was similar in both groups. Also, GCs from patients with endometriosis produced and secreted equal amounts of these proteins compared with controls without the disease, either in freshly isolated cells or in 24-hour cultures.

CONCLUSION(S)

The GC function in terms of VEGF and IL-6 production does not seem to be altered in patients with endometriosis in comparison with those without this condition.

Endocrinological and ultrasonographic variations after immature oocyte retrieval in a natural cycle

BACKGROUND

In-vitro oocyte maturation is an appealing alternative in reproductive medicine but the results obtained are still poor. The aim of our prospective and observational investigation was to study the hormonal modifications that immature follicular aspiration might induce in a natural cycle as well as the implications that these alterations may have in the endometrium.

METHODS

Eleven patients (13 cycles) were included in our in-vitro oocyte maturation programme. Ovaries were scanned with transvaginal probes every day and follicular aspiration was performed when a follicle of 9 mm was visualized. Blood was also drawn for hormonal analysis. Endometrial thickness was recorded every day after oocyte retrieval. Two endometrial biopsies were taken on days 6 and 8 after oocyte retrieval.

RESULTS

We observed a significant drop in serum oestradiol concentrations after immature oocyte retrieval previous to follicle dominance. Immediately after, rises in both FSH and LH were detected. Also, a new dominant follicle started to grow 3-4 days later. Steroid hormones secreted by this newly recruited follicle were significantly lower than in controls, inducing inadequate endometrial thickness.

CONCLUSIONS

These studies show that exogenous hormonal administration might be necessary to achieve a correct endometrial growth when in-vitro oocyte maturation is employed in IVF.

An analysis of spontaneous hatching in a human endometrial epithelial coculture system: is assisted hatching justified?

PURPOSE

To evaluate spontaneous embryo hatching in an endometrial epithelial coculture system, and compare it with cases where coculture was performed because of maternal age, previous repeated implantation failures, or both. To clarify in which cases assisted hatching would be appropriate.

METHODS

Individual human embryos were cocultured on an endometrial epithelial cell monolayer until Day 6.

RESULTS

Blastocyst hatching rate at Day 6, depending on maternal age, was 9.1% (age <37 years) and 3.4% (age > or = 37 years). However, blastocyst hatching rates depending on number of previous IVF failures were similar.

CONCLUSIONS

Maternal age and previous implantation failures are factors affecting the ability of human embryos to reach the blastocyst stage in coculture. However, assisted hatching is not justified in these populations because of the absence of hatching rate differences between blastocysts obtained from these two groups and the control group.

Blastocyst transfer: does it really affect the outcome?

Blastocyst transfer is of great interest to most assisted reproductive technology clinics. The ability to select the best embryos to transfer in order to increase pregnancy rates, and to replace lower numbers of embryos to reduce the likelihood of an unwanted multiple pregnancy have both been realized. The optimal method to prolong embryo culture up to day 5 or 6 is still to be identified, although present techniques offer acceptable blastocyst development rates. Freezing of supernumerary blastocysts is still a matter of discussion, as adequate results are still awaited.

Endometrial receptivity in terms of pinopode expression is not impaired in women with endometriosis in artificially prepared cycles

OBJECTIVE

To assess endometrial receptivity in terms of pinopode expression in women with endometriosis.

DESIGN

Prospective, observational study.

SETTING

Oocyte donation program at the Instituto Valenciano de Infertilidad.

PATIENT(S)

Twelve women with endometriosis as the only cause of infertility.

INTERVENTION(S)

Pinopode expression pattern analysis by scanning electron microscopy in two sequential endometrial biopsies obtained in the same cycle of each patient.

MAIN OUTCOME MEASURE(S)

Pinopode pattern and pregnancy rates.

RESULT(S)

Pinopode expression in women with endometriosis did not differ from that of patients without endometriosis undergoing artificial cycles. Similarly, the clinical outcome in these women was comparable to that of the general population included in the oocyte donation program. The pregnancy rate per transfer was 46.7%.

CONCLUSION(S)

These results show that in women with endometriosis undergoing oocyte donation under hormone replacement therapy, pinopode expression is not altered, suggesting that endometrial receptivity in women with this disease remains unaltered.

