Embryonic platelet-activating factor: an indicator of embryo viability

Events Leading to the Establishment of Pregnancy and Placental Formation: The Need to Fine-Tune the Nomenclature on Pregnancy and Gestation

Today, there is strong and diversified evidence that in humans at least 50% of early embryos do not proceed beyond the pre-implantation period. This evidence comes from clinical investigations, demography, epidemiology, embryology, immunology, and molecular biology. The purpose of this article is to highlight the steps leading to the establishment of pregnancy and placenta formation. These early events document the existence of a clear distinction between embryonic losses during the first two weeks after conception and those occurring during the subsequent months. This review attempts to highlight the nature of the maternal-embryonic dialogue and the major mechanisms active during the pre-implantation period aimed at "selecting" embryos with the ability to proceed to the formation of the placenta and therefore to the completion of pregnancy. This intense molecular cross-talk between the early embryo and the endometrium starts even before the blastocyst reaches the uterine cavity, substantially initiating and conditioning the process of implantation and the formation of the placenta. Today, several factors involved in this dialogue have been identified, although the best-known and overall, the most important, still remains Chorionic Gonadotrophin, indispensable during the first 8 to 10 weeks after fertilization. In addition, there are other substances acting during the first days following fertilization, the Early Pregnancy Factor, believed to be involved in the suppression of the maternal response, thereby allowing the continued viability of the early embryo. The Pre-Implantation Factor, secreted between 2 and 4 days after fertilization. This linear peptide molecule exhibits a self-protective and antitoxic action, is present in maternal blood as early as 7 days after conception, and is absent in the presence of non-viable embryos. The Embryo-Derived Platelet-activating Factor, produced and released by embryos of all mammalian species studied seems to have a role in the ligand-mediated trophic support of the early embryo. The implantation process is also guided by signals from cells in the decidualized endometrium. Various types of cells are involved, among them epithelial, stromal, and trophoblastic, producing a number of cellular molecules, such as cytokines, chemokines, growth factors, and adhesion molecules. Immune cells are also involved, mainly uterine natural killer cells, macrophages, and T cells. In conclusion, events taking place during the first two weeks after fertilization determine whether pregnancy can proceed and therefore whether placenta's formation can proceed. These events represent the scientific basis for a clear distinction between the first two weeks following fertilization and the rest of gestation. For this reason, we propose that a new nomenclature be adopted specifically separating the two periods. In other words, the period from fertilization and birth should be named "gestation", whereas that from the completion of the process of implantation leading to the formation of the placenta, and birth should be named "pregnancy".

Molecular regulators of human blastocyst development and hatching: Their significance in implantation and pregnancy outcome

In humans, blastocyst hatching and implantation events are two sequential, critically linked and rate-limiting events for a prospective pregnancy. These events are regulated by embryo-endometrium derived molecular factors which include hormones, growth factors, cytokines, immune-modulators, cell adhesion molecules and proteases. Due to poor viability of blastocysts, they fail to hatch and implant, leading to a low 'Live Birth Rates', majorly contributing to infertility. Here, embryo-derived biomarkers analysis plays a key role to assess potential biological viability of blastocysts which are capable of implantation and prospective pregnancy. Thus far, embryo-derived biomarkers examined are mostly immune-modulators which are thought to be associated with blastocyst development-implantation and progression of pregnancy, leading to live births. There is an urgent need to develop a quantitative and a reliable non-invasive approach aiding embryo selection for elective single embryo transfer and to minimize recurrent pregnancy loss and multiple pregnancies. In this article, we provide a comprehensive review on our current knowledge and understanding of potential embryo-derived molecular regulators, that is, biomarkers, of development of human blastocysts, their hatching and implantation. We discuss their potential implications in the assessment of blastocyst implantation potential and pregnancy outcome in terms of live births in humans.

Soluble human leukocyte antigen-G is a potential embryo viability biomarker and a positive predictor of live-births in humans

PROBLEM

Human infertility affects 15-20% of reproductive-age couples and it is mitigated by assisted reproductive technology (ART) approaches. Poor biological viability of embryos contributes to implantation failure and live birth rate (LBR). This study is aimed to examine whether or not embryo-secreted soluble human leukocyte antigen-G (sHLA-G) is (i) associated with developing embryos and (ii) able to predict successful pregnancy outcome.

