Increased ammonium in culture medium reduces the development of human embryos to the blastocyst stage

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.

Impact of Group vs Individual Embryo Culture Strategies on Blastocyst and Clinical Outcomes

Embryo culture is one of the most important steps in an assisted reproduction laboratory. Embryos can be cultured individually, one embryo per media drop, or in groups, culturing several embryos in the same media drop. Due to the controversy generated on this subject, we wondered which embryo culture method would have the best results in terms of quality and blastocyst formation rate. We designed a prospective randomized study comparing two different embryo culture strategies: group and individual embryo culture. The data were obtained from 830 embryos from 103 egg donation treatments. The zygotes were randomized into two groups: individual culture (group 1) or group culture (group 2). The embryos were cultured in 35-µl drops until day 5 when they were classified morphologically. We observed a significant increase in the blastocyst formation rate and in the usable embryo rate in individual culture on day 5 compared to group culture. However, good embryo quality (A/B blastocysts), implantation, and pregnancy rates were similar regardless of the type of embryo-culture. As a conclusion, individual culture may increase blastocyst formation rate and may benefit embryo quality on day 5. Our results support previous reports suggesting that individual culture could improve embryo development.

Increased ammonium in culture medium may promote cellular apoptosis and negatively affect pluripotency of human blastocysts

PURPOSE

To determine the association between ammonium concentration in culture medium and blastocyst development and to assess the influence of increased ammonium concentration on the expression of Bax, Bcl-2 and Oct4.

METHODS

A total of 254 cleavage-stage embryos were individually cultured in 30μL G2-plus medium on Day 3, and then culture media samples were collected on Day 5 for ammonium concentration determination immediately after evaluating the embryos morphology. Poor-quality blastocysts (combined score of CC) were used for gene expression analysis. The blastocyst formation rate, good-quality blastocyst rate and relative expression levels of Bax, Bcl-2 and Oct4 were analyzed.

RESULTS

Based on receiver operating characteristic curve, the cutoff value of ammonium concentration produced by embryos was 16.07 μmol/L (AUC = 0.722, 95% CI 0.637-0.807; P = 0.000), so all embryos were assigned to two groups according to the cutoff value: normal group (< 16.07 μmol/L) and increased group (≥ 16.07 μmol/L). There was a significant difference in blastocyst formation rate (80.5% vs 59.0%, P < 0.01) between normal group and increased group, as well as for good-quality blastocyst rate (21.0% vs 3.4%, P < 0.01). A significantly higher expression level of Bax (P < 0.05) and considerably lower expression level of Oct4 (P < 0.01) were observed in increased group compared to normal group.

CONCLUSION

Our data demonstrated for the first time that increased ammonium concentration in culture medium may promote cellular apoptosis and negatively affect pluripotency of human blastocyst.

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.

Effects of embryo density on cell number of day 3 embryos cultured in a 30-μl drop: a retrospective cohort study

For individual cultures, findings on regulating embryo density by changing the microdrop volume are contradictory. The aim of this study was to investigate the relationship between embryo density and the developmental outcome of day 3 embryos after adjusting covariates. In total, 1196 embryos from 206 couples who had undergone in vitro fertilization treatment were analyzed retrospectively. Three embryo densities were used routinely, i.e. one embryo in a drop (30 μl/embryo), two embryos in a drop (15 μl/embryo) and three embryos in a drop (10 μl/embryo). Embryo quality on day 3 was evaluated, both the cell number of day 3 embryos and the proportion of successful implantations served as endpoints. Maternal age, paternal age, antral follicles and level of anti-Müllerian hormone, type of infertility, controlled ovarian stimulation protocol, length of stimulation, number of retrieved oocytes, number of zygotes (two pronuclei) and insemination type were covariates and adjusted. After adjusting fully for all covariates, the cell number of day 3 embryos was significantly increased by 0.40 (95% CI 0.00, 0.79; P = 0.048) and 0.78 (95% CI 0.02, 1.54; P = 0.044) in the 15 μl/embryo and 10 μl/embryo group separately, compared with the 30 μl/embryo group. The proportions of implanted embryos were 42.1%, 48.7% and 0.0% in the 30 μl/embryo, 15 μl/embryo and 10 μl/embryo groups respectively. There was no statistical significance (P = 0.22) between the 30 μl/embryo group and the 15 μl/embryo group. After adjusting for confounders that were significant in univariate analysis, embryo density was still not associated with day 3 embryo implantation potential (P > 0.05). In a 30-μl microdrop, culturing embryos with an embryo density of both 15 and 10 μl/embryo increased the cell number of day 3 embryos, which did not benefit embryo implanting potential, compared with individual culture of 30 μl/embryo.

