Omics as a window to view embryo viability

Recent advancements to increase success in assisted reproductive technologies in cattle

Assisted reproductive technologies (ART) are fundamental for cattle breeding and sustainable food production. Together with genomic selection, these technologies contribute to reducing the generation interval and accelerating genetic progress. In this paper, we discuss advancements in technologies used in the fertility evaluation of breeding animals, and the collection, processing, and preservation of the gametes. It is of utmost importance for the breeding industry to select dams and sires of the next generation as young as possible, as is the efficient and timely collection of gametes. There is a need for reliable and easily applicable methods to evaluate sexual maturity and fertility. Although gametes processing and preservation have been improved in recent decades, challenges are still encountered. The targeted use of sexed semen and beef semen has obliterated the production of surplus replacement heifers and bull calves from dairy breeds, markedly improving animal welfare and ethical considerations in production practices. Parallel with new technologies, many well-established technologies remain relevant, although with evolving applications. In vitro production (IVP) has become the predominant method of embryo production. Although fundamental improvements in IVP procedures have been established, the quality of IVP embryos remains inferior to their in vivo counterparts. Improvements to facilitate oocyte maturation and development of new culture systems, e.g. microfluidics, are presented in this paper. New non-invasive and objective tools are needed to select embryos for transfer. Cryopreservation of semen and embryos plays a pivotal role in the distribution of genetics, and we discuss the challenges and opportunities in this field. Finally, machine learning (ML) is gaining ground in agriculture and ART. This paper delves into the utilization of emerging technologies in ART, along with the current status, key challenges, and future prospects of ML in both research and practical applications within ART.

Leveraging federated learning for boosting data privacy and performance in IVF embryo selection

PURPOSE

To study the effectiveness of federated learning in in vitro fertilization on embryo evaluation tasks.

METHODS

This is a retrospective cohort analysis. Two datasets were used in this study. The ploidy status dataset consisted of 10,065 embryo records, 3760 treatments, and 2479 infertile couples from 5 hospitals. The clinical pregnancy dataset consisted of 4495 embryo records, 4495 treatments, and 3704 infertile couples from 4 hospitals. Federated learning and the gradient boosting decision tree algorithm were utilized for modeling.

RESULTS

On the ploidy status dataset, the areas under the receiver operating characteristic curves of our model trained with federated learning were 71.78%, 73.10%, 69.39%, 69.72%, and 73.46% for 5 hospitals respectively, showing an average increase of 2.5% compared to those of our model trained without federated learning. On the clinical pregnancy dataset, the areas under the receiver operating characteristic curves of our model trained with federated learning were 72.03%, 56.77%, 61.63%, and 58.58% for 4 hospitals respectively, showing an average increase of 3.08%.

CONCLUSIONS

Federated learning can improve data privacy and data security and meanwhile improve the performance of embryo selection tasks by leveraging data from multiple sources. This study demonstrates the effectiveness of federated learning in embryo evaluation, and the results show the promise for future application.

The Role of One-Carbon Metabolism and Methyl Donors in Medically Assisted Reproduction: A Narrative Review of the Literature

One-carbon (1-C) metabolic deficiency impairs homeostasis, driving disease development, including infertility. It is of importance to summarize the current evidence regarding the clinical utility of 1-C metabolism-related biomolecules and methyl donors, namely, folate, betaine, choline, vitamin B12, homocysteine (Hcy), and zinc, as potential biomarkers, dietary supplements, and culture media supplements in the context of medically assisted reproduction (MAR). A narrative review of the literature was conducted in the PubMed/Medline database. Diet, ageing, and the endocrine milieu of individuals affect both 1-C metabolism and fertility status. In vitro fertilization (IVF) techniques, and culture conditions in particular, have a direct impact on 1-C metabolic activity in gametes and embryos. Critical analysis indicated that zinc supplementation in cryopreservation media may be a promising approach to reducing oxidative damage, while female serum homocysteine levels may be employed as a possible biomarker for predicting IVF outcomes. Nonetheless, the level of evidence is low, and future studies are needed to verify these data. One-carbon metabolism-related processes, including redox defense and epigenetic regulation, may be compromised in IVF-derived embryos. The study of 1-C metabolism may lead the way towards improving MAR efficiency and safety and ensuring the lifelong health of MAR infants.

EVATOM: an optical, label-free, machine learning assisted embryo health assessment tool

The combination of a good quality embryo and proper maternal health factors promise higher chances of a successful in vitro fertilization (IVF) procedure leading to clinical pregnancy and live birth. Of these two factors, selection of a good embryo is a controllable aspect. The current gold standard in clinical practice is visual assessment of an embryo based on its morphological appearance by trained embryologists. More recently, machine learning has been incorporated into embryo selection "packages". Here, we report EVATOM: a machine-learning assisted embryo health assessment tool utilizing an optical quantitative phase imaging technique called artificial confocal microscopy (ACM). We present a label-free nucleus detection method with, to the best of our knowledge, novel quantitative embryo health biomarkers. Two viability assessment models are presented for grading embryos into two classes: healthy/intermediate (H/I) or sick (S) class. The models achieve a weighted F1 score of 1.0 and 0.99 respectively on the in-distribution test set of 72 fixed embryos and a weighted F1 score of 0.9 and 0.95 respectively on the out-of-distribution test dataset of 19 time-instances from 8 live embryos.

A comparison of morphokinetic models and morphological selection for prioritizing euploid embryos: a multicentre cohort study

STUDY QUESTION

Are morphokinetic models better at prioritizing a euploid embryo for transfer over morphological selection by an embryologist?

SUMMARY ANSWER

Morphokinetic algorithms lead to an improved prioritization of euploid embryos when compared to embryologist selection.

WHAT IS KNOWN ALREADY

PREFER (predicting euploidy for embryos in reproductive medicine) is a previously published morphokinetic model associated with live birth and miscarriage. The second model uses live birth as the target outcome (LB model).