METHOD OF STUDY

A retrospective, multicentric study using 539 human embryo spent medium samples (E-SMs), analysed for sHLA-G levels by ELISA. Correlation analysis was performed on sHLA-G levels with developing embryonic stages, their quality scores and pregnancy outcome in terms of LBR.

RESULTS

Of 539 E-SMs analysed, 445 had detectable sHLA-G (83%) with levels varying within and across clinics and, between stages of embryonic development. Levels of sHLA-G (ng/mL) were significantly (P < .05) different in E-SMs of cleavage-stage embryos versus blastocysts. There was an insignificant correlation between the sHLA-G levels and morphology scores of embryos. But, sHLA-G levels showed a positive correlation with grades of blastocysts and importantly, its levels were significantly (P < .05) higher in live-birth vis-a-vis no-birth cases. Also, levels were higher in live-births out of blastocysts-ETs versus cleavage-stage-embryo transfers. Altered levels were observed with embryos, which resulted in miscarriages. Overall, a significant (P < .0001) association of sHLA-G with live births was observed.

CONCLUSION

Embryo-derived sHLA-G can be a valuable embryo viability, independent, biomarker, which can predict live-birth outcome and it could be useful as an adjunct to existing criteria for elective single embryo transfer.

Genes and pathways associated with pregnancy loss in dairy cattle

Pregnancy loss directly impairs reproductive performance in dairy cattle. Here, we investigated genetic factors associated with pregnancy loss following detection of a viable embryo around 42 days of gestation. The objectives of this study were to perform whole-genome scans and subsequent gene-set analyses for identifying candidate genes, functional gene-sets and gene signaling pathways implicated in pregnancy loss in US Holstein cows. Data consisted of about 58,000 pregnancy/abortion records distributed over nulliparous, primiparous, and multiparous cows. Threshold models were used to assess the binary response of pregnancy loss. Whole‐genome scans identified at least seven genomic regions on BTA2, BTA10, BTA14, BTA16, BTA21, BTA24 and BTA29 associated with pregnancy loss in heifers and lactating cows. These regions harbor several candidate genes that are directly implicated in pregnancy maintenance and fetal growth, such as CHST14, IGF1R, IGF2, PSEN2, SLC2A5 and WNT4. Moreover, the enrichment analysis revealed at least seven significantly enriched processes, containing genes associated with pregnancy loss, including calcium signaling, cell–cell attachment, cellular proliferation, fetal development, immunity, membrane permeability, and steroid metabolism. Additionally, the pathway analysis revealed a number of significant gene signaling pathways that regulate placental development and fetal growth, including Wnt, Hedgehog, Notch, MAPK, Hippo, mTOR and TGFβ pathways. Overall, our findings contribute to a better understanding of the genetic and biological basis of pregnancy loss in dairy cattle and points out novel strategies for improving pregnancy maintenance via marker‐assisted breeding.

Temporal patterns of gene regulation and upstream regulators contributing to major developmental transitions during Rhesus macaque preimplantation development

The preimplantation period of life in mammals encompasses a tremendous amount of restructuring and remodeling of the embryonic genome and reprogramming of gene expression. These vast changes support metabolic activation and cellular processes that drive early cleavage divisions and enable the creation of the earliest primitive cell lineages. A major question in mammalian embryology is how such vast, sweeping changes in gene expression are orchestrated, so that changes in gene expression are exactly appropriate to meet the developmental needs of the embryo over time. Using the rhesus macaque as an experimentally tractable model species closely related to the human, we combined high quality RNA-seq libraries, in-depth sequencing and advanced systems analysis to discover the underlying mechanisms that drive major changes in gene regulation during preimplantation development. We identified the major changes in mRNA population and the biological pathways and processes impacted by those changes. Most importantly, we identified 24 key upstream regulators that are themselves modulated during development and that are associated with the regulation of over 1000 downstream genes. Through their roles in extensive gene networks, these 24 upstream regulators are situated to either drive major changes in target gene expression or modify the cellular environment in which other genes function, thereby directing major developmental transitions in the preimplantation embryo. The data presented here highlight some of the specific molecular features that likely drive preimplantation development in a nonhuman primate species and provides an extensive database for novel hypothesis-driven studies.

