Embryo Culture Research Articles

O-213 Analysis of risk factors for monozygotic twins following in vitro fertilization-embryo transfer

Abstract Study question To investigate the risk factors associated with the incidence of monozygotic twinning（MZT）following in vitro fertilization and embryo transfer (IVF-ET). Summary answer MZT following IVF-ET may be associated with a reduced endometrial thickness on the day of embryo transfer and a decrease in estradiol levels post-transfer. What is known already MZT pregnancy arises from the division of a single fertilized ovum, resulting in offspring with identical genetic material. These twins exhibit markedly higher rates of complications compared to dizygotic counterparts, including increased incidences of miscarriage, congenital anomalies, intrauterine fetal demise, growth restriction, and preterm delivery. The underlying biological processes leading to MZT remain elusive. Presently, scholarly discourse centers around two predominant models and one hypothesis: the zygote division model, the embryonic membrane fusion model, and the over-mature gametes hypothesis, respectively. IVF-ET has been implicated in the heightened occurrence of MZT, suggesting a potential iatrogenic element to this phenomenon. Study design, size, duration A retrospective cohort study has been conducted. We analyzed 582 IVF-ET cycles at a large teaching hospital from January 2007 to December 2022, including 291 clinically confirmed MZTs, and 291 matched non-MZTs. Participants/materials, setting, methods A total of 582 participants, 291 in both MZT group and non-MZT group. There were 146 fresh embryo transfer cycles and 145 frozen-thawed cycles in the MZT group. Each cycle type was matched on a 1:1 basis by age and embryo transfer date with a control group that did not result in MZT following IVF-ET. We examined the disparities between the MZT group and the non-MZT group, and performed the Logistics regression analysis. Main results and the role of chance Significant differences were observed in the MZT group compared to the non-MZT group in the fresh embryo transfer cycle, particularly regarding estradiol (E2) and progesterone (P) levels on day 7 post-transfer, E2/P ratios on day 14 post-transfer, and endometrial thickness on the day of transfer (p<0.05). Logistic regression analysis indicated a correlation between reduced endometrial thickness on the transfer day and the occurrence of MZT. During the frozen-thawed cycle, significant differences were noted in E2/P ratios, E2 levels on day 7 post-transfer, and endometrial thickness on embryo transfer day (p<0.05). Logistic regression analysis suggested that lower E2 levels on day 7 post-transfer and reduced endometrial thickness on embryo transfer day were predictive of MZT. Additional potential influencing factors included the duration of the participants’ menstrual cycle, the protocol of ovulation induction, and the duration of embryo culture in vitro. Limitations, reasons for caution Primarily, the retrospective design may introduce bias, notably due to the potential absence of comprehensive data. Secondly, the study is constrained by the sample size, with 146 fresh cycles and 145 frozen cycles, which may not provide a fully representative statistical power. Wider implications of the findings The incidence of MZT may implicate signaling pathways at the maternal-fetal interface, with early embryonic split potentially serving as a compensatory mechanism in response to suboptimal estrogen levels or diminished endometrial thickness, thus enhancing embryonic viability. Trial registration number not applicable

P-159 Single-cell high-throughput methylation and transcriptomic analysis indicates variations in sensitivity to Folate-mediated one-carbon metabolism in mouse preimplantation embryos

