Composition of single-step media used for human embryo culture

Culture medium and protein supplementation affect sensitivity of the mouse embryo assay in detecting Triton X-100

RESEARCH QUESTION

To what extent does the type and concentration of protein and the type of culture medium affect the sensitivity of the mouse embryo assay (MEA) to detect Triton X-100 (TX-100) in culture media?

DESIGN

The effect of the concentration of bovine serum albumin (BSA) and human serum albumin (HSA) was assessed by supplementing media with 0.5 or 5 mg/ml. Potassium-supplemented simplex optimized medium (KSOM) and human tubal fluid (HTF) were used as complex and simple formulation media, respectively. Variables were combined, forming study groups where embryos were cultured in test media spiked with a sublethal TX-100 concentration. The conditions of greatest sensitivity were determined by statistical comparison of blastocyst formation rates and total cell counts between groups.

RESULTS

Although all of the study groups showed equal capacity for sustaining proper embryo development, the reported sensitivity of the MEA differed between groups when subjected to TX-100. HTF conferred significantly greater sensitivity than KSOM regardless of the type and concentration of protein used, and medium supplementation with 5 mg/ml BSA rather than 0.5 mg/ml BSA resulted in significantly higher sensitivity regardless of the type of medium used. This increase in concentration also resulted in higher sensitivity when supplementing HTF with HSA. The BSA groups provided more sensitivity than their HSA counterparts, except for the KSOM + 0.5 mg/ml BSA group. Cell count analysis did not provide further significant conclusions.

CONCLUSIONS

For TX-100 detection within culture medium, the type and concentration of protein and the type of culture medium have a direct effect on MEA sensitivity. These results could help to standardize the MEA protocol, and increase its ability to detect sublethal concentrations of embryotoxic substances, especially TX-100, thus avoiding possible clinical harmful effects.

Culture media affect sex after IVF treatment-a detailed analysis of explanatory variables

PURPOSE

The purpose of this study was to provide a detailed analysis of clinical and laboratory factors associated with skewed secondary sex ratio (SSR) after ART.

METHOD

Retrospective cohort study of embryos resulting in live births, from frozen and fresh single blastocyst transfers. Embryos were cultured in either G-TL (n = 686) or Sage media (n = 685). Data was analyzed using a multivariate logistic regression model and a mixed model analysis.

RESULTS

Significantly more male singletons were born after culture in Sage media compared to G-TL media (odds ratio (OR) 1.34, 95% CI (1.05, 1.70), P = 0.02). Inner cell mass grade B vs A (OR 1.36 95% CI (1.05, 1.76), P = 0.02) and one previous embryo transfer (OR 1.49, 95% CI (1.03, 2.16), P = 0.03) were associated with a significantly higher probability of male child at birth. Factors associated with a reduced probability of male child were expansion grade 3 vs 5 (OR 0.66, 95% CI (10.45, 0.96), P = 0.03) and trophectoderm grade B vs A (OR 0.57, 95% CI (0.44, 0.74), P = 0.00). Male embryos developed significantly faster in Sage media compared to G-TL media for the stages of blastocyst (- 1.12 h, 95% CI (- 2.12, - 0.12)), expanded blastocyst (- 1.35 h, 95% CI (- 2.34, - 0.35)), and hatched blastocyst (- 1.75 h, 95% CI (- 2.99, - 0.52)).

CONCLUSION

More male children were born after culture in Sage media compared to G-TL media. Male embryo development was affected by culture media. Our observations suggest that culture media impact male embryo quality selectively, thus potentially favoring the selection of male embryos.

Effect of chemical activators after intracytoplasmic sperm injection (ICSI) on embryo development in alpacas

Low motility and low sperm concentration are characteristics of alpaca semen. Thus, the intracytoplasmic sperm injection (ICSI) technique represents an alternative to improve the reproductive capacity of the male. However, the effect of post-ICSI activation in alpaca is not yet known. The aim of the present study was to compare the effect of chemical activators on alpaca embryo development after ICSI. Alpaca ovaries were collected from a local slaughterhouse and transported to the laboratory. Category I, II and III oocytes were matured for 30 h at 38.5 °C. After ICSI, injected oocytes were randomly divided and activated as follows: i) 5 μM ionomycin for 5 min, ii) 7% ethanol for 4 min, iii) 5 μM ionomycin for 5 min, window period 3 h plus 7% ethanol for 4 min, iv) 5 μM ionomycin for 5 min, window period 3 h, a second ionomycin treatment for 5 min, followed by 1.9 mM 6-DMAP for 3 h, v) 10 mM SrCl2 for 3 h. Culture was carried out for 5 days in SOFaa at 38.5 °C. The cleavage rate was the lowest in the SrCl2 group, morula development was the lowest in the SrCl2 and without activation groups, and blastocyst stage was not different between groups (P<0.05). The rates with SrCl2 were lower in total embryos produced, whereas in transferable embryos they were lower with 2Io/6-DMAP and with SrCl2 (P<0.05). In conclusion, alpaca oocyte activation is more efficient with ionomycin and ethanol to produce transferable embryos.

Do IVF culture conditions have an impact on neonatal outcomes? A systematic review and meta-analysis

PURPOSE

Are embryo culture conditions, including type of incubator, oxygen tension, and culture media, associated with obstetric or neonatal complications following in vitro fertilization (IVF)?

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Library was performed from January 01, 2008, until October 31, 2021. The studies reporting quantitative data on at least one of the primary outcomes (birthweight and preterm birth) for the exposure group and the control group were included. For oxygen tension, independent meta-analysis was performed using Review Manager, comparing hypoxia/normoxia. For culture media, a network meta-analysis was carried out using R software, allowing the inclusion of articles comparing two or more culture media.

RESULTS

After reviewing 182 records, 39 full-text articles were assessed for eligibility. A total of 28 studies were kept for review. Meta-analysis about the impact of incubator type on perinatal outcomes could not be carried out because of a limited number of studies. For oxygen tension, three studies were included. The pairwise meta-analysis comparing hypoxia/normoxia did not show any statistical difference for birthweight and gestational age at birth. For culture media, 18 studies were included. The network meta-analysis failed to reveal any significant impact of different culture media on birthweight or preterm birth.

CONCLUSION

No difference was observed for neonatal outcomes according to the embryo culture conditions evaluated in this review. Further research is needed about the safety of IVF culture conditions as far as future children's health is concerned.

The unbearable ignorance of the composition of IVF culture media

Culture media play an essential role in the success of IVF. Their composition has undergone major modifications over the 45 years since the birth of Louise Brown. Most IVF programmes now rely on commercially produced media, which they buy in small vials, guaranteed to be sterile and non-embryotoxic. Unfortunately, information about the components of the culture media and their concentrations is no longer available. Arguing that culture media recipes are proprietary, relevant commercial interests have stopped labelling their products with this vital information. Given the critical role that is played by culture media in the success of IVF, as well as the subsequent health of the children who are born after IVF, this information should not remain a 'company secret'. Clinicians and scientists working in IVF must insist that the labelling of culture media includes all of the constituents and their concentrations. Only in this way can we monitor the influence of culture media on IVF outcomes, innovate and continue to advance the field of IVF.

Effects of Melatonin, GM-CSF, IGF-1, and LIF in Culture Media on Embryonic Development: Potential Benefits of Individualization

The implantation of good-quality embryos to the receptive endometrium is essential for successful live birth through in vitro fertilization (IVF). The higher the quality of embryos, the higher the live birth rate per cycle, and so efforts have been made to obtain as many high-quality embryos as possible after fertilization. In addition to an effective controlled ovarian stimulation process to obtain high-quality embryos, the composition of the embryo culture medium in direct contact with embryos in vitro is also important. During embryonic development, under the control of female sex hormones, the fallopian tubes and endometrium create a microenvironment that supplies the nutrients and substances necessary for embryos at each stage. During this process, the development of the embryo is finely regulated by signaling molecules, such as growth factors and cytokines secreted from the epithelial cells of the fallopian tube and uterine endometrium. The development of embryo culture media has continued since the first successful human birth through IVF in 1978. However, there are still limitations to mimicking a microenvironment similar to the reproductive organs of women suitable for embryo development in vitro. Efforts have been made to overcome the harsh in vitro culture environment and obtain high-quality embryos by adding various supplements, such as antioxidants and growth factors, to the embryo culture medium. Recently, there has been an increase in the number of studies on the effect of supplementation in different clinical situations such as old age, recurrent implantation failure (RIF), and unexplained infertility; in addition, anticipation of the potential benefits from individuation is rising. This article reviews the effects of representative supplements in culture media on embryo development.