Intracellular localisation of platelet-activating factor during mammalian embryo development in vitro: a comparison of cattle, mouse and human

Platelet-activating factor (PAF) is a well-known marker for embryo quality and viability. For the first time, we describe an intracellular localisation of PAF in oocytes and embryos of cattle, mice and humans. We showed that PAF is represented in the nucleus, a signal that was lost upon nuclear envelope breakdown. This process was confirmed by treating the embryos with nocodazole, a spindle-disrupting agent that, as such, arrests the embryo in mitosis, and by microinjecting a PAF-specific antibody in bovine MII oocytes. The latter resulted in the absence of nuclear PAF in the pronuclei of the zygote and reduced further developmental potential. Previous research indicates that PAF is released and taken up from the culture medium by preimplantation embryos invitro, in which bovine serum albumin (BSA) serves as a crucial carrier molecule. In the present study we demonstrated that nuclear PAF does not originate from an extracellular source because embryos cultured in polyvinylpyrrolidone or BSA showed similar levels of PAF in their nuclei. Instead, our experiments indicate that cytosolic phospholipase A2 (cPLA2) is likely to be involved in the intracellular production of PAF, because treatment with arachidonyl trifluoromethyl ketone (AACOCF3), a specific cPLA2 inhibitor, clearly lowered PAF levels in the nuclei of bovine embryos.

A microwell culture system that allows group culture and is compatible with human single media

PURPOSE

A microwell culture system that facilitates group culture, such as well-of-the-well (WOW), improves embryonic development in an individual culture. We examined the effect of WOW on embryonic development in vitro with commercially available human single culture media.

METHODS

Using four different commercial human single culture media, in vitro development and imprinted gene expression of bovine embryos cultured in WOW were compared to droplet culture (one zygote per drop). To determine the effects of microwell and group culture on embryonic development, different numbers of embryos were cultured in droplet or WOW. Diffusion simulation of accumulating metabolites was conducted using the finite volume method.

RESULTS

WOW had a positive effect on bovine embryonic development, regardless of the type of single culture media. Imprinted gene expression was not different between droplet- and WOW-derived blastocysts. The microwell and group cultures in WOW showed a significant positive effect on the rate of total blastocysts and the rate of development to the expanded and hatching blastocyst stages. The assumed cumulative metabolite concentration of WOW with one embryo was 1.47 times higher than that of droplet culture with one embryo. Furthermore, the concentration of WOW with three embryos was 1.54 times higher than that of WOW with one embryo.

CONCLUSIONS

In using human single culture media, a microwell culture system that allows group culture could be a powerful clinical tool for improving the success of assisted reproductive technologies.

Maternal N-Carbamylglutamate Supply during Early Pregnancy Enhanced Pregnancy Outcomes in Sows through Modulations of Targeted Genes and Metabolism Pathways

Reducing pregnancy loss is important for improving reproductive efficiency for both human and mammalian animals. Our previous study demonstrates that maternal N-carbamylglutamate (NCG) supply during early pregnancy enhances embryonic survival in gilts. However, whether maternal NCG supply improves the pregnancy outcomes is still not known. Here we found maternal NCG supply during early pregnancy in sows significantly increased the numbers of total piglets born alive per litter ( P < 0.05) and significantly changed the levels of metabolites in amniotic fluid and serum involved in metabolism of energy, lipid, and glutathione and immunological regulation. The expression of endometrial progesterone receptor membrane component 1 (PGRMC1) was significantly increased by NCG supplementation ( P < 0.05) as well as the expression of PGRMC1, endothelial nitric oxide synthesases (eNOS), and lamin A/C in fetuses and placentae ( P < 0.05). Among the NCG-associated amino acids, arginine and glutamine, markedly increased PGRMC1 and eNOS expression in porcine trophectoderm cells ( P < 0.05), whereas glutamate could stimulate the expression of vimentin and lamin A/C in porcine trophectoderm (pTr) cells ( P < 0.05) and proline stimulated lamin A/C expression ( P < 0.05). Collectively, these data reveal the mechanisms of NCG in reducing early embryo loss. These findings have important implications that NCG has great potential to improve pregnancy outcomes in human and mammalian animals.