STUDY DESIGN, SIZE, DURATION

Data for this cohort study were obtained from 1958 biopsied blastocysts at nine IVF clinics across the UK from January 2021 to December 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The ability of the PREFER and LB models to prioritize a euploid embryo was compared against arbitrary selection and the prediction of four embryologists using the timelapse video, blinded to the morphokinetic time stamp. The comparisons were made using calculated percentages and normalized discounted cumulative gain (NDCG), whereby an NDCG score of 1 would equate to all euploid embryos being ranked first. In arbitrary selection, the ploidy status was randomly assigned within each cycle and the NDGC calculated, and this was then repeated 100 times and the mean obtained.

MAIN RESULTS AND THE ROLE OF CHANCE

Arbitrary embryo selection would rank a euploid embryo first 37% of the time, embryologist selection 39%, and the LB and PREFER ploidy morphokinetic models 46% and 47% of the time, respectively. The AUC for LB and PREFER model was 0.62 and 0.63, respectively. Morphological selection did not significantly improve the performance of both morphokinetic models when used in combination. There was a significant difference between the NDGC metric of the PREFER model versus embryologist selection at 0.96 and 0.87, respectively (t = 14.1, P < 0.001). Similarly, there was a significant difference between the LB model and embryologist selection with an NDGC metric of 0.95 and 0.87, respectively (t = 12.0, P < 0.001). All four embryologists ranked embryos similarly, with an intraclass coefficient of 0.91 (95% CI 0.82-0.95, P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

Aside from the retrospective study design, limitations include allowing the embryologist to watch the time lapse video, potentially providing more information than a truly static morphological assessment. Furthermore, the embryologists at the participating centres were familiar with the significant variables in time lapse, which could bias the results.

WIDER IMPLICATIONS OF THE FINDINGS

The present study shows that the use of morphokinetic models, namely PREFER and LB, translates into improved euploid embryo selection.

STUDY FUNDING/COMPETING INTEREST(S)

This study received no specific grant funding from any funding agency in the public, commercial or not-for-profit sectors. Dr Alison Campbell is minor share holder of Care Fertility. All other authors have no conflicts of interest to declare. Time lapse is a technology for which patients are charged extra at participating centres.

TRIAL REGISTRATION NUMBER

N/A.

In vitro embryo production in small ruminants: what is still missing?

In vitro embryo production (IVEP) is an extremely important tool for genetic improvement in livestock and it is the biotechnology that has grown the most recently. However, multiple ovulation followed by embryo transfer is still considered the leading biotechnology for embryo production in small ruminants. This review aimed to identify what is still missing for more efficient diffusion of IVEP in small ruminants, going through the IVEP steps and highlighting the main factors affecting the outcomes. Oocyte quality is essential for the success of IVEP and an aspect to be considered in small ruminants is their reproductive seasonality and strategies to mitigate the effect of season. The logistics for oocyte collection from live females is more complex than in cattle, and tools to simplify this collection system and/or to promote an alternative way of recovering oocytes may be an important point in this scenario. The heterogeneity of oocytes collected from growing follicles in live females or from ovaries collected from abattoirs remains a challenge, and there is a demand to standardize/homogenize the hormonal stimulatory protocols and IVM protocols for each source of oocytes. The use of sexed semen is technically possible, however the low market demand associated with the high costs of the sexing process prevents the routine use of this technique, but its higher availability is an important aspect aiming for greater dissemination of IVEP. New noninvasive approaches for embryo selection are key factors since the selection for transfer or cryopreservation is another difficulty faced among laboratories. Embryo selection is based on morphological traits, although these are not necessarily reliable in predicting pregnancy. Several issues described in this review must be considered by researchers in other to promote the diffusion of IVEP in small ruminants.

Machine learning assisted health viability assay for mouse embryos with artificial confocal microscopy (ACM)

The combination of a good quality embryo and proper maternal health factors promise higher chances of a successful in vitro fertilization (IVF) procedure leading to clinical pregnancy and live birth. Of these two factors, selection of a good embryo is a controllable aspect. The current gold standard in clinical practice is visual assessment of an embryo based on its morphological appearance by trained embryologists. More recently, machine learning has been incorporated into embryo selection "packages". Here, we report a machine-learning assisted embryo health assessment tool utilizing a quantitative phase imaging technique called artificial confocal microscopy (ACM). We present a label-free nucleus detection method with novel quantitative embryo health biomarkers. Two viability assessment models are presented for grading embryos into two classes: healthy/intermediate (H/I) or sick (S) class. The models achieve a weighted F1 score of 1.0 and 0.99 respectively on the in-distribution test set of 72 fixed embryos and a weighted F1 score of 0.9 and 0.95 respectively on the out-of-distribution test dataset of 19 time-instances from 8 live embryos.

A validated model for individualized prediction of pregnancy outcome in woman after fresh cycle of Day 5 single blastocyst transfer

The association between the embryo quality, clinical characteristics, miRNAs (secreted by blastocysts in the culture medium) and pregnancy outcomes has been well-established. Studies on prediction models for pregnancy outcome, using clinical characteristics and miRNA expression, are limited. We aimed to establish the prediction model for prediction of pregnancy outcome of woman after a fresh cycle of Day 5 single blastocyst transfer (Day 5 SBT) based on clinical data and miRNA expression. A total of 86 women, 50 with successful pregnancy and 36 with pregnancy failure after fresh cycle of Day 5 SBT, were enrolled in this study. All samples were divided into training set and test set (3:1). Based on clinical index statistics of enrolled population and miRNA expression, the prediction model was constructed, followed by validation of the prediction model. Four clinical indicators, female age, sperm DNA fragmentation index, anti-mullerian hormone, estradiol, can be used as independent predictors of pregnancy failure after fresh cycle of Day 5 SBT. Three miRNAs (hsa-miR-199a-3p, hsa-miR-199a-5p and hsa-miR-99a-5p) had a potential diagnostic value for pregnancy failure after Day 5 SBT. The predictive effect of model combining 4 clinical indicators and 3 miRNAs (area under the receiver operating characteristic curve, AUC = 0.853) was better than models combining single 4 clinical indicators (AUC = 0.755) or 3 miRNAs (AUC = 0.713). Based on 4 clinical indicators and 3 miRNAs, a novel model to predict pregnancy outcome in woman after fresh cycle of Day 5 SBT has been developed and validated. The predictive model may be valuable for clinicians to make the optimal clinical decision and patient selection.

