Analysis of protein expression (secretome) by human and mouse preimplantation embryos

Almost 50 Years of Monomeric Extracellular Ubiquitin (eUb)

Monomeric ubiquitin (Ub) is a 76-amino-acid highly conserved protein found in eukaryotes. The biological activity of Ub first described in the 1970s was extracellular, but it quickly gained relevance due to its intracellular role, i.e., post-translational modification of intracellular proteins (ubiquitination) that regulate numerous eukaryotic cellular processes. In the following years, the extracellular role of Ub was relegated to the background, until a correlation between higher survival rate and increased serum Ub concentrations in patients with sepsis and burns was observed. Although the mechanism of action (MoA) of extracellular ubiquitin (eUb) is not yet well understood, further studies have shown that it may ameliorate the inflammatory response in tissue injury and multiple sclerosis diseases. These observations, compounded with the high stability and low immunogenicity of eUb due to its high conservation in eukaryotes, have made this small protein a relevant candidate for biotherapeutic development. Here, we review the in vitro and in vivo effects of eUb on immunologic, cardiovascular, and nervous systems, and discuss the potential MoAs of eUb as an anti-inflammatory, antimicrobial, and cardio- and brain-protective agent.

The embryo non-invasive pre-implantation diagnosis era: how far are we?

Advancements in assisted reproduction (AR) methodologies have allowed significant improvements in live birth rates of women who otherwise would not be able to conceive. One of the tools that allowed this improvement is the possibility of embryo selection based on genetic status, performed via preimplantation genetic testing (PGT). Even though the widespread use of PGT from TE biopsy helped to decrease the interval from the beginning of the AR intervention to pregnancy, especially in older patients, in AR, there are still many concerns about the application of this invasive methodology in all cycles. Therefore, recently, researchers started to study the use of cell free DNA (cfDNA) released by the blastocyst in its culture medium to perform PGT, in a method called non-invasive PGT (niPGT). The development of a niPGT would bring the diagnostics power of conventional PGT, but with the advantage of being potentially less harmful to the embryo. Its implementation in clinical practice, however, is under heavy discussion since there are many unknowns about the technique, such as the origin of the cfDNA or if this genetic material is a true representative of the actual ploidy status of the embryo. Available data indicates that there is high correspondence between results observed in TE biopsies and the ones observed from cfDNA, but these results are still contradictory and highly debatable. In the present review, the advantages and disadvantages of niPGT are presented and discussed in relation to tradition TE biopsy-based PGT. Furthermore, there are also presented some other possible non-invasive tools that could be applied in the selection of the best embryo, such as quantification of other molecules as quality biomarkers, or the use artificial intelligence (AI) to identify the best embryos based on morphological and/or morphokitetic parameters.

Functional substitution of zona pellucida with modified sodium hyaluronate gel in human embryos

PURPOSE

Zona pellucida-free (ZP-free) embryos often fail to achieve good developmental outcomes and are routinely discarded in assisted reproductive laboratories. Existing attempts to rescue ZP-free embryos are not widely used due to operational complexity and high technical requirements. To handle cases with missing ZP, we applied modified sodium hyaluronate gel (MSHG) to embryo culture to determine if it can function as a substitute for human zona pellucida.

METHODS

The developmental process and the blastocyst formation rate of embryos were analyzed in both mouse and human. The first clinical application of MSHG was reported, and the pregnancy outcome was continuously followed up.

RESULTS

Human and mouse ZP-free embryos cultured with MSHG showed a blastocyst formation rate similar to ZP-intact embryos. MSHG improves blastocysts formation rate by maintaining blastomere spatial arrangement at early stages. Compared to ZP-free embryos, the proportion of tetrahedrally arranged blastomeres at the 4-cell stage increased significantly in embryos cultured with MSHG in humans. A ZP-free blastocyst cultured in MSHG with the highest score was successfully implanted after day 5 transplantation and developed normally.

CONCLUSION

These data demonstrate that MSHG can substitute the function of zona pellucida and rescue human ZP-free embryos during assisted reproductive technology.

Implementing a preimplantation proteomic approach to advance assisted reproduction technologies in the framework of predictive, preventive, and personalized medicine

The evolution of the field of assisted reproduction technology (ART) in the last 40 years has significantly contributed to the management of global infertility. Despite the great numbers of live births that have been achieved through ART, there is still potential for increasing the success rates. As a result, there is a need to create optimum conditions in order to increase ART efficacy. The selection of the best sperm, oocyte, and embryo, as well as the achievement of optimal endometrial receptivity, through the contribution of new diagnostic and treatment methods, based on a personalized proteomic approach, may assist in the attainment of this goal. Proteomics represent a powerful new technological development, which seeks for protein biomarkers in human tissues. These biomarkers may aid to predict the outcome, prevent failure, and monitor in a personalized manner in vitro fertilization (IVF) cycles. In this review, we will present data from studies that have been conducted in the search for such biomarkers in order to identify proteins related to good sperm, oocyte, and embryo quality, as well as optimal endometrial receptivity, which may later lead to greater results and the desirable ART outcome.

GDF9 concentration in embryo culture medium is linked to human embryo quality and viability

PURPOSE

We aimed to evaluate the link between the GDF9 concentration in day 3 human embryo culture medium and embryo quality and viability.

METHODS

Two independent, prospective, observational studies were conducted. In study 1, a total of 280 embryos from 70 patients who obtained at least 4 embryos with 6-10 blastomeres (2 transferable and 2 non-transferable embryos) at day 3 were enrolled. In study 2, a total of 119 embryos from 61 patients (29 fully implanted and 32 non-implanted patients) were enrolled. The corresponding GDF9 concentrations in spent culture medium of embryos were quantified by ELISA assay. The expression pattern of GDF9 in human embryos was investigated using Q-PCR and immunofluorescence.

RESULTS

GDF9 mRNA and protein were detected from human oocytes to eight-cell embryos and displayed a slow decreasing trend. In study 1, GDF9 concentration in culture medium is lower for transferable embryos compared with non-transferable embryos (331 pg/mL (quartiles: 442, 664 pg/mL) vs. 518 pg/mL (quartiles: 328, 1086 pg/mL), P < 0.001), and increased commensurate with the diminution of the embryo quality (P < 0.001). In study 2, significantly lower GDF9 concentration was detected for implanted embryos than non-implanted embryos (331 pg/mL (quartiles: 156, 665 pg/mL) vs. 518 pg/mL (quartiles: 328, 1086 pg/mL), P < 0.001). The same trend was found between the embryos that led to live birth and those that failed.

CONCLUSION

The GDF9 concentration in culture medium is linked to embryo quality and viability, and exhibited the potential to be a non-invasive biomarker for embryo selection.

Early cleaving embryos result in blastocysts with increased aspartate and glucose consumption, which exhibit different metabolic gene expression that persists in placental and fetal tissues

OBJECTIVES

Using time-lapse microscopy, previous research has shown that IVF mouse embryos that cleave earlier at the first division ('fast') develop into blastocysts with increased glucose consumption and lower likelihood of post-implantation loss as compared to slower cleaving embryos ('slow'). Further, metabolomics analysis employing LC-MS conducted on groups of 'fast' blastocysts revealed that more aspartate was consumed. With the worldwide adoption of single blastocyst transfer as the standard of care, the need for quantifiable biomarkers of viability, such as metabolism of specific nutrients, would greatly assist in embryo selection for transfer.

METHODS

Here we describe the development of a targeted enzymatic assay to quantitate aspartate uptake of single blastocysts.