Low-Concentration Essential Amino Acids in PZM-3 Improve the Developmental Competence of Porcine Embryos Produced by Handmade Cloning

Essential amino acids (EAA) of inappropriate concentration have been reported to compromise the development of embryo. This study aimed to investigate the effect of EAA on the developmental competence of porcine embryos produced by either handmade cloning (HMC) or parthenogenetic activation (PA). In experiment 1, we examined the in vitro developmental competence of PA embryos after culture in PZM-3 containing different concentrations (v/v) of EAA (0%, 1%, and 2%). The results indicated that reducing the concentration of EAA from 2% to 1% significantly improved the blastocyst formation (36% vs. 54%), while 0% would compromise the blastocyst formation rate (54% vs. 38%). In experiment 2, we further investigated the effect of EAA concentration (1% and 2%) on the in vitro developmental competence and gene expression of HMC embryos. Blastocyst rate significantly increased by reducing concentration of EAA (41% vs. 53%) and those genes upregulated were enriched in oxidative phosphorylation, PPAR signaling pathway, and metabolism-related pathways. In experiment 3, the in vivo developmental competence of HMC embryos cultured in the medium supplemented with 1% EAA was examined. Embryos derived from both non-gene-modified fetal fibroblasts (FFs) and gene-modified fetal fibroblasts (GMFFs) were transferred to recipients. The pregnancy rates were 83% and 78% separately. Out of the pregnancies, 5 (FFs) and 6 (GMFFs) were successfully developed to term. Our study indicates that supplementing EAA to embryo culture medium at a concentration of 1% can improve the in vitro developmental competence of porcine HMC embryos and the blastocyst obtained can successfully develop to term, which could be beneficial for the production of gene-modified piglets.

Sperm-mediated DNA lesions alter metabolite levels in spent embryo culture medium

Paternal genetic alterations may affect embryo viability and reproductive outcomes. Currently it is unknown whether embryo metabolism is affected by sperm-mediated abnormalities. Hence, using a mouse model, this study investigated the response to paternally transmitted DNA lesions on genetic integrity and metabolism in preimplantation embryos. Spent embryo culture media were analysed for metabolites by nuclear magnetic resonance spectroscopy and embryonic genetic integrity was determined by terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay on embryonic Day 4.5 (E4.5). Metabolic signatures were compared between normally derived embryos (control) and embryos derived from spermatozoa carrying induced DNA lesions (SDL). SDL embryos showed a significant reduction in blastocyst formation on E3.5 and E4.5 (P<0.0001) and had an approximately 2-fold increase in TUNEL-positive cells (P<0.01). A cohort of SDL embryos showing delayed development on E4.5 had increased uptake of pyruvate (P<0.05) and released significantly less alanine (P<0.05) to the medium compared with the corresponding control embryos. On the other hand, normally developed SDL embryos had a reduced (P<0.001) pyruvate-to-alanine ratio compared with normally developed embryos from the control group. Hence, the difference in the metabolic behaviour of SDL embryos may be attributed to paternally transmitted DNA lesions in SDL embryos.

The effects of glycine-glutamine dipeptide replaced l-glutamine on bovine parthenogenetic and IVF embryo development

Relative to alanine and serine amino acid levels, glutamine is highly abundant in follicular fluid, and is an important source of energy required for oocyte maturation and embryo development. Thus, glutamine is an essential component of in vitro embryo culture media. However, glutamine has poor stability and degrades spontaneously in solution to form ammonia and pyrrolidonecarboxylic acid. In the present study, we aimed to explore the effect of substituting l-glutamine with glycine-glutamine, a more stable glutamine, on development of early parthenogenetic embryos and in vitro fertilization (IVF) embryos in bovine. Results revealed that glycine-glutamine can significantly increase cleavage rate (parthenogenetic embryos:87.24% vs. 72.61%, IVF embryos:89.33% vs. 83.79%, P < 0.01), blastocyst number (parthenogenetic embryos:24.98% vs. 18.07%, IVF embryos:33.53% vs. 27.29%, P < 0.01), and blastocyst number (parthenogenetic embryos:96 vs. 76, IVF embryos:114 vs. 109, P < 0.01), reduce blastocyst apoptosis (parthenogenetic embryos:3.72% vs. 6.65%, IVF embryos:2.53% vs.6.23%, P < 0.01), alleviate embryo ammonia toxicity, and reduce the content of reactive oxygen species (ROS) compared with the l-glutamine. In addition, glycine-glutamine can alter epigenetic reprogramming by increasing the expression of HDAC1 (Histone Deacetylase 1) and decreasing the relative expression levels of H3K9 acetylation in early parthenogenetic embryos and IVF embryos. From our present study, we concluded that glycine-glutamine is an effective substitute of glutamine in modified synthetic oviduct fluid with amino acids (mSOFaa).