Embryo Culture Medium Has No Impact on Mosaicism Rates: a Sibling Oocyte Study

Human embryos cultured in vitro can contain two or more cytogenetically distinct cell lineages known as "chromosomal mosaicism". Since mosaicism is produced by mitotic errors after fertilization occurs, culture conditions might contribute to mosaicism origins. Many studies demonstrated that euploidy rates are not affected by culture media; however, whether oocytes cultured under continuous culture media (CCM) or sequential culture media (SCM) has a higher risk of mosaicism occurring remains unsolved. Therefore, this study aims to determine whether mosaicism rates differ when sibling oocytes are cultured in CCM or SCM. A single center observational study was performed including 6072 sibling oocytes. Mature oocytes (MII) were inseminated and cultured in CCM (n = 3,194) or SCM (n = 2,359) until blastocyst stage for trophectoderm (TE) biopsy on day (D) 5, D6, or D7 for preimplantation genetic testing analysis with a semi-automated next-generation sequencing. Mosaicism was classified as low (30-50%) or high (50-80%) based on the percentage of abnormal cells constitution detected in TE samples. As a result, 426 women with a mean age of 34.7 ± 6.4 years were included in the study. Fertilization rates were comparable between CCM and SCM (74.0% vs 72.0%, p = 0.091). Although total blastulation rate and usable blastocyst rate (biopsied blastocysts) were significantly higher in CCM than SCM (75.3 % vs. 70.3%, p < 0.001 and 58.0% vs. 54.5%, p = 0.026), euploidy rates did not differ significantly (45.2% vs. 45.7%, p = 0.810, respectively). Mosaicism rate was not significantly different for blastocysts cultured in CCM or SCM (4.7% vs. 5.1%, p = 0.650), neither the proportion of low or high mosaic rates (3.7% vs. 4.4%, p = 0.353 and 1.0% vs. 0.7%, p = 0.355, respectively). Hence, it was concluded that CCM or SCM does not have an impact on mosaicism rate of embryos cultured until the blastocyst stage.

Culture conditions in the IVF laboratory: state of the ART and possible new directions

In the last four decades, the assisted reproductive technology (ART) field has witnessed advances, resulting in improving pregnancy rates and diminishing complications, in particular reduced incidence of multiple births. These improvements are secondary to advanced knowledge on embryonic physiology and metabolism, resulting in the ability to design new and improved culture conditions. Indeed, the incubator represents only a surrogate of the oviduct and uterus, and the culture conditions are only imitating the physiological environment of the female reproductive tract. In vivo, the embryo travels through a dynamic and changing environment from the oviduct to the uterus, while in vitro, the embryo is cultured in a static fashion. Importantly, while culture media play a critical role in optimising embryo development, a large host of additional factors are equally important. Additional potential variables, including but not limited to pH, temperature, osmolality, gas concentrations and light exposure need to be carefully controlled to prevent stress and permit optimal implantation potential. This manuscript will provide an overview of how different current culture conditions may affect oocyte and embryo viability with particular focus on human literature.

Factors associated with embryo mosaicism: a systematic review and meta-analysis

PURPOSE

Evaluate which factors are involved in the increased rate of mosaicism in embryos.

METHODS

A systematic review and meta-analysis was performed. After an exhaustive search of the literature, a total of seven papers were included in the analysis. In addition, data collected from IVF cycles performed in our fertility clinic were also analysed. Day of biopsy, embryo quality, maternal and paternal age and seminal quality were the chosen factors to be studied.

RESULTS

The results of the meta-analysis show that neither embryo quality nor seminal quality were related to mosaic embryo rate (OR: 1.09; 95% CI: 0.94-1.28 and OR: 1.10; 95% CI: 0.87-1.37, respectively). A positive association was observed for the variable "biopsy day" with embryos biopsied at day 6 or 7 having the highest rate of mosaicism (OR: 1.06; 95% CI: 1.01-1.11). In opposite to what happens with aneuploidy rate, which increases with maternal age, embryo mosaicism is higher in younger women (<34 years) rather than in older ones (≥34 years) (OR: 0.95; 95% CI: 0.92-0.98). However, for the "paternal age" factor, no association with mosaicism was found (OR: 1.04; 95% CI: 0.90-1.21).

CONCLUSIONS

With the present study, we can conclude that the factors related to the presence of mosaicism in embryos are the embryo biopsy day and maternal age. The rest of the studied factors showed no significant relationship with mosaicism. These results are of great importance as knowing the possible causes leading to mosaicism helps to improve the clinical results of reproductive treatments.

Glucose promoting the early embryonic development by increasing the lipid synthesis at 2-cell stage

The optimization of culture conditions is one of the main strategies to improve the embryo development competence in in vitro fertilization (IVF). Glucose is an important carbon source while also exists in the oviductal fluid in vivo, the effect of glucose in embryo development microenvironment is still unclear. Here we employed the LC-MS to detect and analyze the metabolites in the culture medium of different cleavage stages including 2-Cell, 4-Cell and 8-Cell mouse embryos, respectively. The effects of the external glucose were estimated by measuring the development rate at different glucose concentrations from 0 to 5 mmol/L, and the gene expression changes were detected to explore the potential mechanism after the addition of glucose in the media. Our results indicated the 2-Cell and 8-Cell stages had defined characteristic metabolites, while 4-Cell stage was the transition state. Global and contiguous metabolic characteristics showed the glycometabolism play a critical role at each early cleavage stages during the embryo development. The 8-Cell rates demonstrated the addition of glucose in culture media significantly improve the embryo competence, the highest rate was 87.33% using 3 mmol/L glucose in media, in contrast only 9.95% using the media without glucose. Meanwhile, the blocked embryos were mainly enriched at 2-Cell stage. Further transcriptome study found 3 mmol/L glucose in media remarkably upregulated the gene expression of lipid biosynthesis at 2-Cell stage, the increased lipid was confirmed by nile red staining. These data indicated the glucose may promote the development competence through increasing the lipid biosynthesis to overcoming the 2-Cell block. Our findings were helpful for the further optimization of IVF culture media, as well as the estimation of embryo quality using metabolites in the culture media.

PMCA1 depletion in mouse eggs amplifies calcium signaling and impacts offspring growth†

Egg activation in mammals is triggered by oscillations in egg intracellular calcium (Ca2+) level. Ca2+ oscillation patterns can be modified in vitro by changing the ionic composition of culture media or in vivo by conditions affecting mitochondrial function, such as obesity and inflammation. In mice, disruption of Ca2+ oscillations in vitro impacts embryo development and offspring growth. Here we tested the hypothesis that, even without in vitro manipulation, abnormal Ca2+ signaling following fertilization impacts offspring growth. Plasma membrane Ca2+ ATPases (PMCA) extrude cytosolic Ca2+ to restore Ca2+ homeostasis. To disrupt Ca2+ signaling in vivo, we conditionally deleted PMCA1 (cKO) in oocytes. As anticipated, in vitro fertilized cKO eggs had increased Ca2+ exposure relative to controls. To assess the impact on offspring growth, cKO females were mated to wild type males to generate pups that had high Ca2+ exposure at fertilization. Because these offspring would be heterozygous, we also tested the impact of global PMCA1 heterozygosity on offspring growth. Control heterozygous pups that had normal Ca2+ at fertilization were generated by mating wild type females to heterozygous males; these control offspring weighed significantly less than their wild type siblings. However, heterozygous offspring from cKO eggs (and high Ca2+ exposure) were larger than heterozygous controls at 12 week-of-age and males had altered body composition. Our results show that global PMCA1 haploinsufficiency impacts growth and support that abnormal Ca2+ signaling after fertilization in vivo has a long-term impact on offspring weight. These findings are relevant for environmental and medical conditions affecting Ca2+ handling and for design of culture conditions and procedures for domestic animal and human assisted reproduction.

At age 9, the methylome of assisted reproductive technology children that underwent embryo culture in different media is not significantly different on a genome-wide scale

STUDY QUESTION

Can we detect DNA methylation differences between ART children that underwent embryo culture in different media?

SUMMARY ANSWER

We identified no significant differences in site-specific or regional DNA methylation between the different culture medium groups.

WHAT IS KNOWN ALREADY

Embryo culture in G3 or K-SICM medium leads to differences in embryonic, neonatal and childhood outcomes, including growth and weight. The methylome may mediate this association as the period of in vitro culture of ART treatments coincides with epigenetic reprogramming.

STUDY DESIGN, SIZE, DURATION

This study was conducted as a follow-up to a previous culture medium comparison study in which couples were pseudo-randomized to embryo culture in G3 or K-SICM medium. Of the resultant singletons, 120 (n = 65 G3, n = 55 K-SICM), were recruited at age 9.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The ART children provided a saliva sample from which the methylome was analysed using the Infinium MethylationEPIC array. After quality and context filtering, 106 (n = 57 G3, n = 49 K-SICM) samples and 659 708 sites were retained for the analyses. Differential methylation analyses were conducted using mixed effects linear models corrected for age, sex, sample plate and cell composition. These were applied to all cytosine-guanine dinucleotide (CpG) sites, various genomic regions (genes, promoters, CpG Islands (CGIs)) and as a targeted analysis of imprinted genes and birth weight-associated CpG sites. Differential variance was assessed using the improved epigenetic variable outliers for risk prediction analysis (iEVORA) algorithm and methylation outliers were identified using a previously defined threshold (upper or lower quartile plus or minus three times the interquartile range, respectively).

MAIN RESULTS AND THE ROLE OF CHANCE

After correcting for multiple testing, we did not identify any significantly differentially methylated CpG sites, genes, promoters or CGIs between G3 and K-SICM children despite a lenient corrected P-value threshold of 0.1. Targeted analyses of (sites within) imprinted genes and birth weight-associated sites also did not identify any significant differences. The number of DNA methylation outliers per sample was comparable between the culture medium groups. iEVORA identified 101 differentially variable CpG sites of which 94 were more variable in the G3 group.

