Secretion of human leukocyte antigen-G by human embryos is associated with a higher in vitro fertilization pregnancy rate

Relative expression of receptors in uterine natural killer cells compared to peripheral blood natural killer cells

One would expect maternal immune cells to attack the invading trophoblast as the placenta is semi-allogenic. However, they appear to cooperate with the trophoblast in disrupting the arterial wall which has been determined in several studies. uNK cells are a particular type of immune cell that appears to play a role in pregnancy. As in pregnancy, the key contributors to trophoblast invasion appear to be a unique combination of genes, which appear to regulate multiple components of the interactions between placental and maternal cells, called HLA class 1b genes. The HLA class 1b genes have few alleles, which makes them unlikely to be recognized as foreign by the maternal cells. The low polymorphic properties of these particular HLAs may aid trophoblasts in actively avoiding immune attacks. This review gives a complete description of the mechanisms of interaction between HLAs and maternal uNK cells in humans.

The impact of soluble HLA-G in IVF/ICSI embryo culture medium on implantation success

The HLA-G molecule is widely accepted as an important factor for pregnancy success. Its expression has been detected in the extravillous trophoblasts. Soluble HLA-G (sHLA-G) was found in the genital tract, pre-implanted embryos as well as in seminal fluid. In this study, we investigated the concentration of sHLA-G (sHLA-G1 and sHLA-G5) in media from 344 single cultured embryos following in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). The level of sHLA-G (U/ml) was tested with a sandwich enzyme-linked immunosorbent assay (ELISA) kit. We correlated sHLA-G secretion with ovarian stimulation protocols, the type of embryo transfer (fresh or frozen cycle) and the quality of the embryos. The ovarian stimulation protocol affects the secretion of sHLA-G by the embryo. Embryos obtained from the long agonist protocol secreted more sHLA-G than those originating from the short antagonist protocol (p = 0.0001). Embryos whose transfer resulted in a clinical pregnancy and/or live birth secreted more sHLA-G compared to those whose transfer ended without pregnancy. This was particularly observable in embryos following the long ovarian stimulation protocol and from a frozen embryo cycle. In conclusion, sHLA-G secreted by the embryo has an impact on implantation and live birth and could be a developmental potential marker of the embryo. Its concentration depends on the ovarian stimulation protocol used.

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.

Embryo morphokinetic score is associated with biomarkers of developmental competence and implantation

PURPOSE

To study embryo morphokinetics in relation to release in spent media of molecules with possible roles in development and implantation (miR-20a, miR-30c, and sHLA-G).

METHODS

Data were obtained from embryos generated in standard IVF and ICSI cycles. The Eeva system was used for embryo assessment, based on early morphokinetic parameters and producing a score (1-5, best-worst) corresponding to higher/medium/lower chances of development to blastocyst. miRNAs - mm miR-20a-5p and miR-30c-5p - and sHLA-G were quantified in 25 μl of spent blastocyst media (SBM) collected before vitrification or transfer. Statistical analyses were performed applying Kolmogorov-Smirnov, Shapiro-Wilk, and Spearman's correlation coefficient tests, where appropriate.

RESULTS

SBM were collected from a total of 172 viable blastocysts. Their analysis showed that concentration of miR-20a was progressively lower as Eeva score increased and probability of development to blastocyst decreased (P = 0.016). The opposite trend was observed in the case of miR-30c, i.e., concentration was higher as score increased and chances of development to blastocyst decreased (P = 0.004). Analysis of sHLA-G revealed a negative correlation with Eeva score, i.e., levels were progressively lower as Eeva score increased and probability of development to blastocyst decreased (R = - 0.388, N = 141, P = 0.001).

CONCLUSION

Our data suggest that morphokinetic algorithms that predict development to blastocyst stage, in fact, also identify embryos with molecular and cellular profiles more consistent with developmental functions.

Cytokines in embryonic secretome as potential markers for embryo selection

Despite performing certain morphological assessments for selecting the best embryo for transfer, the results have not been satisfactory. Given the global tendency for performing quick and noninvasive tests for embryo selection, great efforts have been made to discover the predictive biomarkers of embryo implantation potential. In recent years, many factors have been detected in embryo culture media as a major source of embryo secretions. Previous studies have evaluated cytokines, miRNAs, extracellular vesicles, and other factors such as leukemia inhibitory factor, colony-stimulating factor, reactive oxygen species, soluble human leukocyte antigen G, amino acids, and apolipoproteins in these media. Given the key role of cytokines in embryo implantation, these factors can be considered promising molecules for predicting the implantation success of assisted reproductive technology (ART). The present study was conducted to review embryo-secreted molecules as potential biomarkers for embryo selection in ART.

Comparison between embryos transferred with self-spent and fresh medium on reproductive outcomes: a prospective randomized trial

As the final and critical step in in vitro fertilization (IVF), embryo transfer has always received much attention and deserves continuous optimization. In the present study, to explore the role of autocrine factors in embryo self-spent culture media, we prospectively compared embryo transfer with self-spent culture medium and fresh medium on clinical pregnancy outcomes. A total of 318 fresh IVF/intracytoplasmic sperm injection (ICSI) cycles were randomly allocated into two subgroups based on their transfer media (using a self-spent culture medium or new pre-equilibrated culture media), and the clinical outcomes were compared between groups. The implantation rates, clinical pregnancy rates and live birth rates for transfer using self-spent medium instead of new pre-equilibrated culture medium were slightly improved without statistical significance. Interestingly, however, biochemical pregnancy rate was found to be significantly decreased after transfer using self-spent medium for Day 3 embryos compared with new pre-equilibrated culture media. In short, embryo transfer with self-spent culture medium has shown some advantages, and large sample size studies are still needed to confirm these observations.