Embryo responses to stress induced by assisted reproductive technologies

Assisted reproductive technology (ART) has led to the birth of millions of babies. In cattle, thousands of embryos are produced annually. However, since the introduction and widespread use of ART, negative effects on embryos and offspring are starting to emerge. Knowledge so far, mostly provided by animal models, indicates that suboptimal conditions during ART can affect embryo viability and quality, and may induce embryonic stress responses. These stress responses take the form of severe gene expression alterations or modifications in critical epigenetic marks established during early developmental stages that can persist after birth. Unfortunately, while developmental plasticity allows the embryo to survive these stressful conditions, such insult may lead to adult health problems and to long-term effects on offspring that could be transmitted to subsequent generations. In this review, we describe how in mice, livestock, and humans, besides affecting the development of the embryo itself, ART stressors may also have significant repercussions on offspring health and physiology. Finally, we argue the case that better control of stressors during ART will help improve embryo quality and offspring health.

A microwell culture system that allows group culture and is compatible with human single media

PURPOSE

A microwell culture system that facilitates group culture, such as well-of-the-well (WOW), improves embryonic development in an individual culture. We examined the effect of WOW on embryonic development in vitro with commercially available human single culture media.

METHODS

Using four different commercial human single culture media, in vitro development and imprinted gene expression of bovine embryos cultured in WOW were compared to droplet culture (one zygote per drop). To determine the effects of microwell and group culture on embryonic development, different numbers of embryos were cultured in droplet or WOW. Diffusion simulation of accumulating metabolites was conducted using the finite volume method.

RESULTS

WOW had a positive effect on bovine embryonic development, regardless of the type of single culture media. Imprinted gene expression was not different between droplet- and WOW-derived blastocysts. The microwell and group cultures in WOW showed a significant positive effect on the rate of total blastocysts and the rate of development to the expanded and hatching blastocyst stages. The assumed cumulative metabolite concentration of WOW with one embryo was 1.47 times higher than that of droplet culture with one embryo. Furthermore, the concentration of WOW with three embryos was 1.54 times higher than that of WOW with one embryo.

CONCLUSIONS

In using human single culture media, a microwell culture system that allows group culture could be a powerful clinical tool for improving the success of assisted reproductive technologies.

Production, Preservation, and Transfer of South American Camelid Embryos

The current review summarizes progress in the field of in vitro and in vivo production of South American Camelid embryos. Both methods require ovarian superstimulation (with FSH and eCG) to obtain multiple ovulations (in vivo embryo production) or to induce follicle growth for oocyte collection (in vitro embryo production). Moreover, superstimulation entails prior administration of hormones that inhibit follicular growth (progesterone, progestagens, and estrogens). Cumulus-oocyte complexes obtained must mature in vivo (buserelin administration) or in vitro to then be subjected to in vitro fertilization or intracytoplasmic sperm injection. All these techniques also require morphologically normal, motile spermatozoa to achieve fertilization. Methods used to decrease semen viscosity and to select the best spermatozoa (Percoll®; Androcoll-ETM) are described. Additionally, nuclear transfer or cloning has been applied in llamas. Up to now, embryo deep-freezing and vitrification have progressed slowly but are at the height of development. Embryos that are obtained by any of these techniques, either in vivo or in vitro, need to be transferred to synchronized recipient females. The best results are achieved after transfer to the left uterine horn with an ipsilateral ovulation. No live offspring have been obtained after the transfer of cryopreserved embryos. Applying reproductive biotechnologies, such as those described, will permit the expansion of genetically selected animals in the population and also that of wild camelid species, vicunas, and guanacos, whose embryos could then be transferred to the uterus of domestic species.

Impact of the IVF laboratory environment on human preimplantation embryo phenotype

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

Ammonium accumulation in commercially available embryo culture media and protein supplements during storage at 2-8°C and during incubation at 37°C

STUDY QUESTION

Does ammonium accumulate in commercially available culture media and protein supplements used for in vitro development of human pre-implantation embryos during storage and incubation?

SUMMARY ANSWER

Ammonium accumulates in ready-to-use in vitro fertilization (IVF) culture media during storage at 2-8°C and in ready-to-use IVF culture media and protein supplements during incubation at 37°C.

WHAT IS KNOWN ALREADY

Both animal and human studies have shown that the presence of ammonium in culture medium has detrimental effects on embryonic development and pregnancy rate. It is, therefore, important to assess the amount of ammonium accumulation in ready-to-use IVF culture media under conditions that are common in daily practice.

STUDY DESIGN, SIZE, DURATION

Ammonium accumulation was investigated in 15 ready-to-use media, 11 protein-free media and 8 protein supplements.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ammonium was measured by the use of an enzymatic method with glutamate dehydrogenase. To simulate the storage and incubation conditions during IVF treatments, ammonium concentrations were measured at different time-points during storage at 2-8°C for 6 weeks and during incubation at 37°C for 4 days.