RESULTS

Results demonstrate that the rates of aspartate and glucose consumption were significantly higher in individual 'fast' blastocysts. Blastocysts, together with placental and fetal liver tissue collected following transfer, were analysed for the expression of genes involved in aspartate and carbohydrate metabolism. In 'fast' blastocysts, expressions of B3gnt5, Slc2a1, Slc2a3, Got1 and Pkm2 were found to be significantly higher. In placental tissue derived from 'fast' blastocysts, expression of Slc2a1, Got1 and Pkm2 were significantly higher, while levels of Got1 and Pkm2 were lower in fetal liver tissue compared to tissue from 'slow' blastocysts.

CONCLUSIONS

Importantly, this study shows that genes regulating aspartate and glucose metabolism were increased in blastocysts that have higher viability, with differences maintained in resultant placentae and fetuses. Consequently, the analysis of aspartate uptake in combination with glucose represents biomarkers of development and may improve embryo selection efficacy and pregnancy rates.

Extracellular vesicles and female reproduction

Extracellular vesicles (EVs) are nano-sized membrane bound complexes that have been identified as a mean for intercellular communication between cells and tissues both in physiological and pathological conditions. These vesicles contain numerous molecules involved in signal transduction including microRNAs, mRNAs, DNA, proteins, lipids, and cytokines and can affect the behavior of recipient cells. Female reproduction is dependent on extremely fine-tuned endocrine regulation, and EVs may represent an added layer that contributes to this regulation. This narrative review article provides an update on the research of the role of EVs in female reproduction including folliculogenesis, fertilization, embryo quality, and implantation. We also highlight potential pitfalls in typical EV studies and discuss gaps in the current literature.

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.

Identifying biomarkers for predicting successful embryo implantation: applying single to multi-OMICs to improve reproductive outcomes

BACKGROUND

Successful embryo implantation is a complex process that requires the coordination of a series of events, involving both the embryo and the maternal endometrium. Key to this process is the intricate cascade of molecular mechanisms regulated by endocrine, paracrine and autocrine modulators of embryonic and maternal origin. Despite significant progress in ART, implantation failure still affects numerous infertile couples worldwide and fewer than 10% of embryos successfully implant. Improved selection of both the viable embryos and the optimal endometrial phenotype for transfer remains crucial to enhancing implantation chances. However, both classical morphological embryo selection and new strategies incorporated into clinical practice, such as embryonic genetic analysis, morphokinetics or ultrasound endometrial dating, remain insufficient to predict successful implantation. Additionally, no techniques are widely applied to analyse molecular signals involved in the embryo-uterine interaction. More reliable biological markers to predict embryo and uterine reproductive competence are needed to improve pregnancy outcomes. Recent years have seen a trend towards 'omics' methods, which enable the assessment of complete endometrial and embryonic molecular profiles during implantation. Omics have advanced our knowledge of the implantation process, identifying potential but rarely implemented biomarkers of successful implantation.

OBJECTIVE AND RATIONALE

Differences between the findings of published omics studies, and perhaps because embryonic and endometrial molecular signatures were often not investigated jointly, have prevented firm conclusions being reached. A timely review summarizing omics studies on the molecular determinants of human implantation in both the embryo and the endometrium will help facilitate integrative and reliable omics approaches to enhance ART outcomes.

SEARCH METHODS

In order to provide a comprehensive review of the literature published up to September 2019, Medline databases were searched using keywords pertaining to omics, including 'transcriptome', 'proteome', 'secretome', 'metabolome' and 'expression profiles', combined with terms related to implantation, such as 'endometrial receptivity', 'embryo viability' and 'embryo implantation'. No language restrictions were imposed. References from articles were also used for additional literature.

OUTCOMES

Here we provide a complete summary of the major achievements in human implantation research supplied by omics approaches, highlighting their potential to improve reproductive outcomes while fully elucidating the implantation mechanism. The review highlights the existence of discrepancies among the postulated biomarkers from studies on embryo viability or endometrial receptivity, even using the same omic analysis.

WIDER IMPLICATIONS

Despite the huge amount of biomarker information provided by omics, we still do not have enough evidence to link data from all omics with an implantation outcome. However, in the foreseeable future, application of minimally or non-invasive omics tools, together with a more integrative interpretation of uniformly collected data, will help to overcome the difficulties for clinical implementation of omics tools. Omics assays of the embryo and endometrium are being proposed or already being used as diagnostic tools for personalised single-embryo transfer in the most favourable endometrial environment, avoiding the risk of multiple pregnancies and ensuring better pregnancy rates.

Extracellular Vesicles, the Road toward the Improvement of ART Outcomes

Nowadays, farm animal industries use assisted reproductive technologies (ART) as a tool to manage herds' reproductive outcomes, for a fast dissemination of genetic improvement as well as to bypass subfertility issues. ART comprise at least one of the following procedures: collection and handling of oocytes, sperm, and embryos in in vitro conditions. Therefore, in these conditions, the interaction with the oviductal environment of gametes and early embryos during fertilization and the first stages of embryo development is lost. As a result, embryos obtained in in vitro fertilization (IVF) have less quality in comparison with those obtained in vivo, and have lower chances to implant and develop into viable offspring. In addition, media currently used for IVF are very similar to those empirically developed more than five decades ago. Recently, the importance of extracellular vesicles (EVs) in the fertility process has flourished. EVs are recognized as effective intercellular vehicles for communication as they deliver their cargo of proteins, lipids, and genetic material. Thus, during their transit through the female reproductive tract both gametes, oocyte and spermatozoa (that previously encountered EVs produced by male reproductive tract) interact with EVs produced by the female reproductive tract, passing them important information that contributes to a successful fertilization and embryo development. This fact highlights that the reproductive tract EVs cargo has an important role in reproductive events, which is missing in current ART media. This review aims to recapitulate recent advances in EVs functions on the fertilization process, highlighting the latest proposals with an applied approach to enhance ART outcome through EV utilization as an additive to the media of current ART procedures.

Extracellular Vesicle Mediated Crosstalk Between the Gametes, Conceptus, and Female Reproductive Tract

Extracellular vesicles (EVs) mediated intracellular communication plays an imperative role in the proper completion of different physiological events. Most of the bio-fluids are enriched with several subpopulations of EVs including exosomes and microvesicles (MVs), with the capacity of transferring different functional molecules (lipids, proteins, and nucleic acids) to target cells. Recipient cells upon receiving the signal molecules undergo different changes that positively affect the structural and functional integrity of the cells. This article was aimed to highlight the role of EVs secreted by gametes, the female reproductive tract, and the growing conceptus in the successful completion of different reproductive events related to gestation. EVs associated with the reproductive system are actively involved in the regulation of different physiological events including gamete maturation, fertilization, and embryo and fetal development. In the reproductive system, EVs mediated intracellular communication is not unidirectional but is rather regulated through crosstalk between the reproductive tract and the growing conceptus. These vesicles are secreted from the ovary, oviductal epithelium, endometrium, developing embryo, and the placenta. The cargo inside these vesicles exerts pleiotropic effects on both maternal and embryonic environments. A better understanding of the EVs-mediated crosstalk will be helpful in the development of useful tools serving both the diagnostic as well as therapeutic needs related to female fertility.

Necessity is the mother of invention and the evolutionary force driving the success of in vitro fertilization

During the last few decades, millions of healthy children have been born with the aid of in vitro fertilization (IVF). This success belies the fact that IVF treatment is comprised of a complex series of interventions starting with a customized control ovarian stimulation protocol. This is followed by the induction of oocyte maturation, the retrieval of mature oocytes and in vitro fertilization, which often involves the microinjection of a single sperm into the oocyte. After fertilization, the resulting embryos are cultured for up to 7 days. The best embryos are transferred into the uterus where the embryo implants and hopefully develops into a healthy child. However, frequently the best embryos are biopsied and frozen. The biopsied cells are analyzed to identify those embryos without chromosomal abnormalities. These embryos are eventually thawed and transferred with pregnancy rates as good if not better than embryos that are not biopsied and transferred in a fresh cycle. Thus, IVF treatment requires the coordinated efforts of physicians, nurses, molecular biologists and embryologists to conduct each of these multifaceted phases in a seamless and flawless manner. Even though complex, IVF treatment may seem routine today, but it was not always the case. In this review the evolution of human IVF is presented as a series of innovations that resolved a technical hurdle in one component of IVF while creating challenges that eventually lead to the next major advancement. This step-by-step evolution in the treatment of human infertility is recounted in this review.

