The development of fertilized human ova to the blastocyst stage in KSOM(AA) medium: is a two-step protocol necessary?

Bovine embryo production in vitro: evolution of culture media and commercial perspectives

In vitro produced embryos exhibit lower viability compared to their in vivo counterparts. Mammalian preimplantation embryos have the ability to reach the blastocyst stage in diverse culture media, showcasing considerable metabolic adaptability, which complicates the identification of optimal developmental conditions. Despite embryos successfully progressing to the blastocyst stage, adaptation to suboptimal culture environments may jeopardize blastocyst viability, cryotolerance, and implantation potential. Enhancing our capacity to support preimplantation embryonic development in vitro requires a deeper understanding of fundamental embryo physiology, including preferred metabolic substrates and pathways utilized by high-quality embryos. Armed with this knowledge, it becomes achievable to optimize culture conditions to support normal, in vivo-like embryo physiology, mitigate adaptive stress, and enhance viability. The objective of this review is to summarize the evolution of culture media for bovine embryos, highlighting significant milestones and remaining challenges.

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

OBJECTIVE

To compare the effect of a fully undisturbed culture strategy over a sequential one on embryo in vitro development and clinical outcomes in intracytoplasmic sperm injection (ICSI) cycles.

DESIGN

Retrospective cohort study.

SETTING

University-affiliated private IVF center.

PATIENT(S)

This study included 4,564 ICSI cycles performed over 5 years, including autologous and oocyte donation treatments with extended embryo culture until blastocyst in one of the two defined culture strategies.

INTERVENTION(S)

Embryo cohorts were cultured in one of two culture systems: a fully undisturbed culture, including an incubator with integrated time-lapse technology, a one-step culture medium and embryo selection assisted by semi-automatic tools on the basis of embryo morphokinetics, or a sequential culture, using a conventional benchtop incubator, sequential media and traditional morphological evaluation under optical microscope. The effect of the culture strategies on embryo development and clinical outcomes was quantified by generalized estimated equations, controlling for possible confounders through the inverse probability of the treatment weighting method.

MAIN OUTCOME MEASURE(S)

Weighted odds ratios (ORs) and 95% confidence intervals (CIs) for live birth rate after fresh single embryo transfer and the cumulative live birth rate. In addition, blastocyst development and morphology and other intermediate outcomes were also assessed.

RESULT(S)

A significant positive association was found between the employment of undisturbed embryo culture and higher live birth rate in the first embryo transfer in both autologous (OR, 1.617; 95% CI, 1.074-2.435) and oocyte donation cycles (OR, 1.316; 95% CI, 1.036-1.672). Cumulative live birth rate after 1-year follow-up was also positively associated with the undisturbed culture strategy in oocyte donation cycles (OR, 1.5; 95% CI, 1.179-1.909), but not in autologous cycles (OR, 1.051; 95% CI, 0.777-1.423). Similarly, blastocyst rate, good morphology blastocyst rate, and utilization rate were positively associated with the employment of undisturbed culture in oocyte donation cycles, but not in autologous cycles.

CONCLUSION(S)

These findings imply that a culture system combining integrated time-lapse incubators with a one-step culture medium may enhance the success rates of patients undergoing ICSI treatment by increasing the production of higher quality blastocysts and improving embryo selection while streamlining laboratory procedures and workflow.

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.

Effects of time-restricted feeding and type of food on fertility competence in female mice

We assessed the effects of feeding regimen (ad libitum vs. time-restricted food access) and type of food (normal chow (NC: 12% fat) vs. moderately high calorie diet (mHCD: 31% fat)) on fertility competence of female mice. Mice fed mHCD had higher number of oocytes than mice fed NC. On the other hand, when mice were fed NC under time-restricted access to food (NT), the developmental rate to the blastocyst per number of normally fertilized ova was significantly decreased compared to others. The reactive oxygen species (ROS) level in oocytes increased in time-restricted food access and NC group. Transcriptome analysis of whole ovarian tissues from these mice showed a change in the cholesterol metabolism among the four groups. Time-restricted food access decreased serum LDL cholesterol level in both NC and mHCD groups. Moreover, the number of atretic follicles increased in NT mice compared to ad libitum food access mice. The present study shows that mHCD feeding increases the number of ovulated oocytes and that time-restricted feeding of NC impairs the developmental competence of oocytes after fertilization, probably due to the changes in serum cholesterol levels and an increase in the ROS content in oocytes.