MAIN RESULTS AND THE ROLE OF CHANCE

All ready-to-use, i.e. protein supplemented, culture media showed ammonium accumulation during storage for 6 weeks (ranging from 9.2 to 99.8 µM) and during incubation for 4 days (ranging from 8.4 to 138.6 µM), resulting in levels that might affect embryo development. The protein supplements also showed ammonium accumulation, while the culture media without protein supplementation did not. The main sources of ammonium buildup in ready-to-use culture media were unstable glutamine and the protein supplements. No additional ammonium buildup was found during incubation when using an oil overlay or with the presence of an embryo in the culture droplet.

LIMITATIONS, REASONS FOR CAUTION

In addition to the unstable glutamine and the protein supplements, other free amino acids might contribute to the ammonium buildup. We did not investigate the deterioration of other components in the media.

WIDER IMPLICATIONS OF THE FINDINGS

Break-down of components into ammonium is more pronounced during incubation at 37°C, however, it is not negligible during storage at 2-8°C. This results in increasing ammonium levels in culture media over time that may affect embryo development. Therefore, it is important that the use of free l-glutamine in human embryo culture media is stopped and that the use of protein supplements is thoroughly evaluated.

STUDY FUNDING/COMPETING INTERESTS

No funding or no competing interests declared.

TRIAL REGISTRATION NUMBER

Not applicable.

Optimizing the culture environment and embryo manipulation to help maintain embryo developmental potential

With increased use of comprehensive chromosome screening (CCS), the question remains as to why some practices do not experience the same high levels of clinical success after implementation of the approach. Indeed, the debate surrounding the efficacy and usefulness of blastocyst biopsy and CCS continues. Importantly, several variables impact the success of an assisted reproductive technology cycle. Transfer of a euploid embryo is but one factor in an intricate system that requires numerous steps to occur successfully. Certainly, the culture environment and the manipulations of the embryo during its time in the laboratory can impact its reproductive potential. Environmental stressors ranging from culture media to culture conditions and even culture platform can impact biochemical, metabolic, and epigenetic patterns that can affect the developing cell independent of chromosome number. Furthermore, accompanying procedures, such as biopsy and vitrification, are complex and, when performed improperly, can negatively impact embryo quality. These are areas that likely still carry room for improvement within the IVF laboratory.

Noninferiority, randomized, controlled trial comparing embryo development using media developed for sequential or undisturbed culture in a time-lapse setup

OBJECTIVE

To study whether a culture medium that allows undisturbed culture supports human embryo development to the blastocyst stage equivalently to a well-established sequential media.

DESIGN

Randomized, double-blinded sibling trial.

SETTING

Independent in vitro fertilization (IVF) clinics.

PATIENT(S)

One hundred twenty-eight patients, with 1,356 zygotes randomized into two study arms.

INTERVENTION(S)

Embryos randomly allocated into two study arms to compare embryo development on a time-lapse system using a single-step medium or sequential media.

MAIN OUTCOME MEASURE(S)

Percentage of good-quality blastocysts on day 5.

RESULT(S)

Percentage of day 5 good-quality blastocysts was 21.1% (standard deviation [SD] ± 21.6%) and 22.2% (SD ± 22.1%) in the single-step time-lapse medium (G-TL) and the sequential media (G-1/G-2) groups, respectively. The mean difference (-1.2; 95% CI, -6.0; 3.6) between the two media systems for the primary end point was less than the noninferiority margin of -8%. There was a statistically significantly lower number of good-quality embryos on day 3 in the G-TL group [50.7% (SD ± 30.6%) vs. 60.8% (SD ± 30.7%)]. Four out of the 11 measured morphokinetic parameters were statistically significantly different for the two media used. The mean levels of ammonium concentration in the media at the end of the culture period was statistically significantly lower in the G-TL group as compared with the G-2 group.

CONCLUSION(S)

We have shown that a single-step culture medium supports blastocyst development equivalently to established sequential media. The ammonium concentrations were lower in the single-step media, and the measured morphokinetic parameters were modified somewhat.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01939626.

Reduced blastocyst formation in reduced culture volume

PURPOSE

The aim of this prospective sibling oocyte study was to evaluate whether reduced culture volume improves blastocyst formation.

METHODS

Twenty-three patients with extended embryo culture until day 5 were selected for the study. After injection, 345 sibling oocytes were individually cultured in either 25 or 7 μl droplets of Origio cleavage medium under oil. On day 3 of development, embryos were transferred to droplets with the corresponding volume of Origio blastocyst culture medium. Fertilization and embryo quality on day 3 and day 5/6 were evaluated.