Reducing time to pregnancy and facilitating the birth of healthy children through functional analysis of embryo physiology†

An ever-increasing number of couples rely on assisted reproductive technologies (ART) in order to conceive a child. Although advances in embryo culture have led to increases in the success rates of clinical ART, it often takes more than one treatment cycle to conceive a child. Ensuring patients conceive as soon as possible with a healthy embryo is a priority for reproductive medicine. Currently, selection of embryos for transfer relies predominantly on the morphological assessment of the preimplantation embryo; however, morphology is not an absolute link to embryo physiology, nor the health of the resulting child. Non-invasive quantitation of individual embryo physiology, a key regulator of both embryo viability and health, could provide valuable information to assist in the selection of the most viable embryo for transfer, hence reducing the time to pregnancy. Further, according to the Barker Hypothesis, the environment to which a fetus is exposed to during gestation affects subsequent offspring health. If the environment of the preimplantation period is capable of affecting metabolism, which in turn will affect gene expression through the metaboloepigenetic link, then assessment of embryo metabolism should represent an indirect measure of future offspring health. Previously, the term viable embryo has been used in association with the potential of an embryo to establish a pregnancy. Here, we propose the term healthy embryo to reflect the capacity of that embryo to lead to a healthy child and adult.

Embryo's Natural Motion (enMotion): a paired randomized controlled trial evaluating a dynamic embryo culture system

OBJECTIVE

To determine if a dynamic embryo culture system affects the reproductive potential of human embryos resulting from in vitro fertilization (IVF).

DESIGN

Paired randomized controlled trial (RCT).

SETTING

IVF center.

PATIENT(S)

IVF patients with normal ovarian reserve eligible for two-embryo transfer.

INTERVENTION

IVF care was routine until fertilization was confirmed. Two-pronuclear embryos (2PNs) were then randomized: One-half of each patient's 2PNs were cultured in dynamic culture and one-half in static culture. Preimplantation genetic testing for embryonic aneuploidy was used to control for aneuploidy and allow for DNA fingerprinting. The best euploid blastocyst from each culture system was selected and patients underwent a frozen two-embryo transfer. If a singleton gestation resulted, DNA-fingerprinting was used to determine which of the two blastocysts implanted. The dynamic platform used was the NSSB-300 (Nepagene).

MAIN OUTCOME MEASURE(S)

The primary outcome was the proportion of usable blastocysts obtained. The secondary outcome was sustained implantation rate (SIR).

RESULT(S)

One hundred participants completed oocyte retrieval and blastocyst vitrification for frozen-thawed embryo transfer; 609 dynamic 2PNs and 615 static 2PNs were followed; and 304 blastocysts developed in dynamic culture and 333 blastocysts developed in static culture. In the paired analysis, the rate of usable blastulation was similar between dynamic and static culture (58.3% vs. 57.1%). In addition, there was no difference in the rate of aneuploidy (20.0% vs. 33.3%) or SIR (67.1% vs. 63.1%) between groups.

CONCLUSION(S)

In this paired RCT, dynamic culture did not improve usable blastulation rate or SIR.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02467725.

In vitro culture and non-invasive metabolic profiling of single bovine embryos

Selecting high-quality embryos for transfer has been a difficult task when producing bovine embryos invitro. The most used non-invasive method is based on visual observation. Molecular characterisation of embryo growth media has been proposed as a complementary method. In this study we demonstrate a culture medium sampling method for identifying potential embryonic viability markers to predict normal or abnormal embryonic development. During single embryo culture, 20µL culture media was removed at Days 2, 5 and 8 after fertilisation from the same droplet (60µL). In all, 58 samples were analysed using liquid chromatography-mass spectrometry. We demonstrate that it is possible to remove samples from the same culture medium droplets and not significantly affect blastocyst rate (25.2%). Changes in any single low molecular weight compound were not predictive enough. Combining multiple low molecular weight signals made it possible to predict Day 2 and 5 embryo development to the blastocyst stage with an accuracy of 64%. Elevated concentrations of lysophosphatidylethanolamines (m/z=453, 566, 588) in the culture media of Day 8 well-developing embryos were observed. Choline (104m/z) and citrate (215m/z) concentrations were increased in embryos in which development was retarded. Metabolic profiling provides possibilities to identify well-developing embryos before transfer, thus improving pregnancy rates and the number of calves born.

Expressed proteins and activated pathways in conditioned embryo culture media from IVF patients are diverse according to infertility factors

OBJECTIVE

Given that the embryo culture medium secretome reflects the embryo development, we hypothesize that protein profiles are affected according to infertility factors, which can be responsible for detrimental embryonic developmental competence. The aim of this study was to screen the protein profile of conditioned embryo culture media in patients presenting deep infiltrating endometriosis (ENDO) and polycystic ovarian syndrome (PCOS) undergoing IVF, by proteomics approaches. The control group was constituted by tubal factor patients.

METHODS

Patients underwent in vitro fertilization (IVF) treatment as routine and oocytes were fertilized by ICSI. The embryos were group cultured until day 3 of development, and after transfer the culture media were collected. For the proteomics analysis, two pools of samples were prepared for groups CONTROL and PCOS, and 4 pools of samples for group DIE. Samples were prepared to deplete high abundant proteins and followed evaluated by high throughput proteomics approach.

RESULTS

The embryonic organ and tissue development were physiological functions activated, based on proteins identified in the 3 study groups of samples. The samples coming from DIE patients presented a high calcium activity and on the other hand, embryos coming from PCOS patients showed a decreased calcium action. Other pathways as grow factors through the EGF signaling pathway overexpressed in ENDO culture medium and protein kinase A in PCOS were also observed.

CONCLUSIONS

Proteomic embryonic secretome will advance our knowledge of early embryogenesis and additionally could lead to improved selection of embryos for transfer warrants further investigation.

Enabling Hamster Embryo Culture System: Development of Preimplantation Embryos

Development of preimplantation embryos, from fertilization to hatched-blastocyst stage, has been a challenging task, regardless of the mammalian species being studied. While the mouse model has been versatile for studying in vitro development of early embryos, other rodent species are important to gain insights into comparative early embryogenesis. The golden hamster (Mesocricetus auratus) offers unique advantages to study cellular and molecular regulation of gamete maturation, fertilization and preimplantation development, including the phenomenon of blastocyst hatching. Achieving in vitro fertilization and first cleavage division is relatively easy; however, subsequent development past the two-/four-cell stage had been difficult in hamsters. Pioneering research, carried out over three decades has markedly enabled successful in vitro development of one-cell embryos to blastocysts. This article provides a comprehensive perspective (historical and current) on the embryo culture systems and details an optimized culture protocols to achieve normal and viable development of preimplantation embryos in the golden hamster.

Secretome profile selection of optimal IVF embryos by matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Purpose

Selecting an embryo at the transfer stage with the best chance of a successful pregnancy is still largely dependent on preceding subjective evaluation of morphokinetics. Expensive prenatal genomic profiling has been so far proved ineffective. Proteomics and metabolomics are promising new approaches to assess embryo viability, but methodologies are often complex and do not lend themselves to rapid analysis in the critical time between blastocyst formation and embryo transfer. Here, we used matrix-assisted laser desorption ionization time-of-flight (MALDI ToF) mass spectrometry to assess the secretome of blastocysts in the minutes prior to embryo transfer and correlated spectral features with pregnancy outcome.