A coarse-grained NADH redox model enables inference of subcellular metabolic fluxes from fluorescence lifetime imaging

Mitochondrial metabolism is of central importance to diverse aspects of cell and developmental biology. Defects in mitochondria are associated with many diseases, including cancer, neuropathology, and infertility. Our understanding of mitochondrial metabolism in situ and dysfunction in diseases are limited by the lack of techniques to measure mitochondrial metabolic fluxes with sufficient spatiotemporal resolution. Herein, we developed a new method to infer mitochondrial metabolic fluxes in living cells with subcellular resolution from fluorescence lifetime imaging of NADH. This result is based on the use of a generic coarse-grained NADH redox model. We tested the model in mouse oocytes and human tissue culture cells subject to a wide variety of perturbations by comparing predicted fluxes through the electron transport chain (ETC) to direct measurements of oxygen consumption rate. Interpreting the fluorescence lifetime imaging microscopy measurements of NADH using this model, we discovered a homeostasis of ETC flux in mouse oocytes: perturbations of nutrient supply and energy demand of the cell do not change ETC flux despite significantly impacting NADH metabolic state. Furthermore, we observed a subcellular spatial gradient of ETC flux in mouse oocytes and found that this gradient is primarily a result of a spatially heterogeneous mitochondrial proton leak. We concluded from these observations that ETC flux in mouse oocytes is not controlled by energy demand or supply, but by the intrinsic rates of mitochondrial respiration.

Fibrin-mediated growth restriction of early-stage human trophoblasts is switched to growth promotion through fibrinolysis

STUDY QUESTION

Does fibrin promote trophoblast growth in human and mouse blastocysts during early embryo implantation?

SUMMARY ANSWER

Mouse blastocysts were unaffected by fibrin; however, human blastocysts were significantly suppressed by fibrin in trophoblast growth and then switched to growth promotion through increased fibrinolysis with urokinase-type plasminogen activator (uPA) activity.

WHAT IS KNOWN ALREADY

Fibrin(ogen) plays an important role in various physiological processes and is also critical for maintaining feto-maternal attachment during pregnancy. The addition of fibrin to embryo transfer media has been used to increase implantation rates in human ART; however, its mechanism of action' in vitro has not yet been characterized.

STUDY DESIGN, SIZE, DURATION

Vitrified mouse and human blastocysts were warmed and individually cultured in vitro for up to 120 and 168 h, respectively, on a fibrin substrate. Blastocysts were cultured at 37°C in 6% CO2, 5% O2 and 89% N2. Blastocyst development and related fibrinolytic factors were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

ICR strain mouse embryos were purchased from a commercial supplier. Human blastocysts were donated with informed consent from two fertility centers. Mouse and human blastocysts cultured on fibrin-coated plates were compared to those on non-coated and collagen-coated plates in vitro. Trophoblast growth and fibrin degradation were assessed based on the cell area and fibrin-free area, respectively. Fibrinolytic factors were detected in supernatants using plasminogen-casein zymography. The fibrinolytic activity of blastocysts was investigated using a selective uPA inhibitor, exogenous uPA, plasminogen activator inhibitor-1 (PAI-1) inhibitor and fibrin degradation products (FDPs). Fibrinolysis-related mRNA expression level was detected using quantitative real-time PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Fibrin did not affect the developmental speed or morphology of mouse blastocysts, and a large fibrin-degrading region was observed in the attachment stage. In contrast, fibrin significantly suppressed the outgrowth of trophoblasts in human blastocysts, and trophoblasts grew after the appearance of small fibrin-degrading regions. uPA was identified as a fibrinolytic factor in the conditioned medium, and uPA activity was significantly weaker in human blastocysts than in mouse blastocysts. The inhibition of uPA significantly reduced the outgrowth of trophoblasts in mouse and human blastocysts. Human blastocysts expressed PLAU (uPA), PLAUR (uPA receptor), SERPINE1 (PAI-1) and SERPINB2 (PAI-2), whereas mouse blastocysts were limited to Plau, Plaur and Serpine1. In a subsequent experiment on human blastocysts, the addition of exogenous uPA and the PAI-1 inhibitor promoted trophoblast growth in the presence of fibrin, as did the addition of FDPs.