RESULTS

No statistically significant difference (p = 0.326) in fertilization rate was observed (81.3 versus 83.0 %). There was no significant difference in terms of the number of excellent and good-quality embryos obtained on day 3 between both groups (p = 0.655). Embryo culture in 25 μl droplets led to more embryos with a higher cell number when compared to 7 μl culture (p = 0.024). On day 3, 132 and 131 embryos were considered for further culture until day 5/6. Blastulation rates were significantly higher in the 25 μl group (75.0 versus 61.6 %; p = 0.017) and significantly more day 5 embryos with excellent and good quality were found in this group (54.5 versus 40.5 %; p = 0.026). Finally, the utilization rates expressed per mature oocyte (41.4 versus 29.8 %; p = 0.043), per fertilized oocyte (50.7 versus 36.6 %; p = 0.023), and per day 3 embryo undergoing extended culture to day 5/6 (54.5 versus 39.7 %; p = 0.019) were all significantly higher in the 25 μl group.

CONCLUSION

Reduced culture volume (7 μl) negatively impacts early development by reducing the cell number on day 3 and both blastocyst formation and quality.

The effects of chemical and physical factors on mammalian embryo culture and their importance for the practice of assisted human reproduction

BACKGROUND

Although laboratory procedures, along with culture media formulations, have improved over the past two decades, the issue remains that human IVF is performed in vitro (literally 'in glass').

METHODS

Using PubMed, electronic searches were performed using keywords from a list of chemical and physical factors with no limits placed on time. Examples of keywords include oxygen, ammonium, volatile organics, temperature, pH, oil overlays and incubation volume/embryo density. Available clinical and scientific evidence surrounding physical and chemical factors have been assessed and presented here.

RESULTS AND CONCLUSIONS

Development of the embryo outside the body means that it is constantly exposed to stresses that it would not experience in vivo. Sources of stress on the human embryo include identified factors such as pH and temperature shifts, exposure to atmospheric (20%) oxygen and the build-up of toxins in the media due to the static nature of culture. However, there are other sources of stress not typically considered, such as the act of pipetting itself, or the release of organic compounds from the very tissue culture ware upon which the embryo develops. Further, when more than one stress is present in the laboratory, there is evidence that negative synergies can result, culminating in significant trauma to the developing embryo. It is evident that embryos are sensitive to both chemical and physical signals within their microenvironment, and that these factors play a significant role in influencing development and events post transfer. From the viewpoint of assisted human reproduction, a major concern with chemical and physical factors lies in their adverse effects on the viability of embryos, and their long-term effects on the fetus, even as a result of a relatively brief exposure. This review presents data on the adverse effects of chemical and physical factors on mammalian embryos and the importance of identifying, and thereby minimizing, them in the practice of human IVF. Hence, optimizing the in vitro environment involves far more than improving culture media formulations.

Mitochondrial SIRT5 is present in follicular cells and is altered by reduced ovarian reserve and advanced maternal age

Women with reduced ovarian reserve or advanced maternal age have an altered metabolic follicular microenvironment. As sirtuin 5 (SIRT5) senses cellular metabolic state and post-translationally alters protein function, its activity may directly impact on oocyte viability and pregnancy outcome. Therefore, we investigated the role of SIRT5 in relation to ovarian reserve and maternal age. Women (n=47) undergoing routine IVF treatment were recruited and allocated to one of three cohorts based on ovarian reserve and maternal age. Surplus follicular fluid, granulosa and cumulus cells were collected. SIRT5 mRNA, protein and protein activity was confirmed in granulosa and cumulus cells via qPCR, immunohistochemistry, western blotting and desuccinylation activity. The presence of carbamoyl phosphate synthase I (CPS1), a target of SIRT5, was investigated by immunohistochemistry and follicular-fluid ammonium concentrations determined via microfluorometry. Women with reduced ovarian reserve or advanced maternal age had decreased SIRT5 mRNA, protein and desuccinylation activity in granulosa and cumulus cells resulting in an accumulation of follicular-fluid ammonium, presumably via alterations in activity of a SIRT5 target, CPS1, which was present in granulosa and cumulus cells. This suggests a role for SIRT5 in influencing oocyte quality and IVF outcomes.

Improved blastocyst formation with reduced culture volume: comparison of three different culture conditions on 1128 sibling human zygotes

PURPOSE

The aim of the present randomized, comparative study was to evaluate the effect of reduced culture volumes on sibling human embryo development.

METHODS

Firstly, sibling injected oocytes obtained from 88 out of 165 consenting couples undergoing infertility treatment were cultured either in large (35 μl) or in small drops (15 μl) of culture medium. Secondly, sibling injected oocytes from 77 couples were cultured either in large (35 μl) or in mini drops (7 μl). Embryo quality on day-2 and day-3 and blastocyst formation rate on day-5 were evaluated.