Human endometrial mucin MUC1 is up-regulated by progesterone and down-regulated in vitro by the human blastocyst

Expression of MUC1 in endometrial epithelium has been suggested to create a barrier to embryo attachment that must be lifted at the time of implantation. In this study, we investigated the hormonal regulation of human endometrial MUC1 in hormone replacement therapy cycles and in the human blastocyst. We also analyzed the embryonic regulation of MUC1 in human endometrial epithelial cells (EECs) during the apposition and adhesion phases of human implantation using two different in vitro models. Our results indicate that endometrial MUC1 mRNA and immunoreactive protein increase in receptive endometrium compared to nonreceptive endometrium. Human blastocysts express MUC1, as demonstrated by reverse transcription-polymerase chain reaction and immunocytochemistry, localized at the trophectoderm. In vitro, MUC1 was present at the surface of primary cultures of human EEC, and presence of a human blastocyst (i.e., apposition phase) increases EEC MUC1 protein and mRNA compared to control EEC lacking embryos. Interestingly, when human blastocysts were allowed to attach to the EEC monolayer (i.e., adhesion phase), MUC1 was locally removed in a paracrine fashion on EEC at the implantation site. These results demonstrate a coordinated hormonal and embryonic regulation of EEC MUC1. Progesterone combined with estradiol priming induces an up-regulation of MUC1 at the receptive endometrium. During the apposition phase, presence of a human embryo increases EEC MUC1. However, at the adhesion phase, the embryo induces a paracrine cleavage of EEC MUC1 at the implantation site. These findings strongly suggest that MUC1 may act as an endometrial antiadhesive molecule that must be locally removed by the human blastocyst during the adhesion phase.

The effect of intercourse on pregnancy rates during assisted human reproduction

Intercourse during an IVF cycle has the potential to improve pregnancy rates since exposure to semen is reported to promote embryo development and implantation in animals. Conversely, coitus-induced uterine contractions or introduction of infection may have a detrimental effect. A multicentre prospective randomized control trial was conducted to determine if intercourse during the peri-transfer period of an IVF cycle has any influence on pregnancy success. Participants undergoing thawed embryo transfer (Australian centre) or fresh embryo transfers (Spanish centres) were randomized either to abstain or to engage in vaginal intercourse around the time of embryo transfer. The transfer of 1343 embryos during 478 cycles of IVF resulted in 107 pregnancies (22.4%), with 125 viable embryos remaining by 6-8 weeks gestation. There was no significant difference between the intercourse and abstain groups in relation to the pregnancy rate (23.6 and 21.2% respectively), but the proportion of transferred embryos that were viable at 6-8 weeks was significantly higher in women exposed to semen compared to those who abstained (11.01 versus 7.69 viable embryos per 100 transferred embryos, P = 0.036, odds ratio 1.48, 95% confidence interval 1.01-2.19). Hence exposure to semen around the time of embryo transfer increases the likelihood of successful early embryo implantation and development.

Embryonic regulation of endometrial epithelial apoptosis during human implantation

Apoptosis is a mechanism of cell death in which cells undergo a genetically determined programme. The implanting blastocyst has to appose and adhere to the endometrial epithelium and subsequently invade it. Locally regulated uterine epithelial apoptosis induced by the embryo is a crucial step in epithelial invasion in rodents. To address the physiological relevance of this process in humans, we have investigated the effect of single human blastocysts on the regulation of apoptosis in cultured human endometrial epithelial cells (EEC) in the apposition and adhesion phases of implantation. We report a co-ordinated embryonic regulation of EEC apoptosis. In the apposition phase, the presence of a blastocyst rescues EEC from the apoptotic pathway. However, when the blastocyst adheres to the EEC monolayer it induces a paracrine apoptotic reaction.

Clinical experience employing co-culture of human embryos with autologous human endometrial epithelial cells

Attempts to improve the outcome in IVF and related techniques has drawn our attention to the development of culture systems that can grow embryos up to the blastocyst stage. We have developed a co-culture system with autologous human endometrial epithelial cells (EEC) that retained many features of the endometrium. In this review, we analyse our experience over the last 4 years; in particular, we address the question of whether the system would be safe and useful in cases of IVF and oocyte donation with previous implantation failure, and which factors may contribute to the failure of human embryos to develop in vitro up to the blastocyst stage. In all, 168 IVF cycles were carried out in 127 patients with 3.8+/-0.2 previous implantation failure, and 80 cycles in 57 women having oocyte donation with 3.0+/-0.2 previous implantation failure. In 168 IVF cycles, a 48.9% blastocyst formation rate was recorded; 2.3+/-0.1 blastocysts were transferred per cycle and 30 clinical pregnancies obtained (11.9% implantation and 19.6% pregnancy rates). A total of 20 IVF and 15 oocyte donation patients with three previous implantation failures in whom a day 2 embryo transfer was performed were the controls. In 88% of oocyte donation cycles, a 61.0% blastocyst formation rate was observed; 2.3+/-0.1 blastocysts were transferred per cycle and resulted in 38 clinical pregnancies (32.7% implantation and 54.3% pregnancy rates). In all, 15 cycles were cancelled (9%). In oocyte donation patients with implantation failure undergoing day 2 embryo transfer, implantation and pregnancy rates were significantly lower (4.5 and 13.3%; P < 0.01) than with co-culture; however, in IVF patients with implantation failure with day 2 transfer, results (10.7 and 35%) were similar to those with co-culture. A second question addressed was whether chromosomal abnormalities may contribute to the failure of human embryos to develop in vitro. We observed the performance of human embryos from our preimplantation diagnosis programme, which were biopsied and subsequently cultured in EEC before transfer. Out of 68 chromosomally normal embryos, 37 reached the blastocyst stage (54.4%) compared with 35 out of 104 abnormal embryos (33.6%). The present study demonstrates that co-culture of human embryos with EEC and blastocyst transfer is safe, effective, and may be a new approach to improve implantation in patients with implantation failure undergoing oocyte donation, but not in IVF patients. The system shows that abnormal embryos can also grow to the blastocyst stage, although to a lower rate. Prospective randomized studies are needed to confirm the preliminary conclusion that co-culture is an acceptable system to select good quality embryos, and the endometrium is a limiting factor in implantation that needs to be carefully managed.