LIMITATIONS, REASONS FOR CAUTION

This model excludes maternal factors and may not be fully reproduced in vivo. Donated human embryos are surplus embryos that may inherently exhibit reduced embryonic development. In addition, donated ART-derived embryos may exhibit weak uPA activity, because women with sufficient uPA-active embryos may not originally require ART. The present study used orthodox culture methods, and results may change with the application of recently developed protocols for culture blastocysts beyond the implantation stage.

WIDER IMPLICATIONS OF THE FINDINGS

The present results suggest that the distinct features of trophoblast outgrowth in human blastocysts observed in the presence of fibrin are regulated by a phenotypic conversion induced by contact with fibrin and FDPs. Mouse embryos did not exhibit the human phenomenon, indicating that the present results may be limited to humans.

STUDY FUNDING/COMPETING INTEREST(S)

The present study was supported by the Department of Obstetrics and Gynecology at the Hamamatsu University School of Medicine and Kishokai Medical Corporation. None of the authors have any conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Quality of embryos on day 7 after medium refreshment on day 6: a prospective trial

STUDY QUESTION

Are embryos that fail to meet biopsy or freezing criteria on day 6 (D6) more likely to meet these criteria on day 7 (D7) if cultured in fresh medium from D6 to D7?

SUMMARY ANSWER

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7, with an adverse effect for women ≥40 years old.

WHAT IS KNOWN ALREADY

Embryo development in continuous single-step medium, from fertilization to the blastocyst stage, is equivalent to that using a sequential media protocol. However, there remains a theoretical benefit of refreshing the culture environment by transitioning slowly developing D6 embryos to a fresh medium droplet of the same composition, with a renewed source of nutrients and a milieu free of metabolic toxins.

STUDY DESIGN, SIZE, DURATION

This was a prospective trial of culture media exposure in which embryos were randomized on D6 to remain in the same culture medium from D3 to D7 (continuous, n = 620) or be moved to fresh medium (fresh, n = 603) on D6, with re-evaluation on D7. Data were collected from IVF cycles, with or without ICSI, between 29 March 2019 and 17 February 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Embryos from 298 women, aged 18-44 years, from cycles with or without preimplantation genetic testing (PGT) that did not meet criteria for biopsy and/or freeze on D6 were included in the study. Embryos were only included if there was a minimum of two embryos meeting the inclusion criteria in any cohort. Only the first cycle undertaken by each woman in the study period from which embryos were randomized was included.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1254 embryos were randomized from 312 cycles (209 non-PGT and 103 PGT) including 200 women undergoing IVF without PGT and 98 women who underwent PGT. The proportion of usable blastocysts on D7 did not differ between groups: 10.1% (61/603) in fresh versus 9.7% (60/620) in continuous medium (relative risk (RR) 1.05, 95% CI 0.74-1.47)). Embryos from women ≥40 years old had a significantly decreased likelihood of achieving a usable blastocyst on D7 after culture in fresh versus continuous medium: 3.5% versus 12.2%; RR 0.29, 95% CI 0.08-0.98. In total, 9.9% of embryos otherwise discarded on D6 met the criteria for biopsy and/or freeze on D7.

LIMITATIONS, REASONS FOR CAUTION

Future work investigating implantation, clinical pregnancy and miscarriage rates with D7 embryos is still needed.