Methods

Four hundred one samples of spent blastocyst culture media were collected from embryo cultures at the time of embryo transfer, of which 136 were used to construct the predictive model. The media samples were frozen at − 20 °C and stored for analysis. Sample analysis was conducted in batches using 1 μl of spent embryo in direct MALDI ToF mass spectral analysis. Quantitative characteristics within this mass range (2000–17,000 m/z) were used to generate a score for selected mass regions (bins) in order to predict pregnancy outcome for each sample.

Results

With a simple algorithm based on nine mass bins within the 2000–10,000 m/z region, it was possible to identify samples with the best chance of becoming an ongoing pregnancy (positive predictive value of 82.9%, p = 0.0018).

Conclusion

A simple, direct and rapid analysis of spent culture fluid from blastocysts at the point of embryo transfer can quickly identify optimal embryos with the best chance of achieving ongoing pregnancy. Methods like this, which take less than 20 min to perform, could dramatically improve the approach to embryo selection and live births.

Proteomics of reproduction: Prospects and perspectives

In recent years, proteomics has been used widely in reproductive research in order to understand the molecular mechanisms related to gametes at the cellular level and the role of proteins involved in fertilization. Network and pathway analysis using bioinformatic tools have paved way to obtain a wider picture on the possible pathways associated with the key differentially expressed proteins (DEPs) and its implication in various infertility scenarios. A brief overview of advanced techniques and bioinformatic tools used for reproductive proteomics is presented. Key findings of proteomic-based studies on male and female reproduction are also presented. Furthermore, the chapter sheds light on the cellular pathways and potential biomarkers associated with male and female infertility. Proteomics coupled with bioinformatic analysis provides an ideal platform for non-invasive management of infertility in couples.

Antioxidants improve IVF outcome and subsequent embryo development in the mouse

STUDY QUESTION

What is the effect of a combination of three antioxidants (Acetyl-L-Carnitine, N-Acetyl-L-Cysteine and α-Lipoic Acid), present in IVF medium during mouse oocyte and sperm collection, on fertilization and subsequent IVF embryo development?

SUMMARY ANSWER

A combination of antioxidants resulted in faster developmental times from the 2-cell stage through to expanded blastocyst stage, accompanied by a significant increase in blastocyst cell number and a reduction of intracellular hydrogen peroxide (H2O2) levels.

WHAT IS KNOWN ALREADY

The antioxidant combination Acetyl-L-Carnitine, N-Acetyl-L-Cysteine and α-Lipoic Acid, when present in embryo culture media, has a significant beneficial effect on in vitro fertilized mouse pronucleate oocyte development, especially under oxidative stress.

STUDY DESIGN, SIZE, DURATION

IVF was conducted with combined antioxidants supplemented in IVF medium that was used for mouse oocyte collection and fertilization (oocyte IVF medium, 4 h exposure) and sperm collection and preparation (sperm IVF medium, 1 h exposure).

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

IVF was conducted under 20% oxygen, in the presence or absence of a combination of antioxidants (10 μM Acetyl-L-Carnitine, 10 μM N-Acetyl-L-Cysteine, 5 μM α-Lipoic Acid) and resultant embryos cultured with and without antioxidants under 20% oxygen. Subsequently, the effects of antioxidants on either oocytes or sperm was evaluated. Embryo development was analysed through time-lapse microscopy followed by differential nuclear staining to determine cell allocation in the blastocyst. Intracellular levels of H2O2 were assessed using an aryl boronate probe after 4 h of incubation with antioxidants. Controls were gametes and embryos that had no antioxidants in the medium. In a separate series of experiments, pronucleate oocytes were collected in handling medium with and without antioxidants for 20 min and subsequent cell numbers analysed.

MAIN RESULTS AND THE ROLE OF CHANCE

Antioxidant treatment during both IVF and culture resulted in significantly faster development times to two cell cleavage (P < 0.01), which continued through to the expanded blastocyst stage (P < 0.05). Resultant blastocysts had a significant increase in both trophectoderm (TE) cell numbers, inner cell mass (ICM) and total cell numbers (P < 0.001). The addition of antioxidants to IVF medium or embryo culture media exclusively also resulted in a significant increase in both blastocyst TE and ICM numbers leading to an increase in total cell numbers (P < 0.001). Antioxidant supplementation of either oocyte IVF medium alone, or in both oocyte and sperm IVF medium, lead to significantly faster times to two cell cleavage, which continued through to the expanded blastocyst stage. Blastocyst cell number in both these groups had significantly higher TE cell numbers resulting in an increase in total cell numbers. In contrast, there were no differences in embryo developmental rates and blastocyst cell number when antioxidants were present only in the sperm IVF medium. Levels of H2O2 were significantly reduced in pronucleate oocytes that were cultured in the presence of antioxidants (P < 0.001) compared to control, untreated embryos. Similarly, pronucleate oocytes treated with the combined antioxidants during pronucleate oocyte collection resulted in significantly increased blastocyst ICM numbers compared with controls (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Embryo development was only examined in the mouse.

WIDER IMPLICATIONS OF THE FINDINGS

These findings suggest that supplementation of antioxidants to the IVF medium, as well as to embryo culture media, may further assist in maintaining the viability of human embryos in ART, conceivably through the reduction of oxidative stress.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Alpha-1 chain of human haptoglobin as viability marker of in vitro fertilized human embryos: information beyond morphology

Only one third of the in vitro fertilization treatments result in successful delivery following morphological viability assessment worldwide. A paper by Montskó et al. (2015) describes the identification of the alpha-1 chain of human haptoglobin as a potential marker of embryo viability. Using mass spectrometry, the concentration of the haptoglobin alpha-1 chain was determined in spent culture media samples of in vitro fertilized embryos and correlation was found with the outcome of the respective transfer. In the present study we investigated, whether the concentration of haptoglobin alpha-1 chain shows any correlation with morphological scores to clarify whether levels of the alpha-1 chain provide additional information on embryo viability unnoticed by the morphological assessment. In the study, pregnancy and live birth rates were examined in 143 transferred samples of 86 patients, retrospectively. Two sample groups were created. The control group contained embryos classified as 'good' or 'fair' based on the Istanbul Consensus Criteria System, while the double-assay group contained embryos assessed as 'good' or 'fair' by the morphological evaluation and as 'viable' by the haptoglobin assay. Clinical pregnancy rate was 30.2% in the control group, while 47.6% in the group scored parallel with morphological criteria and proteomic analysis (p < 0.05). The increased clinical pregnancy rate observed in the double-assayed group can be attributed to decreased false-positivity of the double assay. Abbreviations: IVF: in vitro fertilization; SEC: spent embryo culture medium; HSA: human serum albumin; Hpt: haptoglobin; HptA1: haptoglobin alpha-1 chain; ICCS: Istanbul Consensus Criteria System; BMI: body mass index; ICSI: intracytoplasmic sperm injection.

Extracellular Vesicles in Human Reproduction in Health and Disease

Extensive evidence suggests that the release of membrane-enclosed compartments, more commonly known as extracellular vesicles (EVs), is a potent newly identified mechanism of cell-to-cell communication both in normal physiology and in pathological conditions. This review presents evidence about the formation and release of different EVs, their definitive markers and cargo content in reproductive physiological processes, and their capacity to convey information between cells through the transfer of functional protein and genetic information to alter phenotype and function of recipient cells associated with reproductive biology. In the male reproductive tract, epididymosomes and prostasomes participate in regulating sperm motility activation, capacitation, and acrosome reaction. In the female reproductive tract, follicular fluid, oviduct/tube, and uterine cavity EVs are considered as vehicles to carry information during oocyte maturation, fertilization, and embryo-maternal crosstalk. EVs via their cargo might be also involved in the triggering, maintenance, and progression of reproductive- and obstetric-related pathologies such as endometriosis, polycystic ovarian syndrome, preeclampsia, gestational diabetes, and erectile dysfunction. In this review, we provide current knowledge on the present and future use of EVs not only as biomarkers, but also as therapeutic targeting agents, mainly as vectors for drug or compound delivery into target cells and tissues.

