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

Characterization of secreted proteins of 2-cell mouse embryos cultured in vitro to the blastocyst stage with and without protein supplementation

PURPOSE

To identify the secreted proteins of murine embryos grown in vitro.

METHODS

Two-cell mouse embryos (n=432) were randomly allocated to culture to the blastocyst stage in protein-free and in protein-supplemented (3 % BSA) media. Proteins were separated by SDS-PAGE; bands were visualized by coomassie staining, followed by in-gel trypsin digestion and liquid chromatography-tandem mass spectrometry. RT-PCR and confocal microscopy were used to confirm gene/protein expression in blastocysts.

RESULTS

Of all individually identified proteins, 34 and 23 were found in embryos cultured without and with BSA, respectively, and 20 were common. Identified proteins having an N-terminal secretory sequence or transmembrane domains located on the extracellular backbone were postulated as secreted proteins. Gene and protein expression for two selected molecules were confirmed. Functional analysis revealed over-represented processes related to lipid metabolism, cyclase activity, and cell adhesion/membrane functions.

CONCLUSIONS

This study provided evidence to further characterize secreted proteins by mouse embryos grown from the 2-cell to the blastocyst stage in vitro. Because of homology between murine and human, these results may provide information to be translated to the clinical setting.

Soluble ligands and their receptors in human embryo development and implantation

Extensive evidence suggests that soluble ligands and their receptors mediate human preimplantation embryo development and implantation. Progress in this complex area has been ongoing since the 1980s, with an ever-increasing list of candidates. This article specifically reviews evidence of soluble ligands and their receptors in the human preimplantation stage embryo and female reproductive tract. The focus will be on candidates produced by the human preimplantation embryo and those eliciting developmental responses in vitro, as well as endometrial factors related to implantation and receptivity. Pathways to clinical translation, including innovative diagnostics and other technologies, are also highlighted, drawing from this collective evidence toward facilitating joint improvements in embryo quality and endometrial receptivity. This strategy could not only benefit clinical outcomes in reproductive medicine but also provide broader insights into the peri-implantation period of human development to improve fetal and neonatal health.

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.

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.

The role of proteomics in defining the human embryonic secretome

Non-invasive gamete and embryo assessment is considered an important focus in assisted reproductive technologies (ART). Currently, the selection of embryos for transfer is based on morphological indices. Though successful, the field of ART would benefit from a non-invasive quantitative method of viability determination. Omics technologies, including transcriptomics, proteomics and metabolomics, have already begun providing evidence that viable gametes and embryos possess unique molecular profiles with potential biomarkers that can be utilized for developmental and/or viability selection. Unlike the human genome that is relatively fixed and steady throughout the human body, the human proteome, estimated at over a million proteins, is more complex, diverse and dynamic. It is the proteins themselves that contribute to the physiological homeostasis in any cell or tissue. Of particular interest in ART is the secretome, those proteins that are produced within the embryo and secreted into the surrounding environment. Defining the human embryonic secretome has the potential to expand our knowledge of embryonic cellular processes, including the complex dialogue between the developing embryo and its maternal environment, and may also assist in identifying those embryos with the highest implantation potential. Advances in proteomic technologies have allowed the non-invasive profiling of the human embryonic secretome with ongoing research focused on correlation with outcome. From a clinical perspective, embryo selection based on morphological assessment and non-invasive analysis of the human embryonic secretome may improve IVF success and lead to routine single embryo transfers.

Symposium: innovative techniques in human embryo viability assessment. Can proteomics help to shape the future of human assisted conception?

Proteomics describes the changes in all proteins expressed and translated from a single genome. At present little is known regarding either the genome or proteome of human gametes or the preimplantation embryo. The unravelling of this information is fundamental to understanding the complexity of reproductive physiology, including the dialogue between the developing embryo and its maternal environment. To date, a lack of sensitivity has been the main reason behind the inability to introduce proteomics technology into assisted reproduction techniques. Proteomics alone involves several sophisticated techniques including imaging, mass spectrometry and bioinformatics to identify, quantify and characterize a proteome. The recent increased sensitivity of these techniques has allowed for the development of new protocols that are capable of not only profiling the proteome of individual human oocytes and embryos, but also the proteins produced by the embryo into the surrounding medium (the secretome). Hence, the identification of proteins that are involved in oocyte maturation, embryo development and implantation could lead to further improvements in assisted reproduction techniques as well as the development of new diagnostic tests. Furthermore, proteomics may contribute in the design of a non-invasive viability assay to assist in the selection of embryos for transfer in human assisted reproduction.

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.

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.

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.

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.