LARGE SCALE DATA

Gene Expression Omnibus (GEO) GSE196432.

LIMITATIONS, REASONS FOR CAUTION

To detect significant methylation differences with a magnitude of <10% between the groups many more participants would be necessary; however, the clinical relevance of such small differences is unclear.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study are reassuring, suggesting that if there is an effect of the culture medium on DNA methylation (and methylation-mediated diseases risk), it does not differ between the two media investigated here. The findings concur with other methylome studies of ART neonates and children that underwent embryo culture in different media, which also found no significant methylome differences.

STUDY FUNDING/COMPETING INTEREST(S)

Study funded by March of Dimes (6-FY13-153), EVA (Erfelijkheid Voortplanting & Aanleg) specialty programme (grant no. KP111513) of Maastricht University Medical Centre (MUMC+) and the Horizon 2020 innovation (ERIN) (grant no. EU952516) of the European Commission. The authors do not report any conflicts of interest relevant to this study.

TRIAL REGISTRATION NUMBER

Dutch Trial register-NL4083.

Methylome-wide analysis of IVF neonates that underwent embryo culture in different media revealed no significant differences

A growing number of children born are conceived through in vitro fertilisation (IVF), which has been linked to an increased risk of adverse perinatal outcomes, as well as altered growth profiles and cardiometabolic differences in the resultant individuals. Some of these outcomes have also been shown to be influenced by the use of different IVF culture media and this effect is hypothesised to be mediated epigenetically, e.g. through the methylome. As such, we profiled the umbilical cord blood methylome of IVF neonates that underwent preimplantation embryo development in two different IVF culture media (G5 or HTF), using the Infinium Human Methylation EPIC BeadChip. We found no significant methylation differences between the two groups in terms of: (i) systematic differences at CpG sites or regions, (ii) imprinted sites/genes or birth weight-associated sites, (iii) stochastic differences presenting as DNA methylation outliers or differentially variable sites, and (iv) epigenetic gestational age acceleration.

The Impact of Culture Medium on Morphokinetics of Cleavage Stage Embryos: An Observational Study

To study the impact of culture media on preimplantation morphokinetics used for predicting clinical outcomes. All IVF and ICSI cycles performed between 2012 and 2017 with time-lapse information available were included. In November 2014, culture medium was changed from Vitrolife G-1 PLUS to SAGE 1-Step. Each embryo was retrospectively assigned a morphokinetic-based KIDScore for prediction of implantation. Clinical outcomes were retrieved from medical records. Linear mixed models were used to study differences in morphokinetic parameters, a proportional odds model for KIDScore ranking and logistic regression for differences in clinical outcomes. All analyses were adjusted for patient and treatment characteristics. In 253 (63.1%) cycles, embryos (n = 671) were cultured in Vitrolife, and in 148 (36.9%) cycles, embryos (n = 517) were cultured in SAGE. All cleavage divisions occurred earlier for SAGE embryos than for Vitrolife embryos (2-cell: -2.28 (95%CI: -3.66, -0.89), 3-cell: -2.34 (95%CI: -4.00, -0.64), 4-cell: -2.41 (95%CI: -4.11, -0.71), 5-cell: -2.54 (95%CI: -4.90, -0.18), 6-cell: -3.58 (95%CI: -6.08, -1.08), 7-cell: -5.62 (95%CI: -8.80, -2.45) and 8-cell: -5.32 (95%CI: -9.21, -1.42) hours, respectively). Significantly more embryos cultured in SAGE classified for the highest KIDScore compared to embryos cultured in Vitrolife (p < 0.001). No differences were observed in clinical outcomes. Our results demonstrate an impact of culture medium on preimplantation embryo developmental kinetics, which affects classification within the KIDScore algorithm, while pregnancy outcomes were comparable between the groups. This study underscores the need to include the type of culture medium in the development of morphokinetic-based embryo selection tools.

Culture medium is associated with the risks of placenta previa and macrosomia in pregnancies after in vitro fertilization

PURPOSE

The culture medium plays an important role in embryonic development and subsequent pregnancy outcomes of in vitro fertilization (IVF) cycles. The sequential culture media of Vitrolife and Cook are the two most commonly used reagents in China. This study aimed to assess their effects on IVF success rates, obstetric outcomes and neonatal outcomes.

METHODS

This was a retrospective cohort study on 6352 patients undergoing first IVF attempts between January 2018 and December 2019, resulting in 3153 clinical pregnancies, 2646 live births, and 2668 babies. Patients were grouped according to the culture media they used. There were 4680 patients in the Vitrolife group and 1672 patients in the Cook group. The primary outcome measures were maternal and neonatal outcomes. ANOVA and Chi-square tests were used for statistical comparison, and multivariate logistic regression and multivariate general linear model were used to adjust for potential confounders.

RESULTS

The rates of live birth, clinical pregnancy, monozygotic twins, miscarriage, and ectopic pregnancy were all comparable between the groups of Vitrolife and Cook. The incidence of placenta previa was higher in the Vitrolife group [4.86 vs. 3.09%, adjusted odds ratio = 2.048 (1.146-3.657)]. The incidence of macrosomia was higher in the Cook group [7.51 vs. 5.39%, adjusted odds ratio = 1.445 (1.010-2.069)].

CONCLUSION

The culture media of Vitrolife and Cook are comparably effective in IVF success. Vitrolife is associated with a higher risk of placenta previa, while Cook is associated with a higher risk of macrosomia.

Interplay of Oxidants and Antioxidants in Mammalian Embryo Culture System

One principal purpose of assisted reproductive technology (ART) is to produce viable and good quality embryos. However, a variety of environmental factors may induce epigenetic changes in the embryo. Moreover, laboratory conditions including the culture media may also affect embryo development. Therefore, media change is an important factor in maintaining proper oxidant/antioxidant balance during embryo culture. Alterations in the oxidant/antioxidant balance are related to various cellular responses such as an increase in the level of reactive oxygen species (ROS) and consequent lipid peroxidation (LPO), DNA damage, and apoptosis. The current study focuses on the role of external factors on embryo culture and the ability of antioxidants to enhance in vitro fertilization (IVF) outcomes. Indeed, an optimization of media culture by the addition of enzymatic and nonenzymatic antioxidants in animal models and human embryos in ART has been updated in this study, with an emphasis on comparing the available results and their possible reasons.

Comparison of two culture media on morphokinetics and ploidy status of sibling embryos

To investigate the effects of culture media with different lactate concentrations on early embryonic development, data collected from our patients undergoing preimplantation genetic testing (PGT) were assessed using the EmbryoScope™ time-lapse culturing system. After intracytoplasmic sperm injection (ICSI), sibling oocytes were cultured in the same EmbryoScope (Vitrolife) slides including two different commercially available media. The patients with fewer than five mature oocytes were not included in the analyses. All embryos were hatched on day 3, and trophectoderm biopsies (n = 212) were performed accordingly. PGT for aneuploidy (PGT-A) on biopsied materials was carried out using next generation sequencing. Morphokinetic parameters, fertilization, irregular division, degeneration, blastulation, euploidy, and pregnancy rates of embryos cultured in LifeGlobal Global Total medium (LGGT) and Continuous Single Culture-NX Complete medium (CSCM-NXC) were compared. There were no differences observed in time to pronuclear fade, or in time spent as 2-cell (cc2) and 3-cell (s2), to 4-cell, 5-cell, morula and blastocyst stages (P > 0.05). Embryos reached the 2-cell (t2) and 3-cell (t3) stages significantly faster in LGGT (P < 0.05), whereas embryos grown in CSCM-NXC with lower lactate reached starting blastulation significantly sooner (P = 0.026). However, there were no statistical differences observed in fertilization, blastulation, degeneration, irregular division euploidy, and pregnancy rates between the two groups (P > 0.05). Even though pregnancy and fertilization rates did not indicate statistical differences, results are significant to provide better insight on potential roles of lactate in embryo development. These finding will advance the fundamental knowledge of human embryo development and assisted reproductive technologies.

Aneuploidy rates and morphokinetic parameters of embryos cultured in distinct culture media: a sibling oocyte study

STUDY QUESTION

Do embryos from sibling oocytes assigned to distinct single-step media culture systems demonstrate differences in early embryo development, morphokinectics or aneuploidy rates?

SUMMARY ANSWER

Embryo quality, morphokinetic parameters and aneuploidy rates from trophectoderm biopsy were similar between sibling embryos cultured in distinct media systems from the time of gamete isolation.

WHAT IS KNOWN ALREADY

Studies on the effect of commercially available embryo culture media systems have demonstrated inconsistent impact on human embryonic development, morphokinetics, aneuploidy rates and clinical outcomes. In addition, these studies have been primarily randomized at the level of the embryo or the patient to culture media.