NGS Analysis of Human Embryo Culture Media Reveals miRNAs of Extra Embryonic Origin

Our objective in this work was to isolate, identify, and compare micro-RNAs (miRNAs) found in spent culture media of euploid and aneuploid in vitro fertilization (IVF) embryos. Seventy-two embryos from 62 patients were collected, and their spent media were retained. A total of 108 spent conditioned media samples were analyzed (n = 36 day 3 euploid embryos, n = 36 day 3 aneuploid embryos, and n = 36 matched control media). Fifty hed-control media embryos were analyzed using next-generation sequencing (NGS) technology. We detected 53 known human miRNAs present in the spent conditioned media of euploid and aneuploid IVF embryos. miR-181b-5p and miR-191-5p were found the most represented. We validated our results by quantitative polymerase chain reaction (qPCR), but no significant results were obtained between the groups. In conclusion, we obtained the list of miRNAs present in the spent conditioned media from euploid and aneuploid IVF embryos, but our data suggest that these miRNAs could have a nonembryonic origin.

Impact of the IVF laboratory environment on human preimplantation embryo phenotype

The phenotype of the human embryo conceived through in vitro fertilization (IVF), that is its morphology, developmental kinetics, physiology and metabolism, can be affected by numerous components of the laboratory and embryo culture system (which comprise the laboratory environment). The culture media formulation is important in determining embryo phenotype, but this exists within a culture system that includes oxygen, temperature, pH and whether an embryo is cultured individually or in a group, all of which can influence embryo development. Significantly, exposure of an embryo to one suboptimal component of the culture system of laboratory typically predisposes the embryo to become more vulnerable to a second stressor, as has been well documented for atmospheric oxygen and individual culture, as well as for oxygen and ammonium. Furthermore, the inherent viability of the human embryo is derived from the quality of the gametes from which it is created. Patient age, aetiology, genetics, lifestyle (as well as ovarian stimulation in women) are all known to affect the developmental potential of gametes and hence the embryo. Thus, as well as considering the impact of the IVF laboratory environment, one needs to be aware of the status of the infertile couple, as this impacts how their gametes and embryos will respond to an in vitro environment. Although far from straight forward, analysing the interactions that exist between the human embryo and its environment will facilitate the creation of more effective and safer treatments for the infertile couple.

The Use of Proteomics in Assisted Reproduction

Despite the explosive increase in the use of Assisted Reproductive Technologies (ART) over the last 30 years, their success rates remain suboptimal. Proteomics is a rapidly-evolving technology-driven science that has already been widely applied in the exploration of human reproduction and fertility, providing useful insights into its physiology and leading to the identification of numerous proteins that may be potential biomarkers and/or treatment targets of a successful ART pregnancy. Here we present a brief overview of the techniques used in proteomic analyses and attempt a comprehensive presentation of recent data from mass spectrometry-based proteomic studies in humans, regarding all components of ARTs, including the male and female gamete, the derived zygote and embryo, the endometrium and, finally, the ART offspring both pre- and postnatally.

Haploid parthenotes express differential response to in vitro exposure of ammonia compared to normally fertilized embryos

In the present study, we assessed whether absence of paternal genome imparts any differential response in embryos to chemical stress such as ammonia. Parthenogenesis was induced in MII stage oocytes using 10 mM SrCl₂ in M16 medium. Parthenotes and normally fertilized embryos at 2 cell stage were exposed to different concentrations of ammonia and cultured till blastocyst. Exposure of ammonia to normally fertilized embryos resulted in significant decrease in the developmental potential (p < 0.0001) and blastocyst quality (p < 0.001). Whereas, in parthenotes, even though lower concentrations of ammonia did not have any effect, at 200 μM concentration the blastocyst rate was two times higher than control. The baseline apoptotic index was higher in parthenotes compared to normally fertilized embryos, which further increased after ammonium exposure (p < 0.001). Unlike in normally fertilized embryos ammonia exposure altered the mitochondrial distribution pattern and lead to increased expression of Oct4, Nanog and Na⁺/K⁺ ion exchange channel, while the cytochrome C expression was downregulated. This indicates that haploidy and/or absence of paternal factors in the embryo results in differential tolerance to stress induced by ammonia.

Proteomic profile of maternal-aged blastocoel fluid suggests a novel role for ubiquitin system in blastocyst quality

PURPOSE

The etiology of maternal aging, a common cause of female factor infertility and a rate-limiting step in vitro fertilization (IVF) success, remains still unclear. Proteomic changes responsible for the impaired successful pregnancy outcome after IVF with aged blastocysts have not been yet evaluated. The objective of this prospective study was to employ proteomic techniques and bioinformatic tools to enlight differences at the protein level in blastocoel fluid of aged and younger woman.

METHODS

Protein composition of human blastocoel fluid isolated by micromanipulation from 46 blastocysts of women aged <37 years (group A) and 29 of women aged ≥37 years (group B) have been identified by a shotgun proteomic approach based on high-resolution nano-liquid chromatography electrospray-ionization-tandem mass spectrometry (nLC-ESI-MS/MS) using label free for the relative quantification of their expression levels.

RESULTS

The proteomic analysis leads to the identification and quantification of 148 proteins; 132 and 116 proteins were identified in groups A and B, respectively. Interestingly, the identified proteins are mainly involved in processes aimed at fine tuning embryo implantation and development. Among the 100 proteins commonly expressed in both groups, 17 proteins are upregulated and 44 downregulated in group B compared to group A. Overall, the analysis identified 33 proteins, which were increased or present only in B while 76 were decreased in B or present only in A.

CONCLUSIONS

Data revealed that maternal aging mainly affects blastocyst survival and implantation through unbalancing the equilibrium of the ubiquitin system known to play a crucial role in fine-tuning several aspects required to ensure successful pregnancy outcome.

Protein expression in human cumulus cells as an indicator of blastocyst formation and pregnancy success

PURPOSE

The goal for the present study was to implement a technique for protein extraction and identification in human cumulus cells (CCs).

METHODS

Forty samples of CCs were collected after ovum pick-up from patients undergoing intracytoplasmic sperm injection (ICSI). Samples were split into the blastocyst group (n = 10), including patients in which all embryos converted into blastocysts, and the non-blastocyst group (n = 10), including patients in which none of the embryos reached the blastocyst stage or the positive-pregnancy (n = 10) and negative-pregnancy group (n = 10). Proteins were extracted and injected into a liquid chromatography system coupled to a mass spectrometer. The spectra were processed and used to search a database.

RESULTS

There were 87 different proteins in samples from the blastocyst and non-blastocyst groups, in which 30 were exclusively expressed in the blastocyst group and 17 in the non-blastocyst group. Among the 72 proteins detected in the pregnancy groups, 19 were exclusively expressed in the positive, and 16 were exclusively expressed in the negative-pregnancy group.

CONCLUSIONS

CC proteomics may be useful for predicting pregnancy success and the identification of patients that should be included in extended embryo culture programs.