Abstract Study question Do Folate-mediated one-carbon metabolism (FOCM) supplements impose methylating conditions that influence methylation and transcriptomic profiles during preimplantation period of mouse embryos? Summary answer Subtle differences in embryo methylation profiles were induced by FOCM supplements, despite transcriptomic signatures remained stable and selective genes related to metabolism were activated. What is known already Previous human studies of populations affected by seasonal variations in diet including folate availability have shown methylation changes in specific loci known as metastable epialleles (MEs). MEs exhibit stability across tissues, indicating these could be potential biosensors for heightened sensitivity to external methylating influences in early embryonic stages. Despite significant progress in IVF embryo culture conditions, the sensitivity to the outer metabolic environment during the extensive genomic transformation of embryo reprogramming remains inadequately understood. Study design, size, duration This is a prospective experimental study conducted from January 2023 to December 2023. A total of 111 fresh mouse zygotes (F1 hybrid (B6/CBA)) were subjected embryo culture conditions with different FOCM supplies of 5-MTHF and betaine up to expanded blastocyst stage (105 hours). At different timepoints, individual embryos were collected and disaggregated in individual cells for downstream single-cell analysis. Participants/materials, setting, methods Mouse zygotes were collected from the oviduct, washed and culture in KSOM supplemented with 5-MTHF and betaine at respectively concentrations of 50μM and 50μg/mL (THF/bet(50)), 10μM and 10μg/mL (THF/bet(10)) and no supplement till blastocyst stage at 37 °C, 6%CO2 and 5%O2. Individual embryos were collected at 2 cells, 4 cells, 8 cells, Morula and Blastocyst stage and disaggregated into single cells for subsequent single-cell RNAseq (SmartSeq2) and single-cell methylome analysis through Splinted Ligation Adapter Tagging (scSPLAT). Main results and the role of chance The methylation analysis conducted though scSPLAT revealed a comprehensive reduction in global methylation levels throughout developmental stages. Notably, zygotes exhibited a maximal proportion of methylated cytosines at CpG sites, while blastocysts displayed minimal methylation levels, with sporadic increases in isolated cells. Quantitative profiling indicated lower methylation intensities in treated embryos from zygote to 4 cells, followed by a reversal trend from 8 cells to blastocyst, suggestive of an enhanced assimilation of one-carbon metabolism (FOCM) supplements. Transcriptomic profiles obtained through scRNAseq exhibited correlation with developmental trajectories from zygote to blastocyst. However, no discernible variations were attributed to the combined exposure of Betaine and 5-MTHF. Gene enrichment analysis of differentially expressed genes at various timepoints highlighted specific metabolic responses, including mitochondrial oxidative stress and variations in glutathione metabolism. This suggests that the folate forms utilized in this study may possess a protective role as antioxidants, contributing to the observed effects on gene expression during embryonic development. Limitations, reasons for caution The methylation analysis shown in this study was a pilot carried out with low coverage of sequencing deepness, further analysis are ongoing to increase reads coverage. Wider implications of the findings Exposure of mouse embryos to FOCM enhanced global methylation during cell division from 8 cells to blastocyst, indicating heightened assimilation during DNA synthesis. While the transcriptomic signature remained stable, increased expression of genes linked to mitochondrial oxidative stress and glutathione metabolism suggests FOCM’s potential antioxidant role. Trial registration number not applicable

P-504 Examining the success rates following a second embryo biopsy for inconclusive results in preimplantation genetic testing for monogenic diseases (PGT-M): a matched case-control study

Abstract Study question Can an embryo re-biopsy for a previous inconclusive result influence clinical pregnancy compared to a successful PGT-M diagnosis from the first biopsy? Summary answer The embryo re-biopsy intervention for PGT-M seems to reduce the implantation potential of a blastocyst. What is known already PGT-M allows embryo genetic profiling prior to transfer in couples with hereditary genetic disorders, as part of in vitro fertilization process. The need of a trophectoderm biopsy for the retrieval of a fragment of about 8-10 blastomeres is generally sufficient for optimal DNA amplification and molecular analysis. However, a proportion of embryos (approximately 10-12%) fails to be properly diagnosed after PGT-M testing due to inconclusive results. Therefore, as an attempt to obtain a genetic diagnosis, the embryo biopsy can be repeated on the same embryos although retesting involves a second round of biopsy and a second round of vitrification. Study design, size, duration Twenty-seven embryos from women undergoing PGT-M at an infertility center and transferred after two biopsies for genetic analysis were matched for age, fertility status, and study period, to embryos transferred after a conclusive PGT-M result after the first biopsy. The main outcome was the clinical pregnancy rate following embryo transfers in cases in whom embryos had a single biopsy, and when a re-biopsy was performed. The secondary outcome was the live birth rate. Participants/materials, setting, methods Ovarian stimulation, oocyte collection and fertilization were performed according to standard protocols. Embryos were cultured to blastocyst stage in groups of up to five, using one-step media. Blastocysts were biopsied on day 5, 6, or 7, employing either the pulling or flicking method based on their appearance. Biopsied cells were stored at -20 °C for genetic analysis. Vitrification was performed using Kitazato protocol. If results were inconclusive, a second biopsy was performed in surviving blastocysts. Main results and the role of chance The median [interquartile range] number of retrieved and injected oocytes was similar between the two groups, as well as fertilization rate and number of blastocysts obtained. No difference between the two groups was also observed pertaining to the day of embryo culture in which the first biopsy was performed. Conversely, the number of non-diagnosticated and transferable blastocysts was lower in patients whose blastocysts were re-biopsied. In 90% of the re-biopsies an informative result was obtained. Clinical pregnancy rate was 52% (95% CI: 34-69) following the transfer of a single-biopsy blastocyst and 30% (95% CI: 16-48) following the transfer of a re-biopsied blastocyst. The likelihood to have a healthy baby was 33% (95% CI: 19-52) following the transfer of a blastocyst biopsied once and 22% (95% CI: 11-41) following the transfer of a re-biopsied blastocyst. Limitations, reasons for caution The matching design, which aligns women’s age and fertility status in the two groups, allowed the assessment of pregnancy rates while avoiding potential confounding factors associated with retrospective analysis. Given that it is the first study with this design, a larger sample size is necessary to further elucidate these findings. Wider implications of the findings Despite the limited sample size, these results are of extreme clinical relevance. They offer valuable insights for guiding decisions about embryos with unclear results, contributing to the improvement of strategies for selecting those with the highest probability of pregnancy. Trial registration number not applicable