Fitting the data from embryo implantation prediction: Learning from label proportions

Machine learning techniques have been previously used to assist clinicians to select embryos for human-assisted reproduction. This work aims to show how an appropriate modeling of the problem can contribute to improve machine learning techniques for embryo selection. In this study, a dataset of 330 consecutive cycles (and associated embryos) carried out by the Unit of Assisted Reproduction of the Hospital Donostia (Spain) throughout 18 months has been analyzed. The problem of the embryo selection has been modeled by a novel weakly supervised paradigm, learning from label proportions, which considers all the available data, including embryos whose fate cannot be certainly established. Furthermore, all the collected features, describing cycles and embryos, have been considered in a multi-variate data analysis. Our integral solution has been successfully tested. Experimental results show that the proposed technique consistently outperforms an equivalent approach based on standard supervised classification. Embryos in this study were selected for transference according to the criteria of the Spanish Association for Reproduction Biology Studies. Obtained classification models outperform these criteria, specifically reordering medium-quality embryos.

The effects of chemical and physical factors on mammalian embryo culture and their importance for the practice of assisted human reproduction

BACKGROUND

Although laboratory procedures, along with culture media formulations, have improved over the past two decades, the issue remains that human IVF is performed in vitro (literally 'in glass').

METHODS

Using PubMed, electronic searches were performed using keywords from a list of chemical and physical factors with no limits placed on time. Examples of keywords include oxygen, ammonium, volatile organics, temperature, pH, oil overlays and incubation volume/embryo density. Available clinical and scientific evidence surrounding physical and chemical factors have been assessed and presented here.

RESULTS AND CONCLUSIONS

Development of the embryo outside the body means that it is constantly exposed to stresses that it would not experience in vivo. Sources of stress on the human embryo include identified factors such as pH and temperature shifts, exposure to atmospheric (20%) oxygen and the build-up of toxins in the media due to the static nature of culture. However, there are other sources of stress not typically considered, such as the act of pipetting itself, or the release of organic compounds from the very tissue culture ware upon which the embryo develops. Further, when more than one stress is present in the laboratory, there is evidence that negative synergies can result, culminating in significant trauma to the developing embryo. It is evident that embryos are sensitive to both chemical and physical signals within their microenvironment, and that these factors play a significant role in influencing development and events post transfer. From the viewpoint of assisted human reproduction, a major concern with chemical and physical factors lies in their adverse effects on the viability of embryos, and their long-term effects on the fetus, even as a result of a relatively brief exposure. This review presents data on the adverse effects of chemical and physical factors on mammalian embryos and the importance of identifying, and thereby minimizing, them in the practice of human IVF. Hence, optimizing the in vitro environment involves far more than improving culture media formulations.

Quality control and standardization of embryo morphology scoring and viability markers

A so-called 'good-quality embryo' may be defined as an embryo that has the potential to implant into the uterine endometrium and give rise to the birth of a healthy child. A standardized and objective scoring of embryo 'quality' is therefore crucial in the classification and selection of embryos. However, embryo scoring is still being performed mainly via ocular evaluation, which often results in different interpretations of embryo quality. The addition of viability markers, such as measuring gene expression or the uptake/release of metabolites, proteins or RNA/DNA molecules in the culture media, would increase the possibility of standardized measurements. However, no single biomarker has yet been introduced into standard clinical practice, mainly due to the complexity of the techniques and the influence of biological variations and differences in culture conditions. In this paper different methods for the scoring of embryos and the possibility of standardizing and implementing quality control systems are discussed.

Trends, fads and ART!

Morphological selection techniques of gametes and embryos are of current interest to clinical practice in ART. Although intracytoplasmic morphologically selected sperm injection (IMSI), time lapse imaging morphometry (TLIM) or quantification of chromosome numbers (PGS) are potentially useful in research, they have not been shown to be of statistically predictive value and, thus, have only limited clinical usefulness. We make the point that morphological markers alone cannot predict the success of the early embryo, which depends on the correct orchestration of a myriad of physiological and biochemical activation events that progress independently of the maternal or zygotic genome. Since previous attempts to identify metabolic markers for embryo quality have failed and there is no evidence that the intrinsic nature of gametes and embryos can be improved in the laboratory, embryologists can only minimize environmental or operator induced damage while these cells are manipulated ex vivo.