Combined effects of individual culture and atmospheric oxygen on preimplantation mouse embryos in vitro

Embryos are routinely cultured individually, although this can reduce blastocyst development. Culture in atmospheric (20%) oxygen is also common, despite multiple detrimental effects on embryos. Although frequently occurring together, the consequences of this combination are unknown. Mouse embryos were cultured individually or grouped, under physiological (5%) or atmospheric (20%) oxygen. Embryos were assessed by time-lapse and blastocyst cell allocation. Compared with the control group (5% oxygen group culture), 5-cell cleavage (t5) was delayed in 5% oxygen individual culture and 20% oxygen group culture (59.91 ± 0.23, 60.70 ± 0.29, 63.06 ± 0.32 h post-HCG respectively, P < 0.05). Embryos in 20% oxygen individual culture were delayed earlier (3-cell cleavage), and at t5 cleaved later than embryos in other treatments (66.01 ± 0.40 h, P < 0.001), this delay persisting to blastocyst hatching. Compared with controls, hatching rate and cells per blastocyst were reduced in 5% oxygen single culture and 20% oxygen group culture (134.1 ± 3.4, 104.5 ± 3.2, 73.4 ± 2.2 cells, P < 0.001), and were further reduced in 20% oxygen individual culture (57.0 ± 2.8 cells, P < 0.001), as was percentage inner cell mass. These data indicate combining individual culture and 20% oxygen is detrimental to embryo development.

Characterization and quantification of proteins secreted by single human embryos prior to implantation

The use of in vitro fertilization (IVF) has revolutionized the treatment of infertility and is now responsible for 1–5% of all births in industrialized countries. During IVF, it is typical for patients to generate multiple embryos. However, only a small proportion of them possess the genetic and metabolic requirements needed in order to produce a healthy pregnancy. The identification of the embryo with the greatest developmental capacity represents a major challenge for fertility clinics. Current methods for the assessment of embryo competence are proven inefficient, and the inadvertent transfer of non-viable embryos is the principal reason why most IVF treatments (approximately two-thirds) end in failure. In this study, we investigate how the application of proteomic measurements could improve success rates in clinical embryology. We describe a procedure that allows the identification and quantification of proteins of embryonic origin, present in attomole concentrations in the blastocoel, the enclosed fluid-filled cavity that forms within 5-day-old human embryos. By using targeted proteomics, we demonstrate the feasibility of quantifying multiple proteins in samples derived from single blastocoels and that such measurements correlate with aspects of embryo viability, such as chromosomal (ploidy) status. This study illustrates the potential of high-sensitivity proteomics to measure clinically relevant biomarkers in minute samples and, more specifically, suggests that key aspects of embryo competence could be measured using a proteomic-based strategy, with negligible risk of harm to the living embryo. Our work paves the way for the development of “next-generation” embryo competence assessment strategies, based on functional proteomics.

Antioxidants improve mouse preimplantation embryo development and viability

STUDY QUESTION

What is the effect of three antioxidants (acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid), when used individually and in combination, on mouse embryo development in culture, and subsequent fetal development post-transfer?

SUMMARY ANSWER

A combination of antioxidants resulted in significant increases in blastocyst cell number, maintained intracellular glutathione (GSH) levels, supported earlier cleavage times from 5-cell stage to expanded blastocyst, and improved fetal developmental irrespective of incubator oxygen concentration.

WHAT IS KNOWN ALREADY

Acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid have been shown to have beneficial effects individually in several tissues, and most recently on developing embryos, in the presence of oxidative stress.

STUDY DESIGN, SIZE, DURATION

Morphokinetics of mouse embryos were quantitated using time-lapse imaging. GSH levels in pronucleate oocytes were measured. Blastocysts underwent differential nuclear staining for inner cell mass and trophectoderm cells or were transferred to recipient females to assess implantation and fetal development.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Pronucleate oocytes from F1 mice were cultured in 5 or 20% oxygen either individually or in groups of 10, in media G1/G2, in the presence or absence of 10 µM acetyl-L-carnitine /10 µM N-acetyl-L-cysteine /5 µM α-lipoic acid, either individually or in combination. Controls were embryos cultured without antioxidants. Intracellular levels of reduced glutathione were quantitated in pronucleate oocytes. Embryo development and viability were analysed through time-lapse microscopy and embryo transfers.

MAIN RESULTS AND THE ROLE OF CHANCE

Antioxidants significantly increased mouse blastocyst cell numbers compared with control when used individually (P< 0.05) and to a greater effect when all three were used in combination (P< 0.01) in 20% oxygen. The combination of antioxidants resulted in faster development rates to 5-cell cleavage stage, which continued until the expanded blastocyst stage when cultured in 20% oxygen. The beneficial effects of combining the antioxidants were greater for embryos cultured individually as opposed to in groups of 10 and for those embryos cultured in 20% compared to 5% oxygen. Levels of GSH were significantly decreased in control embryos that were incubated in the absence of antioxidants in 20% oxygen (P< 0.01), compared with in vivo flushed embryos. However, when embryos were cultured with antioxidants the level of GSH was not different to that of in vivo developed embryos. Embryos cultured in the presence of antioxidants in 20% oxygen and transferred resulted in significantly longer crown-rump length (11.6 ± 0.1 mm versus 11.3 ± 0.1 mm; P< 0.01), heavier fetuses (209.8 ± 11.8 mg versus 183.9 ± 5.9 mg; P< 0.05) and heavier placentas (103.5 ± 3.1 mg versus 93.6 ± 2.7 mg; P< 0.01) compared with controls (all data are mean ± SEM). Further, a post-implantation benefit of the antioxidant combination was also evident after culture in 5% oxygen.

LIMITATIONS, REASONS FOR CAUTION

Embryo development and implantation was only examined in the mouse.

WIDER IMPLICATIONS OF THE FINDINGS

These findings show that a combination of antioxidants in the culture media has a highly beneficial effect on mouse preimplantation embryo development in vitro and on subsequent fetal development post-transfer. These data indicate a potential role for the inclusion of specific antioxidant combinations in human embryo culture media irrespective of oxygen concentration. However, before application to human embryos, a proper evaluation of this approach in prospective, preferably randomized, trials will be required.

STUDY FUNDING/COMPETING INTERESTS

This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Omics in Reproductive Medicine: Application of Novel Technologies to Improve the IVF Success Rate

Treatment for many infertile couples often consists of in vitro fertilization (IVF) but an estimated 70% of IVF cycles fail to produce a live birth. In an attempt to improve the live birth rate, the vast majority of IVF cycles performed in the United States involve the transfer of multiple embryos, a practice that increases the risk of multiple gestation pregnancy. This is a concern because multiple gestation pregnancies are associated with an increased incidence of maternal and fetal complications and significant cost associated with the care of preterm infants. As the ideal outcome of each IVF cycle is the birth of a single healthy baby, significant effort has focused on identifying embryos with the greatest developmental potential. To date, selection of euploid embryos using comprehensive chromosome screening (CCS) is the most promising approach while metabolomic and proteomic assessment of spent culture medium have the potential to noninvasively assess embryo viability. Endometrial gene expression profiling may help determine the optimal time to perform embryo transfer. While CCS has been implemented in some clinics, further development and optimization will be required before analysis of spent culture medium and endometrial gene expression profiling make the transition to clinical use. This review will describe efforts to identify embryos with the greatest potential to result in a healthy, live birth, with a particular emphasis on detection of embryo aneuploidy and metabolic profiling of spent embryo culture medium. Assessment of endometrial receptivity to identify the optimal time to perform embryo transfer will also be discussed.

Extracellular vesicles: roles in gamete maturation, fertilization and embryo implantation

BACKGROUND

Extracellular vesicles (EVs) are membrane-bound vesicles, found in biofluids, that carry and transfer regulatory molecules, such as microRNAs (miRNAs) and proteins, and may mediate intercellular communication between cells and tissues. EVs have been isolated from a wide variety of biofluids, including plasma, urine, and, relevant to this review, seminal, follicular and uterine luminal fluid. We conducted a systematic search of the literature to review and present the currently available evidence on the possible roles of EVs in follicular growth, resumption of oocyte development and maturation (meiosis), sperm maturation, fertilization and embryo implantation.