O-240 Embryo assessment: the Istanbul consensus revised

Abstract Study question What are the current recommended criteria for morphological assessment of oocytes, zygotes and embryos? Summary answer The present ESHRE/Alpha Scientists in Reproductive Medicine consensus document provides several novel recommendations to assess oocyte and embryo morphology and rank embryos for transfer. What is known already A previous Alpha Scientists in Reproductive Medicine / ESHRE consensus on oocyte and embryo morphological assessment was published in 2011. After more than a decade, a thorough review and update was needed. Study design, size, duration A working group consisting of Alpha Scientists in Reproductive Medicine executive board members and ESHRE Special interest group of Embryology members formulated recommendations on oocyte and embryo morphological assessment. Participants/materials, setting, methods The working group included 17 internationally recognized experts with extensive experience in clinical embryology. Seven members represented Alpha Scientists in Reproductive Medicine and 8 members represented ESHRE, in addition to two methodological experts from the ESHRE central office. Based on a systematic literature search and discussion of existing evidence, the recommendations of the Istanbul Consensus (2011) were reassessed and, where appropriate, updated based on consensus within the working group. After stakeholder review, the final version will be approved by the working group, the Alpha executive board and the ESHRE Executive Committee. Main results and the role of chance This updated consensus paper provides 20 recommendations focused on the timeline of preimplantation developmental events and morphological criteria for oocyte, zygote, and embryo assessment. Based on duration of embryo culture, recommendations are given on the frequency and timing of assessments to ensure safety and effectiveness. Limitations, reasons for caution Several criteria relevant to oocyte and embryo morphology have not been well studied, leading to either a recommendation against their use for grading or for use in ranking rather than grading. Future updates may require further revision of these recommendations. Wider implications of the findings This document provides embryologists with clear advice on best practices when assessing oocyte and embryo quality based on the most recent evidence.

P-261 A comparative analysis of artificial intelligence models for blastulation in In vitro fertilization: single-frame vs. full-frame approach

Abstract Study question How does the performance of an blastulation prediction model using full-frame data over 3 days compare to a single-frame model using day 3 data? Summary answer The single-frame model, based on a day 3 embryo image, demonstrated comparable predictive performance to the full-frame model What is known already Pregnancy rates following blastocyst transfer have been reported to be higher than those after cleavage transfer. However, not all cleavage embryos reach the blastocyst stage, leading to the exploration of predictive models using embryo images and artificial intelligence. Clinical practice often involves the decision to culture embryos to the blastocyst stage on day 3 based on embryo quality assessments. Recently, there has been interest in using morphokinetics data for predicting blastulation and pregnancy outcomes. While the importance of morphokinetics in IVF outcomes is acknowledged, the specific time frames and features contributing significantly to accurate predictions remain unclear. Study design, size, duration This retrospective study analyzed a dataset of 15,615 timelapse images from 906 patients at a single IVF center. The Single-Frame Model used a single image collected at 66.7 hours post-ICSI, and the Full-Frame Model used 145 frames collected from fertilization to 66.7 hours post-ICSI. Blastulation criteria included reaching a blastocyst on day 5, deemed suitable for transfer or freezing by an experienced embryologist. Participants/materials, setting, methods We trained the data using ResNet for the one-frame model and 3D CNN for the full-frame model. The ResNet model used pre-trained weights, while the 3D CNN model was built from scratch with no pre-trained weights. The models were evaluated using the AUROC, accuracy, and F1 score metrics. The statistical significance of the AUC performance differences was assessed using DeLong’s test. Main results and the role of chance Our study revealed similar AUC performance between the Single-Frame and Full-Frame Models for day 3 embryos. The Single-Frame Model exhibited an AUROC of 0.76, accuracy of 0.71, and an F1 score of 0.75, while the Full-Frame Model demonstrated comparable performance with an AUROC of 0.75, accuracy of 0.70, and an F1 score of 0.72. DeLong’s test was employed to assess the statistical significance of the difference in AUROC, yielding a non-significant p-value of 0.4884. This study underscores that the Single-Frame Model provides similar predictive performance for blastulation compared to the Full-Frame Model. Limitations, reasons for caution Our analysis was limited to images taken at 66.7 hours post-ICSI to mirror clinical practice. Further investigations at different time points are necessary to determine the optimal time for blastulation prediction. Additional analysis of the Day 1 and Day 2 single frames may offer further insights. Wider implications of the findings Accurate prediction of blastulation on day 3 is pivotal for embryo survival and IVF success. Our study challenges the assumption that more data improves AI models, highlighting the importance of day 3 observations. Further research is warranted to identify key time points and features for better predictive accuracy. Trial registration number not applicable