Predicting Embryo Presence and Viability

Pregnancy establishment, followed by birth of live offspring, is essential to all mammals. The biological processes leading up to pregnancy establishment, maintenance, and birth are complex and dependent on the coordinated timing of a series of events at the molecular, cellular, and physiological level. The ability to ovulate a competent oocyte, which is capable of undergoing fertilization, is only the initial step in achieving a successful pregnancy. Once fertilization has occurred and early embryonic development is initiated, early pregnancy detection is critical to provide proper prenatal care (humans) or appropriate management (domestic livestock). However, the simple presence of an embryo, early in gestation, does not guarantee the birth of a live offspring. Pregnancy loss (embryonic mortality, spontaneous abortions, etc.) has been well documented in all mammals, especially in humans and domestic livestock species, and is a major cause of reproductive loss. It has been estimated that only about 25-30% of all fertilized oocytes in humans result in birth of a live offspring; however, identifying the embryos that will not survive to parturition has not been an easy task. Therefore, investigators have focused the identification of products in maternal circulation that permit the detection of an embryo and assessment of its well-being. This review will focus on the advances in predicting embryonic presence and viability, in vivo.

Individual commitment to a group effect: strengths and weaknesses of bovine embryo group culture

Recently, new culture devices such as Corral and Primo Vision dishes have been designed for the culture of human embryos to allow the combination of group culture plus follow-up of individual embryos. Bovine inseminated oocytes were allocated to Primo Vision dishes, Corral dishes, individual culture or classical group culture. Blastocyst development in Primo Vision dishes was similar to classical group culture (34.3 and 39.0% respectively), and better than Corral dishes or individual culture (28.9 and 28.5% respectively). In Primo Vision dishes, a higher number of ‘slow’ embryos developed to the blastocyst stage compared with their individually cultured counterparts, while no differences were observed for ‘fast’ embryos. ‘Slow’ embryos in a ‘standard drop’ had a higher chance of becoming a blastocyst compared with individual culture (OR: 2.3), whereas blastulation of ‘fast’ embryos was less efficient in a ‘delayed drop’ than in individual culture (OR: 0.3). The number of non-cleaved embryos in Primo Vision dishes did not negatively influence blastocyst development. Likewise, removing non-cleaved embryos (NC removed) and regrouping the cleaved embryos afterwards (ReGR) did not affect blastocyst development and quality compared with group culture in Primo Vision dishes (CTRL, 31.6%, NC removed, 29.3% and ReGR, 29.6%). The experiments revealed that group culture of bovine embryos in Primo Vision dishes is superior to individual culture, primarily because of the higher blastocyst rate achieved by slow embryos. Non-cleaved or arrested embryos do not hamper the ability of co-cultured bovine embryos to reach the blastocyst stage in group culture.

Elective single embryo transfer: guidelines for practice British Fertility Society and Association of Clinical Embryologists

Assisted conception treatment is the single most important cause in the increase in multiple pregnancy and births over the last 25 years. Multiple births are associated with significant peri natal morbidity and mortality. Europe has led the way in reducing multiple births by widespread adoption of an elective single embryo policy, which in Belgium is linked to an increase in state funding. Randomized controlled trials suggest that an eSET policy must include the ability to cryopreserve and transfer any remaining quality embryos to obtain parity with a double embryo transfer. This document provides a review of the available evidence with guidelines for practice, to help facilitate the introduction of an eSET policy in the UK.

Soluble HLA-G release by the human embryo: an interesting artefact?

Several publications have recently claimed that early human embryos release soluble human leukocyte antigen-G (HLA-G), and that there is a direct positive relationship between the quantity of this protein secreted and embryo quality and viability. These publications report a detection limit of 1 or 10 ng/ml of medium, and the quantity of material released was of the order of magnitude from 3 to 80 ng per day and per embryo. The protein content of a human preimplantation embryo can be estimated at 45-50 ng. This means that the HLA-G release reported could be from 10 to 100% and above the total protein content of the embryo. In recent decades, bio-industry has intensively engineered Chinese hamster ovary cells and optimized their gene expression in order to achieve extremely high yields of recombinant protein secretions reaching 50 pg per cell and per day. This is 100 times lower than what is proposed for soluble HLA-G release by the embryo. It is obvious that the embryo releases signals, but these are unlikely to be secreted at the order of magnitude of the concentrations that have been so far estimated.

Pregnancy prediction models and eSET criteria for IVF patients--do we need more information?

PURPOSE

The purpose of the present study was to evaluate statistical prediction models and simple allocation criteria, based on predictors for pregnancy, as tools to identify a good prognosis group in a possible eSET setting.