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

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

Mining RNAseq data reveals dynamic metaboloepigenetic profiles in human, mouse and bovine pre-implantation embryos

Metaboloepigenetic regulation has been reported in stem cells, germ cells, and tumor cells. Embryonic metaboloepigenetics, however, have just begun to be described. Here we analyzed RNAseq data to characterize the metaboloepigenetic profiles of human, mouse, and bovine pre-implantation embryos. In embryos, metaboloepigenetic reprogramming was species-specific, varied with the developmental stage and was disrupted with in vitro culture. Metabolic pathways and gene expressions were strongly correlated with early embryo DNA methylation and were changed with in vitro culture. Although the idea that the in vitro environment may influence development is not new, there has been little progress on improving pregnancy rates after decades using in vitro fertilization. Hence, the present data will contribute to understanding how the in vitro manipulation affects the metaboloepigenetic status of early embryos, which can be used to establish culture strategies aimed at improving the in vitro environment and, consequently, pregnancy rates and offspring health.

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Embryonic metaboloepigenetic reprogramming is stage- and species-specific

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In vitro culture disrupts the in vivo embryonic metaboloepigenetic reprogramming

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Metabolic genes and pathways are highly correlated with embryo methylome

Non invasive assessment of human oocytes and embryos in assisted reproduction: Review on present practices and future trends

Oocyte and embryo grading is one of the most important steps in assisted reproductive technology to identify the best among cultured embryos for transfer or vitrification. The most commonly used non-invasive method is morphological assessment of gametes and embryos using a microscope. This method despite being simple and cost-effective has interobserver and intraobserver variability and subjectivity and has little to offer about the physiological state of embryos. This review sourced research articles and reviews pertaining to other non-invasive assessment methodologies from Medline and PubMed to collate latest technologies in vogue and identify novel methodologies of the future. The review assesses the current understanding in oocyte and embryo grading and touches upon novel non-invasive techniques and potential biomarkers to identify the best embryo. The latest available literature on time-lapse imaging, hierarchical algorithms, omics (consisting of proteomics and secretomes), miRNAs, mitochondrial RNAs and artificial intelligence has been accessed to summarize the enormous information available, to identify gaps in current interpretations, to identify emerging technologies and to provide direction for future research. This review will greatly benefit anyone practicing assisted reproduction and clinical embryology.

An artificial intelligence model (euploid prediction algorithm) can predict embryo ploidy status based on time-lapse data

BACKGROUND

For the association between time-lapse technology (TLT) and embryo ploidy status, there has not yet been fully understood. TLT has the characteristics of large amount of data and non-invasiveness. If we want to accurately predict embryo ploidy status from TLT, artificial intelligence (AI) technology is a good choice. However, the current work of AI in this field needs to be strengthened.

METHODS

A total of 469 preimplantation genetic testing (PGT) cycles and 1803 blastocysts from April 2018 to November 2019 were included in the study. All embryo images are captured during 5 or 6 days after fertilization before biopsy by time-lapse microscope system. All euploid embryos or aneuploid embryos are used as data sets. The data set is divided into training set, validation set and test set. The training set is mainly used for model training, the validation set is mainly used to adjust the hyperparameters of the model and the preliminary evaluation of the model, and the test set is used to evaluate the generalization ability of the model. For better verification, we used data other than the training data for external verification. A total of 155 PGT cycles from December 2019 to December 2020 and 523 blastocysts were included in the verification process.

RESULTS

The euploid prediction algorithm (EPA) was able to predict euploid on the testing dataset with an area under curve (AUC) of 0.80.

CONCLUSIONS

The TLT incubator has gradually become the choice of reproductive centers. Our AI model named EPA that can predict embryo ploidy well based on TLT data. We hope that this system can serve all in vitro fertilization and embryo transfer (IVF-ET) patients in the future, allowing embryologists to have more non-invasive aids when selecting the best embryo to transfer.

Glucose metabolomic profile during embryogenesis in the tick Rhipicephalus microplus

INTRODUCTION

Metabolomic approaches can assess the actual state of an organism's energy metabolism during a specific morphological event, providing a more accurate insight into the correlations between physiology and metabolic regulation.

METHODS

The study of the metabolomic profile aim to identify the largest possible number of biomolecules in a certain organism or specific structures. For this purpose, mass spectrometry (MS) and chromatography have been used in the present study.

OBJECTIVES

In this context, the aim of the present work is to evaluate the glucose metabolomic profile during embryogenesis in Rhipicephalus microplus tick, investigating the dynamics of nutrient utilization during tick embryo formation, as well as the control of glucose metabolism.

RESULTS

We show that glycogen reserves are preferentially mobilized to sustain the energy-intensive process of embryogenesis. Subsequently, the increase in concentration of specific amino acids indicates that protein degradation would provide carbons to fuel gluconeogenesis, supplying the embryo with sufficient glucose and glycogen during development.

CONCLUSION

Altogether, these results demonstrated the presence of a very refined catabolic and anabolic control during embryogenesis in R. microplus tick, suggesting the pronounced gluconeogenesis as a strategy to secure embryo development. Moreover, this research contributes to the understanding of the mechanisms that control glucose metabolism during tick embryogenesis and may aid the identification of putative targets for novel chemical or immunological control methods, which are essential to improve the prevention of tick infestations.