ABBREVIATIONS

ART: assisted reproductive technologies; ICSI: intracytoplasmic sperm injection; IVF: in vitro fertilization; ET: embryo transfer.

The HLA-G 14-bp polymorphism and recurrent implantation failure: a meta-analysis

PURPOSE

The human leucocyte antigen-G (HLA-G) 14-bp insertion/deletion polymorphism was implicated in recurrent implantation failure (RIF), but individual published studies showed inconclusive results. Thus, a meta-analysis was performed to clarify the effect of HLA-G 14-bp polymorphism on RIF risk.

METHODS

A comprehensive search for relevant articles was conducted. The odds ratios (ORs) and 95% confidence intervals (CIs) for HLA-G 14-bp polymorphism and RIF were calculated.

RESULTS

A total of five studies were included. In studies conducted in RIF patients and controls who had at least one spontaneous pregnancy, meta-analysis revealed no statistically significant association between the HLA-G 14-bp polymorphism and RIF in allele contrast and all genetic models in the overall population, but significant association was found in the population of Caucasian origin under allele contrast (OR = 1.73, 95% CI, 1.20, 2.50) and genetic models of +14 bp/+14 bp vs. -14 bp/-14 bp (OR = 3.09, 95% CI, 1.43, 6.65). In studies conducted in RIF patients and controls who had successful pregnancy following IVF-ET, the meta-analysis showed that there was statistically significant association between the HLA-G 14 bp polymorphism and RIF in allele contrast (OR = 1.74, 95% CI, 1.13, 2.67) and genetic models of +14 bp/+14 bp vs. -14 bp/-14 bp (OR = 10.20, 95% CI, 2.47, 42.14) and dominant model (OR = 4.34, 95% CI, 1.72, 10.92). No publication bias was found in the present studies.

CONCLUSIONS

This meta-analysis suggested that the HLA-G 14-bp insertion allele may increase the risk of RIF in Caucasians. Further studies with large sample size of different ethnic populations are necessary.

The effect of the biochemical marker soluble human leukocyte antigen G on pregnancy outcome in assisted reproductive technology--a multicenter study

OBJECTIVE

To determine whether the presence of soluble human leukocyte antigen G (sHLA-G) affects implantation and pregnancy outcomes in vitro.

DESIGN

A multicenter retrospective study.

SETTING

Six certified in vitro fertilization (IVF) units.

PATIENT(S)

Embryos obtained from 2,040 patients from six different IVF clinics.

INTERVENTION(S)

Soluble HLA-G determination on day-2 embryos after intracytoplasmic sperm injection, with embryos transferred on day 3 using the sHLA-G data.

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy rate (10- to 12-week ultrasound finding).

RESULT(S)

All embryos were individually cultured, and a chemiluminescence enzyme-linked immunosorbent assay was used to detect the presence of sHLA-G in the culture medium surrounding the embryos. Embryos were selected based on a positive sHLA-G result and a graduated embryo scoring (GES) score >70, or on embryo morphology if the test was negative. In all centers, a positive sHLA-G result was associated with an increase in the odds of an ongoing pregnancy. The incidence of an ongoing pregnancy was 2.52 times greater in embryos transferred on day 3 with a positive sHLA-G test result than the incidence of an ongoing pregnancy in embryos with a negative sHLA-G test result.

CONCLUSION(S)

Data from this multicenter study confirm that sHLA-G expression is a valuable noninvasive embryo marker to assist in improving pregnancy outcomes, with the theoretical potential to reduce multiple pregnancies.

In vitro up-regulation of HLA-G using dexamethasone and hydrocortisone in first-trimester trophoblast cells of women experiencing recurrent miscarriage

The trophoblast cells at the maternal-fetal interface express an unusual combination of human leukocyte antigen (HLA)-C, HLA-E and HLA-G. Altered expression of HLA-G on the extravillous cytotrophoblast has been implicated in the etiology of recurrent miscarriages (RMs). We have assessed HLA-G expression in extravillous cytotrophoblast in cell cultures prepared from RM patients and compared with those of first-trimester voluntarily terminated normal pregnancies (control). Glucocorticoids, dexamethasone and hydrocortisone were examined for their role in modulation of the HLA-G expression. HLA-G promoter and 3'UTR variants were investigated for their effect on the transcription of HLA-G. Cultured cytotrophoblast cells from the first-trimester RM patients were treated with dexamethasone and hydrocortisone (dose concentration 0-1000 ng/ml). HLA-G gene transcription was determined by semiquantitative and quantitative real-time polymerase chain reaction (RT-PCR), while protein expression was determined by a specific enzyme-linked immunosorbent assay (ELISA), flow cytometry and western blot analyses. HLA-G polymorphisms were detected by PCR and/or sequence-based typing. Low level of HLA-G was observed in untreated trophoblast cells obtained from RM patients as compared with controls. Upon treatment with glucocorticoids, the expression of HLA-G in these cells was up-regulated in a dose-dependent manner (P < 0.05), with no change in cellular proliferation and viability. There was no significant association between HLA-G polymorphism in RM patients and controls. HLA-G is minimally expressed in cultured trophoblast cells of RM patients. It can be up-regulated upon exposure with both dexamethasone and hydrocortisone. Glucocorticoids have the potential to modulate HLA-G expression in vitro, and can be further examined for their therapeutic applicability in RM.