Increased adhesiveness in cultured endometrial-derived cells is related to the absence of moesin expression

Human endometrial epithelial cells (EECs) are nonadhesive for embryos throughout most of the menstrual cycle. During the so-called implantation window, the apical plasma membrane of EECs acquire adhesive properties by undergoing a series of morphological and biochemical changes. The human endometrial-derived epithelial cell line, RL95-2, serves as an in vitro model for receptive uterine epithelium because of its high adhesiveness for trophoblast-derived cells. In contrast, the HEC-1-A cell line, which displays poor adhesive properties for trophoblast cells, is considered to be less receptive. The ezrin, radixin, and moesin protein family members, which are present underneath the apical plasma membrane, potentially act to link the cytoskeleton and membrane proteins. In the present study, we have further investigated the adhesive features in these two unrelated endometrial-derived cell lines using an established in vitro model for embryonic adhesion. We have also analyzed the protein pattern and mRNA expression of ezrin and moesin in RL95-2 cells versus HEC-1-A cells. The results demonstrate that RL95-2 cells were indeed more receptive (81% blastocyst adhesion) compared with HEC-1-A cells (46% blastocyst adhesion). An intermediate adhesion rate was found in primary EECs cultured on extracellular matrix gel, thus allowing a partial polarization of these cells (67% blastocyst adhesion). Furthermore, we found that moesin was absent from RL95-2 cells. In contrast, ezrin is expressed in both cell lines, yet it is reduced in adherent RL95-2 cells. Data are in agreement with the hypothesis that uterine receptivity requires down-regulation or absence of moesin, which is a less-polarized actin cytoskeleton.

High doses of gonadotrophins combined with stop versus non-stop protocol of GnRH analogue administration in low responder IVF patients: a prospective, randomized, controlled trial

Recent evidence suggests that early cessation of gonadotrophin releasing hormone analogue (GnRHa) administration may offer some benefit to low responder patients undergoing IVF. A prospective, randomized controlled trial was designed to evaluate whether early cessation of GnRHa in an ovarian stimulation regimen is more beneficial than just increasing the doses of gonadotrophins. Seventy low responder patients (less than three mature follicles in a previous cycle) with normal basal follicle stimulating hormone concentrations and a previous cancelled IVF cycle were randomly allocated into two protocols: (i) non-stop protocol: long GnRHa suppression with high doses of gonadotrophins, and (ii) stop protocol, in which GnRHa administration is stopped with the onset of menses, while gonadotrophin doses remained similar to the non-stop protocol. A significantly higher number of mature oocytes were obtained in the study group (stop protocol) compared to the control group (non-stop protocol) (8.7 +/- 0.9 versus 6.2 +/- 0.7, P: = 0. 027). The stop protocol reduced the number of ampoules of gonadotrophins required (56.6 +/- 2.7 versus 68.0 +/- 3.5, P: = 0. 013). Both protocols resulted in a similar cancellation rate (2.7 versus 5.8%) (with no cycles cancelled due to ovulation), pregnancy rate (14.3 versus 18.7%), and implantation rate (12.1 versus 8.8%). The early cessation of GnRHa combined with high doses of gonadotrophins permitted the retrieval of a significantly higher number of oocytes.