RESULTS

No statistically significant difference in terms of embryo quality was detected comparing embryos cultured either in large (35 μl) or small (15 μl) drops until blastocyst stage. Similarly, no difference appeared between large (35 μl) or mini (7 μl) drops until day-3, however a significantly higher blastocyst formation rate was observed in mini (7 μl) drops on day-5.

CONCLUSIONS

Reduced culture volume seems not to influence early embryo development but a reduction of medium appears to positively affect blastocyst development. This supports the hypothesis that the pre-implantation embryo produces autocrine factors which exert a positive effect on embryo development when culture is performed in a reduced volume.

Effect of Dipeptides on In vitro Maturation, Fertilization and Subsequent Embryonic Development of Porcine Oocytes

The effects of amino acids and dipeptides on in vitro production of porcine embryos and accumulation of ammonia in culture medium during developmental stages were examined in this study. The maturation, fertilization and development of embryonic cultures were performed in modified Tissue culture medium (mTCM)-199 supplemented with 10% (v/v) porcine follicular fluid, modified Tyrode's albumin lactate pyruvate (mTALP) medium, and modified North Carolina State University (mNCSU)-23 medium, respectively. In addition, amino acids and dipeptides of different concentrations and combinations were used to treat the embryos. The addition of L-alanyl-L-glutamine (AlnGln)+L-glycyl-L-glutamine (GlyGln) significantly (p<0.05) improved oocyte maturation, fertilization and the incorporation and oxidation of (14)C(U)-glucose when compared to the control group and other treatment groups. Additionally, 2-4 cell, 8-16 cell, morula and blastocyst development increased significantly (p<0.05) following treatment with AlnGln+GlyGln when compared to the control group and other treatment groups, while this treatment reduced the accumulation of ammonia. Taken together, these findings suggest that treatment with AlnGln+GlyGln may play an important role in increasing the rate of porcine oocyte maturation, fertilization and embryonic development by reducing the level of accumulated ammonia measured in the culture media.

IVF culture media: past, present and future

BACKGROUND

The advances in the world of IVF during the last decades have been rapid and impressive and culture media play a major role in this success. Until the 1980s fertility centers made their media in house. Nowadays, there are numerous commercially available culture media that contain various components including nutrients, vitamins and growth factors. This review goes through the past, present and future of IVF culture media and explores their composition and quality assessment.

METHODS

A computerized search was performed in PubMed regarding IVF culture media including results from 1929 until March 2014. Information was gathered from the websites of companies who market culture media, advertising material, instructions for use and certificates of analysis. The regulation regarding IVF media mainly in the European Union (EU) but also in non-European countries was explored.

RESULTS

The keyword 'IVF culture media' gave 923 results in PubMed and 'embryo culture media' 12 068 results dating from 1912 until March 2014, depicting the increased scientific activity in this field. The commercialization of IVF culture media has increased the standards bringing a great variety of options into clinical practice. However, it has led to reduced transparency and comparisons of brand names that do not facilitate the scientific dialogue. Furthermore, there is some evidence suggesting that suboptimal culture conditions could cause long-term reprogramming in the embryo as the periconception period is particularly susceptible to epigenetic alterations. IVF media are now classified as class III medical devices and only CE (Conformité Européene)-marked media should be used in the EU.

CONCLUSION

The CE marking of IVF culture media is a significant development in the field. However, the quality and efficiency of culture media should be monitored closely. Well-designed randomized controlled trials, large epidemiological studies and full transparency should be the next steps. Reliable, standardized models assessing multiple end-points and post-implantation development should replace the mouse embryo assay. Structured long-term follow-up of children conceived by assisted reproduction technologies and traceability are of paramount importance.

Human and mouse embryonic development, metabolism and gene expression are altered by an ammonium gradient in vitro

Ammonium is generated in culture media by the spontaneous deamination of amino acids at 37 °C and through the metabolism of amino acids by human embryos. The appearance of ammonium is a time-dependent phenomenon and can compromise embryo physiology, development and viability. In this study, the effects of a gradient of ammonium on the development, metabolism and transcriptome of human and mouse embryos were investigated. Pronucleate oocytes were cultured in the presence of an ammonium gradient that mimicked the spontaneous deamination of Eagle's amino acids together with 1 mM glutamine. All embryos were cultured in sequential media G1/G2 at 5% O2, 6% CO2 and 89% N2. Human embryo metabolism was assessed through a non-invasive fluorometric analysis of pyruvate consumption. Transcriptome analysis was performed on the resultant blastocysts from both species using a microarray technology. Embryo development prior to compaction was negatively affected by the presence of low levels of ammonium in both species. Human embryo metabolism was significantly inhibited after just 24 and 48 h of culture. Transcriptome analysis of blastocysts from both species revealed significantly altered gene expression profiles, both decreased and increased. Functional annotation of the altered genes revealed the following over represented biological processes: metabolism, cell growth and/or maintenance, transcription, cell communication, transport, development and transcription regulation. These data emphasize the enhanced sensitivity of the cleavage-stage embryo to its environment and highlight the requirement to renew culture media at frequent intervals in order to alleviate the in vitro induced effects of ammonium build-up in the environment surrounding the embryo.