The immunosuppressive molecule HLA-G and its clinical implications

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) class I molecule that, through interaction with its receptors, exerts important tolerogenic functions. Its main physiological expression occurs in placenta where it seems to participate in the maternal tolerance toward the fetus. HLA-G has been studied as a marker of pregnancy complications such as abortion or pre-eclapmsia. Although HLA-G is not expressed in most adult tissues, its ectopic expression has been observed in some diseases such as viral infections, autoimmune disorders, and especially cancer. HLA-G neo-expression in cancer is associated with the capability of tumor cells to evade the immune control. In this review, we will summarize HLA-G biology and how it participates in these physiopathological processes. Special attention will be paid to its role as a diagnostic tool and also as a therapeutic target.

Identification of apolipoprotein A1 in the human embryonic secretome

OBJECTIVE

To identify factors secreted by the human embryo and correlate levels with embryo morphology and pregnancy outcome.

DESIGN

A laboratory-based study of human embryo protein synthesis and secretion and a retrospective analysis of spent embryo culture media as it relates to pregnancy outcome.

SETTING

University-based academic IVF program.

PATIENT(S)

IVF patients who had donated cryopreserved human pronuclear-stage embryos. Patients undergoing fresh IVF cycles resulting in a blastocyst transfer who donated spent media drops.

INTERVENTION(S)

In vitro embryo culture and collection of spent media.

MAIN OUTCOME MEASURE(S)

Protein analysis and identification by two-dimensional gel electrophoresis and mass spectrometry, ApoA1 quantification by ELISA, and mRNA analysis by quantitative reverse transcriptase-polymerase chain reaction.

RESULT(S)

By protein gel electrophoresis, apolipoprotein A1 (ApoA1) was increased in the culture media from good-quality blastocysts (n = 6 embryos) compared to either cleavage-arrested embryos (n = 6 embryos) or poor-quality blastocysts (n = 6 embryos) using spent media from culture days 4 and 5, respectively. Apolipoprotein A1 concentrations were 23.1% greater in day 5 spent culture media from good-grade blastocysts (n = 30) when compared to poor-grade embryos (n = 30). However, in a group of patients (n = 20) with transfer of two good-quality blastocysts, ApoA1 levels from day 5 spent media did not correlate with embryo implantation and pregnancy. Quantitative reverse transcriptase-polymerase chain reaction confirmed the presence of ApoA1 mRNA transcripts in human blastocysts.

CONCLUSION(S)

Apolipoprotein A1 is produced by human preimplantation embryos, and increased levels are present in spent culture media containing blastocysts of higher morphologic grade. These results suggest a role for lipoproteins in early embryologic development.

The importance of HLA-G expression in embryos, trophoblast cells, and embryonic stem cells

The nonclassical HLA-G molecule is a trophoblast-specific molecule present in almost every pregnancy. It differs from classical HLA class I molecules by the low degree of allelic variants and the high diversity of protein structures. HLA-G is reported to be a tolerogenic molecule that acts on cells of both innate and adaptive immunity. At the maternal-fetal interface HLA-G seems to be responsible largely for the reprogramming of local maternal immune response. This review will focus on the HLA-G gene expression profile in pregnancy, in preimplantation embryos, and in human embryonic stem cells with emphasis on the structural diversity of the HLA-G protein and its potential functional and diagnostic implications.

Endosomal signaling and a novel pathway defined by the natural killer receptor KIR2DL4 (CD158d)

In addition to ligand-induced activation of receptors at the cell surface, certain internalized receptor-ligand complexes are activated in endosomes which are, now recognized as important intracellular platforms of signal transduction. The major receptor families that signal from endosomes and illustrate the diversity and complexity of endosomal signaling include receptor tyrosine kinases (RTKs), G-protein-coupled receptors (GPCRs) and toll-like receptors (TLRs). Natural killer (NK) cells, an important component of the innate immune system, not only provide a rapid defense against foreign invaders, such as bacteria and viruses, but also positively shape local responses by cytokine and chemokine secretion. The NK cell receptor KIR2DL4 (CD158d) utilizes a new mode of endosomal signaling after binding its ligand, soluble HLA-G, in the extracellular milieu. Internalization of the receptor and its ligand into endosomes and initiation of signaling at this site result in a proinflammatory and proangiogenic response with important functions at sites of ligand expression, such as at the maternal-fetal interface during early pregnancy. After a brief overview of the modes of endosomal signaling and its value in generating distinct physiological responses, this review will highlight the mechanism and physiological significance of a novel intracellular signaling pathway used by the endosome-resident immune receptor KIR2DL4.

Embryo selection criteria based on morphology VERSUS the expression of a biochemical marker (sHLA-G) and a graduated embryo score: prediction of pregnancy outcome

PURPOSE

To compare pregnancy and implantation rates when embryos are selected based on a single Day 3 (D 3) morphology score vs. a GES score plus sHLA-G expression.