METHODS

A pregnancy prediction model based on logistic regression models was generated by analysis of 1675 DET treatment cycles. The model was evaluated and compared to simple eSET allocation criteria.

RESULTS

Embryo quality, patient age, and basal FSH were identified as significant predictors (at 5% significance level) of pregnancy. Although comparable to previously generated models, the predictive ability of the present model was relatively poor and practically similar to simple allocation criteria based on age and embryo quality.

CONCLUSIONS

Existing prediction models, or simple allocation criteria, are limited in identifying good prognosis patients. Future studies of the applicability of improved pregnancy prediction models will need very comprehensive and detailed patient and embryo information.

Development of a respirometric biochip for embryo assessment

A prototype respirometric biochip dedicated to monitoring oxygen consumption of preimplantation embryos has been developed. The biochip comprises a linear array of eight flow-through microchambers profiled on silicon substrate, and functions together with a phosphorescent oxygen sensitive probe and fluorescence plate reader detection. A high level of sensitivity to changes in dissolved oxygen was achieved through miniaturisation and optimization of biochip geometry, and incorporation of appropriate sealing and humidification systems. The biochips have allowed characterisation of oxygen consumption, by 2 cell and blastocyst stage preimplantation mouse embryos, through monitoring as few as ten preimplantation embryos over a one-hour time period. They provide a non-invasive, simple and convenient means for assessing preimplantation embryo metabolism.

Influence of the preimplantation embryo development (Ped) gene on embryonic platelet-activating factor (PAF) levels

PURPOSE

A major gene responsible for the control of preimplantation cleavage rate is the Ped gene, the product of which is the Qa-2 protein. Fast, but not slow developing mouse embryos express the Qa-2 protein. Platelet-activating factor (PAF) is a novel and potent signaling phospholipid that has unique pleiotropic properties in addition to platelet activation. PAF plays a significant role in virtually every reproductive event, including ovulation, fertilization, implantation, and parturition. The role of the Ped gene in PAF production by preimplantation embryos is yet to be established. The presence of this gene provides embryos with a reproductive advantage over those that are Ped negative, and may also serve as a regulator of PAF synthesis. The study hypothesis is that the amount of PAF produced is dependent upon the presence or absence of the Ped gene.

METHODS

B6.K1 (Ped negative) and B6.K2 (Ped positive) mouse embryo-conditioned culture media were assayed for PAF content by a PAF-specific radioimmunoassay.

RESULTS

There was a significant (p < 0.001) difference in blastocyst development rates between the Ped+ B6.K2 (61.0%) and the Ped- B6.K1 (25.3%) embryo culture groups. There was a significant difference (p < 0.05) in PAF production between the Ped+ B6.K2 (4.70+/-0.46 pmol per embryo) embryo culture group and the Ped- B6.K1 (10.02+/-3.49 pmol per embryo) embryo group. The B6.K1 (Ped-) embryo group produced >2x more PAF than did the B6.K2 (Ped+) group.

CONCLUSIONS

The Ped gene plays a role in PAF production and release in preimplantation stage embryos. The use of two mouse identical strains, except for the Ped gene, show that its presence is associated with an increase in developmental potential. Embryos where the Ped gene was absent produced significantly higher levels of PAF, which may aid in their survival.

Secretion of soluble HLA-G by day 3 human embryos associated with higher pregnancy and implantation rates: assay of culture media using a new ELISA kit

Identification of chemical markers in human embryo culture media that relate to embryo quality and implantation potential could be an invaluable tool in embryo selection for transfer. Embryonic secretion of soluble human leukocyte antigen G (sHLA-G) has been postulated to be a marker for 'embryonic competence'. This study examines sHLA-G concentrations in day 3 culture media droplets of embryos that were selected for transfer, as well as those being cryopreserved. A total of 712 embryo culture supernatants from 83 patients were assayed. Soluble HLA-G was detected in 306 of the 712 samples tested. In the 58 transfers in which at least one embryo selected for embryo transfer was positive for sHLA-G, the pregnancy rate was 64% (37/58) and the implantation rate per embryo transferred was 38%. In contrast, patients receiving only embryos that were negative for sHLA-G had both a lower pregnancy rate of 36% (9/25; P < 0.05) and a decreased implantation rate (19%; P < 0.05). Expression of sHLA-G was also related to increasing cell stage. Concentration of sHLA-G in embryo culture media was variable and in the low range (3-10 ng/ml). These data suggest an association between implantation potential and embryonic secretion of sHLA-G. The commercial assay kit utilized allowed for same day assessment of sHLA-G secretion. Addition of sHLA-G status to traditional morphological criteria may be useful as a clinical tool for embryo selection.