CRISPR-based genome editing of a diurnal rodent, Nile grass rat (Arvicanthis niloticus)

BackgroundDiurnal and nocturnal mammals have evolved distinct pathways to optimize survival for their chronotype-specific lifestyles. Conventional rodent models, being nocturnal, may not sufficiently recapitulate the biology of diurnal humans in health and disease. Although diurnal rodents are potentially advantageous for translational research, until recently, they have not been genetically tractable. The present study aims to address this major limitation by developing experimental procedures necessary for genome editing in a well-established diurnal rodent model, the Nile grass rat (Arvicanthis niloticus).ResultsA superovulation protocol was established, which yielded nearly 30 eggs per female grass rat. Fertilized eggs were cultured in a modified rat 1-cell embryo culture medium (mR1ECM), in which grass rat embryos developed from the 1-cell stage into blastocysts. A CRISPR-based approach was then used for gene editing in vivo and in vitro, targeting Retinoic acid-induced 1 (Rai1), the causal gene for Smith-Magenis Syndrome, a neurodevelopmental disorder. The CRISPR reagents were delivered in vivo by electroporation using an improved Genome-editing via Oviductal Nucleic Acids Delivery (i-GONAD) method. The in vivo approach produced several edited founder grass rats with Rai1 null mutations, which showed stable transmission of the targeted allele to the next generation. CRISPR reagents were also microinjected into 2-cell embryos in vitro. Large deletion of the Rai1 gene was confirmed in 70% of the embryos injected, demonstrating high-efficiency genome editing in vitro.ConclusionWe have established a set of methods that enabled the first successful CRISPR-based genome editing in Nile grass rats. The methods developed will guide future genome editing of this and other diurnal rodent species, which will promote greater utility of these models in basic and translational research.

Undisturbed culture: a clinical examination of this culture strategy on embryo in vitro development and clinical outcomes

To compare the effect of a fully undisturbed culture strategy over a sequential one on embryo in vitro development and clinical outcomes in ICSI cycles. Retrospective cohort study. This study included 4,564 ICSI cycles performed over 5 years, including autologous and oocyte donation treatments with extended embryo culture until blastocyst in one of the two defined culture strategies. Embryo cohorts were cultured in one of two culture systems: a fully undisturbed culture, including an incubator with integrated time-lapse technology, one-step culture medium and embryo selection assisted by semi-automatic tools based on embryo morphokinetics, or a sequential culture, using a conventional benchtop incubator, sequential media and traditional morphological evaluation under optical microscope. The effect of the culture strategies over embryo development and clinical outcomes was quantified by generalized estimated equations, controlling for possible confounders through the inverse probability of treatment weighting method. Weighted odds ratios (OR) and 95% confidence intervals (CI) for live birth rate after fresh single embryo transfer and the cumulative live birth rate. Additionally, blastocyst development and morphology and other intermediate outcomes were also assessed. A significant positive association was found between the employment of undisturbed embryo culture and higher live birth rate in the first embryo transfer in both autologous (OR=1.617, 95%CI: 1.074-2.435) and oocyte donation cycles (OR=1.316, 95%CI: 1.036-1.672). Cumulative live birth rate after one year follow-up was also positively associated with the undisturbed culture strategy in oocyte donation cycles (OR=1.5, 95%CI: 1.179-1.909), but not in autologous cycles (OR=1.051, 95%CI: 0.777-1.423). Similarly, blastocyst rate, good morphology blastocyst rate and utilisation rate were positively associated with the employment of undisturbed culture in oocyte donation cycles, but not in autologous cycles. These findings imply that a culture system combining integrated time-lapse incubators with a one-step culture medium, may enhance the success rates of patients undergoing ICSI treatment by increasing the production of higher-quality blastocysts and improving embryo selection while streamlining laboratory procedures and workflow.