STUDY DESIGN, SIZE, DURATION

Prospective sibling oocyte cohort derived from 200 subjects undergoing IVF at a tertiary academic medical center between February 2018 and November 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sibling oocytes were allocated to Global® or SAGE® media system based upon laterality of ovary from which they were retrieved. All embryos were cultured in a time-lapse incubator. Blastocysts underwent trophectoderm biopsy for preimplantation genetic testing for aneuploidy using next-generation sequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

One hundred twenty-seven subjects (n = 127) had paired blastocysts for biopsy in each culture media system. There was no difference in top quality blastocyst formation (47.1 ± 31.0 vs 48.1 ± 27.2%; P = 0.87) nor aneuploidy rate (62.3 ± 34.0 vs 56.1 ± 34.4%; P = 0.07) for sibling embryos cultured in Global versus SAGE media system. Embryo morphokinetic parameters including time to each cell division from two cells (t2) to eight cells (t8), time to morula stage (tM), time to blastocele formation (tSB), time to fully formed blastocyst (tB) and time to expansion of the blastocyst (tEB) were similar between paired blastocysts from each culture media system.

LIMITATIONS, REASONS FOR CAUTION

Pregnancy outcomes and offspring health data were not available for analysis.

WIDER IMPLICATIONS OF THE FINDINGS

Commercially available culture media may not have a differential impact on embryo development and blastocyst aneuploidy rate when patient and stimulation-related factors are held constant.

STUDY FUNDING/COMPETING INTEREST(S)

There was no external funding for this study. C.H. is owner of a consultancy company, IVF Professionals, Chief Scientific Officer at Apricity, Executive Director at TMRW and co-owner and shareholder of Aria Fertility. She has received speaker fees, consulting fees and travel support from Cooper Surgical and Vitrolife. J.B. is an employee and shareholder of vitrolife.

TRIAL REGISTRATION NUMBER

N/A.

Embryo culture media differentially alter DNA methylating enzymes and global DNA methylation in embryos and oocytes

The effects of culture media on DNA methylation process, which is one of the epigenetic mechanisms, have not been clearly elucidated although it is known that in vitro culture conditions alter epigenetic mechanisms. This study was designed to address the question: does embryo culture media approach, sequential or single step, differentially affect DNA methylating enzymes and global DNA methylation. Mouse zygotes were cultured either in single step or sequential culture media until the blastocyst stage and in vivo developed blastocyst were utilized as control. Similarly, GV stage oocytes were in vitro matured either in single step or first step of sequential culture media. In vivo matured MII oocytes were used as control. The expression levels and cellular localization of Dnmt1 and 3a enzymes were analyzed by immunofluorescence and western blot analysis while global DNA methylation was evaluated by immunofluorescence. We found that signal intensities of Dnmt1 and Dnmt3a enzymes were significantly low in embryos or oocytes cultured in sequential media compared to single step media and control, which were comparable amongst themself. Similarly, global DNA methylation level in single step media and control groups was comparable but both was higher than the sequential media. This study demonstrated that composition of culture media may differentially affect DNA methylation levels in mouse embryos and oocytes. Since abnormal DNA methylation may cause aberrant oocyte or embryo development, we think that further studies are needed to test human embryos and oocyte, and to explain molecular mechanisms.

Occurrence of Calcium Oscillations in Human Spermatozoa Is Based on Spatial Signaling Enzymes Distribution

In human spermatozoa, calcium dynamics control most of fertilization events. Progesterone, present in the female reproductive system, can trigger several types of calcium responses, such as low-frequency oscillations. Here we aimed to identify the mechanisms of progesterone-induced calcium signaling in human spermatozoa. Progesterone-induced activation of fluorophore-loaded spermatozoa was studied by fluorescent microscopy. Two computational models were developed to describe the spermatozoa calcium responses: a homogeneous one based on a system of ordinary differential equations and a three-dimensional one with added space dimensions and diffusion for the cytosolic species. In response to progesterone, three types of calcium responses were observed in human spermatozoa: a single transient rise of calcium concentration in cytosol, a steady elevation, or low-frequency oscillations. The homogenous model provided qualitative description of the oscillatory and the single spike responses, while the three-dimensional model captured the calcium peak shape and the frequency of calcium oscillations. The model analysis demonstrated that an increase in the calcium diffusion coefficient resulted in the disappearance of the calcium oscillations. Additionally, in silico analysis suggested that the spatial distribution of calcium signaling enzymes governs the appearance of calcium oscillations in progesterone-activated human spermatozoa.

The influence of the type of embryo culture media on the outcome of IVF/ICSI cycles

OBJECTIVE

Embryo culture media are important factors in IVF, which can significantly influence clinical outcome of IVF/ICSI cycles. Despite this, it is still not completely clear which formulation is most optimal and whether sequential or continuous media should be favored.

MATERIALS AND METHODS

This study retrospectively analyzed the outcome of IVF/ICSI cycles with regard to different types of culture media used to culture embryos, namely sequential and two types of single step continuous embryo culture media.

RESULTS

If the data were combined for both types of single step continuous embryo culture media the only significant difference we observed was the proportion of poor quality embryos on day 3, which was significantly higher (16.9% vs. 22.5%; P = 0.017) in the sequential media. The pregnancy (55.1% vs. 40.5%; P = 0.113) and live birth rates (42.9% vs. 33.8%; P = 0.308) were lower in continuous media, although the difference was not statistically significant. Furthermore, the blastocyst rate (sequential vs. continuous; 47.4% vs. 47.3%; P = 1), and birthweight (3280 ± 630g vs. 3272 ± 575g; P = 0.96) did not significantly differ regardless of the medium used to culture embryos. Additional comparison of each type of continuous medium to sequential media revealed that the difference in the quality of cleavage stage embryos for combined data of both continuous culture media may be derived from the group of cycles were SAGE 1-Step was used to culture embryos.

CONCLUSION

These results therefore indicate that continuous media can be equivalent to sequential media and could help lower the workload in busy IVF labs without impairing the clinical results. Although, caution is needed because this study is limited by its retrospective design. To confirm the results, especially in terms of live birth rates and perinatal outcome, a prospective study is needed with a higher number of included couples.

Clinical efficacy of hyaluronate-containing embryo transfer medium in IVF/ICSI treatment cycles: a cohort study

STUDY QUESTION

Does the duration of embryo exposure to hyaluronic acid (HA) enriched medium improve the rate of live birth events (LBEs)?

SUMMARY ANSWER

The use of embryo transfer (ET) medium rich in HA improves LBE (a singleton or twin live birth) regardless of the duration of exposure evaluated in this study, but does not alter gestation or birthweight (BW).

WHAT IS KNOWN ALREADY

HA-enriched medium is routinely used for ET in ART to facilitate implantation, despite inconclusive evidence on safety and efficacy.

STUDY DESIGN SIZE DURATION

A cohort study was performed evaluating clinical treatment outcomes before and after HA-enriched ET medium was introduced into routine clinical practice. In total, 3391 fresh ET procedures were performed using low HA and HA-rich medium in women undergoing publicly funded IVF/ICSI treatment cycles between May 2011 and April 2015 were included in this cohort study.

PARTICIPANTS/MATERIALS SETTING METHODS

A total of 1018 ET performed using low HA medium were compared with 1198, and 1175 ET following exposure to HA-rich medium for 2-4 h (long HA exposure) or for 10-30 min (short HA exposure), respectively. A multiple logistic regression analysis was used to compare clinical outcomes including BW, gestational age and sex ratios between groups, whilst adjusting for patient age, previous attempt, incubator type and the number of embryos transferred.

MAIN RESULTS AND THE ROLE OF CHANCE

The use of HA-rich medium for ET was positively and significantly associated with improved clinical pregnancy rate and LBE, for both exposure durations: long HA (odds ratio (OR) = 1.21, 95% CI: 0.99-1.48), short HA (OR = 1.32, 95% CI: 1.02-1.72) and pooled OR = 1.26, 95% CI: 1.03-1.54, relative to the use of low HA medium. A comparative analysis of the risks of early pregnancy loss following long HA exposure (OR = 0.76, 95% CI: 0.54-1.06), short HA exposure (OR = 0.84, 95% CI: 0.54-1.30) and late miscarriage (OR = 0.88, 95% CI: 0.51-1.53) (OR = 1.41, 95% CI 0.72-2.77), were lower and not statistically significant. Similarly, ordinary regression analysis of the differences in BW at both HA exposures; pooled OR = -0.9 (-117.1 to 115.3), and adjusted BW between both HA cohorts; pooled OR = -13.8 (-106.1 to 78.6) did not show any differences. However, a difference in gestational age (pooled OR -0.3 (-3.4 to 2.9)) and sex ratio (pooled OR 1.43 (0.95-2.15)) were observed but these were not statistically significant relative to low HA medium.

LIMITATIONS REASONS FOR CAUTION

The strength of a randomized treatment allocation was not available in this evaluation study, therefore effects of unmeasured or unknown confounding variables cannot be ruled out.

WIDER IMPLICATIONS OF THE FINDINGS

The result of this large cohort study strengthens the case for using HA-rich medium routinely at transfer, while adding the important clinical information that duration of exposure may not be critical. The composition and effects of commercial IVF culture media on success rate and safety remains a major controversy despite increasing calls for transparency and evidence-based practice in ART. Nonetheless, the lack of differences in BW and gestational age observed in this study were reassuring. However, an appraisal of clinical outcomes and appropriate research investigations are required for the continuous evaluation of efficacy and safety of HA.

STUDY FUNDING/COMPETING INTERESTS

T.A. is funded by a Clinical Doctoral Research Fellowship (CDRF) grant (reference: ICA-CDRF-2015-01-068) from the National Institute for Health Research (NIHR). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health. The authors declare no conflict of interest.