METHODS

A prospective randomized study (n = 214) undergoing fresh ICSI cycles. Embryos were selected for transfer based on either Day 3 morphology score (Group A) or GES-scoring plus sHLA-G expression (Group B).

RESULTS

Clinical [35/107 (33%) vs. 52/107 (49%)] and ongoing pregnancy [20/107 (19%) vs. 52/107 (49%)] rates were significantly different between Group A and Group B (p < 0.05). Implantation rates were not significantly different between Group A [52/353 (15%)] and Group B [73/417 (18%)] (p < 0.05). The number of pregnancies lost during the first trimester was nearly 12 times higher in Group A [25/52 (48%)].

CONCLUSION

The miscarriage rate was significantly lower in Group B than Group A and the pregnancy results were superior when embryos were selected based on GES plus sHLA-G expression.

On the role of placental Major Histocompatibility Complex and decidual leukocytes in implantation and pregnancy success using non-human primate models

While there is broad agreement that interactions of the human maternal immune system with the tissues and cells of the implanting embryo are likely to be critical contributors to pregnancy success, there remains a dearth of information which directly confirms this expectation. Although animal models of reproductive function often provide opportunities for confirming such hypotheses, progress in this area has been sporadic due to limitations of traditional laboratory or agricultural animal models, such as rodents, sheep, pigs and cattle. Many of these limitations derive from divergent modes of implantation and placentation across mammalian species. Over the past decade there has been progress in the development of the nonhuman primate as a model in which to address questions of pregnancy success in the area of immunology. The purpose of this review is to compare available model species, summarize current knowledge and recent progress with an emphasis on experimental in vivo manipulations, and suggest areas available for additional study and growth.

Soluble HLA-G in IVF/ICSI embryo culture supernatants does not always predict implantation success: a multicentre study

Several reports have described an association between the presence of soluble human leukocyte antigen G (sHLA-G) in human embryo culture supernatants (ES) and implantation success. However, not all studies agree with these findings. To further document this debate, a multicentre blinded study was performed to investigate, on a large number of IVF ES and ICSI ES, whether sHLA-G is a useful criterion for embryo selection before transfer. A total of 1405 ES from 355 patients were collected from three assisted reproductive technique (ART) centres and evaluated for their sHLA-G content in a single laboratory, using a chemiluminescence enzyme-linked immunosorbent assay. In only one centre was a significant association between sHLA-G-positive ES and successful implantation established (P = 0.0379), whereas no such association was observed in the other centres. It was found that the percentages and concentrations of sHLA-G-positive ES varied between centres, depending on culture media and ART conditions. The percentage of sHLA-G-positive ES was significantly higher in IVF ES than ICSI ES (P < 0.001 and P < 0.01 for two centres). These data demonstrate that substantial variations of sHLA-G content in ES occur between different ART centres, highlighting the influence of several technical parameters that differ from one centre to another.

Symposium: innovative techniques in human embryo viability assessment. Soluble human leukocyte antigen-G and pregnancy success

Non-invasive methods of assessing embryo quality are critical for pregnancy success following IVF or intracytoplasmic sperm injection (ICSI). The addition of new non-invasive morphological and biochemical analyses may further improve pregnancy success, allowing the transfer of a single embryo, thereby reducing the risks involved in multiple births following IVF/ICSI. The presence of a protein, soluble human leukocyte antigen-G (sHLA-G), in embryo cultures has been suggested as a way to non-invasively predict embryo quality and pregnancy success, especially when used in conjunction with current embryo quality assessment methods. Detection of sHLA-G in embryo culture medium has been correlated with pregnancy success in 12 studies, but three studies were not able to detect sHLA-G. This is a review of the literature on sHLA-G detection in IVF/ICSI, and reasons are proposed for the reported discrepancies, as well as guidelines for reporting of data in future studies. Furthermore, it is suggested that the use of an HLA-G transgenic mouse model would advance understanding of the mechanism of action of sHLA-G in preimplantation embryos and its correlation to embryo health and viability. Research on a mouse model, combined with clinical studies, should enable the development of a fast and reliable method for utilizing sHLA-G detection to improve pregnancy success after IVF/ICSI.

Release of sICAM-1 in oocytes and in vitro fertilized human embryos

Background

During the last years, several studies have reported the significant relationship between the production of soluble HLA-G molecules (sHLA-G) by 48–72 hours early embryos and an increased implantation rate in IVF protocols. As consequence, the detection of HLA-G modulation was suggested as a marker to identify the best embryos to be transferred. On the opposite, no suitable markers are available for the oocyte selection.

Methodology/Principal Findings

The major finding of the present paper is that the release of ICAM-1 might be predictive of oocyte maturation. The results obtained are confirmed using three independent methodologies, such as ELISA, Bio-Plex assay and Western blotting. The sICAM-1 release is very high in immature oocytes, decrease in mature oocytes and become even lower in in vitro fertilized embryos. No significant differences were observed in the levels of sICAM-1 release between immature oocytes with different morphological characteristics. On the contrary, when the mature oocytes were subdivided accordingly to morphological criteria, the mean sICAM-I levels in grade 1 oocytes were significantly decreased when compared to grade 2 and 3 oocytes.