Embryo reduction of multifetal pregnancies following assisted reproduction treatment: a modification of the transvaginal ultrasound-guided technique

First-trimester transvaginal embryo reduction is an effective alternative for the management of multifetal pregnancy in assisted reproduction. We have modified the transvaginal technique by performing an intracardiac embryo puncture until asystolia is verified, without the injection of any substances. Any aspiration of embryo tissues or amniotic fluid was avoided. A total of 149 multifetal pregnancies was reduced to twins (n = 134) or singletons (n = 15) at early gestational age (7.8 +/- 0.8 weeks). Eleven cases (7.3%) of miscarriage, two cases (1.3%) of chorioamnionitis, and 17 cases (11.4%) of transient spotting were recorded as postoperative complications. Vanishing of one embryo occurred in four cases (3.0%) of those reduced to twins. The baby take-home rate was 89.5% for twins and 80.0% for singletons. Pregnancy outcome was analysed and compared with a control group of women with non-reduced multiple pregnancies. The birth weight of singleton pregnancies after reduction was lower (2929 +/- 160 versus 3291 +/- 422 g; P < 0.02). These studies show that early transvaginal intracardiac embryo puncture is an effective and safe technique.

Paracrine regulators of implantation

Classical and contemporary studies have shown that endocrine regulation exerted by ovarian hormones priming the endometrium is essential for embryo implantation. Increasing evidence indicates that steroid-induced molecules acting as paracrine modulators are necessary for embryo-uterine interactions. That is the case for calcitonin, heparin-binding epidermal growth factor (EGF)-like growth factor, leukaemia inhibitory factor and other molecules. Furthermore, when the blastocyst enters the uterine cavity, it starts the complex signals that will drive embryo adhesion. The paracrinology of this process is based on the local interplay of molecules, such as the secretion of cytokines that may facilitate the acquisition of endometrial receptivity by controlling the expression of adhesion and anti-adhesion proteins. Finally, during the embryonic invasive phase, uterine stromal-trophoblast dialogue may modulate this self-controlled proteolytic and immunological process to avoid damage to both the embryo and maternal environment.

The human blastocyst regulates endometrial epithelial apoptosis in embryonic adhesion

The implanting blastocyst must appose and adhere to the endometrial epithelium and, subsequently, invade it. Locally regulated uterine epithelial apoptosis induced by the embryo is a crucial step of the epithelial invasion in rodents. To address the physiological relevance of this process in humans, we investigated the effect of single human blastocysts on the regulation of apoptosis in cultured human endometrial epithelial cells (hEEC) in both apposition and adhesion phases of implantation. Here, we report a co-ordinated embryonic regulation of hEEC apoptosis. In the apposition phase, the presence of a blastocyst rescues hEEC from the apoptotic pathway. However, when the human blastocyst adheres to the hEEC monolayer, it induces a paracrine apoptotic reaction. Fas ligand (Fas-L) was present at the embryonic trophoectoderm. Fas was localized at the apical cell surface of hEEC, and flow cytometry revealed that 60% of hEEC express Fas. Neutralizing adhesion assays revealed that the Fas/Fas-L death system may be an important mechanism to cross the epithelial barrier, which is crucial for embryonic adhesion, and the manipulation of this system could have potential clinical implications as an interceptive mechanism.

Embryonic regulation of endometrial molecules in human implantation

Embryonic implantation requires co-ordinated development of the blastocyst and the maternal endometrium. Considerable advances have been made in understanding the cell biology of these partner tissues separately. Nevertheless, communication between these tissues and the reciprocal effects of these tissues on each other constitutes an exciting and as yet unsolved paradigm in reproductive medicine. Crosstalk between the embryo, endometrium and the corpus luteum is known to occur in ruminants and primates, and, more specifically, endometrial-embryonic interactions are reported in rodents and primates. In this review, an in vitro model for analysing the interactions between human endometrial epithelium and blastocyst in the adhesion phase of embryonic implantation is presented. The results of investigations of embryonic regulation of endometrial epithelial molecules such as adhesion molecules, mucins, chemokines and cytoskeleton proteins are also presented.

Is there a place for preimplantation genetic diagnosis screening in recurrent miscarriage patients?

Chromosomal abnormalities are one of the factors known to interfere with normal embryo development; thus preimplantation genetic diagnosis (PGD) for chromosome anomalies may be a new tool for improving the pregnancy rate in selected groups of patients. Embryos from three groups of patients (control, aged and recurrent miscarriage patients) were screened by PGD using specific DNA probes for chromosomes 13, 16, 18, 21, 22, X and Y. The control and aged groups were included in the PGD study because the women carried sex-linked genetic disease. The frequencies of chromosome anomalies observed in older women (46.3%) and in recurrent miscarriage patients (53%) were significantly higher (P < 0.05) than the frequency in the control group (19.3%). After PGD screening and transfer of normal embryos, pregnancies were obtained in women who had undergone repeated abortions (approximate 25% pregnancy rate per transfer) but not in older women. On the basis of these data, it seems that PGD screening of embryos can help some women undergoing repeated abortions, as these techniques allow successful pregnancies to be obtained or, if no pregnancy can be obtained, the results may help the couple to decide whether to enter an embryo or gamete donation programme.