Ex Vivo Culture for Preimplantation Mouse Embryo to Analyze Pluripotency

A couple of days after fertilization of a mouse oocyte by a sperm, two sequential cell differentiation events segregate pluripotent cells that can be identified by the presence of specific markers. Early mammalian embryos are relatively easy to recover as they are not yet implanted in the uterus matrix. Several decades of experimentation have enabled to find appropriate media to culture them, and therefore provide an excellent way to test different experimental setups such as the use of signaling inhibitors. We provide here a commonly used protocol to culture preimplantation embryos as well as a method to detect pluripotent cells in blastocysts.

Developmental kinetics and viability of bovine embryos produced in vitro with sex-sorted semen

The present study aimed to elucidate the developmental kinetics, growth potential, and viability of bovine embryos produced in vitro with sexed semen. Bovine oocytes were fertilized in vitro using unsorted and X-sorted semen from the same Holstein bulls, and the kinetics of in vitro development were continuously monitored for 10 d through time-lapse cinematography. The blastocyst formation rate was lower in the X-sorted group than in the unsorted group (P < 0.01), whereas the normal fertilization rate did not differ between groups. Morphokinetic evaluation revealed that the incidence of blastomere fusion during the first cleavage division, termed reverse cleavage, was higher in the X-sorted group (P < 0.01). Furthermore, embryos produced with X-sorted semen showed slower growth throughout the developmental period than embryos produced with unsorted semen (P < 0.01). The cell number of the trophectoderm and inner cell mass of blastocysts was reduced in the X-sorted group (P < 0.01). In embryos that developed to the blastocyst stage, the hatchability (P < 0.05), chromosomal normality (P < 0.01), and survivability after the conventional frozen-thawing process (P < 0.05) were reduced in the X-sorted group compared to that in the unsorted group, indicating a compromised viability of embryos derived from X-sorted semen. Taken together, the first cleavage dysmorphism, delayed embryo growth, and impaired viability of embryos developed to the blastocyst stage may explain the mechanism of reduced fertility in embryos derived from sexed semen. The kinetic evaluation of early embryo development and de-selection of embryos presenting the aberrant first cleavage would be valid for clinical application to produce sexed embryos with high implantation potential.

The utility of nuclear magnetic resonance spectroscopy in assisted reproduction

Infertility affects approximately 15-20% of individuals of reproductive age worldwide. Over the last 40 years, assisted reproductive technology (ART) has helped millions of childless couples. However, ART is limited by a low success rate and risk of multiple gestations. Devising methods for selecting the best gamete or embryo that increases the ART success rate and prevention of multiple gestation has become one of the key goals in ART today. Special emphasis has been placed on the development of non-invasive approaches, which do not require perturbing the embryonic cells, as the current morphology-based embryo selection approach has shortcomings in predicting the implantation potential of embryos. An observed association between embryo metabolism and viability has prompted researchers to develop metabolomics-based biomarkers. Nuclear magnetic resonance (NMR) spectroscopy provides a non-invasive approach for the metabolic profiling of tissues, gametes and embryos, with the key advantage of having a minimal sample preparation procedure. Using NMR spectroscopy, biologically important molecules can be identified and quantified in intact cells, extracts or secretomes. This, in turn, helps to map out the active metabolic pathways in a system. The present review covers the contribution of NMR spectroscopy in assisted reproduction at various stages of the process.

Prevalence, types and possible factors influencing mosaicism in IVF blastocysts: results from a single setting

RESEARCH QUESTION

Are intrinsic or extrinsic factors associated with embryo mosaicism prevalence in IVF cycles?

DESIGN

Retrospective cohort study of preimplantation genetic testing for aneuploidy (PGT-A) cycles carried out at a university-affiliated IVF clinic between October 2017 and October 2019. Trophectoderm biopsies were analysed by next generation sequencing. Mosaicism prevalence, type of anomaly and the chromosomes involved were analysed. Intrinsic and extrinsic factors potentially inducing mosaicism were studied: maternal and paternal age, antral follicle count, cumulus-oocyte complexes retrieved, female body mass index, PGT-A indication, sperm concentration, total dosage of gonadotrophins, embryo quality and day of blastocyst formation, single-step commercial media used and biopsy operator.

RESULTS

Overall prevalence of mosaicism in our PGT-A setting was 13.9%. In segmental mosaicism, larger chromosomes tended to be more affected, which was not observed in whole-chromosome mosaicism. Additionally, segmental mosaicism was mostly observed in monosomy (69.6%; P < 0.01) compared with whole-chromosome mosaicism (49.7% monosomies versus 50.3% trisomies; P = 0.83). Although a high inter-patient variability was observed, only paternal age showed a positive association with mosaicism (adjusted OR 1.26, 95% CI 1.02 to 1.54) among the analysed variables.

CONCLUSIONS

Our results suggest remarkable differences in the mechanisms generating segmental and whole-chromosome mosaicism, indicating that they may deserve different consideration when studying them and when prioritizing them for transfer. Male factor seems to be associated with mosaicism and may be worthy of specific assessment in future studies.

Elimination of stress factors by continuous embryo culture and its influence on in vitro fertilization outcomes

Recently, infertility has become one of the most important endemic conditions, affecting approximately 15-20 % of couples worldwide. Among others, the careerist lifestyle, the increasing maternal age and the parallel increment in the aneuploidy rate of embryos play a crucial role in this phenomenon. In this study, embryological parameters and pregnancy outcomes were investigated in IVF cycles using either sequential embryo culture or a single step culture system. By sequential media, oocytes/embryos are needlessly exposed to the potentially negative effects of light exposure, temperature decrement and altered oxygen tension. In comparison with sequential media, single step media induced 1.28, 1.21 and 1.21-fold increments in implantation, biochemical pregnancy and clinical pregnancy rates, respectively. Pregnancy outcomes showed strong maternal age-dependency, so the difference between the two investigated culture systems was equalized by the increasing maternal ages (35-44 years) and the supposed incidence of embryo aneuploidy. Nevertheless, the significant enlargements in the outcomes of the younger ages (25-34) induced by the single step cultures suggest that, beside the resultant maternal aneuploidy, aneuploidy (reduced pregnancy rates) may evolve from exposure to the mentioned environmental stress factors.

The composition of human preimplantation embryo culture media and their stability during storage and culture

STUDY QUESTION

What is the composition and stability during storage and culture of fifteen commercially available human preimplantation embryo culture media?

SUMMARY ANSWER

No two culture media had the same composition, and both storage and culture had an effect on the concentrations of multiple components.

WHAT IS KNOWN ALREADY

The choice of embryo culture medium not only affects the success rate of an IVF treatment, but also affects the health of the future child. Exact formulations of embryo culture media are often not disclosed by manufacturers. It is unknown whether the composition of these media changes during storage or culture in the IVF laboratory. Without details on the exact concentrations, it is not possible to determine which components might be responsible for the differences in IVF success rates and health of the resulting children.

STUDY DESIGN, SIZE, DURATION

Between October 2014 and October 2015, all complete human preimplantation embryo culture media, i.e. ready to use for IVF, that were commercially available at that time, were included (n = 15). Osmolality and the concentration of thirty seven components including basic elements, metabolites, immunoglobulins, albumin, proteins and 21 amino acids were tested immediately upon arrival into the IVF laboratory, after three days of culture without embryos (sham culture) starting from the day of arrival, just before the expiry date, and after three days of sham culture just before the expiry date.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ions, glucose, immunoglobulins, albumin and the total amount of proteins were quantified using a combination of ion selective electrodes and photometric analysis modules, and lactate, pyruvate and 21 amino acids were analysed by ultra performance liquid chromatography mass spectrometry. Osmolality was analysed by an advanced micro-osmometer. Statistical analysis was done using multivariate general linear models.

MAIN RESULTS AND THE ROLE OF CHANCE

The composition varied between media, no two media had the same concentration of components. Storage led to significant changes in 17 of the 37 analyzed components (magnesium, chloride, phosphate, albumin, total amount of proteins, tyrosine, tryptophan, alanine, methionine, glycine, leucine, glutamine, asparagine, arginine, serine, proline, and threonine). Storage affected the osmolality in 3 of the 15 media, but for all media combined this effect was not significant (p = 0.08). Sham culture of the analyzed media had a significant effect on the concentrations of 13 of the 37 analyzed components (calcium, phosphate, albumin, total amount of proteins, tyrosine, alanine, methionine, glycine, leucine, asparagine, arginine, proline, and histidine). Sham culture significantly affected the osmolality of the analysed culture media. Two media contained 50% D-lactate, which a toxic dead-end metabolite. In a secondary analysis we detected human liver enzymes in more than half of the complete culture media.

LIMITATIONS, REASONS FOR CAUTION

The analyzed culture media could contain components that are not among the 37 components that were analyzed in this study. The clinical relevance of the varying concentrations is yet to be determined.

WIDER IMPLICATIONS OF THE FINDINGS

The presence of D-lactate could be avoided and the finding of human liver enzymes was surprising. The wide variation between culture media shows that the optimal composition is still unknown. This warrants further research as the importance of embryo culture media on the efficacy and safety in IVF is evident. Companies are urged to fully disclose the composition of their culture media, and provide clinical evidence supporting the composition or future changes thereof.