The role of paf in embryo physiology

Embryo-derived paf (1-o-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is produced by de novo synthesis. This synthesis commences soon after fertilization and persists throughout the preimplantation phase. Paf is produced and released by the embryos of all mammalian species studied to date. Its release from the embryo involves binding to extracellular albumin in a manner that protects paf from enzymatic degradation. Released paf causes a range of alterations in maternal physiology, including platelet activation, changes in oviductal, endometrial and maternal immune function. Paf also acts in an autocrine fashion as a trophic/survival factor for the early embryo. In vitro, supplementation of culture media with paf improves embryo development. Embryo-derived paf's autocrine actions are transduced by 1-o-phosphatidylinositol-3-kinase, which induces characteristic calcium transients within the early embryo. The calcium transients require both the influx of external calcium and release of inositol trisphosphate-dependent internal calcium stores. Buffering these transients compromised embryo development in a manner that was reversed by exogenous paf. Assisted reproductive technologies compromise the production of paf by some embryos and retard the expression of the paf receptor. This deprivation of paf's action is one of the factors limiting the survivability of embryos produced by assisted reproductive technologies. Paf is one of several autocrine and paracrine trophic/survival factors that act on the early embryo. These factors probably act cooperatively and may, to some degree, be mutually redundant. As the earliest-released and the best-described embryotrophin, paf provides an important exemplar for understanding the role of ligand-mediated trophic support of the early embryo.

Exposure of preimplantation embryos to platelet-activating factor increases birth rate

PROBLEM

Platelet-activating factor (PAF) plays a significant role in fertility. Preimplantation stage embryos produce PAF (ePAF) which is required for development. PAF's mechanism of action is receptor-mediated and its presence has been reported in the developing mouse and human embryo. Exposure of preimplantation stage mouse embryos results in higher implantation rates. However, the effect of such treatment on live-birth rates and birth weights has not been reported. Therefore, the objective the study was to determine the effect of exposing preimplantation mouse embryos to PAF on subsequent birth rate and weight.

DESIGN

Two-cell stage preimplantation stage mouse embryos exposed to PAF (10(-7) M) for 15 min prior to intraoviductal transfer.

METHODS

Preimplantation stage embryos were recovered from eCG/hCG primed BDF1 female mice. Embryos were exposed to synthetic PAF (10(-7) M) for 15 min. PAF-treated embryos were transferred to the oviducts of pseudopregnant female CD-1 female mice. Superovulated and cultured BDF1 embryos not treated with PAF served as in vitro controls and naturally ovulated embryos with no collection/culture served as in vivo controls. Embryos were permitted to develop to term (18-21 days). The number of pups born per litter and litter weights subsequently were recorded.

RESULTS

A total of 160 BDF1 mouse embryos were collected, treated, and transferred (20 per CD-1 recipient) as described. There was a significant (P < 0.05) increase in the number of pups born to the PAF treatment group (56/80; 70%) as compared to the control group (44/80; 55%). There was also a significant difference (P < 0.05) in litter birth weights between the PAF (1.31 g/litter) and controls groups (1.25 g/litter). There was a significant difference (P < 0.05) in birth weights between the PAF treatment group and the in vivo group (1.51 g/litter). There was a significant difference in birth weights between the in vitro-control and in vivo groups (1.51 g/litter). There were no observational malformaties to pups born in any group.

CONCLUSIONS

Brief exposure of preimplantation stage embryos to PAF will result in a significant increase of delivery rates (pups/litter) as well as birth weights. However, the increase of birth weight was significantly below that found naturally. Additional studies are warranted to elucidate the mechanism of PAF's action in the preimplantation stage embryo and subsequent uterine development.

Embryonic soluble HLA-G as a marker of developmental potential in embryos

BACKGROUND

In human reproduction, embryo implantation is complex and poorly understood. At present, no single markers are used in routine treatment to assay biochemical functions of the human embryo. Soluble human leukocyte antigen-G (sHLA-G) could be considered a possible marker of embryo developmental potential. It is localized primarily on the extravillous trophoblast, making this antigen a potential mediator of immune interaction at the maternal-fetal interface during gestation.