Development of the first equine blastocyst produced by conventional IVF and in vitro culture in Europe resulting in the birth of a foal

In this case report, the production of the first equine blastocyst using conventional in vitro fertilization (IVF) and in vitro embryo culture methods in Europe is described. A healthy foal was born after transfer of a blastocyst using a complete in vitro production process, including in vitro oocyte maturation, in vitro sperm capacitation, fertilization in vitro and culture to the blastocyst stage in vitro. Oocytes were recovered from ovaries of slaughtered mares. After in vitro maturation, the oocytes were fertilized by conventional IVF and cultured for nine days. One embryo reached the blastocyst stage and was vitrified. After the selection of a suitable recipient mare that had ovulated four days earlier, the blastocyst was thawed and transferred. Five days after embryo transfer, a single embryonic vesicle was detected by transrectal ultrasonography. After a normal pregnancy of 323 days, a healthy colt was born. Parentage testing via microsatellite genotyping confirmed that the recipient was excluded as the foal’s dam and that the stallion whose semen was used, qualified as the sire.

Role of Follicular Size on Oocyte Recovery Rate and in Vitro Embryo Production Stages in Local Iraqi Sheep

In vitro embryo production (IVEP) encompasses a series of three basic steps, namely in vitro maturation (IVM), in vitro fertilisation (IVF), and in vitro embryo culture. IVEP approach has shown to be a valuable tool in advancing our comprehension of early mammalian development and expediting genetic enhancement in livestock. The aim of this research was to compare the impact of small and large follicles on the total number of oocytes recovered through the IVEP process. Therefore, 305 Ewe genitalia were collected at the Al-Fallujah abattoir in the Al-Anbar province. The follicles were identified, and their diameter was measured using an automated vernier calliper. Subsequently, the oocytes were classified into three distinct groups, namely excellent (A), acceptable (B), and poor (C). The results of the maturation rate of large follicles were 43.9% (51/116) and small follicles 30.7% (20/65). There was a statistical difference in maturation rate (p<0.05). The fertilization rate of matured oocytes collected from large follicles was 60.7% (31/51) and 50% (10/20) from small follicles. There was no statistical difference. The results of Blastocyst production rate. showed a higher percentage 58.06 (18/31) of Blastocyst produced from large follicles as compared a percentage of 30% (3/10) of Blastocyst production from small follicles. There was a statistical difference (P<0.05). It was concluded from the current study that the size of the follicle has an effect on IVM, IVF and IVC.

Ketoconazole blocks progesterone production without affecting other parameters of cumulus-oocyte complex maturation

Ketoconazole (KTZ) is widely used as a fungicide, but it is also known to target steroid hormone formation which may affect female reproductive health. Our study aims to investigate the effects of KTZ on in vitro matured bovine cumulus-oocyte complexes (COCs), as a model for female reproductive toxicity. Cumulus cells of in vitro maturing COCs produce progesterone and pregnenolone, but exposure to 10−6 M KTZ effectively blocked the synthesis of these hormones. Exposure to lower concentrations of KTZ (i.e. 10−7 M and 10−8 M) had no such effect on steroidogenesis compared to the 0.1 % v/v DMSO vehicle control. Classical parameters of in vitro COC maturation, such as oocyte nuclear maturation to the metaphase II stage and expansion of the cumulus investment, were not affected by any KTZ concentration tested. Apoptosis and necrosis levels were also not altered in cumulus cells or oocytes exposed to KTZ. Moreover, oocytes exposed to KTZ during maturation showed normal cleavage and early embryo development up to day 8 post fertilization; albeit a statistically significant decrease was observed in day 8 blastocysts produced from oocytes exposed to the lowest concentration of 10−8 M KTZ. When unexposed mature oocytes were fertilized, followed by embryo culture for 8 days under KTZ exposure, no adverse effects in embryo cleavage and blastocyst formation were observed. In conclusion, KTZ has no major impact on in vitro bovine oocyte maturation and blastocyst formation in our study, even at concentrations blocking steroidogenesis.

The walnut-derived peptide TW-7 improves mouse parthenogenetic embryo development of vitrified MII oocytes potentially by promoting histone lactylation

BackgroundPrevious studies have shown that the vitrification of metaphase II (MII) oocytes significantly represses their developmental potential. Abnormally increased oxidative stress is the probable factor; however, the underlying mechanism remains unclear. The walnut-derived peptide TW-7 was initially isolated and purified from walnut protein hydrolysate. Accumulating evidences implied that TW-7 was a powerful antioxidant, while its prospective application in oocyte cryopreservation has not been reported.ResultHere, we found that parthenogenetic activation (PA) zygotes derived from vitrified MII oocytes showed elevated ROS level and delayed progression of pronucleus formation. Addition of 25 μmol/L TW-7 in warming, recovery, PA, and embryo culture medium could alleviate oxidative stress in PA zygotes from vitrified mouse MII oocytes, furtherly increase proteins related to histone lactylation such as LDHA, LDHB, and EP300 and finally improve histone lactylation in PA zygotes. The elevated histone lactylation facilitated the expression of minor zygotic genome activation (ZGA) genes and preimplantation embryo development.ConclusionsOur findings revealed the mechanism of oxidative stress inducing repressed development of PA embryos from vitrified mouse MII oocytes and found a potent and easy-obtained short peptide that could significantly rescue the decreased developmental potential of vitrified oocytes, which would potentially contribute to reproductive medicine, animal protection, and breeding.