WIDER IMPLICATIONS OF THE FINDINGS

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7 overall. Younger women were more likely to develop D7 embryos after refreshment of medium on D6, while an adverse effect was seen in women ≥40 years old. However, by extending the culture of embryos to D7, additional blastocysts become available for clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided through the Department of Obstetrics and Gynecology at Brigham and Women's Hospital. I.G.I. works with Teladoc Health. A.L. has no disclosures. E.S.G. works as a consultant for Teladoc Health, and a writer and editor for UpToDate and BioMed Central. C.R. is a board member of the American Society for Reproductive Medicine and works with UpToDate.

TRIAL REGISTRATION NUMBER

N/A.

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.

Treatment with Laevo (L)-carnitine reverses the mitochondrial function of human embryos

PURPOSE

Laevo (l)-carnitine plays important roles in reducing the cytotoxic effects of free fatty acids by forming acyl-carnitine and promoting beta-oxidation, leading to alleviation of cell damage. Recently, the mitochondrial functions in morula has been shown to decrease with the maternal age. Here, we assessed the effect of l-carnitine on mitochondrial function in human embryos and embryo development.

METHODS

To examine the effect of L-carnitine on mitochondrial function in morulae, 38 vitrified-thawed embryos at the 6-11-cell stage on day 3 after ICSI were donated from 19 couples. Each couple donated two embryos. Two siblings from each couple were divided randomly into two groups and were cultured in medium with or without 1 mM L-carnitine. The oxygen consumption rates (OCRs) were measured at morula stage. The development of 1029 zygotes cultured in medium with or without L-carnitine was prospectively analyzed.

RESULTS

Addition of L-carnitine to the culture medium significantly increased the OCRs of morulae and improved the morphologically-good blastocyst formation rate per zygote compared with sibling embryos. Twenty healthy babies were born from embryos cultured in L-carnitine-supplemented medium after single embryo transfers.

CONCLUSION(S)

L-carnitine is a promising culture medium supplement that might be able to counteract the decreased mitochondrial function in human morula stage embryos.

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

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

Mitochondrial oxygen consumption rate of human embryos declines with maternal age

PURPOSE

The fertility of women decreases with age because of factors such as an increased incidence of aneuploidies and-possibly-decreased mitochondrial activity in oocytes. However, the relationship between maternal aging and mitochondrial function of their embryos remains unknown. Here, we assessed the relationship between maternal age and mitochondrial functions in their oocytes and embryos METHODS: The relationships between maternal age and oxygen consumption rates (OCRs), mitochondrial DNA (mtDNA) copy numbers, or blastocyst development was investigated using 81 embryos donated from 63 infertility couples. The developmental rates from morulae to blastocysts were retrospectively analyzed using data of 105 patients.

RESULTS

The OCRs of morulae decreased with maternal age (r² = 0.48, P < 0.05) although there were no relationships between maternal age and mtDNA copy number in any stages. The more oxygen consumed at the morula stage, the shorter time was required for embryo development to the mid-stage blastocyst (r² = 0.236, P < 0.05). According to the clinical data analysis, the developmental rate from morulae to blastocysts decreased with maternal age (P < 0.05, < 37 years, 81.1%, vs. ≥ 37 years, 64.1%).

CONCLUSIONS

The data of the present study revealed that mitochondrial function at the morula stage of human embryos decreased with their maternal age and a decrease of mitochondrial function led to slow-paced development and impaired developmental rate from morulae to blastocysts.