Biochemical markers for pregnancy in the spent culture medium of in vitro produced bovine embryos†

The present study aimed to identify biomarkers to assess the quality of in vitro produced (IVP) bovine embryos in the culture media. IVP embryos on Day (D) 5 of development were transferred to individual drops, where they were maintained for the last 48 h of culture. Thereafter, the medium was collected and the embryos were transferred to the recipients. After pregnancy diagnosis, the media were grouped into the pregnant and nonpregnant groups. The metabolic profiles of the media were analyzed via electrospray ionization mass spectrometry, and the concentrations of pyruvate, lactate, and glutamate were assessed using fluorimetry. The spectrometric profile revealed that the media from embryos from the pregnant group presented a higher signal intensity compared to that of the nonpregnant group; the ions 156.13 Da [M + H]+, 444.33 Da [M + H]+, and 305.97 Da [M + H]+ were identified as biomarkers. Spent culture medium from expanded blastocysts (Bx) that established pregnancy had a greater concentration of pyruvate (p = 0.0174) and lesser concentration of lactate (p = 0.042) than spent culture medium from Bx that did not establish pregnancy. Moreover, pyruvate in the culture media of Bx can predict pregnancy with 90.9% sensitivity and 75% specificity. In conclusion, we identified markers in the culture media that helped in assessing the most viable IVP embryos with a greater potential to establish pregnancy.

Exploiting Microfluidics for Extracellular Vesicle Isolation and Characterization: Potential Use for Standardized Embryo Quality Assessment

Recent decades have seen a growing interest in the study of extracellular vesicles (EVs), driven by their role in cellular communication, and potential as biomarkers of health and disease. Although it is known that embryos secrete EVs, studies on the importance of embryonic EVs are still very limited. This limitation is due mainly to small sample volumes, with low EV concentrations available for analysis, and to laborious, costly and time-consuming procedures for isolating and evaluating EVs. In this respect, microfluidics technologies represent a promising avenue for optimizing the isolation and characterization of embryonic EVs. Despite significant improvements in microfluidics for EV isolation and characterization, the use of EVs as markers of embryo quality has been held back by two key challenges: (1) the lack of specific biomarkers of embryo quality, and (2) the limited number of studies evaluating the content of embryonic EVs across embryos with varying developmental competence. Our core aim in this review is to identify the critical challenges of EV isolation and to provide seeds for future studies to implement the profiling of embryonic EVs as a diagnostic test for embryo selection. We first summarize the conventional methods for isolating EVs and contrast these with the most promising microfluidics methods. We then discuss current knowledge of embryonic EVs and their potential role as biomarkers of embryo quality. Finally, we identify key ways in which microfluidics technologies could allow researchers to overcome the challenges of embryonic EV isolation and be used as a fast, user-friendly tool for non-invasive embryo selection.

An artificial intelligence model based on the proteomic profile of euploid embryos and blastocyst morphology: a preliminary study

RESEARCH QUESTION

The study aimed to develop an artificial intelligence model based on artificial neural networks (ANNs) to predict the likelihood of achieving a live birth using the proteomic profile of spent culture media and blastocyst morphology.

DESIGN

This retrospective cohort study included 212 patients who underwent single blastocyst transfer at IVI Valencia. A single image of each of 186 embryos was studied, and the protein profile was analysed in 81 samples of spent embryo culture medium from patients included in the preimplantation genetic testing programme. The information extracted from the analyses was used as input data for the ANN. The multilayer perceptron and the back-propagation learning method were used to train the ANN. Finally, predictive power was measured using the area under the curve (AUC) of the receiver operating characteristic curve.

RESULTS

Three ANN architectures classified most of the embryos correctly as leading (LB+) or not leading (LB-) to a live birth: 100.0% for ANN1 (morphological variables and two proteins), 85.7% for ANN2 (morphological variables and seven proteins), and 83.3% for ANN3 (morphological variables and 25 proteins). The artificial intelligence model using information extracted from blastocyst image analysis and concentrations of interleukin-6 and matrix metalloproteinase-1 was able to predict live birth with an AUC of 1.0.

CONCLUSIONS

The model proposed in this preliminary report may provide a promising tool to select the embryo most likely to lead to a live birth in a euploid cohort. The accuracy of prediction demonstrated by this software may improve the efficacy of an assisted reproduction treatment by reducing the number of transfers per patient. Prospective studies are, however, needed.

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.

Comparative secretome profile analysis of cultured immortalized human endometrial stromal cells supplemented with implanted versus nonimplanted blastocyst-conditioned medium: A preliminary analysis

AIM

Human endometrial stromal cells (HESCs) were previously shown to be capable of discriminating embryos with different qualities. Here we aimed to compare the specific response of the HESC secretome to implanted blastocyst-conditioned medium (BCM) versus nonimplanted medium and identify cytokine candidates useful for the assessment of blastocyst implantation.

METHODS

Cleavage embryos were individually cultured in one microdrop of medium for blastocyst formation. The BCM was collected after fresh blastocyst transfer on day 5 and used to supplement HESC culture medium. A high-throughput antibody array covering 440 cytokines was used to detect the secretory proteins of HESCs supplemented with implanted or nonimplanted BCM.

RESULTS

A total of 22 differentially expressed proteins were found out of 440 cytokines in the supernatant of HESCs supplemented with BCM from the implanted group compared to the nonimplanted group, including seven upregulated and 15 downregulated proteins. Gene Ontology enrichment analysis showed that the differentially expressed proteins were mainly involved in cell chemotaxis and motility, and ERK1/2 cascade regulation. Kyoto Encyclopedia of Genes and Genomes analysis suggested that the mitogen-activated protein kinase and phosphatidylinositol 3 kinase/Akt pathways were mainly involved.

CONCLUSION

HESCs specifically responded to BCM from different quality blastocysts, a finding that can be used to develop a novel approach for blastocyst quality assessment.

Pregnancy outcomes after frozen-thawed single euploid blastocyst transfer following IVF cycles using GNRH agonist or HCG trigger for final oocyte maturation

PURPOSE

To assess whether GnRH agonist trigger impacts the implantation potential of euploid embryos.

METHODS

Retrospective cohort study done at an academic IVF center evaluating frozen-thawed embryo transfer (FET) cycles in which single-euploid blastocysts were transferred between 2014 and 2019. All embryos were generated in an IVF cycle which used GnRHa or hCG trigger and then were transferred in a programmed or natural FET cycle. Only the first FET cycle was included for each patient. Primary outcome was ongoing pregnancy rate or live birth rate (OPR/LBR). Secondary outcomes were implantation rate (IR), clinical pregnancy rate (CPR), clinical loss rate (CLR), and multiple pregnancy rate (MPR). Logistic regression was performed to control for confounding variables. A p value of < 0.05 was considered statistically significant.