STUDY FUNDING/COMPETING INTEREST(S)

None.

Altered cytoplasmic maturation in rescued in vitro matured oocytes

STUDY QUESTION

Do culture conditions affect cytoplasmic maturation in denuded immature non-GV oocytes?

SUMMARY ANSWER

The maturation rate of denuded non-GV oocytes is not affected by culture media, but in vitro maturation seems to alter the mitochondrial membrane potential, endoplasmic reticulum (ER) and actin cytoskeleton compared with in vivo maturation.

WHAT IS KNOWN ALREADY

In vitro maturation of denuded immature non-GV oocytes benefits cycles with poor in vivo MII oocyte collection, but maturation levels of non-GV oocytes are only scored by polar body extrusion. Since oocyte maturation involves nuclear as well as cytoplasmic maturation for full meiotic competence, further knowledge is needed about cytoplasmic maturation in in vitro culture.

STUDY DESIGN, SIZE, DURATION

This basic research study was carried out between January 2017 and September 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 339 denuded immature non-GV oocytes were cultured in SAGE 1-Step (177) or G-2 PLUS (162) for 6-8 h after retrieval, and 72 in vivo matured MII oocytes were used as controls. Cultured immature non-GV oocytes were scored for polar body extrusion and analysed for mitochondrial membrane potential (ΔΨm), ER clusters, cortical granules number and distribution, spindle morphology and actin cytoskeleton organization. The obtained parameter values were compared to in vivo matured MII oocyte parameter values.

MAIN RESULTS AND THE ROLE OF CHANCE

The maturation rates of oocytes cultured in G-2 PLUS and SAGE 1-Step were similar (65% vs 64.2%; P = 0.91). The differences observed in cortical granule density were not statistically significant. Also spindle morphometric parameters were mostly similar between in vitro and in vivo matured MII oocytes. However, the number of ER clusters, the ΔΨm and the cortical actin thickness showed significant differences between in vivo MII oocytes and denuded immature non-GV oocytes cultured in vitro until meiosis completion.

LIMITATIONS, REASONS FOR CAUTION

Frozen-thawed oocytes together with fresh oocytes were used as controls. Due to technical limitations (fixation method and fluorochrome overlap), only one or two parameters could be studied per oocyte. Thus, a global view of the maturation status for each individual oocyte could not be obtained.

WIDER IMPLICATIONS OF THE FINDINGS

Characterization of in vitro matured oocytes at the cellular level will help us to understand the differences observed in the clinical outcomes reported with rescue IVM compared to in vivo MII oocytes and to improve the culture methods applied.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by intramural funding of Clinica Eugin and by the Torres Quevedo Program to A.F.-V. from the Spanish Ministry of Economy and Competitiveness. No competing interests are declared.

Differences in blastomere totipotency in 2-cell mouse embryos are a maternal trait mediated by asymmetric mRNA distribution

It is widely held that the first two blastomeres of mammalian embryos are equally totipotent and that this totipotency belongs to the group of regulative properties. However, this interpretation neglects an important aspect: evidence only came from successful monozygotic twins which can speak only for those pairs of half-embryos that are able to regulate in the first place. Are the frequently occurring incomplete pairs simply an artefact, or do they represent a real difference, be it in the imperfect blastomere's ability to regulate growth or in the distribution of any compound X that constrains regulation? Using the model system of mouse embryos bisected at the 2-cell stage after fertilization, we present evidence that the interblastomere differences evade regulation by external factors and are already latent in oocytes. Specifically, an interblastomere imbalance of epiblast production persists under the most diverse culture conditions and applies to the same extent in parthenogenetic counterparts. As a result, cases in which twin blastocysts continued to develop in only one member account for 65 and 57% of zygotic and parthenogenetic pairs, respectively. The interblastomere imbalance is related to the subcellular distribution of gene products, as documented for the epiblast-related gene Cops3, using mRNA FISH in super-resolution mode confocal microscopy. Blastomere patterns of Cops3 mRNA distribution are α-amanitin-resistant. Thus, the imbalance originates not from de novo transcription, but from influences which are effective before fertilisation. These data expose previously unrecognized limits of regulative capacities of 2-cell stage blastomeres and point to aspects of cytoplasmic organization of the mouse oocyte that segregate unequally to blastomeres during cleavage.

A novel culture medium with reduced nutrient concentrations supports the development and viability of mouse embryos

Further refinement of culture media is needed to improve the quality of embryos generated in vitro. Previous results from our laboratory demonstrated that uptake of nutrients by the embryo is significantly less than what is supplied in traditional culture media. Our objective was to determine the impact of reduced nutrient concentrations in culture medium on mouse embryo development, metabolism, and quality as a possible platform for next generation medium formulation. Concentrations of carbohydrates, amino acids, and vitamins could be reduced by 50% with no detrimental effects, but blastocyst development was impaired at 25% of standard nutrient provision (reduced nutrient medium; RN). Addition of pyruvate and L-lactate (+PL) to RN at 50% of standard concentrations restored blastocyst development, hatching, and cell number. In addition, blastocysts produced in RN + PL contained more ICM cells and ATP than blastocysts cultured in our control (100% nutrient) medium; however, metabolic activity was altered. Similarly, embryos produced in the RN medium with elevated (50% control) concentrations of pyruvate and lactate in the first step medium and EAA and Glu in the second step medium were competent to implant and develop into fetuses at a similar rate as embryos produced in the control medium. This novel approach to culture medium formulation could help define the optimal nutrient requirements of embryos in culture and provide a means of shifting metabolic activity towards the utilization of specific metabolic pathways that may be beneficial for embryo viability.

Reactive oxygen species in reproduction: harmful, essential or both?

The process of embryonic development is crucial and radically influences preimplantation embryo competence. It involves oocyte maturation, fertilization, cell division and blastulation and is characterized by different key phases that have major influences on embryo quality. Each stage of the process of preimplantation embryonic development is led by important signalling pathways that include very many regulatory molecules, such as primary and secondary messengers. Many studies, both in vivo and in vitro, have shown the importance of the contribution of reactive oxygen species (ROS) as important second messengers in embryo development. ROS may originate from embryo metabolism and/or oocyte/embryo surroundings, and their effect on embryonic development is highly variable, depending on the needs of the embryo at each stage of development and on their environment (in vivo or under in vitro culture conditions). Other studies have also shown the deleterious effects of ROS in embryo development, when cellular tissue production overwhelms antioxidant production, leading to oxidative stress. This stress is known to be the cause of many cellular alterations, such as protein, lipid, and DNA damage. Considering that the same ROS level can have a deleterious effect on the fertilizing oocyte or embryo at certain stages, and a positive effect at another stage of the development process, further studies need to be carried out to determine the rate of ROS that benefits the embryo and from what rate it starts to be harmful, this measured at each key phase of embryonic development.

The impact of selected embryo culture conditions on ART treatment cycle outcomes: a UK national study

STUDY QUESTION

Are selected embryo culture conditions namely media, oxygen level, and incubator type, associated with IVF live birth rate (LBR) and the health of singleton offspring at birth?

SUMMARY ANSWER

There were statistically significant differences in LBR between the eight culture media systems analysed; however, none of the embryo culture factors showed statistically significant associations with birth weight (BW) in multivariable regression analyses.

WHAT IS KNOWN ALREADY

In clinical ART culture media is the initial environment provided for the growth of human embryos. Pre-implantation development is a critical period of developmental plasticity, which could have long-lasting effects on offspring growth and health. Although some studies have shown an impact of culture medium type on BW, the interaction between culture medium type and associated culture conditions on both treatment success rates (LBR) and offspring BW is largely unexplored. This study aimed to examine these factors in a large multicentre national survey capturing the range of clinical practice.

STUDY DESIGN, SIZE, DURATION

In this cross-sectional study, data from a survey circulated to all UK IVF clinics requesting information regarding culture medium type, incubator type, and oxygen level used in ART between January 2011 and December 2013 were merged with routinely recorded treatment and outcome data held in the Human Fertilisation and Embryology Authority Register up to the end of 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty-six (62%) UK clinics responded to the survey. A total of 75 287 fresh IVF/ICSI cycles were captured, including 18 693 singleton live births. IVF success (live birth, singleton or multiple; LB), singleton gestation and singleton gestation-adjusted BW were analysed using logistic and linear regression models adjusting for patient/treatment characteristics and clinic-specific effects.

MAIN RESULTS AND THE ROLE OF CHANCE

Culture medium type was shown to have some impact on LBR (multivariable logistic regression, (MRL); post-regression Wald test, P < 0.001), but not on BW (MLR; post-regression Wald test, P = 0.215). However, blastocyst culture had the largest observed effect on odds of LBR (odds ratio (OR) = 1.35, CI: 1.29–1.42), increased the risk of pre-term birth even when controlling for oxygen tension (MLR; OR = 1.42, CI: 1.23–1.63), and gestation-adjusted BW (MLR, β = 38.97 g, CI: 19.42–58.53 g) when compared to cleavage-stage embryo culture. We noted a very strong effect of clinic site on both LBR and BW, thus confounding between treatment practices and clinic site may have masked the effect of culture conditions.