Conclusions/Significance

The reduction of the number of fertilized oocytes and transferred embryos represents the main target of assisted reproductive medicine. We propose sICAM-1 as a biochemical marker for oocyte maturation and grading, with a possible interesting rebound in assisted reproduction techniques.

Expression and regulation of non-classical HLA-G in renal cell carcinoma

Under physiological conditions, the non-classical major histocompatibility complex class Ib molecule human leukocyte antigen G (HLA-G) is selectively expressed in placental trophoblasts, thymus and cornea. In pathological situations, HLA-G expression was frequently found in tumour cells of distinct origin, thereby allowing these tumour cells to escape immune surveillance. Although HLA-G expression occurs at a relatively high frequency in renal cell carcinoma (RCC) of the clear cell subtype, the molecular mechanisms of its aberrant expression in RCC has not yet been determined. Therefore, the constitutive and cytokine-mediated HLA-G expression as well as its mode of regulation was investigated. In addition to HLA-G-specific mRNA expression, membrane-bound and soluble/shed HLA-G protein was determined. Eight of 14 RCC cell lines analysed (57%) exhibited HLA-G-specific transcripts, whereas only 6 of 14 RCC cell lines (43%) expressed HLA-G protein, suggesting a post-transcriptional control of HLA-G in some cases. Treatment of RCC cell lines with either interferon-gamma or interleukin-10, respectively, increased HLA-G-specific mRNA and protein in six of eight HLA-G(+) RCC lines (75%), but not in HLA-G(-) RCC cells. A 5'-aza-2-deoxycytidine (5-Aza-dC)-mediated demethylation of the HLA-G promoter DNA resulted in an enhanced HLA-G expression in four of six RCC cell lines, whereas a de novo induction of HLA-G was only observed in one HLA-G(-) RCC cell line on treatment with 5-Aza-dC. Thus, there exist multiple mechanisms controlling HLA-G expression in RCC, which might also have an impact on the development of RCC-specific immunotherapies.

Assessment of embryo viability in assisted reproductive technology: shortcomings of current approaches and the emerging role of metabolomics

PURPOSE OF REVIEW

The present article describes the current status of embryo assessment in assisted reproductive technologies and discusses two important issues that derive, at least in part, from our inability to adequately assess the reproductive potential of individual embryos: low implantation rates and high multiple pregnancy rates. After an overview of studies evaluating embryo metabolism as a predictor of embryo viability, use of metabolomics and additional emerging approaches for rapid, noninvasive, embryo assessment are discussed.

RECENT FINDINGS

Morphology and cleavage rate remain the mainstay of embryo assessment. A number of technologies are, however, under investigation. These include the assessment of glucose, lactate, pyruvate, and amino acid metabolism, proteomic profiling, evaluation of oxygen consumption, and most recently, examination of the metabolome.

SUMMARY

As the number of assisted reproductive technology cycles increases worldwide, improvements in the ability to quickly and noninvasively determine the best embryos for transfer remain a critical goal for reproductive medicine. Recent studies suggest that metabolomic profiling of embryo culture media may provide a useful adjunct to the current embryo assessment strategies based on morphology and cleavage rate.

HLA-G gene polymorphism in human placentas: possible association of G*0106 allele with preeclampsia and miscarriage

Definite causes for several pathologies of pregnancy remain unknown. In light of several recent studies, however, diminished or aberrant HLA-G expression may be associated with certain complication of pregnancy and be linked to HLA-G polymorphism. We analyzed DNA from 60 normal placentas (controls), 140 placentas from miscarriage, 36 placentas from preeclampsia, 76 placentas from fetal hypotrophy, and 34 placentas with hypoxia for variations in coding regions (allelic groups G*0101 to G*0107) and the 14-bp deletion/insertion into the 3'-untranslated region. No statistically significant differences were observed in the distribution of allelic group between pathological placentas and controls with the exception of G*0106 allele frequency in preeclamptic compared with control placentas (21.2% and 6.6%, respectively). A greater frequency of this allele also was observed in the two subgroups of miscarriage and hypoxia compared with that in controls. In addition, presence of the 14-bp sequence was prominent in preeclampsia compared with controls (60.8% vs. 35%, respectively), and homozygotes with deletion were not detected in the pathology. The results suggest that the G*0106 allele, which is coupled with the presence of the 14-bp sequence, contributes and/or is a relevant marker in some specific complications of pregnancy, especially preeclampsia.

Accuracy of soluble human leukocyte antigen-G for predicting pregnancy among women undergoing infertility treatment: meta-analysis

BACKGROUND

There have been concerns about validity and accuracy of the measurement of sHLA-G in embryo culture supernatants. In this systematic review, we quantified the diagnostic accuracy of sHLA-G for predicting the ability to achieve clinical pregnancy in women who are undergoing infertility treatment.

METHODS

Medline and Embase were searched up to 7 September 2007, for full English and non-English articles concerning cohort studies evaluating sHLA-G in embryo culture for predicting clinical pregnancy in women undergoing IVF and ICSI.