RESULTS

Two hundred sixty-three FET cycles were included for analysis (GnRHa = 145; hCG = 118). The GnRHa group was significantly younger (35.2 vs. 37.5 years) and had higher AMH values (4.50 ng/ml vs. 2.03 ng/ml) than the hCG group, respectively (p < 0.05). There was no significant difference in OPR/LBR (64.1% (93/145) vs. 65.3% (77/118); p = 0.90) between the GnRHa and hCG groups, respectively. There was also no significant difference in IR, CPR, CLR, or MPR between groups. After controlling for confounding variables, the adjusted odds ratio for OPR/LBR was 0.941 (95% CI, 0.534-1.658); p = 0.83) comparing GnRHa to hCG. Pregnancy outcomes did not significantly differ when groups were stratified by age (< 35 vs. > 35 years old).

CONCLUSIONS

Our findings confirm that euploid embryos created after hCG or GnRHa trigger have the same potential for pregnancy.

Reproductive technologies in swine

This chapter highlights the importance of reproductive technologies that are applied to porcine breeds. Nowadays the porcine industry, part of a high technological and specialized sector, offers high-quality protein food. The development of the swine industry is founded in the development of breeding/genetics, nutrition, animal husbandry, and animal health. The implementation of reproductive technologies in swine has conducted to levels of productivity never reached before. In addition, the pig is becoming an important species for biomedicine. The generation of pig models for human disease, xenotransplantation, or production of therapeutic proteins for human medicine has in fact generated a growing field of interest.

Levels of caspase-3 and histidine-rich glycoprotein in the embryo secretome as biomarkers of good-quality day-2 embryos and high-quality blastocysts

Morphological assessment at defined developmental stages is the most important method to select viable embryos for transfer and cryopreservation. Timing of different developmental stages in embryo development has been shown to correlate with its potential to develop into a blastocyst. However, improvements in pregnancy rates by using time-lapse techniques have been difficult to validate scientifically. Therefore, there is a need for new methods, preferably non-invasive methods based on metabolomics, genomics and proteomics, to improve the evaluation of embryo quality even further. The aim of this study was to investigate if different levels of caspase-3 and histidine-rich glycoprotein (HRG), secreted by the embryo into the culture media, can be used as biomarkers of embryo quality. In this study, a total of 334 samples of culture media were collected from in vitro fertilization (IVF) treatments at three different clinics. Protein analysis of the culture media was performed using multiplex proximity extension protein analysis to detect levels of caspase-3 and HRG in the embryo secretome. Protein levels were compared in secretome samples from high- and low-quality blastocysts and embryos that became arrested during development. Correlation between protein levels and time to morula formation was also analyzed. Furthermore, protein levels in secretomes from day-2 cultured embryos were compared on the basis of whether or not pregnancy was achieved. The results showed that caspase-3 levels were lower in secretomes from high-quality vs. low-quality blastocysts and those that became arrested (p ≤ 0.05 for both). In addition, higher HRG levels correlated with a shorter time to morula formation (p ≤ 0.001). Caspase-3 levels were also lower in secretomes from day-2 cultured embryos resulting in a pregnancy vs. those that did not (p ≤ 0.05). Furthermore, it was shown that caspase-3 might be used as a marker for predicting potential success rate after transfer of day-2 cultured embryos, where a caspase-3 cutoff level of 0.02 gave a prediction probability of 68% (p = 0.038). In conclusion, in future prediction models, levels of caspase-3 and HRG might be used as potential markers of embryo quality, and secreted caspase-3 levels could to some extent predict the outcome after transfer of day-2 cultured embryos.

Molecular Signaling Regulating Endometrium-Blastocyst Crosstalk

Implantation of the embryo into the uterine endometrium is one of the most finely-regulated processes that leads to the establishment of a successful pregnancy. A plethora of factors are released in a time-specific fashion to synchronize the differentiation program of both the embryo and the endometrium. Indeed, blastocyst implantation in the uterus occurs in a limited time frame called the "window of implantation" (WOI), during which the maternal endometrium undergoes dramatic changes, collectively called "decidualization". Decidualization is guided not just by maternal factors (e.g., estrogen, progesterone, thyroid hormone), but also by molecules secreted by the embryo, such as chorionic gonadotropin (CG) and interleukin-1β (IL-1 β), just to cite few. Once reached the uterine cavity, the embryo orients correctly toward the uterine epithelium, interacts with specialized structures, called pinopodes, and begins the process of adhesion and invasion. All these events are guided by factors secreted by both the endometrium and the embryo, such as leukemia inhibitory factor (LIF), integrins and their ligands, adhesion molecules, Notch family members, and metalloproteinases and their inhibitors. The aim of this review is to give an overview of the factors and mechanisms regulating implantation, with a focus on those involved in the complex crosstalk between the blastocyst and the endometrium.

Applications of omics and nanotechnology to improve pig embryo production in vitro

An appropriate environment to optimize porcine preimplantation embryo production in vitro is required as genetically modified pigs have become indispensable for biomedical research and agriculture. To provide suitable culture conditions, omics technologies have been applied to elucidate which metabolic substrates and pathways are involved during early developmental processes. Metabolomic profiling and transcriptional analysis comparing in vivo- and in vitro-derived embryos have demonstrated the important role of amino acids during preimplantation development. Transcriptional profiling studies have been helpful in assessing epigenetic reprogramming agents to allow for the correction of gene expression during the cloning process. Along with this, nanotechnology, which is a highly promising field, has allowed for the use of engineered nanoplatforms in reproductive biology. A growing number of studies have explored the use of nanoengineered materials for sorting, labeling, and targeting purposes; which demonstrates their potential to become one of the solutions for precise delivery of molecules into gametes and embryos. Considering the contributions of omics and the recent progress in nanoscience, in this review, we focused on their emerging applications for current in vitro pig embryo production systems to optimize the generation of genetically modified animals.