LIMITATIONS, REASONS FOR CAUTION

Larger datasets with more inter-centre variation are also needed, with key embryo culture variables comprehensively recorded in national treatment registries.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the largest investigation of laboratory environmental effects in IVF on both LBR and singleton BW. Our findings largely agree with the literature, which has failed to show a consistent advantage of one culture media type over another. However, we noted some association of LBR with medium type, and the duration of embryo exposure to laboratory conditions (blastocyst culture) was associated with both LBR and singleton health at birth. Because of the strong effect of clinic site noted, further randomized controlled trials are needed in order to reliably determine the effect of embryo culture on IVF success rates and the growth and health of subsequent offspring.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the EU FP7 project grant EpiHealthNet (FP7-PEOPLE-2012-ITN -317 146). The authors have no competing interests to declare.

DNA methylation, environmental exposures and early embryo development

The first crucial step in the developmental program occurs during pre-implantation, the time after the oocyte has been fertilized and before the embryo implants in the uterus. This period represents a vulnerable window as the epigenome undergoes dynamic changes in DNA methylation profiles. Alterations in the early embryonic reprogramming wave can impair DNA methylation patterns and induce permanent changes to the developmental program, leading to the onset of adverse health outcomes in offspring. Although there is an increasing body of evidence indicating that harmful exposures during pre-implantation embryo development can trigger lasting epigenetic alterations in offspring, the mechanisms are still not fully understood. Since physiological or pathological changes in DNA methylation can occur as a response to environmental cues, proper environmental milieu plays a critical role in the success of embryonic development. In this review, we depict the mechanisms behind the embryonic epigenetic reprogramming of DNA methylation and highlight how maternal environmental stressors (e.g., alcohol, heat stress, nutrient availability) during pre-implantation and assisted reproductive technology procedures affect development and DNA methylation marks.

Tracking quality: can embryology key performance indicators be used to identify clinically relevant shifts in pregnancy rate?

STUDY QUESTION

Can embryology key performance indicators (KPIs) detect shifts in laboratory performance that precede changes in clinical outcomes?

SUMMARY ANSWER

Day 5 usable blastocyst rate (D5BUR) is an important embryology KPI that complements total usable blastocyst rate (TBUR) in its ability to rapidly identify adverse embryology outcomes, prior to changes in clinical outcomes.

WHAT IS KNOWN ALREADY

The hypothesis that monitoring performance of an IVF laboratory using statistical process controls (SPCs) can act as an early warning signal of shifts in laboratory conditions is a hypothesis that requires validation. The Vienna consensus report recently defined KPIs for monitoring fresh IVF and ICSI cycles, but the effectiveness of using these KPIs for detecting clinically relevant shifts following changes in laboratory processes is unknown.

STUDY DESIGN, SIZE, DURATION

A retrospective, multicentre, analysis of KPIs for 1971 fresh IVF and ICSI cycles during three consecutive 5-month periods (P1, P2 and P3) during which the culture medium was changed in the middle period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ICSI fertilisation rate, IVF fertilisation rate, D5BUR, TBUR and clinical pregnancy rate (CPR) were tracked monthly and analysed for SPC using Shewhart control charts. Out-of-control KPIs were identified by warning (2-sigma) and control (3-sigma) limits. The effect of the laboratory culture medium change on embryology KPIs and cumulative CPR was investigated using a one-way ANOVA or Pearson Chi-squared test and logistic regression.

MAIN RESULTS AND THE ROLE OF CHANCE

D5BUR decreased from 32 to 25% after the culture medium was changed, and the decrease was detected within 1 week after the change (P < 0.0001). D5BUR subsequently increased after a change back to the original medium. A decrease in CPR (51-36%) after the medium change was also observed but was not detected until 3 months after the shift in D5BUR (P = 0.0005). Overall, the change in culture medium independently influenced D5BUR, CPR and cumulative CPR. Importantly, TBUR (41%) was not affected by the change in culture medium, remaining within control limits for all three culture periods, indicating that the overall blastocyst rate alone may not sufficiently monitor embryology laboratory performance.

LIMITATIONS REASONS FOR CAUTION

The statistical KPI monitoring system demonstrated by the current study may be less effective at identifying KPI shifts in smaller clinics with lower cycle volumes. Live-birth rate per cycle started was not included as a clinical KPI.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates that statistical KPI monitoring systems have the potential to provide systematic, early detection of adverse outcomes in ART laboratories after planned or unexpected shifts in conditions.

STUDY FUNDING/COMPETING INTEREST(S)

No external funds were used for the study. The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Estimation of embryo transfer media viscosity and consideration of its effect on media and uterine fluid interactions

RESEARCH QUESTION

What are the viscosities of media used for human embryo transfer and what is the possible effect of viscosity as it relates to interactions between transfer media and uterine fluid.

DESIGN

Chamber slide filling times, in seconds, were used to calculate viscosity for each commercial and in-house modified medium, with 12 or 24 replicates per medium under standard operating procedure temperature and gas equilibration conditions used for embryo transfer. Means, standard deviations and coefficients of variation were calculated, and each viscosity was estimated using a regression equation; viscosities for each medium were presented for comparative purposes.

RESULTS

Complete culture media (G1-Plus, G2-Plus, G-TL, 1-Step, Global Total, Global Total HEPES, and Sperm Wash Medium) had viscosity estimates of 1.65 cP, 1.77 cP, 1.68 cP, 1.29cP, 1.18 cP, 1.15 cP, and 1.20 cP, respectively. Complete transfer media (EmbryoGlue, UTM), had viscosity estimates of 3.59 cP and 1.28 cP, respectively. Global HEPES medium with 10%, 20%, 30%, and 50% synthetic serum substitute (SSS) volume per volume had viscosity estimates 1.16 cP, 1.23 cP, 1.25 cP, and 1.34 cP, respectively. For reference, water had a viscosity estimate of 1.06 cP.

CONCLUSIONS

A relatively narrow distribution of viscosities was observed across several transfer media despite the various commercial or in-house modifications. These data demonstrate the vast difference between viscosities of embryo transfer media and the assumed viscosity of uterine fluid (1000 cP). Contemporary embryo transfer media may be well-suited for IVF, but evaluation of all variables, e.g. media viscosity in the context of embryo transfer, adds to the knowledge base that should be available to practitioners.

Historical Note: Lessons Learned from Developing the First Semi-Defined Medium for Culture of One-Cell Rabbit Embryos to Expanding Blastocysts

In a review written in 1987 entitled "Pioneering mammalian embryo culture," John Biggers (The mammalian preimplantation embryo: regulation of growth and differentiation in vitro, Plenum Press, New York, 1987) summarized the history of early preimplantation embryo culture as follows "The culture of early mammalian embryos has been studied predominantly in two species: the rabbit and the mouse. Up to 1949, the rabbit was used almost exclusively, with media composed of ill-defined biological fluids. After this time, techniques for the culture of preimplantation mouse embryos rapidly developed using simple, defined media with relatively few components… In the 1960s, there was renewed interest in the culture of early rabbit embryos and a marked difference in the nutritional requirements of the two species was found." This chapter describes the history of the development of the semi-defined medium that stimulated this "renewed interest" referred to above and includes some of the initial difficulties in getting the work published. The phrase "semi-defined medium" is understood here to mean a defined medium (all of whose components are chemically known) supplemented with an undefined component such as albumin.

Should extended blastocyst culture include Day 7?

Extended culture to the blastocyst stage is widely practised, improving embryo selection and promoting single embryo transfer. Selection of useable blastocysts typically occurs on Days 5 and 6 of embryo culture. Embryos not suitable for transfer, biopsy or cryopreservation after Day 6 are routinely discarded. Some embryos develop at a slower rate, however, forming blastocysts on Day 7 of culture. Day 7 blastocysts can be viable, they can be of top morphological grade, euploid and result in a healthy live birth. Since ending culture on Day 6 is current practice in most clinics, viable Day 7 blastocysts may be prematurely discarded. Although Day 7 blastocysts make up only 5% of useable blastocysts, those which are suitable for cryopreservation or biopsy are clinically significant. Overall, culturing embryos an additional day increases the number of useable embryos per IVF cycle and provides further opportunity for pregnancy for patients, especially those who have only a few or low-quality blastocysts.

In Vitro Culture of Embryos from Horses

Establishment of optimal methods for equine embryo culture has been slow when compared to some domestic species. In part, this delay was caused by the failure of standard in vitro fertilization techniques in horses. However, the development of intracytoplasmic sperm injection (ICSI) for the assisted fertilization of equine oocytes has resulted in a renewed interest in establishing optimal methods for embryo culture. Currently, ICSI-produced equine embryos are cultured using media designed for other species or other cell cultures and, typically, with the addition of serum. Although systems specifically for horse embryo culture still have not been established, ICSI-produced embryos are developmentally competent and capable of producing live offspring.