RESULTS

Eleven studies including 1813 patients met our inclusion criteria. In the individual studies, sensitivity ranged from 0.01 to 0.97, specificity from 0.18 to 0.98, the positive likelihood ratio from 0.34 to 3.21 and the negative likelihood ratio from 0.08 to 1.01. These values were highly heterogeneous with, in each case, I(2) values of >75%, and P-values for the Q statistic of <0.001, arguing against generating a pooled estimate for these diagnostic test properties. The diagnostic odds ratios (DORs) ranged from 0.92 to 24.82 in the individual studies with an I(2) value of 49% indicating moderate heterogeneity. Therefore, the meta-analysis combined the logs of the DORs, which are derived from sensitivity and specificity. A random-effects model yielded a summary DOR of 4.38 (95% CI, 2.93-6.55), consistent with modest diagnostic accuracy. Interestingly, an a priori defined subgroup analysis restricted to six studies with good quality embryos showed a better diagnostic performance with a DOR of 12.67 (95% CI, 3.66-43.80) to predict the ability to achieve clinical pregnancy in women undergoing infertility treatment.

CONCLUSIONS

Further research is needed with single-embryo culture, single-embryo transfer and highly sensitive detection techniques to determine the potential application of measuring sHLA-G in culture supernatant.

Paternal contribution of HLA-G*0106 significantly increases risk for pre-eclampsia in multigravid pregnancies

Pre-eclampsia (PE) is a leading cause of maternal and fetal mortality and morbidity. Structural or functional alterations of human leukocyte antigen (HLA)-G present at the maternal-fetal interface may predispose women to PE. We tested the HLA-G gene for association with PE in a case-control study of 83 PE and 240 normotensive Malay women. HLA-G was amplified in a single-tube multiplex-PCR reaction and genotyped for 18 single nucleotide polymorphisms (SNPs) by multiplex-minisequencing. Case-control comparisons were performed, and associations with disease were expressed as odds ratios (ORs). Risk for PE was significantly associated with fetal allele G*0106 only in multigravid pregnancies (P = 0.002, OR = 5.0, 95% CI = 1.8-13.8). Among multigravid pregnancies, the frequency of PE babies heterozygous or homozygous for G*0106 was also significantly higher compared with normal control babies (P = 0.002, OR = 5.4, 95% CI = 1.9-15.4). Multivariate analyses with adjustment for factors associated with PE revealed similar results (P = 0.003, OR = 10.1, 95% CI = 2.2-46.8). Additionally, a significantly higher frequency of fetal-maternal G*0106 genotype mismatch was observed in PE compared with normal multigravid pregnancies (P = 0.001, OR = 9.6, 95% CI = 2.4-38.7). Thus, paternal HLA-G G*0106 contribution significantly increases risk for PE in multigravidas who do not carry this allele, potentially mediated by a gradual maternal alloimmune response to repeated exposure to the paternal HLA-G variant.

MicroRNA expression in preimplantation mouse embryos from Ped gene positive compared to Ped gene negative mice

PURPOSE

The mouse preimplantation embryo development (Ped) gene product, Qa-2, influences the rate of preimplantation embryonic development and overall reproductive success. Here we investigated the expression pattern of two microRNAs, miR-125a and miR-125b, known to be involved in development in lower organisms, in preimplantation embryos from the two-cell, four-cell, eight-cell, morula, and blastocyst stages of development from the congenic B6.K1 (Ped negative) and B6.K2 (Ped positive) strains of mice.

METHOD

B6.K1 and B6.K2 congenic mice differ only in the absence (B6.K1) or presence (B6.K2) of the genes encoding Qa-2 protein. We analyzed the expression of miR-125a and miR-125b in B6.K1 and B6.K2 preimplantation embryos by using real-time PCR.

RESULT

We found no variability in miR-125b expression at any developmental stage in both strains. However, miR-125a expression increased during development in both strains and was ten times higher in Ped negative (B6.K1) embryos than in Ped positive (B6.K2) embryos by the blastocyst stage of development.

CONCLUSION

Our results show that the absence of the Ped gene profoundly affects the level of a miRNA (miR-125a) known to regulate early development. The implication is that miR-125a is likely involved in the regulation of timing of early development in mice.

Preimplantation embryos cooperate with oviductal cells to produce embryotrophic inactivated complement-3b

Human oviductal epithelial (OE) cells produce complement protein 3 (C3) and its derivatives, C3b and inactivated complement-3b (iC3b). Among them, iC3b is the most potent embryotrophic molecule. We studied the production of iC3b in the oviductal cell/embryo culture system. In the immune system, C3 convertase converts C3 into C3b, and the conversion of C3b to iC3b requires factor I (fI) and its cofactors, such as factor H or membrane cofactor protein. Human oviductal epithelium and OE cells expressed mRNA and protein of the components of C3 convertase, including C2, C4, factor B, and factor D. The OE cell-conditioned medium contained active C3 convertase activity that was suppressed by C3 convertase inhibitor, H17 in a dose and time-dependent manner. Although the oviductal epithelium and OE cells produced fI, the production of its cofactor, factor H required for the conversion of C3b to iC3b, was weak. Thus, OE cell-conditioned medium was inefficient in producing iC3b from exogenous C3b. On the contrary, mouse embryos facilitated such conversion to iC3b, which was taken up by the embryos, resulting in the formation of more blastocysts of larger size. The facilitatory activity was mediated by complement receptor 1-related gene/protein Y (Crry) with known membrane cofactor protein activity on the trophectoderm of the embryos as anti-Crry antibody inhibited the conversion and embryotrophic activity of C3b in the presence of fI. In conclusion, human oviduct possesses C3 convertase activity converting C3 to C3b, and Crry of the preimplantation embryos may be involved in the production of embryotrophic iC3b on the surface of the embryos.