Cytokines hold promise for human embryo culture in vitro: results of a randomized clinical trial

OBJECTIVE

To evaluate the effects of cytokine enrichment of culture medium on embryological and clinical outcomes after intracytoplasmic sperm injection (ICSI).

DESIGN

A randomized clinical trial.

SETTING

In vitro fertilization centers.

PATIENT(S)

This trial included 443 ICSI cycles randomized into two groups.

INTERVENTION(S)

This study evaluated the influence of integration of granulocyte-macrophage colony-stimulating factor, heparin-binding epidermal growth factor-like growth factor, and leukemia inhibitory factor into culture media on human embryo development after ICSI.

MAIN OUTCOME MEASURE(S)

Ongoing pregnancy rate per a randomized participant.

RESULT(S)

Cytokine enrichment of culture medium showed improvement in ongoing pregnancy rate compared with no cytokines (106/224 [47%] vs. 78/219 [36%]; absolute rate difference [ARD] = 12; 95% confidence interval [CI], 2.5-21). This integration of cytokines also showed better rates of live birth (101/224 [45%] vs. 71/219 [33%]; ARD = 13; 95% CI, 4-21) and cumulative live birth (132/224 [60%] vs. 97/219 [44%]; ARD = 12; 95% CI, 4-20) and lower rate of pregnancy loss (27/124 [22%] vs. 37/103 [36%]; ARD = -14; 95% CI, -26 to -2) than conventional medium. Embryos developed in the cytokine-supplemented medium showed better blastocyst formation, quality, cryopreservation, and use than control medium.

CONCLUSION(S)

Integration of cytokines into human embryo culture media showed improvement in embryological and clinical outcomes after ICSI. However, the long-term effect of cytokine enrichment of a medium is still unclear and warrants further studies with longitudinal follow-up.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02420886 at ClinicalTrials.gov.

Can trophectoderm RNA analysis predict human blastocyst competency?

A systematic review of the literature showed that trophectoderm biopsy could assist in the selection of healthy embryos for uterine transfer without affecting implantation rates. However, previous studies attempting to establish the relationship between trophectoderm gene expression profiles and implantation competency using either microarrays or RNA sequencing strategies, were not sufficiently optimized to handle the exceptionally low RNA inputs available from biopsied material. In this pilot study, we report that differential gene expression in human trophectoderm biopsies assayed by an ultra-sensitive next generation RNA sequencing strategy could predict blastocyst implantation competence. RNA expression profiles from isolated human trophectoderm cells were analysed with established clinical pregnancy being the primary endpoint. Following RNA sequencing, a total of 47 transcripts were found to be significantly differentially expressed between the trophectoderm cells from successfully implanted (competent) versus unsuccessful (incompetent) blastocysts. Of these, 36 transcripts were significantly down-regulated in the incompetent blastocysts, including Hydroxysteroid 17-Beta Dehydrogenase 1 (HSD17B1) and Cytochrome P450 Family 11 Subfamily A Member 1 (CYP11A1), while the remaining 11 transcripts were significantly up-regulated, including BCL2 Antagonist/Killer 1 (BAK1) and KH Domain Containing 1 Pseudogene 1 (KHDC1P1) of which the latter was always detected in the incompetent and absent in all competent blastocysts. Ontological analysis of differentially expressed RNAs revealed pathways involved in steroidogenic processes with high confidence. Novel differentially expressed transcripts were also noted by reference to a de novo sequence assembly. The selection of the blastocyst with the best potential to support full-term pregnancy following single embryo transfer could reduce the need for multiple treatment cycles and embryo transfers. The main limitation was the low sample size (N = 8). Despite this shortcoming, the pilot suggests that trophectoderm biopsy could assist with the selection of healthy embryos for embryo transfer. A larger cohort of samples is needed to confirm these findings. Abbreviations: AMA: advanced maternal age; ART: assisted reproductive technology; CP: clinical pregnancy; DE: differential expression; FDR: false discovery rate; IVF: in vitro fertilization; LD PCR: long distance PCR; qRT-PCR: quantitative real-time PCR; SET: single embryo transfer; TE: trophectoderm.

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.

Differences in secretome in culture media when comparing blastocysts and arrested embryos using multiplex proximity assay

OBJECTIVES

The aim of this study was to assess different patterns of the human embryo secretome analysed as protein levels in culture media. Furthermore, analyses to correlate protein levels with quality and timing to development of human embryos were performed.

MATERIAL AND METHODS

Human day-2 cryopreserved embryos were cultured for four days in an EmbryoScope^® with a time-lapse camera, and embryo quality was evaluated retrospectively. After culture, the media were collected and relative levels of secreted proteins were analysed using Proseek Multiplex Assays. Protein levels were evaluated in relation to timing to development and the ability to form a blastocyst.

RESULTS

Specific patterns of timing of development of blastocysts were found, where a difference in time to start of cavitation was found between high- and low-quality blastocysts. There appeared to be a correlation between specific protein patterns and successful formation of morulae and blastocysts. Embryos developing into blastocysts had higher levels of EMMPRIN than arrested embryos, and levels of caspase-3 were lower in high- versus low-quality blastocysts. Also, higher levels of VEGF-A, IL-6, and EMMPRIN correlated with shorter times to morula formation.

CONCLUSIONS

The secretome and timing to development differ in embryos forming blastocysts and those that become arrested, and in high- versus low-quality blastocysts. The levels of certain proteins also correlate to specific times to development.