Impact of Mycotoxin Metabolites Deepoxy-Deoxynivalenol and Beta-Zearalenol on Bovine Preimplantation Embryo Development in the Presence of Acetonitrile.

The quality of animal feed is increasingly affected by weather conditions, high humidity, and damage to grains, which have led to various mycotoxin-producing moulds. The aim of this study was to determine the effects of the combination of deepoxy-deoxynivalenol and beta-zearalenol on the development of preimplantation bovine embryos, the extent to which the presence of both mycotoxin metabolites affects the development of in vitro cultured bovine embryos, or whether the effect of both toxins enhances embryotoxicity. Ovaries were transported from the abattoir to the laboratory and, after maturation and fertilisation, zygotes were placed in an embryo culture medium (IVC) with different mycotoxin metabolite concentrations diluted in acetonitrile. It was found that the blastocyst rate of cleaved embryos was affected by 1 μL acetonitrile in 400 μL medium (0.25%) compared to the group without acetonitrile. For this reason, it was decided to use acetonitrile as a control group, and the desired mycotoxin metabolite concentrations were diluted in the lowest possible amount of acetonitrile (0.5 μL) that could be accurately added to the study groups. There was no statistical difference when the higher mycotoxin metabolite concentrations were added.

The biological characteristics of long cell-free DNA in spent embryos culture medium as noninvasive biomarker in in-vitro embryo selection

An improved understanding of the cfDNA fragmentomics has proved it as a promising biomarker in clinical applications. However, biological characteristics of cfDNA in spent embryos culture medium (SECM) remain unsolved obstacles before the application in non-invasive in-vitro embryo selection. In this study, we developed a Tn5 transposase and ligase integrated dual-library construction sequencing strategy (TDual-Seq) and revealed the fragmentomic profile of cfDNA of all sizes in early embryonic development. The detected ratio of long cfDNA (>500 bp) was improved from 4.23 % by traditional NGS to 12.80 % by TDual-Seq. End motif analysis showed long cfDNA molecules have a more dominance of fragmentation intracellularly in apoptotic cells with higher predominance of G-end, while shorter cfDNA undergo fragmentation process both intracellularly and extracellularly. Moreover, the mutational pattern of cfDNA and the correlated GO biological process were well differentiated in cleavage and blastocyst embryos. Finally, we developed a multiparametric index (TQI) that employs the fragmentomic profiles of cfDNA, and achieved an area under the ROC curve of 0.927 in screening top quality embryos. TDual-Seq strategy has facilitated characterizing the fragmentomic profile of cfDNA of all sizes in SECM, which are served as a class of non-invasive biomarkers in the evaluation of embryo quality in in-vitro fertilization. And this improved strategy has opened up potential clinical utilities of long cfDNA analysis.

In Vitro Culture of Mammalian Embryos: Is There Room for Improvement?

Preimplantation embryo culture, pivotal in assisted reproductive technology (ART), has lagged in innovation compared to embryo selection advancements. This review examines the persisting gap between in vivo and in vitro embryo development, emphasizing the need for improved culture conditions. While in humans this gap is hardly estimated, animal models, particularly bovines, reveal clear disparities in developmental competence, cryotolerance, pregnancy and live birth rates between in vitro-produced (IVP) and in vivo-derived (IVD) embryos. Molecular analyses unveil distinct differences in morphology, metabolism, and genomic stability, underscoring the need for refining culture conditions for better ART outcomes. To this end, a deeper comprehension of oviduct physiology and embryo transport is crucial for grasping embryo-maternal interactions' mechanisms. Research on autocrine and paracrine factors, and extracellular vesicles in embryo-maternal tract interactions, elucidates vital communication networks for successful implantation and pregnancy. In vitro, confinement, and embryo density are key factors to boost embryo development. Advanced dynamic culture systems mimicking fluid mechanical stimulation in the oviduct, through vibration, tilting, and microfluidic methods, and the use of innovative softer substrates, hold promise for optimizing in vitro embryo development.