The pathophysiology of endometriosis-associated infertility: follicular environment and embryo quality

Several retrospective analyses of IVF and oocyte donation programmes, performed to gain clinical knowledge of the factors implicated in the aetiology of endometriosis-associated infertility, have demonstrated that the quality of the embryo is affected in patients with endometriosis. To understand the mechanisms of this alteration, the endocrine, paracrine and autocrine conditions induced during folliculogenesis in women with and without endometriosis were investigated. The first approach was to study ovarian steroid secretion in women undergoing IVF. Progesterone concentrations in follicular fluid increased with the severity of the disease and an increase in progesterone accumulation in vitro was observed in basal and hCG-stimulated granulosa cell cultures. It is proposed that the pattern of progesterone secretion may be related to changes in the release of cytokines by ovarian and white blood cells. Hence, a second trial measured interleukin 1 (IL-1), IL-6 and vascular endothelial growth factor (VEGF) concentrations in serum, follicular fluid and granulosa cell cultures. IL-6 concentrations in serum were higher in the natural cycles of women with endometriosis than in women in the control group, and were modulated by ovarian stimulation, decreasing significantly in serum from stimulated cycles. In addition, IL-6 concentrations were higher in the follicular fluid of women with endometriosis than in those in the control group and IL-6 was released in higher amounts by granulosa luteal cells of patients with endometriosis. VEGF was accumulated in lower concentrations in the follicular fluid of patients with endometriosis. These observations indicate that infertility in patients with endometriosis may be related to alterations within the follicle which, in turn, result in oocytes and embryos of lower quality, as demonstrated in the IVF programme. In addition, these embryos have a reduced ability to implant, as observed in the oocyte donation model. These alterations may be induced by functional changes in the process of folliculogenesis that affect steroid synthesis, as well as by cytokine release by ovarian and blood cells.

Impact of stage III-IV endometriosis on recipients of sibling oocytes: matched case-control study

OBJECTIVE

To evaluate the impact of severe endometriosis on IVF-ET outcome in women receiving oocytes from the-same donor.

DESIGN

A matched case-control study.

SETTING

Oocyte donation program at the Instituto Valenciano de Infertilidad.

PATIENT(S)

Fifty-eight recipients were included in a matched case-control study of IVF-ET in our oocyte donation program. Twenty-five patients were diagnosed by laparoscopy with stage III-IV endometriosis (group I), while the remaining 33 were free of the disease (group II). On the day of retrieval, oocytes from a single donor were donated to recipients from both groups. Some of the donors supplied oocytes for more than 2 patients. Recipients received steroid replacement therapy for endometrial preparation.

INTERVENTION(S)

Ovarian stimulation and oocyte retrieval in donors. Uterine embryo transfer (ET) in recipients after appropriate exogenous hormone replacement therapy (HRT).

MAIN OUTCOME MEASURE(S)

Pregnancy, implantation, miscarriage, and live birth rates.

RESULT(S)

The number of oocytes donated and fertilized, as well as the number of available and transferred embryos, was not statistically different between the two groups. Pregnancy, implantation, and miscarriage rates were not affected by stage III-IV endometriosis when compared with the control group. The live birth rate was 28.0% in the group with endometriosis and 27.2% in the control group.

CONCLUSION(S)

These results show that implantation is not affected by stage III-IV endometriosis. Given the contemporary methods of endometrial preparation for transfer of embryos derived from donor oocytes, any potential negative effect of severe endometriosis on the uterine environment is undetectable.

Embryonic regulation in implantation

Maternal steroid hormones play a critical role in establishing the receptive phase of implantation. In addition to that, the embryo is able to modulate endometrial molecules during the apposition phase (chemokines) and the adhesion phase (adhesion and anti-adhesion molecules). Moreover, the human embryo also exerts a coordinated regulation of endometrial epithelial apoptosis during these implantation phases. In this work, we analyze the embryonic regulation of implantation in humans using an in vitro model.

The potential use of maturation in vitro of human oocytes in low responder patients

PURPOSE

To assess whether maturation in vitro of human oocytes (MIVHO) could be an alternative treatment in low responders to ovarian stimulation for in vitro fertilization (IVF).

METHODS

Prospective case-control study. Spontaneously ovulatory women who volunteered were included in our program of MIVHO at the Instituto Valenciano de Infertilidad. Rates of oocyte retrieval, in vitro maturation, fertilization, and development up to the blastocyst stage were studied.

RESULTS

A significantly increased rate of oocyte retrieval was found when the pickup was performed before follicular selection. No differences were found when MIVHO was used in a low responder patient with an ovarian content of early antral follicles > 5 as compared to normal responders.

CONCLUSIONS

MIVHO could be a successful choice in low responder patients with an acceptable number of early antral follicles. Oocyte retrieval should be performed before follicular selection in order to obtain more oocytes.