Type of protein supplement in cryopreservation solutions impacts on the degree of ultrastructural damage in frozen-thawed human oocytes

Protein sources used as supplements of IVF culture media are known to have several implications for the function and stability of embryo culture environment. In fact, they i) transport biologically active molecules ii) chelate heavy metals, iii) regulate media pH, iii) scavenge reactive oxygen species (ROS) and iv) attenuate osmotic stress to which cells are exposed in sub-optimal culture conditions. Instead, their specific relevance to the formulation of cryopreservation solutions used for gamete and embryo cryopreservation remains uncertain. In the present work, we tested the hypothesis that different protein supplements present in cryopreservation solutions, serum or plasma protein solution (PPS), or different concentrations of the same supplement (serum), are associated with different types and/or magnitude of cryopreservation-derived cell damage. To this end, using cryopreservation solutions containing serum or PPS, donated supernumerary human mature oocytes were frozen-thawed by slow freezing and compared with fresh controls. Ultrastructural markers of oocyte quality were adopted as objective measure to assess possible damage from cryopreservation. The study results indicate that the adoption of serum minimises cell damage induced by cryopreservation. Indeed, typical hallmarks of cryodamage in human oocytes, i.e. loss of cortical granules, zona pellucida hardening and above all vacuolization, were largely reduced in oocytes cryopreserved with solutions containing serum, especially if used a higher concentration. This suggest that oocyte cryopreservation still has significant margins of improvement that may derive also from composition of cryopreservation media.

Systematic Development, Validation and Optimization of a Human Embryo Culture System

Objective: To develop and validate a reliable in vitro culture system for human embryos. Design: Retrospective analyses of a series of four studies were conducted between 2006 and 2010 to assess the effect of incubator type (CO2 box versus Tri-gas minibox), media type, oil type, and hyaluronate supplementation. Optimization of in vitro blastocyst development was verified by assessing our National CDC/ART Surveillance reports between 2010 and 2016. Material and Methods: All patients experienced controlled ovarian hyperstimulation, followed by egg retrieval 35 h post-hCG. Cumulus-oocyte complexes were temporarily cultured in P1 or LG Fert medium plus HSA. Eggs were moved to a more complex media (G-medium or Global®-LG medium) containing a synthetic protein and embryo adhesion supplement (SPS and EAS, respectively; mLG) post-ICSI insemination. Zygotes were assigned to group culture in 25 µl droplets under oil (light mineral oil or paraffin oil; 37 °C) and embryo development was evaluated on Days 3, 5, and 6 and transferred on Day 3 to 5 depending on the number/quality of embryos available and the IVF history of the patient. Transfers were performed under ultrasound guidance, primarily using a Sureview-Wallace catheter, and enriched ET medium containing 500 µg/mL EAS. Results: Pilot study results (Expt. 1) showed that a mLG single-step medium could be effectively used in combination with Sanyo MCO-5 tri-gas (TG) incubators. Once adapted to SCIRS Lab in 2007 (Expt. 2), the latter culture system yielded improved blastocyst production and pregnancy outcomes compared to CO2 in air sequential incubation in P1/Multi-blast medium. In Expt. 3, the mLG/TG system yielded high levels of ≥2BB quality blastocysts (51 to 66%) across all age groups, and greater (p < 0.05) pregnancy success/live birth rates using fewer embryos transferred on Day 5 versus Day 3. After validating its clinical effectiveness, mLG was then prospectively compared to a new generation G-media (1.5 & 2.5; Expt. 4) and determined that the crossover treatment using paraffin oil (Ovoil™) allowed the mLG system to be optimized. Subsequently, a compilation of our Annual CDC/ART reported data over six years verified the overall viability of in vitro cultured and vitrified blastocysts produced in the mLG/TG system. Conclusion: By systematically evaluating and implementing various components of an embryo culture system we were able to optimize blastocyst development over the last decade. Our mLG/TG culture system modified an exceptionally well designed KSOMAA LG medium using endotoxin-free EAS and SPS additives to support cellular membrane wellness under stressful in vitro conditions (e.g., culture, cell biopsy, vitrification). Our use of the mLG/TG culture system has proven to be effective, creating reliably high blastocyst production, implantation, and healthy live births.

Deep learning as a predictive tool for fetal heart pregnancy following time-lapse incubation and blastocyst transfer

STUDY QUESTION

Can a deep learning model predict the probability of pregnancy with fetal heart (FH) from time-lapse videos?

SUMMARY ANSWER

We created a deep learning model named IVY, which was an objective and fully automated system that predicts the probability of FH pregnancy directly from raw time-lapse videos without the need for any manual morphokinetic annotation or blastocyst morphology assessment.