Preimplantation embryo development (Ped) gene copy number varies from 0 to 85 in a population of wild mice identified as Mus musculus domesticus

The preimplantation embryo development (Ped) gene regulates the rate of preimplantation embryonic cleavage division and subsequent embryo survival. In the mouse, the Ped gene product is Qa-2 protein, a nonclassical MHC class I molecule encoded by four tandem genes, Q6/Q7/Q8/Q9. Most inbred strains of mice have all four genes on each allelic chromosome, making a total of eight Qa-2 encoding genes, but there are a few strains that are missing all eight genes, defining a null allele. Mouse strains with the presence of the Qa-2 encoding genes express Qa-2 protein and produce embryos with a faster rate of preimplantation embryonic development and a greater chance of embryo survival compared to mouse strains with the null allele. There is extensive evidence that the human homolog of Qa-2 is HLA-G. HLA-G in humans, like Qa-2 in mice, is associated with enhanced reproductive success. The human population is an outbred population. Therefore, for a better comparison to the human population, we undertook an investigation of the presence of the genes encoding Qa-2 in an outbred population of mice. We used Real-Time Quantitative PCR to quantify the number of Qa-2 encoding genes in a population of 32 wild mice identified as Mus musculus domesticus both by morphologic assessment and by PCR analysis of their DNA. We found great variability in the number of Qa-2 encoding genes in the wild mice tested. The wild mouse with the highest number of Qa-2 encoding genes had 85 such genes, whereas we discovered one wild mouse without any Qa-2 encoding genes. Evolutionary implications of a range of Qa-2 encoding gene numbers in the wild mouse population are discussed, as well as the relevance of our findings to humans.

In vitro-produced bovine embryos: dealing with the warts

Bovine in vitro embryo production is an inefficient process; while maturation and fertilization proceed apparently normally, the proportion of embryos reaching the transferable (blastocyst) stage is rarely over 40% and those that do reach this stage are often compromised in quality and competence. There is considerable evidence of a significant influence of follicular origin on oocyte developmental potential and it appears that once the oocyte is removed from the follicle its developmental capacity is capped. Evidence suggests that while culture conditions during bovine in vitro embryo production can impact somewhat the developmental potential of the early embryo, the intrinsic quality of the oocyte is the key factor determining the proportion of oocytes developing to the blastocyst stage. This paper highlights some of the problems associated with in vitro production of embryos and discusses some of the ways of overcoming these problems.

Synthesis of beta(2)-microglobulin-free, disulphide-linked HLA-G5 homodimers in human placental villous cytotrophoblast cells

Human leucocyte antigen-G (HLA-G) is a natural immunosuppressant produced in human placentas that binds differently to the inhibitory leucocyte immunoglobulin-like receptors LILRB1 (ILT2) and LILRB2 (ILT4) according to its biochemical structure. To predict the binding functions of the HLA-G5 soluble isoform synthesized in placental villous cytotrophoblast (vCTB) cells, we investigated structural features of this protein. Biochemical and immunological studies showed that vCTB cell HLA-G5 heavy (H)-chain proteins are disulphide-bonded homodimers unassociated with beta(2)-microglobulin (beta2m) light-chain proteins. Although comparatively low levels of beta2m messenger RNA (mRNA) were identified by real-time reverse transcription-polymerase chain reaction, immunoprecipitation studies failed to detect beta2m protein even when specific mRNA was doubled by transduction of a lentivirus-beta2m complementary DNA into vCTB cells. No abnormalities were identified in the translational start codon of vCTB cell beta2m mRNA and differentiation into syncytium did not promote beta2m synthesis. The failure of vCTB cells to exhibit beta2m in vitro was paralleled by a lack of detectable beta2m in vCTB cells in vivo. Lack of the beta2m protein could be the result of low levels of beta2m transcripts or of as yet unidentified translational defects. Experiments with recombinant ectodomains of LILRB indicate that beta2m-free HLA-G binds strongly to LILRB2, a receptor that is expressed by macrophages. This potentially immunosuppressive cell type is abundant in the pregnant uterus. Thus, our findings are consistent with the postulate that the natural beta2m-free homodimeric form of HLA-G5 synthesized in primary vCTB cells could comprise a particularly effective tolerogenic molecule at the maternal-fetal interface.

sHLA-G production by human IVF embryos: Can it be measured reliably?

A number of reports have demonstrated that sHLA-G can be detected in the culture medium of human IVF embryos and that levels correlate with the potential of an embryo to implant. This has aroused considerable interest in the IVF field. If sHLA-G can be used as a non-invasive marker of embryo quality, it will facilitate selection of the best embryos to transfer to the mother and thereby increase IVF pregnancy rates. However, there have been concerns about some aspects of these studies, including the sensitivity of the sHLA-G ELISAs used, the IVF culture conditions and the levels of sHLA-G which have been reported. A recent study by Sageshima et al. [J. Reprod. Immunol. 75, 11-22, 2007] attempts to address some of these concerns. However, despite using a sensitive ELISA, they were unable to detect sHLA-G in 111 embryo culture supernatants, or sHLA-G secretion by less than 10,000 sHLA-G transfected cells. They concluded that it is not possible to measure sHLA-G production by human embryos. This study has highlighted technical differences between IVF culture techniques and sHLA-G ELISAs that are currently confounding the system. Further collaboration between the research groups involved is required to establish robust reproducible systems that function identically in all laboratories.