Short- and long-term outcomes of the absence of protein during bovine blastocyst formation in vitro

In cattle, individual in vitro embryo culture after Day 6 benefits development, allowing non-invasive analysis of culture medium. However, undefined supplements in culture reduce analytical reliability. In this study we assayed the short- and long-term performance of embryos after bovine serum albumin removal over a 24-h period in individual culture. The absence of protein decreased embryo development and cell counts in the inner cell mass without affecting blastocyst sex ratio. However, the absence of protein produced embryos with an improved tendency to survive vitrification after 24h in culture (P=0.07). After transfer to recipients, birth rates of embryos that had been cultured with protein tended to decrease (P<0.06) mostly as a result of a higher number of miscarriages (P<0.013), reflecting lower viability. Birthweight, gestation length, height and thorax circumference did not differ between embryos cultured with or without protein. In fresh blastocysts cultured without protein, gene expression analysis showed higher abundance (P<0.05) of insulin-like growth factor 2 receptor (IGF2R; imprinting) and activating transcription factor 4 (ATF4) and DNA-damage-inducible transcript 3 (DDIT3; endoplasmic reticulum stress) transcripts, with DNA methyltransferase 3A (DNMT3A; imprinting) tending to increase (P=0.062). However, in hatched blastocysts that survived cryopreservation, glucose-6-phosphate dehydrogenase (G6PD) was overexpressed in embryos cultured without protein (P<0.01). The absence of protein results in fewer blastocysts but improved long-term viability after cryopreservation.

Cumulus cell transcriptome profiling is not predictive of live birth after in vitro fertilization: a paired analysis of euploid sibling blastocysts

OBJECTIVE

To compare the transcriptome of cumulus cells associated with a euploid embryo that resulted in live birth with that of a sibling euploid embryo without sustained implantation.

DESIGN

Paired analysis.

SETTING

Academic institution.

PATIENT(S)

Couples undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection with preimplantation genetic screening with female age ≤42 years and normal ovarian reserve.

INTERVENTION(S)

Transcriptome profiling of cumulus cells from sibling oocytes for correlation with live birth after euploid blastocyst transfer. Embryos were individually cultured to facilitate association with clinical outcomes. The cumulus cell transcriptome from the embryo resulting in live birth was compared with that of its sibling embryo without sustained implantation to investigate potential biomarkers that may aid in embryo selection.

MAIN OUTCOME MEASURE(S)

Differential gene expression in cumulus cells associated with a euploid embryo resulting in live birth and its sibling euploid embryo without sustained implantation using next-generation RNA sequencing (RNAseq).

RESULT(S)

Cumulus cell RNAseq of 34 samples (from 17 patients) generated an average of 10.4 ± 4 × 10⁶ reads per sample. A total of 132 differentially expressed genes between sibling embryos that resulted in a live birth and those that did not were identified (P<.05). However, after correcting for multiple testing none of the genes remained significantly differentially expressed (false discovery rate <.05).

CONCLUSION(S)

The RNAseq profiles were similar between cumulus cells associated with a euploid embryo resulting in live birth and its sibling embryo that did not sustain implantation. The cumulus cell transcriptome is not predictive of live birth within an individual patient's cohort of euploid embryos.

Exogenous growth factors do not affect the development of individually cultured murine embryos

PURPOSE

The objective of this study was to evaluate the effects of multiple growth factors on the development of individually cultured murine embryos.

METHODS

Embryos produced by in vitro fertilization using in vitro (IVM) or in vivo (IVO) matured oocytes from three strains of mice (CF1, Swiss Webster, B6D2F1) were cultured individually (10 μl) in the absence (control) or presence of growth factors (paf, epidermal growth factor [EGF], insulin-like growth factor 1 [IGF-1], and granulocyte-macrophage colony-stimulating factor [GM-CSF]). Blastocyst formation, hatching, and blastocyst cell numbers (trophectoderm, inner cell mass, and total) were evaluated on days 4 and 5 of culture. Post-hatching development of CF1 IVO embryos was also evaluated in vitro and in vivo.

RESULTS

The presence of growth factors did not improve the proportion of embryos forming blastocysts or initiating hatching for any of the types of embryos tested. The only significant (P < 0.05) effect of growth factors was a decrease in the proportion of embryos that formed blastocysts by day 5 in CF1 IVM embryos. The presence of growth factors also did not affect blastocyst cell numbers. For CF1 IVO embryos, the presence of growth factors during culture did not affect the proportion of embryos that attached to fibronectin-coated dishes, the size of the resulting outgrowths, or in vivo development following transfer.

CONCLUSION

Combinations of paf, EGF, GM-CSF, and IGF-1 did not improve development of murine embryos cultured individually in a sequential medium containing a defined protein source.

Predictive value of spindle retardance in embryo implantation rate

PURPOSE

We evaluated the relationship between meiotic spindle characteristics and in vitro fertilization cycle outcome.

METHODS

Five hundred sixty-nine oocytes from 86 in vitro fertilization cycles were analyzed for fertilization and subsequent implantation rates. Oocytes were assessed for maturation status. The oocytes and embryos were cultured in sequential and nonsequential media (G Series, Vitrolife, Sweden) and incubated in 6% CO₂, 5% O₂ at 37 °C. Two hours following oocyte decumulation (38-39 h post-hCG/GnRH administration) and prior to microinjection, the structure of the meiotic spindle was assessed using the Oosight Imaging System (CRI, UK).

RESULTS

Four hundred fifty-six oocytes (80.5%) had a visible meiotic spindle, 82 (14.7%) had no meiotic spindle, and 31 (5.5%) were in telophase I. Oocytes exhibiting a meiotic spindle had a significantly higher fertilization rate and a lower rate of abnormal fertilization. Implantation data were obtained for 195 of the embryos transferred. The implantation rate for embryos derived from oocytes with a meiotic spindle was 32.9%, while in embryos originating from oocytes without a meiotic spindle and oocytes in telophase, this value dropped significantly (8.8 and 0%, respectively). To determine the correlation between retardance values and implantation rate for each oocyte, we established four groups, finding a range of retardance values with significantly higher implantation rates (27.5, 21, 29.3, and 53.8%, respectively).

CONCLUSION

Meiotic spindle imaging may be a valuable tool for prediction of oocyte quality, and retardance values of meiotic spindles, together with classical morphological classification, can be useful to select embryos with a higher implantation potential.