Leptin and reproduction

Leptin, the product of the ob gene, is a small peptide molecule synthesized by white adipocytes with an important role in the regulation of body fat and food intake. Leptin and leptin receptor mRNA were first detected in the brain and hypothalamus but now their ubiquitous presence has been demonstrated. Leptin receptor signal transduction involves the activation of signal transducer and activator of transcription (STAT)-3, a member of the transcription family of proteins. Leptin is regulated by hormones and cytokines, interleukin-1, tumour necrosis factor-alpha and transforming growth factor-beta, linking this molecule with the inflammatory response. In addition, emerging evidence has demonstrated that this molecule is related to reproductive function. This small protein is present in the ovary and decidua, in mature oocytes and during embryonic development and trophoblast invasion. Animal models have demonstrated that leptin-deficient ob/ob mice are sterile; however, fertility can be restored by exogenous leptin. In addition, embryos implanted in STAT-3-deficient mice degenerate rapidly and are the target disruption of STAT-3-provoked embryonic lethality. Leptin acts as a novel placental hormone participating in the control of fetal growth and development. Leptin could be a modulator for invasive features of cytotrophoblast cells. We postulate that leptin may have an autocrine/paracrine role in human implantation and placentation.

Follicular hormonal environment and embryo quality in women with endometriosis

The use of in-vitro fertilization (IVF) as a therapeutic tool in patients with endometriosis has provided information about the disease and, in particular, aspects of the reproductive process in humans, particularly folliculogenesis, fertilization, embryo development and implantation. Retrospective analyses of IVF and oocyte donation programmes showed impaired implantation in patients with endometriosis. Otherwise, the observation that embryo development was blocked more frequently in cases of endometriosis, suggested that impaired embryo quality may be responsible for the reduced implantation rates. Similarly, women with the disease undergoing oocyte donation had the same chance of implantation as patients without endometriosis, suggesting that the endometrial milieu is not affected in patients with endometriosis. The quality of the oocyte may, therefore, be altered in patients with endometriosis. To investigate this, we studied steroid secretion in women undergoing IVF. Progesterone concentrations in follicular fluid increased with the severity of the disease and an increase in progesterone accumulation in vitro was observed in basal and human chorionic gonadotrophin (HCG)-induced granulosa cell cultures. We postulated that the pattern of progesterone secretion may be related to the release of cytokines by ovarian and/or immune cells. To test this, we measured interleukin (IL)-1, IL-6 and vascular endothelial growth factor (VEGF) concentrations in serum, follicular fluid and granulosa cell cultures. IL-6 concentrations in serum were increased in natural cycles in women with endometriosis and showed a significant decrease in stimulated cycles in IVF. Also, IL-6 concentrations were increased in the follicular fluid of women with endometriosis and released in higher amounts by granulosa-luteal cells from patients with endometriosis. VEGF was accumulated in lower concentrations in the follicular fluid of endometriosis patients. These observations show that the follicular environment is different in cases with endometriosis and suggest that infertility in patients with endometriosis may be related to alterations within the oocyte which, in turn, result in embryos of lower quality, and with a reduced ability to implant.

Ovarian stimulation and endometrial receptivity

Endometrial receptivity is a limiting step in the success of in-vitro fertilization (IVF). To investigate this issue, we selected a specific population of high responder patients in whom implantation was impaired, even when good quality embryos were transferred. We present a series of studies showing that high oestradiol concentrations on the day of human chorionic gonadotrophin (HCG) administration are detrimental to uterine receptivity. In addition, we suggest clinical strategies to improve endometrial receptivity in high responder patients using a step-down regimen.

Early pregnancy losses in in vitro fertilization and oocyte donation

OBJECTIVE

To evaluate prospectively the incidence of early pregnancy losses (before menstruation occurs) in IVF and ovum donation cycles.

DESIGN

Prospective case-control study.

SETTING

Tertiary care, university-associated center.

PATIENT(S)

One hundred forty-five patients undergoing IVF and 92 undergoing oocyte donation were recruited. The control group for IVF consisted of 15 ovum donors who had no ET and were instructed to avoid intercourse. The control group for oocyte donation included 10 women undergoing a mock cycle of steroid replacement.

INTERVENTION(S)

Starting on day 6 after ET, the women were instructed to collect the first urine sample of the day every 2 days. Each patient collected six different specimens of urine (days 6, 8, 10, 12, 14, and 16 after ET for cases or the same days without ET for controls.

MAIN OUTCOME MEASURE(S)

beta-HCG was measured with a standardized microparticle enzyme immunoassay, and IVF reproductive outcome was assessed.