Prediction of porcine blastocyst formation using morphological, kinetic, and amino acid depletion and appearance criteria determined during the early cleavage of in vitro-produced embryos

The determination for early cleavage-stage embryos of noninvasive morphologic and metabolic criteria that are predictive of blastocyst development and/or full-term viability remains an important research target. We describe the derivation of a logistic regression model that predicts the probability of porcine blastocyst formation in vitro. Pig zygotes, derived by in vitro maturation and fertilization of slaughterhouse oocytes, were cultured in NCSU-23 medium that was supplemented with a mixture of 20 amino acids (NCSU-23(aa)). On Day 1, at 21, 23, 25, 27, 29 and 31 h postinsemination, cleaving embryos were evaluated morphologically in terms of the: i) number of blastomeres, ii) evenness of division, and iii) degree of fragmentation. These embryos were then placed in 1.5-microl drops of NCSU-23(aa) for 24 h, after which time the three morphologic criteria were re-evaluated and 1.2 microl of spent medium were removed for analysis by HPLC, in order to determine the net rates of amino acid depletion and appearance. Embryos were then cultured singly in NCSU-23(aa) by placing them between the filaments of a woven polyester mesh until Day 6, in order to permit the identification of individual embryos. Of 256 cleaved embryos, 28.7 +/- 6.2% (n = 5 replicates) developed into blastocysts. Discriminant analysis was used to select a subset of amino acids (threonine, valine, lysine, and phenylalanine) that discriminated optimally between embryos that became blastocysts or degenerated. These discriminant scores were entered into the logistic regression. Significant univariate relationships were established between the probability of blastocyst development and amino acid score (odds ratio [OR] 0.53, 95% confidence interval [CI] 0.40-0.69, P < 0.001), cleavage time (OR 0.79, 95% CI 0.71-0.87, P < 0.001), degree of fragmentation on Day 1 (OR 0.55, 95% CI 0.35-0.84, P = 0.009) and Day 2 (OR 0.53, 95% CI 0.35-0.78, P = 0.002), evenness of division on Day 2 (OR 0.66, 95% CI 0.46-0.96, P = 0.028), and categorical values of blastomere number on Day 2 (all P < 0.02), although no single variate could accurately predict blastocyst formation. However, multivariate analysis of the cell numbers on Day 1 and Day 2 correctly classified 51.9% of the predicted blastocysts. The inclusion of cleavage time in the regression analysis raised this rate to 63.5%, which was increased to 66.2% by the addition of evenness of division and degree of fragmentation. Finally, the full logistic regression model, which incorporated amino acid score together with all the other morphologic and kinetic variables, correctly classified 80.8% of the predicted blastocysts. This represented 51.2% of the observed blastocysts. Our data are novel in that they not only define in a quantitative manner the influence of previously undescribed predictors of porcine blastocyst formation, but they also provide a simple model of preimplantation development with reasonable predictive accuracy. The present study also provides a basic model for the examination and incorporation of additional early morphologic and metabolic correlates of developmental competence and could potentially be applied to the selection of human embryos for transfer in clinical IVF.

Quantification and identification of soluble HLA-G isoforms

In order to clarify the diagnostic relevance of soluble human leukocyte antigen-G (sHLA-G) molecules, reliable methods for the measurement of sHLA-G in various body fluids are of interest. Therefore, the aims of the 'Wet-Workshop for Quantification of Soluble HLA-G' held in Essen, Germany (at the Institute of Immunology, 18-20 October 2004) were to select and to validate HLA-G-specific enzyme-linked immunosorbent assay (ELISA) formats and purified standard HLA-G proteins, which can be easily generated and used as consensual references. We chose two ELISA formats, one for the simultaneous determination of shed HLA-G1 + sHLA-G5 (sHLA-G1 + G5) and one for the exclusive detection of HLA-G5 molecules. The first ELISA uses the antibody pair monoclonal antibody (mAb) MEM-G/9 + anti-beta2-microglobulin (beta2m), whereas the latter uses mAbs 5A6G7 + W6/32. Purified and well-defined HLA-G5 protein derived from insect SF9 cells transfected with HLA-G5 + human beta2m served as standard reagent. Twenty-five members of 13 international laboratories participated in the 3-day Wet-Workshop. The workshop demonstrated that the HLA-G5 protein was equally detected by both ELISA formats allowing direct comparison of quantitative results obtained by these two ELISA formats, and that sHLA-G1 + G5 and HLA-G5 molecules, respectively, were specifically and reproducibly quantified by the two ELISA formats. The comparison of the two ELISA results obtained allows the conclusion that sHLA-G1 and HLA-G5 molecules can exist in the blood of healthy donors. Moreover, there was evidence for a novel soluble HLA-G structure recognized by the mAbs 5A6G7 + W6/32 antibody combination but not by the one of mAb MEM-G/9 + anti-beta2m.