Effect of Ergothineine and Quercetin Additions in to the In Vitro Embriyo Development

Aim: This study aimed to investigate the effects of ergothioneine and quercetin on the in vitro development of bovine embryos Materials and Methods: Cumulus-oocyte complexes (COCs) were collected via ovary aspiration from a local abattoir and cultured in vitro for maturation. After maturation, in vitro fertilization was performed. The pronuclear embryos were divided into three groups: control, 10 μM L-ergothioneine, and 10 μM quercetin supplemented. After the addition of antioxidants to the CR1aa medium, in vitro culture of embryos were performed. The cleavage and morula rates were assessed on days 2 and 5, respectively. Blastocyst formation and quality were assessed on days 7-8. Results: Statistical analysis showed cleavage and morula rates were significantly higher in the ergothioneine group compared to the quercetin and control groups (P<0.05). While no blastocysts formed in the quercetin group, the blastocyst rate reached to 17.96% with ergothioneine supplementation on day 8. Conclusion: In conclusion, supplementation with 10 μM ergothioneine enhanced the in vitro development of bovine oocytes. However, 10 μM quercetin supplementation impaired development, and no blastocyst formation observed. Further studies utilizing different concentrations are warranted to better understand the effects. This study provides insights into modulating oxidative stress during in vitro embryonic production.

Amniotic fluid-derived stem cells: potential factories of natural and mimetic strategies for congenital malformations.

Mesenchymal stem cells (MSCs) from gestational tissues represent promising strategies for in utero treatment of congenital malformations, but plasticity and required high-risk surgical procedures limit their use. Here we propose natural exosomes (EXOs) isolated from amniotic fluid-MSCs (AF-MSCs), and their mimetic counterparts (MIMs), as valid, stable, and minimally invasive therapeutic alternatives. MIMs were generated from AF-MSCs by combining sequential filtration steps through filter membranes with different porosity and size exclusion chromatography columns. Physiochemical and molecular characterization was performed to compare them to EXOs released from the same number of cells. The possibility to exploit both formulations as mRNA-therapeutics was explored by evaluating cell uptake (using two different cell types, fibroblasts, and macrophages) and mRNA functionality overtime in an in vitro experimental setting as well as in an ex vivo, whole embryo culture using pregnant C57BL6 dams. Molecular and physiochemical characterization showed no differences between EXOs and MIMs, with MIMs determining a 3-fold greater yield. MIMs delivered a more intense and prolonged expression of mRNA encoding for green fluorescent protein (GFP) in macrophages and fibroblasts. An ex-vivo whole embryo culture demonstrated that MIMs mainly accumulate at the level of the yolk sac, while EXOs reach the embryo. The present data confirms the potential application of EXOs for the prenatal repair of neural tube defects and proposes MIMs as prospective vehicles to prevent congenital malformations caused by in utero exposure to drugs.

Development of a Novel Non-invasive Metabolomics Assay to Predict Implantation Potential of Human Embryos.

Can a set of metabolites present in embryo culture media correlate with embryo implantation? Case-control study in two phases: discovery phase (101 samples) and validation phase (169 samples), collected between 2018 and 2022, with a total of 218 participants. Culture media samples with known implantation outcomes were collected after blastocyst embryo transfer (including both PGT and non-PGT cycles) and were analyzed using chromatography followed by mass spectrometry. The spectra were processed and analyzed using statistical and machine learning techniques to identify biomarkers associated with embryo implantation, and to develop a predictive model. In the discovery phase, 148 embryo implantation biomarkers were identified using high resolution equipment, and 47 of them were characterized. Our results indicate a significant enrichment of tryptophan metabolism, arginine and proline metabolism, and lysine degradation biochemical pathways. After transferring the method to a lower resolution equipment, a model able to assign a Metabolite Pregnancy Index (MPI) to each embryo culture media was developed, taking the concentration of 36 biomarkers as input. Applying this model to 20% of the validation samples (N=34) used as the test set, an accuracy of 85.29% was achieved, with a PPV (Positive Predictive Value) of 88% and a NPV (Negative Predictive Value) of 77.78%. Additionally, informative results were obtained for all the analyzed samples. Metabolite concentration in the media after in vitro culture shows correlation with embryo implantation potential. Furthermore, the mathematical combination of biomarker concentrations using Artificial Intelligence techniques can be used to predict embryo implantation outcome with an accuracy of around 85%.