Culture systems: single step

Culture media to support development of zygotes to the blastocyst stage is based either on a single medium or sequential (two-step) media. Single medium culture either with or without day 3 renewal is associated with simplified laboratory protocols and lower costs compared with sequential medium. There are currently insufficient clinical data to conclude that one system, either single or sequential, is superior to the other with regard to clinical performance. This chapter summarizes the rationale for use of a single medium, along with supporting animal and human data for culturing embryos in a single medium, renewed or not renewed.

Embryo culture: can we perform better than nature?

Culture of preimplantation-stage embryos has always been a key element of laboratory embryology and has contributed substantially to the success of many assisted reproduction procedures. During the past decade, its importance has increased as extended in-vitro embryo culture and single blastocyst transfer have become indispensable parts of the approach to decreasing the chance of multiple pregnancy while preserving the overall efficiency of the treatment. However, in spite of the scientific and commercial challenge stimulating research worldwide to optimize embryo culture conditions, a consensus is missing even in the basic principles, including composition and exchange of media, the required physical and biological environment and even the temperature of incubation. This review attempts to summarize the controversies, demonstrate the fragility of some widely accepted dogmas and generate an open-minded debate towards rapid and efficient optimization. New approaches expanding the traditional frames of mammalian embryo culture are also discussed. Although some researchers suppose that the efficiency of the presently applied in-vitro culture systems have already approached the biological limits, authors are confident that substantial improvement may be achieved that may expand considerably the possibilities of future assisted reproduction in humans.

An auto-controlled prospective comparison of two embryos culture media (G III series versus ISM) for IVF and ICSI treatments

PURPOSE

To compare the effects of 2 different media on embryo morphology and development at days 2/3.

METHOD

Six hundred seventy-six attempts from 512 couples were included in this prospective auto-controlled study. Sibling oocytes of all couples undergoing an IVF (n = 286) or ICSI (n = 390) attempt were randomly assigned to either GIII series (Vitrolife) or ISM (Medicult) media. Primary end points were fertilization and embryo morphology rates.

RESULTS

Fertilization rates in GIII series and ISM (IVF: 59.9 vs 62.0% and ICSI: 65.7 vs 66.8%) respectively were not different. GIII series showed an increase, compared to ISM, of early cleavage rate, (IVF: 25.8 vs 16.2% (p = 0.005); ICSI: 40.8 vs 25.5% (p < 0.0001), and good embryo morphology rate at day 2 [IVF: 64.6 vs 57.3% (p = 0.01); ICSI: 74.2 vs 69.4 (p = 0.03)] and at day 3 [IVF: 57.5 vs 49.0% (p = 0.02); ICSI: 67.2 vs 61.6% (p = 0.01)].

CONCLUSIONS

Embryo morphology at days 2/3 was significantly enhanced when the embryos were cultured in GIII series.

Effect of ammonium during in vitro maturation on oocyte nuclear maturation and subsequent embryonic development in pigs

The effects of ammonium in a chemically defined maturation medium on oocyte nuclear maturation and subsequent embryonic development of pigs after in vitro fertilization (IVF) and parthenogenetic activation (PA) were examined. Cumulus-oocyte complexes were matured in Purdue Porcine Medium (PPM) supplemented with 0mM, 0.02mM, 0.2mM, 2mM, or 20mM ammonium chloride, or TCM199 with 10% porcine follicle fluid (TCM+pFF; positive control) at 38.7 degrees C in 7% CO(2) in air for 40-44h. No significant difference (P>0.05) in nuclear maturation was found between oocytes matured in TCM+pFF or PPM with 0mM, 0.02mM and 0.2mM ammonium chloride. However, nuclear maturation was decreased (P<0.05) in oocytes matured in PPM with 2mM or 20mM ammonium. After IVF, oocytes matured in PPM with 20mM ammonium resulted in embryos with reduced (P<0.05) embryonic cleavage and blastocyst development than all other treatment groups. After PA, oocytes matured in PPM with 20mM ammonium resulted in embryos with lesser (P<0.05) embryonic cleavage compared to TCM+pFF. However, PA embryos derived from oocytes matured in PPM with both 2mM and 20mM ammonium had reduced (P<0.05) blastocyst development compared with TCM+pFF. These results demonstrate the detrimental effect of ammonium during in vitro oocyte maturation on nuclear progression to metaphase II. Additionally, the presence of ammonium during in vitro maturation negatively influences subsequent embryonic development, although PA embryos appear to be more sensitive to the negative effects of ammonium during oocyte maturation than do IVF embryos.