RESULT(S)

For IVF, positive implantation was registered in 88 of 145 cycles of embryo replacement (60.7%). Only 30 (20.7%) resulted in viable pregnancies, whereas the remaining 58 miscarried. Forty-two of these miscarriages (72.4%) were early pregnancy losses and 13 (22.4%) were classified as clinical abortions. In ovum donation, positive implantation was recorded in 64 of 92 cycles of ET (69.6%). A total of 30 (32.6%) ended in viable pregnancies, whereas the remaining 34 (37.0%) were miscarriages. Early pregnancy loss accounted for 70.6% of pregnancy losses, whereas biochemical pregnancies and clinical abortions accounted for 11.8% and 17.6%, respectively.

CONCLUSION(S)

Our results demonstrate that patients undergoing assisted reproductive technology have an increased rate of early pregnancy loss compared with fertile patients. In addition, these data indicate that implantation is more frequently impaired in IVF than in oocyte donation cycles, resulting in a high incidence of early pregnancy loss. This suggests that implantation may be subjected to abnormal conditions in assisted reproduction.

Interleukin-1beta (IL-1beta) is a modulator of human luteal cell steroidogenesis: localization of the IL type I system in the corpus luteum

The present investigation examined the effect of interleukin-1beta (IL-1beta) on progesterone production by human luteal cells and the expression and localization of the IL-1 system in the human corpus luteum (CL). Luteal cells were isolated from corpora lutea collected throughout the luteal phase. After dispersion, luteal cells were treated with a panel of monoclonal antibodies directed to leukocyte-specific molecules. The leukocytes were isolated with immunomagnetic beads. Leukocyte-free luteal cells exhibited greater steroidogenic responsiveness to hCG toward the end of the luteal phase. The treatment of mixed luteal cells (total luteal cells) with IL-1beta inhibited by 60% hCG-stimulated progesterone production. Interestingly, the treatment of leukocyte-free luteal cells with IL-1beta did not affect progesterone production. In addition, the treatment of mixed luteal cells with monoclonal antibodies against IL-1 receptor type I (IL-1RtI) resulted in a 2.5-fold increase in the hCG-supported progesterone production. IL-1RtI and IL-1 receptor antagonist were localized by immunohistochemistry in both somatic and immune cells of the CL. Flow cytometric analysis indicated that both nonleukocyte luteal cells and leukocyte-luteal cells exhibited IL-1Rt-I positive cells, representing 56% and 31% of the total luteal cells, respectively. However, 13% of nonleukocyte luteal cells did not express IL-1Rt-I. Northern analysis demonstrated the presence of the 5.1-kb IL-1RtI messenger ribonucleic acid transcript in CL of different ages. RT-PCR indicated that both leukocyte-free luteal cells and luteal leukocytes express IL-1RtI messenger ribonucleic acid. We conclude that 1) luteal leukocytes have an inhibitory effect on hCG-stimulated progesterone production; 2) IL-1beta inhibits hCG-stimulated progesterone production only in mixed luteal cell cultures, indicating that leukocytes mediate the effect; 3) the somatic and immune cells of the CL are sites of action and expression of the IL-1 system; and 4) interaction between the steroidogenic and immune cells of the CL suggests a functional intraovarian role for IL-1beta in CL physiology.

Coculture of human embryos with autologous human endometrial epithelial cells in patients with implantation failure

We have developed a coculture system with autologous human endometrial epithelial cells (AEEC) that retained many features of human endometrial epithelium. Implantation failure (IF; >3 previous cycles failed with 3-4 good quality embryos transferred) is a distressing condition in which 2-day embryo transfer repetition is the routine option. The objective of this study was to investigate the basics and to evaluate prospectively the clinical value of embryo coculture on AEEC and blastocyst transfer with their own oocytes [in vitro fertilization (IVF) patients] or with donated oocytes (oocyte donation patients) compared to a routine day 2 embryo transfer for patients with IF. Scanning electron microscopy and mouse embryo assays demonstrate that EEC from fertile and IF patients were morphologically and functionally similar; similar findings were observed in EEC obtained from fresh or frozen endometria. Clinically, 168 IVF cycles were performed in 127 patients with 3.8+/-0.2 previously failed cycles, and 80 cycles were performed in 57 patients undergoing oocyte donation with 3.0+/-0.2 previously failed cycles. Twenty IVF patients and 15 ovum donation patients with 3 previously failed cycles in whom a 2-day embryo transfer was performed were used as controls. In 88% of ovum donation cycles, at least 2 blastocysts were available for transfer, with 60.1% blastocyst formation; 2.2+/-0.1 blastocysts were transferred/cycle, and 36 pregnancies (determined by fetal cardiac activity) were obtained (32.7% implantation and 54.5% pregnancy rates). In 168 IVF cycles, 8.1+/-0.2 embryos/cycle started coculture, resulting in 49.2% blastocyst formation; 2.3+/-0.2 blastocysts were transferred/cycle, and 29 clinical pregnancies were obtained (11.8% implantation and 20.2% pregnancy rates). Fifteen cycles were canceled (9%). In oocyte donation patients with IF undergoing 2-day embryo transfer, implantation and pregnancy rates were significantly lower (4.5% and 13.3%; P < 0.01) than with coculture; however, in IVF patients with IF, results with day 2 transfer (10.7% and 35%) were similar to those with coculture. The present study demonstrates that coculture of human embryos with AEEC and blastocyst transfer is safe, ethical, and effective and constitutes a new approach to improve implantation in patients with IF undergoing ovum donation, but not in IVF patients.