Total blastocyst usable rate is a predictor of cumulative live birth rate in IVF cycles

PurposeDespite advances in IVF techniques, determining the prognostic factors influencing cumulative live birth rate (CLBR) remains crucial for optimizing outcomes. Among the various key performance indicators in the lab, blastulation rate, and more specifically Total Blastocyst Usable Rate (TBUR), has gained particular interest. In this study we aimed at determining if TBUR was significantly associated with CLBR. Basic proceduresThis monocentric retrospective case-control study was conducted in 317 consecutive IVF/ICSI cycles in 2014–2020 and leading to the formation of 3 usable blastocysts, including freeze all cycles. TBUR (usable blastocysts / 2PNs) was calculated and CLBR after 2-year follow up was recorded, including both fresh and frozen embyro transfers. CLBR was then compared between 2 groups according to TBUR (group 1: TBUR ≥50 % vs group 2: TBUR ≤30 %). Main findingsCLBR was significantly higher in group 1 than in group 2 (57 vs. 41 %, p = 0.02). Adjusted logistic regression showed a statistically significant relationship between CLBR and TBUR, with a significantly lower chance of achieving a live birth in group 2 than in group 1 (OR = 0.408 [0.17–0.96]; p = 0.04). Principal conclusionsAlthough the monocentric design and the arbitrary choice of thresholds for TBUR and number of blastocysts call for caution when generalizing the findings and advocates for external validation, our results illustrate that TBUR is a valuable prognostic factor of CLBR in IVF cycles which might serve as a tool for lab monitoring, cycle analysis by medical staff and patients’ counselling. These results fit well within the P4 medicine concept (Predictive, Preventive, Personalized, and Participatory), and advocate for further research in order to improve embryo culture conditions.

Non-invasive pre-implantation genetic testing's reliability for aneuploidy using Cell-free DNA in embryo culture media

ObjectiveThe presence of embryonic cell-free DNA (cfDNA) in spent embryo culture media (SECM) may offer valuable advantages for non-invasive testing of embryo ploidy or genetic characteristics compared to trophectoderm (TE) biopsy. This study aimed to assess the diagnostic potential of SECM cfDNA as a non-invasive sample for chromosomal copy number testing in blastocysts within the clinical setting of in-vitro fertilization. MethodThis prospective observational study collected 28 SECM cfDNA samples matched with TE biopsy samples from 21 infertile couples who underwent IVF-PGT-A cycles. SECM samples were obtained from blastocysts that were cultured for approximately 5/6 days in an uninterrupted time-lapse incubator. Both sets of samples were collected during the biopsy procedure. The Variseq Illumina platform was utilized for ploidy measurement. The study evaluated the informativity and interpretability of SECM cfDNA, concordance of general ploidy status, and sex chromosome agreement between the two sample types. ResultsSECM cfDNA had a high informativity rate (100 %) after double amplification procedure, with a result interpretability of 93 %. Two out of the 28 SECM cfDNA samples were uninterpretable and regarded as overall noise samples. The diagnostic potential of SECM cfDNA, when compared to TE biopsy the standard reference, was relatively low at 50 %. Maternal DNA contamination remains the major obstacle that hinders the widespread clinical adoption of SECM cfDNA in the routine practice of pre-implantation genetic testing for aneuploidy within IVF settings. ConclusionA significant modification must be implemented in the IVF laboratory to minimize DNA contamination and this necessitates suggesting adjustments to oocyte denudation, embryo culture media preparation, and sample collection procedures.

Embryos from Prepubertal Hyperglycemic Female Mice Respond Differentially to Oxygen Tension In Vitro.

Reduced oxygen during embryo culture in human ART prevents embryo oxidative stress. Oxidative stress is also the major mechanism by which maternal diabetes impairs embryonic development. This study employed induced hyperglycemia prepubertal mice to mimic childhood diabetes to understand the effects of varying oxygen tension during in vitro embryonic development. The oocytes were fertilized and cultured at low (≈5%) oxygen (LOT) or atmospheric (≈20%) oxygen tension (HOT) for up to 96 h. Embryo development, apoptosis in blastocysts, inner cell mass (ICM) outgrowth proliferation, and Hif1α expression were assessed. Though the oocyte quality and meiotic spindle were not affected, the fertilization rate (94.86 ± 1.18 vs. 85.17 ± 2.81), blastocyst rate (80.92 ± 2.92 vs. 69.32 ± 2.54), and ICM proliferation ability (51.04 ± 9.22 vs. 17.08 ± 3.05) of the hyperglycemic embryos were significantly higher in the LOT compared to the HOT group. On the other hand, blastocysts from the hyperglycemic group, cultured at HOT, had a 1.5-fold increase in apoptotic cells compared to the control and lower Hif1α transcripts in ICM outgrowths compared to the LOT. Increased susceptibility of embryos from hyperglycemic mice to higher oxygen tension warrants the need to individualize the conditions for embryo culture systems in ART clinics, particularly when an endogenous maternal pathology affects the ovarian environment.