Oviductal microsomal epoxide hydrolase (EPHX1) reduces reactive oxygen species (ROS) level and enhances preimplantation mouse embryo development

Somatic cell-embryo coculture enhances embryo development in vitro by producing embryotrophic factor(s) and/or removing harmful substances from the culture environment. Yet, the underlying molecular mechanisms on how somatic cells remove the toxicants from the culture medium remain largely unknown. By using suppression subtractive hybridization, we identified a number of mouse oviductal genes that were up-regulated when developing preimplantation embryos were present in the oviduct. Epoxide hydrolase 1, microsomal (Ephx1 previously known as mEH) was one of these genes. EPHX1 detoxifies genotoxic compounds and participates in the removal of reactive oxygen species (ROS). The transcript of Ephx1 increases in the oviductal epithelium at the estrus stage and in Day 3 of pregnancy as well as in the uterus of ovariectomized mice injected with estrogen or progesterone. Human oviductal epithelial cells OE-E6/E7 express EPHX1 and improve mouse embryo development in vitro. Addition of an EPHX1 inhibitor, cyclohexene oxide (CHO) or 1,1,1-trichloropropene 2,3-oxide (TCPO), to the culture medium increased intracellular and extracellular ROS levels of OE-E6/E7 cells and suppressed the beneficial effect of the cells on embryo development; CHO and TCPO at these concentrations had no adverse effect on OE-E6/E7 growth and embryo development in vitro. Taken together, EPHX1 in oviductal cells may enhance the development of cocultured embryos by protecting them from oxidative stress. Our result supports the notion that somatic cell coculture may enhance embryo development via removal of deleterious substances in the culture medium.

Dissection of culture media for embryos: the most important and less important components and characteristics

Improvements in culture media formulations have led to an increase in the ability to maintain the mammalian embryo in culture throughout the preimplantation and pre-attachment period. Amino acids and specific macromolecules have been identified as being key medium components, whereas temporal dynamics have been recognised as important media characteristics. Furthermore, other laboratory factors that directly impact embryo development and viability have been identified. Such factors include the use of a reduced oxygen tension, an appropriate incubation system and an adequate prescreening of all contact supplies. With rigourous quality systems in place, it is possible to obtain in vivo rates of embryo development in vitro using new media formulations while maintaining high levels of embryo viability. The future of embryo culture will likely be based on novel culture chips capable of providing temporal dynamics while facilitating real-time analysis of embryo physiology.

To QC or not to QC: the key to a consistent laboratory?

A limiting factor in every embryology laboratory is its capacity to grow ‘normal’ embryos. In human in vitro fertilisation (IVF), there is considerable awareness that the environment of the laboratory itself can alter the quality of the embryos produced and the industry as a whole has moved towards the implementation of auditable quality management systems. Furthermore, in some countries, such as Australia, an established quality management system is mandatory for clinical IVF practice, but such systems are less frequently found in other embryology laboratories. Although the same challenges of supporting consistent and repeatable embryo development are paramount to success in all embryology laboratories, it could be argued that they are more important in a research setting where often the measured outcomes are at an intracellular or molecular level. In the present review, we have outlined the role and importance of quality control and quality assurance systems in any embryo laboratory and have highlighted examples of how simple monitoring can provide consistency and avoid the induction of artefacts, irrespective of the laboratory’s purpose, function or species involved.

Embryo culture medium: which is the best?

With the growing move in in-vitro fertilization (IVF) clinics to transfer fewer embryos to women, there is an increasing reliance on the IVF laboratory to maximize embryo viability. Subsequently, there is justified scrutiny on the culture system and the media used to sustain the human embryo in vitro. The transfer of fewer embryos to patients also creates an increased dependence on the ability to cryopreserve embryos successfully. Therefore, in addition to the ability of a culture system to produce a single top-quality embryo for transfer, it is also necessary to enhance the cryotolerance of sibling embryos so that they can survive freezing or vitrification. Therefore, when examining which culture media is the best, it is prudent to not only examine the ability of a culture system to produce a pregnancy with the one or two highest-grade embryos, but also to determine how many embryos from the entire cohort (both fresh and frozen embryos) are capable of producing a live birth. Additionally, research on animal models has demonstrated that stress, and the resultant adaptation to conditions during pre-implantation stages, can affect pregnancy loss and fetal growth. It is therefore important to understand the role of each medium component and to identify possible sources of cellular stress to the embryo that will ultimately affect the function and viability of the conceptus.