Maturation in vitro of human oocytes from unstimulated cycles: selection of the optimal day for ovum retrieval based on follicular size

The potential use of immature oocytes for in-vitro fertilization (IVF) requires the conditions for successful maturation to be defined. This study focused on the day of oocyte retrieval. The selection of a dominant follicle may induce endocrine changes in the remaining cohort that may be detrimental to their subsequent fertilization and embryonic development. Natural cycles in volunteer donors were followed by measurement of serum oestradiol and by vaginal ultrasound, starting on day 3 of the cycle. Cycles were randomly allocated to one of two groups: group 1 (n = 10), in which follicles were aspirated before the leading follicle was 10 mm in diameter; and group 2 (n = 9), in which follicles were aspirated when a dominant follicle was clearly visible with diameter >10 mm. Oocytes were cultured in vitro to metaphase II (MII) stage, donated, and inseminated by intracytoplasmic sperm injection (ICSI) with husband's spermatozoa. Those that became fertilized within 24 h were further co-cultured in autologous endometrial epithelial cells up to the blastocyst stage, and cryopreserved. There was a significantly (P < 0.05) increased rate of oocyte retrieval in group 1 (70.8% of aspirated follicles) compared with group 2 (50.5%). Maturation to MII and fertilization were similar between the groups. However, development to blastocyst stage was significantly (P < 0.05) higher in group 1 embryos (56.5%) compared with group 2 (35.7%). There was a positive correlation (r2 = 0.1978) between the appearance of the cumulus cells and the ability to develop to blastocyst stage when both parameters were analysed in group 1, whereas no such correlation was found in group 2. In conclusion, our data suggest the importance of retrieving immature oocytes before follicular selection, and define the conditions for the first stage in the use of immature oocytes. Further stages must be defined before this technique can be used clinically.

Embryonic implantation

Embryo implantation is a progressive process which requires a communication between two different organisms, and consists of three consecutive phases: apposition, adhesion and invasion. It must be realized throughout the period called "window of implantation", which is characterized by morphological and biochemical changes in the endometrium, as the plasma membrane transformation and the presence of some specific adhesion molecules, chemokines, cytokines, growth factors, and invasive proteinases. All of then acting in a paracrine/autocrine manner, and drive by endocrine hormones.

In vitro fertilization plus preimplantation genetic diagnosis in patients with recurrent miscarriage: an analysis of chromosome abnormalities in human preimplantation embryos

OBJECTIVE

To analyze the incidence of numeric chromosomal abnormalities in preimplantation embryos from women with unexplained recurrent miscarriage (RM) so as to seek an etiology and to determine whether the use of IVF may be indicated to treat these cases.

DESIGN

Prospective controlled study.

SETTING

University laboratory of reproductive genetics and a tertiary referral center for infertility.

PATIENT(S)

Nine women with a mean (+/-SD) of 3.9 +/- 0.6 RMs who were undergoing IVF and preimplantation genetic diagnosis, and a control group of young (n = 10) and older (n = 6) patients who were undergoing preimplantation genetic diagnosis because of sex-linked diseases.

INTERVENTION(S)

In vitro fertilization, embryo culture for 72 hours, blastomere biopsy, and analysis of chromosomes 13, 16, 18, 21, 22, X, and Y with the use of fluorescent in situ hybridization. Transfer of chromosomally normal embryos into the uterus.

MAIN OUTCOME MEASURE(S)

Numeric chromosomal abnormalities in human embryos.

RESULT(S)

Sixty-six embryos from patients with RM were compared with 62 embryos from young patients and 41 embryos from older patients. There was a significant increase in the rate of abnormal embryos in the patients with RM and the older patients compared with the controls. Abnormalities in most of the chromosomes studied were higher in the RM group than in the control group, especially those affecting chromosome 13.

CONCLUSION(S)

There was an increase in numeric chromosomal abnormalities in preimplantation embryos from women with RM that could be the cause of infertility in many couples with unexplained RM. The use of IVF in such circumstances may be indicated if successful preimplantation genetic diagnosis is added to the procedure.