METHODS

MEDLINE, Embase and Web of Science databases were searched using keywords pertaining to EVs, including 'extracellular vesicles', 'microvesicles', 'microparticles' and 'exosomes', combined with a range of terms associated with the period of development between fertilization and implantation, including 'oocyte', 'sperm', 'semen', 'fertilization', 'implantation', 'embryo', 'follicular fluid', 'epididymal fluid' and 'seminal fluid'. Relevant research articles published in English (both animal and human studies) were reviewed with no restrictions on publication date (i.e. from earliest database dates to July 2015). References from these articles were used to obtain additional articles.

RESULTS

A total of 1556 records were retrieved from the three databases. After removing duplicates and irrelevant titles, we reviewed the abstracts of 201 articles, which included 92 relevant articles. Both animal and human studies unequivocally identified various types of EVs in seminal, follicular and ULFs. Several studies provided evidence for the roles of EVs in these biofluids. In men, EVs in seminal fluid were linked with post-testicular sperm maturation, including sperm motility acquisition and reduction of oxidative stress. In women, EVs in follicular fluid were shown to contain miRNAs with potential roles in follicular growth, resumption of oocyte meiosis, steroidogenesis and prevention of polyspermy after fertilization. EVs were also detected in the media of cultured embryos, suggesting that EVs released from embryos and the uterus may mediate embryo-endometrium cross-talk during implantation. It is important to note that many of the biologically plausible functions of EVs in reproduction discussed in the current literature have not yet been substantiated by conclusive experimental evidence.

CONCLUSIONS

A detailed understanding of the contributions of EVs in the series of events from gametogenesis to fertilization and then on to implantation, in both normal and pathological cases, may enable the development of valuable tools to advance reproductive health. Because of the early stage of the field, it is unsurprising that the current literature includes not only growing experimental evidence, but also as-yet unproven hypotheses pertaining to the roles of EVs in key reproductive processes. In this review, we present a comprehensive survey of the rapidly expanding literature on this subject, highlighting both relevant findings and gaps in knowledge.

Autocrine embryotropins revisited: how do embryos communicate with each other in vitro when cultured in groups?

In the absence of the maternal genital tract, preimplantation embryos can develop in vitro in culture medium where all communication with the oviduct or uterus is absent. In several mammalian species, it has been observed that embryos cultured in groups thrive better than those cultured singly. Here we argue that group-cultured embryos are able to promote their own development in vitro by the production of autocrine embryotropins that putatively serve as a communication tool. The concept of effective communication implies an origin, a signalling agent, and finally a recipient that is able to decode the message. We illustrate this concept by demonstrating that preimplantation embryos are able to secrete autocrine factors in several ways, including active secretion, passive outflow, or as messengers bound to a molecular vehicle or transported within extracellular vesicles. Likewise, we broaden the traditional view that inter-embryo communication is dictated mainly by growth factors, by discussing a wide range of other biochemical messengers including proteins, lipids, neurotransmitters, saccharides, and microRNAs, all of which can be exchanged among embryos cultured in a group. Finally, we describe how different classes of messenger molecules are decoded by the embryo and influence embryo development by triggering different pathways. When autocrine embryotropins such as insulin-like growth factor-I (IGF-I) or platelet activating factor (PAF) bind to their appropriate receptor, the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway will be activated which is important for embryo survival. On the other hand, the mitogen-activated protein kinase (MAPK) pathway is activated when compounds such as hyaluronic acid and serotonin bind to their respective receptors, thereby acting as growth factors. By activating the peroxisome-proliferator-activated receptor family (PPAR) pathway, lipophilic autocrine factors such as prostaglandins or fatty acids have both survival and anti-apoptotic functions. In conclusion, considering different types of messenger molecules simultaneously will be crucial to understanding more comprehensively how embryos communicate with each other in group-culture systems. This approach will assist in the development of novel media for single-embryo culture.

MetazSecKB: the human and animal secretome and subcellular proteome knowledgebase

The subcellular location of a protein is a key factor in determining the molecular function of the protein in an organism. MetazSecKB is a secretome and subcellular proteome knowledgebase specifically designed for metazoan, i.e. human and animals. The protein sequence data, consisting of over 4 million entries with 121 species having a complete proteome, were retrieved from UniProtKB. Protein subcellular locations including secreted and 15 other subcellular locations were assigned based on either curated experimental evidence or prediction using seven computational tools. The protein or subcellular proteome data can be searched and downloaded using several different types of identifiers, gene name or keyword(s), and species. BLAST search and community annotation of subcellular locations are also supported. Our primary analysis revealed that the proteome sizes, secretome sizes and other subcellular proteome sizes vary tremendously in different animal species. The proportions of secretomes vary from 3 to 22% (average 8%) in metazoa species. The proportions of other major subcellular proteomes ranged approximately 21–43% (average 31%) in cytoplasm, 20–37% (average 30%) in nucleus, 3–19% (average 12%) as plasma membrane proteins and 3–9% (average 6%) in mitochondria. We also compared the protein families in secretomes of different primates. The Gene Ontology and protein family domain analysis of human secreted proteins revealed that these proteins play important roles in regulation of human structure development, signal transduction, immune systems and many other biological processes.

Database URL:http://proteomics.ysu.edu/secretomes/animal/index.php

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.

Omics as a window to view embryo viability

The advent of advanced omics technologies and the application of these techniques to the analysis of extremely limited material have opened the door to the investigation of embryo physiology in a focused, in-depth approach never before possible. The application of noninvasive metabolomic and proteomic platforms to understanding embryo viability permits the characterization of individual embryos in culture. Initial clinical data have highlighted the promise of these technologies for the development of noninvasive embryo selection criteria. In this way, a complex view of embryo function can be compiled and related to embryo development, quality, and outcome. Application of knowledge gained from omics will transform both our understanding of embryo physiology as well as our ability to select viable embryos for transfer in assisted reproductive technology.

Numerical calculations for diffusion effects in the well-of-the-well culture system for mammalian embryos

Recent studies suggest that the microenvironment and embryo density used during embryo culture considerably affect development to the blastocyst stage. High embryo density allows for autocrine secretions to diffuse to neighbouring embryos during group culture, with a positive effect on further development. A variation of group culture is the well-of-the-well (WOW) culture system, allowing for individual identification of embryos cultured in small holes in a microdroplet. Bovine blastocyst development is higher in the WOW culture system than in conventional group culture. To compare the concentration of chemical factors between conventional and WOW culture, a model was constructed to calculate the concentration of secreted factors based on Fick's second law of diffusion using spreadsheet software. Furthermore, model was used to determine the concentration of growth factors and waste materials adjacent to the embryo periphery. The results of these calculations suggest that the highest difference in the concentration of secreted small molecules and macromolecules was at the most two- to threefold, with the concentrations reduced more and diffusion kinetics facilitated to a greater extent in the WOW culture system. The average ratio of the concentration of secreted macromolecules (10nm diameter) around the embryos was also compared between systems with well widths of 0.1 and 0.3mm. The concentration of secreted materials surrounding embryos increased in a narrow tapered well. The findings suggest that the WOW culture system is better than conventional group culture because of the increased final concentration of autocrine factors and higher diffusion kinetics of waste materials.

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.

Noninvasive embryo viability assessment by quantitation of human haptoglobin alpha-1 fragment in the in vitro fertilization culture medium: an additional tool to increase success rate

OBJECTIVE

To find new candidate molecules to assess embryo viability in a noninvasive manner.

DESIGN

Prospective, blinded study with randomized sample collection.

SETTING

University research center.

PATIENTS(S)

Ninety embryos implanted in 53 randomly selected patients (mean ± SD age, 32.3 ± 5.1 years) were analyzed.

INTERVENTION(S)

Superovulation treatment was initiated by the administration of the GnRh agonist triptorelin and individual dosages of recombinant FSH. Ovulation was induced by the injection of hCG. Oocytes were fertilized by intracytoplasmic sperm injection.

MAIN OUTCOME MEASURE(S)

Liquid chromatography coupled mass spectrometric quantification of the α-1 fragment of human haptoglobin in the culture medium.