Embryo wastage rates remain high in assisted reproductive technology (ART): a look at the trends from 2004-2013 in the USA

This work examined the trend in "embryo wastage" rates after ART in USA and its relationship to the number of embryos transferred, live born infants delivered across patient age, and the yearly percentage of embryos wasted. The data were obtained from the US-clinics SART databank for the years 2004-2013. A total of 1,808,082 non-donor embryos were transferred in 748,394 fresh cycles resulting in 358,214 liveborn. During the years of analysis, the mean number of embryos transferred has progressively decreased leading to an overall significant decrease in Embryo Wastage rates (83.2 to 76.5%, p < 0.001) while the percentage of transfers leading to a live born increased (24.8 to 27.8%, p = 0.002). Embryo Wastage negatively correlated with percentage of transfers resulting in live birth (p = 0.001), and the average number of embryos transferred positively correlated with the percentage of embryos wasted (p < 0.001). The overwhelming majority of embryos transferred still do not result into a live birth confirming that only few embryos per ART cycle are competent. The overall "Embryo Wastage" rates have consistently decreased from a high of 90% in 1995 to a rate of 76.5% in 2013. Transferring fewer embryos particularly at the blastocyst-stage and improved methods of embryo selection may further decrease "Embryo Wastage" rates.

In Vitro Fertilization Research is Translational Research

In vitro fertilization (IVF) is the perfect example of translational research. Changes in IVF and the IVF laboratory have been transmitted to clinical care, showing dramatic improvements in health outcomes, including notable increases in the cumulative pregnancy rate. Current research in the laboratory focusing on culture media, embryo selection criteria, and implementation of genetic testing and manipulation promises to translate to further improvements in our ability to assist human reproduction. The field of IVF and ART remains a large source for clinical and scientific discovery and development, and will require the proper interested and invested personnel, occupational structuring, and funding for continued success.

Laser assisted zona hatching does not lead to immediate impairment in human embryo quality and metabolism

Laser assisted zona hatching (LAH) is a routinely used therapeutic intervention in assisted reproductive technology for patients with poor prognosis. However, results are not conclusive in demonstrating the benefits of zona hatching in improving the pregnancy rate. Recent observations on LAH induced genetic instability in animal embryos prompted us to look into the effects of laser assisted zona hatching on the human preimplantation embryo quality and metabolic uptake using high resolution nuclear magnetic resonance (NMR) technology. This experimental prospective study included fifty embryos from twenty-five patients undergoing intra cytoplasmic sperm injection. Embryo quality assessment followed by profiling of spent media for the non-invasive evaluation of metabolites was performed using NMR spectroscopy 24 hours after laser treatment and compared with that of non-treated sibling embryos. Both cell number and embryo quality on day 3 of development did not vary significantly between the two groups at 24 hours post laser treatment interval. Time lapse monitoring of the embryos for 24 hours did not reveal blastomere fragmentation adjacent to the point of laser treatment. Similarly, principal component analysis of metabolites did not demonstrate any variation across the groups. These results suggest that laser assisted zona hatching does not affect human preimplantation embryo morphology and metabolism at least until 24 hours post laser assisted zona hatching. However, studies are required to elucidate laser induced metabolic and developmental changes at extended time periods.

ABBREVIATIONS

AH: assisted hatching; ART: assisted reproductive technology; DNA: deoxy-ribo nucleic acid; LAH: laser assisted hatching; MHz: megahertz; NMR: nuclear magnetic resonance; PCA: principal component analysis; PGD: preimplantation genetic diagnosis; TLM: time lapse monitoring.

Chromosomal instability in mammalian pre-implantation embryos: potential causes, detection methods, and clinical consequences

Formation of a totipotent blastocyst capable of implantation is one of the first major milestones in early mammalian embryogenesis, but less than half of in vitro fertilized embryos from most mammals will progress to this stage of development. Whole chromosomal abnormalities, or aneuploidy, are key determinants of whether human embryos will arrest or reach the blastocyst stage. Depending on the type of chromosomal abnormality, however, certain embryos still form blastocysts and may be morphologically indistinguishable from chromosomally normal embryos. Despite the implementation of pre-implantation genetic screening and other advanced in vitro fertilization (IVF) techniques, the identification of aneuploid embryos remains complicated by high rates of mosaicism, atypical cell division, cellular fragmentation, sub-chromosomal instability, and micro-/multi-nucleation. Moreover, several of these processes occur in vivo following natural human conception, suggesting that they are not simply a consequence of culture conditions. Recent technological achievements in genetic, epigenetic, chromosomal, and non-invasive imaging have provided additional embryo assessment approaches, particularly at the single-cell level, and clinical trials investigating their efficacy are continuing to emerge. In this review, we summarize the potential mechanisms by which aneuploidy may arise, the various detection methods, and the technical advances (such as time-lapse imaging, "-omic" profiling, and next-generation sequencing) that have assisted in obtaining this data. We also discuss the possibility of aneuploidy resolution in embryos via various corrective mechanisms, including multi-polar divisions, fragment resorption, endoreduplication, and blastomere exclusion, and conclude by examining the potential implications of these findings for IVF success and human fecundity.

Measuring embryo metabolism to predict embryo quality

Measuring the metabolism of early embryos has the potential to be used as a prospective marker for post-transfer development, either alone or in conjunction with other embryo quality assessment tools. This is necessary to maximise the opportunity of couples to have a healthy child from assisted reproduction technology (ART) and for livestock breeders to efficiently improve the genetics of their animals. Nevertheless, although many promising candidate substrates (e.g. glucose uptake) and methods (e.g. metabolomics using different spectroscopic techniques) have been promoted as viability markers, none has yet been widely used clinically or in livestock production. Herein we review the major techniques that have been reported; these are divided into indirect techniques, where measurements are made from the embryo’s immediate microenvironment, or direct techniques that measure intracellular metabolic activity. Both have strengths and weaknesses, the latter ruling out some from contention for use in human ART, but not necessarily for use in livestock embryo assessment. We also introduce a new method, namely multi- (or hyper-) spectral analysis, which measures naturally occurring autofluorescence. Several metabolically important molecules have fluorescent properties, which we are pursuing in conjunction with improved image analysis as a viable embryo quality assessment methodology.

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.