TRPM7 and CaV3.2 channels mediate Ca2+ influx required for egg activation at fertilization

The success of mammalian development following fertilization depends on a series of transient increases in egg cytoplasmic Ca²⁺, referred to as Ca²⁺ oscillations. Maintenance of these oscillations requires Ca²⁺ influx across the plasma membrane, which is mediated in part by T-type, Ca_V3.2 channels. Here we show using genetic mouse models that TRPM7 channels are required to support this Ca²⁺ influx. Eggs lacking both TRPM7 and Ca_V3.2 stop oscillating prematurely, indicating that together they are responsible for the majority of Ca²⁺ influx immediately following fertilization. Fertilized eggs lacking both channels also frequently display delayed resumption of Ca²⁺ oscillations, which appears to require sperm-egg fusion. TRPM7 and Ca_V3.2 channels almost completely account for Ca²⁺ influx observed following store depletion, a process previously attributed to canonical store-operated Ca²⁺ entry mediated by STIM/ORAI interactions. TRPM7 serves as a membrane sensor of extracellular Mg²⁺ and Ca²⁺ concentrations and mediates the effects of these ions on Ca²⁺ oscillation frequency. When bred to wild-type males, female mice carrying eggs lacking TRPM7 and Ca_V3.2 are subfertile, and their offspring have increased variance in postnatal weight. These in vivo findings confirm previous observations linking in vitro experimental alterations in Ca²⁺ oscillatory patterns with developmental potential and offspring growth. The identification of TRPM7 and Ca_V3.2 as key mediators of Ca²⁺ influx following fertilization provides a mechanistic basis for the rational design of culture media that optimize developmental potential in research animals, domestic animals, and humans.

Comparison of two commercial embryo culture media (SAGE-1 step single medium vs. G1-PLUSTM/G2-PLUSTM sequential media): Influence on in vitro fertilization outcomes and human embryo quality

OBJECTIVE

To compare embryo quality, fertilization, implantation, miscarriage and clinical pregnancy rates for embryos cultured in two different commercial culture media until D-2 or D-3.

METHODS

In this retrospective study, we analyzed 189 cycles performed in 2016. Metaphase II oocytes were microinjected and allocated into single medium (SAGE 1-STEP, Origio) until transferred, frozen or discarded; or, if sequential media were used, the oocytes were cultured in G1-PLUSTM (Vitrolife) up to D-2 or D-3 and in G2-PLUSTM (Vitrolife) to transfer. On the following day, the oocytes were checked for normal fertilization and on D-2 and D-3 for morphological classification. Statistical analysis was performed using the chi-square and Mann-Whitney tests in PASW Statistics 18.0.

RESULTS

The fertilization rates were 70.07% for single and 69.11% for sequential media (p=0.736). The mean number of embryos with high morphological quality (class A/B) was higher in the single medium than in the sequential media: D-2 [class A (190 vs. 107, p<0.001), B (133 vs. 118, p=0.018)]; D-3 [class A (40 vs. 19, p=0.048) but without differences in class B (40 vs. 49)]. Consequently, a higher number of embryos cultured in single medium were frozen: 197 (21.00%) vs. sequential: 102 (11.00%), p<0.001. No differences were found in implantation rates (30.16% vs. 25.57%, p=0.520), clinical pregnancy rates (55.88% vs. 41.05%, p=0.213), or miscarriage rates (14.29% vs. 9.52%, p=0.472).

CONCLUSION

Embryo culture in single medium yields greater efficiency per cycle than in sequential media. Higher embryo quality and quantity were achieved, resulting in more frozen embryos. There were no differences in clinical pregnancy rates.

[Culture conditions for gametes and embryos: Which culture medium? Which impact on newborn?]

Many studies have examined the impact of cell/embryo culture media on the development of human embryo during IVF process, but few studies have followed up and compared the effects of these culture media on the developmental outcome of children conceived by IVF. As recurrent experimental evidence from animal studies suggests potential long-term effects of embryo culture media on the health outcome of IVF-conceived children, more studies are needed to clarify the role of the culture media and mechanisms underlying such effects. In human, however, the effects of culture media are difficult to pinpoint due to complications stem from both the influence of maternal nutrition during the gestational period and the parental genetic. Based on a simple review of the literature integrating animal experimentations and human clinic studies, we suggest that the composition of culture medium should be considered beyond the character of unique or sequential medium, corresponding to "let embryo choose" or "back to nature" respectively. Instead, we suggest that the main components of embryo culture media should be considered from the point of view of metabolic consequences and potential epigenetic effects. Given that energetic metabolites can regulate epigenetic machinery, we hypothesize that metabolic abnormalities linked to morphological abnormalities could reveal epigenetic defects in embryos.

Culture conditions affect Ca2+ release in artificially activated mouse and human oocytes

Inconsistent fertilisation and pregnancy rates have been reported by different laboratories after application of ionomycin as a clinical method of assisted oocyte activation (AOA) to overcome fertilisation failure. Using both mouse and human oocytes, in the present study we investigated the effects of ionomycin and Ca2+ concentrations on the pattern of Ca2+ release and embryonic developmental potential. In the mouse, application of 5 μM ionomycin in potassium simplex optimisation medium (KSOM) or 10 µM ionomycin in Ca2+-free KSOM significantly reduced the Ca2+ flux and resulted in failure of blastocyst formation compared with 10 μM ionomycin in KSOM. Increasing the Ca2+ concentration up to three- or sixfold did not benefit mouse embryonic developmental potential. Similarly, 10 μM ionomycin-induced rise in Ca2+ in human oocytes increased with increasing total calcium concentrations in the commercial medium. Remarkably, we observed significantly reduced mouse embryo development when performing AOA over a period of 10 min in Quinn’s AdvantageTM Fertilisation medium (Cooper Surgical) and IVFTM medium (Vitrolife) compared with Sydney IVF COOK cleavage medium (Cook Ireland), using the same sequential culture system from the post-activation stage to blastocyst formation stage in different AOA groups. In conclusion, concentrations of both ionomycin and Ca2+ in culture media used during AOA can have significant effects on Ca2+ release and further embryonic developmental potential.

Phase modulated 2D HSQC-TOCSY for unambiguous assignment of overlapping spin systems

We present a new method that allows one to unambiguously resolve overlapping spin systems often encountered in biomolecular systems such as peptides and proteins or in samples containing a mixture of different molecules such as in metabolomics. We address this problem using the recently proposed phase modulation approach. By evolving the ¹H chemical shifts in a conventional two dimensional (2D) HSQC-TOCSY experiment for a fixed delay period, the phase/intensity of set of cross peaks belonging to one spin system are modulated differentially relative to those of its overlapping counterpart, resulting in their discrimination and recognition. The method thus accelerates the process of identification and resonance assignment of individual compounds in complex mixtures. This approach facilitated the assignment of molecules in the embryo culture medium used in human assisted reproductive technology.

Blastocyst utilization rates after continuous culture in two commercial single-step media: a prospective randomized study with sibling oocytes

PURPOSE

The aim of this study is to determine whether blastocyst utilization rates are different after continuous culture in two different commercial single-step media.

METHODS

This is a paired randomized controlled trial with sibling oocytes conducted in infertility patients, aged ≤40 years with ≥10 oocytes retrieved assigned to blastocyst culture and transfer. Retrieved oocytes were randomly allocated to continuous culture in either Sage one-step medium (Origio) or Continuous Single Culture (CSC) medium (Irvine Scientific) without medium renewal up to day 5 post oocyte retrieval. Main outcome measure was the proportion of embryos suitable for clinical use (utilization rate).

RESULTS

A total of 502 oocytes from 33 women were randomly allocated to continuous culture in either Sage one-step medium (n = 250) or CSC medium (n = 252). Fertilization was performed by either in vitro fertilization or intracytoplasmic sperm injection, and embryo transfers were performed on day 5. Two patients had all blastocysts frozen due to the occurrence of severe ovarian hyperstimulation syndrome. Fertilization and cleavage rates, as well as embryo quality on day 3, were similar in the two media. Blastocyst utilization rates (%, 95% CI) [55.4% (46.4-64.1) vs 54.7% (44.9-64.6), p = 0.717], blastocyst formation rates [53.6% (44.6-62.5) vs 51.9 (42.2-61.6), p = 0.755], and proportion of good quality blastocysts [36.8% (28.1-45.4) vs 36.1% (27.2-45.0), p = 0.850] were similar in Sage one-step and CSC media, respectively.

CONCLUSIONS

Continuous culture of embryos in Sage one-step and CSC media is associated with similar blastocyst development and utilization rates. Both single-step media appear to provide adequate support during in vitro preimplantation embryo development. Whether these observations are also valid for other continuous single medium protocols remains to be determined.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02302638.

Morphokinetic parameters from a time-lapse monitoring system cannot accurately predict the ploidy of embryos

PURPOSE

This study aimed to test whether there is an association between embryo morphokinetic parameters and ploidy status.

METHODS

Patients with high risk of aneuploidy were analyzed by time-lapse microscopy combined with preimplantation genetic screening (PGS). Accordingly, 256 blastocysts from 75 patients were subjected to trophectoderm biopsy and microarray comparative genomic hybridization (array-CGH). Blastocyst development process was analyzed using time-lapse images.

RESULTS

Morphokinetic parameters: tPNf, t2, t3, t4, t5, t8, t9, tcom, tM, tSB, tB, tEB, CC1, CC2, CC3, S2, S3, t5-t2, and tB-tSB showed no significant difference in euploid embryos compared to aneuploid counterparts. In addition, two risk models based on previously published morphokinetic parameters failed to segregate euploid from aneuploid embryos.

CONCLUSIONS

Morphokinetic parameters subjected to investigation in the present study failed to improve the chance of selecting euploid embryos.