METHODS

Soluble-HLA-G levels were evaluated by an enzyme-linked immunosorbent assay (ELISA) employing monoclonal antibody MEM-G9. It was evaluated in 318 media of single embryo cultures. We correlated the presence of sHLA-G with embryo morphology and the pregnancy obtained in that treatment cycle.

RESULTS

No correlation was found between embryo morphology and sHLA-G levels. Pregnancy was observed only when the medium of at least one transferred embryo contained sHLA-G. In 26 out of 66 patients, none of the obtained embryos showed any detectable sHLA-G molecules and no pregnancy occurred.

CONCLUSIONS

From our results, we propose sHLA-G as a potential marker of embryo development: the sHLA-G ELISA can be a useful biochemical assay in addition to embryo morphology in embryo selection for transfer in IVF treatment if there are other embryos with the same morphology.

Role of messenger RNA expression of platelet activating factor and its receptor in porcine in vitro-fertilized and cloned embryo development

Platelet activating factor (PAF) is known as an autocrine growth/survival factor in mammalian preimplantation embryos. This study investigated the expression of porcine PAF receptor (PAFr) mRNA and its role in porcine in vitro fertilized (IVF) or somatic cell nuclear transfer (SCNT) embryo development. The expression of PAFr mRNA in IVF or SCNT blastocysts was shown by reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analysis. Semiquantitative RT-PCR and Southern blot analysis demonstrated that PAFr mRNA was expressed during preimplantation embryo development, it was highly expressed through the 2-cell to 8-cell embryo stage, and it decreased at the morula stage. PAFr mRNA expression was detected steadily in IVF embryos, whereas it was varied at the 2-cell, 4-cell, and blastocyst stages in SCNT embryos. To determine the role of PAF in IVF and SCNT embryo development, embryos were cultured in North Carolina State University (NCSU)-23 medium supplemented with different concentrations of PAF (0, 0.037, 0.37, 3.72, or 37.2 nM). The PAF supplement significantly increased the rate of blastocyst formation in SCNT embryos, but not in IVF embryos. The PAF supplement for the entire 168 h of culture showed significantly higher blastocyst formation in SCNT embryos. Upregulation of PAFr mRNA by PAF in SCNT embryos indicated that the embryotrophic effect of PAF was mediated through its functional receptors in SCNT embryos. In conclusion, the present study demonstrated that PAFr mRNA was expressed in porcine IVF and SCNT embryos, and that PAF supplement improved the developmental competence of SCNT embryos through its specific receptors.

Pronuclear morphology evaluation with subsequent evaluation of embryo morphology significantly increases implantation rates

OBJECTIVE

To elucidate the relative predictive value of implantation markers at different stages of preimplantation development.

DESIGN

Correlation of pronuclear morphology with embryo morphology and implantation rates in retrospective and prospective analysis of in vitro fertilization/intracytoplasmic sperm injection (IVF-ICSI) treatment cycles.

SETTING

Private infertility center.

PATIENT(S)

A total of 441 couples undergoing infertility treatment.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Size of pronuclei and distance between them, the number and polarization of nucleolus precursor bodies (NPB) at the one-cell stage, embryo cleavage and fragmentation rates on days 2 and 3, and pregnancy and implantation rates.

RESULT(S)

Polarization of the NPB in both pronuclei had a statistically significant correlation with normal membrane breakage during ICSI (40%, compared with 33% easy, and 31% difficult membrane breakage) and also with faster cleavage and lower fragmentation rates of embryos. Sixty-one percent of implanting embryos had polarization of the NPB in both pronuclei compared with 37% for all embryos. Larger distance between pronuclei and their unequal size had a statistically significant correlation with slower cleavage and inferior embryo quality. Embryo selection based on only pronuclear morphology or on only day-3 embryo morphology yielded implantation rates of 15.1% and 12.1%, respectively. Embryo selection based on sequential evaluation of both pronuclear morphology and embryo morphology on day 3 resulted in a 21.1% implantation rate.

CONCLUSION(S)

Polarization of NPB in both pronuclei is as reliable marker of implantation as embryo morphology on day 3. However, pronuclear morphology assessment improves embryo selection only when it is combined with embryo morphology evaluation on day 3.