RESULT(S)

A novel polypeptide marker was found that might be helpful to differentiate between potentially viable and nonviable embryos. This molecule was identified with tandem mass spectrometry as the α-1 fragment of human haptoglobin. Significant correlation was found in the amount of the peptide fragment and the outcome of pregnancy. In the culture media of embryos that were assigned in the biochemical assay as nonviable (according to the amount of the haptoglobin fragment), there were no pregnancies detected; this assay revealed a 100% successful selection of the nonviable embryos. In the group assigned as viable, the rate of pregnancy was 54.7%.

CONCLUSION(S)

Viability of the embryo during the IVF process is assessed by microscopic inspection, resulting in a pregnancy rate of 25%-30%. Detection and quantitation of the α-1 haptoglobin fragment of the culture medium proved to be a useful additional method for identifying nonviable embryos, increasing the success rate to 50%.

Diagnosis of human preimplantation embryo viability

BACKGROUND

Transfer of more than a single embryo in an IVF cycle comes with the finite possibility of a multiple gestation. Even a twin pregnancy confers significant risk to both mother and babies. The move to single-embryo transfer for all patients will be greatly facilitated by the ability to quantify embryo viability. Developments in time-lapse incubation systems have provided new insights into the developmental kinetics of the human preimplantation embryo. Advances in molecular methods of chromosomal analysis have created platforms for highly effective screening of biopsied embryos, while noninvasive analysis of embryo physiology reveals more about the embryo than can be determined by morphology alone.

METHODS

Recent developments in time-lapse microscopy, molecular karyotyping and in proteomics and metabolomics have been assessed and presented here in a descriptive review.

RESULTS AND CONCLUSIONS

New algorithms are being created for embryo selection based on their developmental kinetics in culture, and the impact of factors such as patient etiology and treatment are being clarified. Potential links between morphokinetic data and embryo karyotype are being elucidated. The introduction of new molecular methods of determining embryo chromosomal complement is proving to be accurate and reproducible, with the future trending toward CGH arrays or next generation sequencing as a rapid and reliable means of analysis, that should be suitable for each IVF clinic to adopt. A relationship between embryo metabolism and viability is established and is now being considered together with morphokinetic data to create more robust algorithms for embryo selection. Microfluidic devices have the capacity and potential to be used in human IVF clinics for the routine diagnosis of embryo biomarkers.

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.

Unconditioned commercial embryo culture media contain a large variety of non-declared proteins: a comprehensive proteomics analysis

STUDY QUESTION

Which non-declared proteins (proteins not listed on the composition list of the product data sheet) are present in unconditioned commercial embryo culture media?

SUMMARY ANSWER

A total of 110 non-declared proteins were identified in unconditioned media and between 6 and 8 of these were quantifiable and therefore represent the majority of the total protein in the media samples.

WHAT IS KNOWN ALREADY

There are no data in the literature on what non-declared proteins are present in unconditioned (fresh media in which no embryos have been cultured) commercial embryo media.

STUDY DESIGN, SIZE, DURATION

The following eight commercial embryo culture media were included in this study: G-1 PLUS and G-2 PLUS G5 Series from Vitrolife, Sydney IVF Cleavage Medium and Sydney IVF Blastocyst Medium from Cook Medical and EmbryoAssist, BlastAssist, Sequential Cleav and Sequential Blast from ORIGIO. Two batches were analyzed from each of the Sydney IVF media and one batch from each of the other media. All embryo culture media are supplemented by the manufacturers with purified human serum albumin (HSA 5 mg/ml). The purified HSA (HSA-solution from Vitrolife) and the recombinant human albumin supplement (G-MM from Vitrolife) were also analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

For protein quantification, media samples were in-solution digested with trypsin and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). For in-depth protein identification, media were albumin depleted, dialyzed and concentrated before sodium dodecyl sulfate polyacrylamide gel electrophoresis. The gel was cut into 14 slices followed by in-gel trypsin digestion, and analysis by LC-MS/MS. Proteins were further investigated using gene ontology (GO) terms analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Using advanced mass spectrometry and high confidence criteria for accepting proteins (P < 0.01), a total of 110 proteins other than HSA were identified. The average HSA content was found to be 94% (92-97%) of total protein. Other individual proteins accounted for up to 4.7% of the total protein. Analysis of purified HSA strongly suggests that these non-declared proteins are introduced to the media when the albumin is added. GO analysis showed that many of these proteins have roles in defence pathways, for example 18 were associated with the innate immune response and 17 with inflammatory responses. Eight proteins have been reported previously as secreted embryo proteins.

LIMITATIONS, REASONS FOR CAUTION

For six of the commercial embryo culture media only one batch was analyzed. However, this does not affect the overall conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

The results showed that the HSA added to IVF media contained many other proteins and that the amount varies from batch to batch. These variations in protein profiles are problematic when attempting to identify proteins derived from the embryos. Therefore, when studying the embryo secretome and analyzing conditioned media with the aim of finding potential biomarkers that can distinguish normal and abnormal embryo development, it is important that the medium used in the experimental and control groups is from the same batch. Furthermore, the proteins present in unconditioned media could potentially influence embryonic development, gestation age, birthweight and perhaps have subsequent effects on health of the offspring.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by the Danish Agency for Science, Technology and Innovation. Research at the Fertility Clinic, Aarhus University Hospital is supported by an unrestricted grant from Merck Sharp & Dohme Corp and Ferring. The authors declare no conflicts of interest.

Power of proteomics in linking oxidative stress and female infertility

Endometriosis, PCOS, and unexplained infertility are currently the most common diseases rendering large numbers of women infertile worldwide. Oxidative stress, due to its deleterious effects on proteins and nucleic acids, is postulated to be the one of the important mechanistic pathways in differential expression of proteins and in these diseases. The emerging field of proteomics has allowed identification of proteins involved in cell cycle, as antioxidants, extracellular matrix (ECM), cytoskeleton, and their linkage to oxidative stress in female infertility related diseases. The aim of this paper is to assess the association of oxidative stress and protein expression in the reproductive microenvironments such as endometrial fluid, peritoneal fluid, and follicular fluid, as well as reproductive tissues and serum. The review also highlights the literature that proposes the use of the fertility related proteins as potential biomarkers for noninvasive and early diagnosis of the aforementioned diseases rather than utilizing the more invasive methods used currently. The review will highlight the power of proteomic profiles identified in infertility related disease conditions and their linkage with underlying oxidative stress. The power of proteomics will be reviewed with regard to eliciting molecular mechanisms for early detection and management of these infertility related conditions.

Improvement of cloned embryos development by co-culturing with parthenotes: a possible role of exosomes/microvesicles for embryos paracrine communication

It is well known that embryos cultured in a group can create a microenvironment through secretion of autocrine and paracrine factors that can support and improve the embryos' development when compared to the embryos cultured individually. In this study, we used a co-culture system for paracrine communication between different kinds of embryos. The results showed that co-culture of porcine parthenogenetic (PA) embryos significantly improved the in vitro development of cloned (nuclear transfer, NT) embryos. To reveal the possible mechanism of communication between the two groups, we isolated exosomes/microvesicles (EXs/MVs) from the PA embryos conditioned medium (PA-CM) through differential centrifugation and identified them through transmission electron microscope and immunoflourescence against exosomal/membrane marker CD9. Furthermore, these EXs/MVs were found to contain mRNA of pluripotency genes (Oct4, Sox2, Klf4, c-Myc, and Nanog), and the PKH67-labeled EXs/MVs could be internalized by the NT embryos. The current study demonstrates that cloned embryos' developmental competence can be improved through co-culturing with PA embryos and revealed, for the first time, that in vitro-produced embryos can secrete EXs/MVs as a possible communication tool within their microenvironment. Moreover, it provides a new paradigm for embryo-to-embryo communication in vitro.