WHAT IS KNOWN ALREADY

The contribution of time-lapse imaging in effective embryo selection is promising. Existing algorithms for the analysis of time-lapse imaging are based on morphology and morphokinetic parameters that require subjective human annotation and thus have intrinsic inter-reader and intra-reader variability. Deep learning offers promise for the automation and standardization of embryo selection.

STUDY DESIGN, SIZE, DURATION

A retrospective analysis of time-lapse videos and clinical outcomes of 10 638 embryos from eight different IVF clinics, across four different countries, between January 2014 and December 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The deep learning model was trained using time-lapse videos with known FH pregnancy outcome to perform a binary classification task of predicting the probability of pregnancy with FH given time-lapse video sequence. The predictive power of the model was measured using the average area under the curve (AUC) of the receiver operating characteristic curve over 5-fold stratified cross-validation.

MAIN RESULTS AND THE ROLE OF CHANCE

The deep learning model was able to predict FH pregnancy from time-lapse videos with an AUC of 0.93 [95% CI 0.92-0.94] in 5-fold stratified cross-validation. A hold-out validation test across eight laboratories showed that the AUC was reproducible, ranging from 0.95 to 0.90 across different laboratories with different culture and laboratory processes.

LIMITATIONS, REASONS FOR CAUTION

This study is a retrospective analysis demonstrating that the deep learning model has a high level of predictability of the likelihood that an embryo will implant. The clinical impacts of these findings are still uncertain. Further studies, including prospective randomized controlled trials, are required to evaluate the clinical significance of this deep learning model. The time-lapse videos collected for training and validation are Day 5 embryos; hence, additional adjustment would need to be made for the model to be used in the context of Day 3 transfer.

WIDER IMPLICATIONS OF THE FINDINGS

The high predictive value for embryo implantation obtained by the deep learning model may improve the effectiveness of previous approaches used for time-lapse imaging in embryo selection. This may improve the prioritization of the most viable embryo for a single embryo transfer. The deep learning model may also prove to be useful in providing the optimal order for subsequent transfers of cryopreserved embryos.

STUDY FUNDING/COMPETING INTEREST(S)

D.T. is the co-owner of Harrison AI that has patented this methodology in association with Virtus Health. P.I. is a shareholder in Virtus Health. S.C., P.I. and D.G. are all either employees or contracted with Virtus Health. D.G. has received grant support from Vitrolife, the manufacturer of the Embryoscope time-lapse imaging used in this study. The equipment and time for this study have been jointly provided by Harrison AI and Virtus Health.

Blastocyst culture and transfer in clinically assisted reproduction: a committee opinion

The purposes of this Practice Committee Opinion, which replaces the 2013 ASRM Practice Committee Opinion of the same name (Fertil Steril 2013; 99:667-72), are to review the literature regarding the clinical application of blastocyst transfer and identify the potential risks and laboratory issues related to the use of this technology. This document does not apply to patients undergoing blastocyst culture and transfer for preimplantation genetic testing.

Feline embryo development in commercially available human media supplemented with fetal bovine serum

Feline embryo development was examined for 7 days after fertilization using commercially available human media supplemented with 0.3% bovine serum albumin (BSA) or 5% fetal bovine serum (FBS). Cumulus-oocyte complexes were categorized as Grades 1, 2, and 3 according to morphology. Only-One Medium (OM) was used for in vitro culture (IVC) in OM + BSA, OM + FBS, and OM + BSA/FBS, with BSA supplementation for the first 2 days and FBS for the subsequent 5 days. Embryos cultured in Early Culture Medium (1–2 days) and Blastocyst Medium (3–7 days) were defined as EB + BSA and EB + BSA/FBS. The developmental rate until the blastocyst stage of Grade 1 and 2 oocytes cultured in OM + BSA/FBS was higher than for the other groups and was significantly higher than for the OM + BSA and EB + BSA groups (P<0.01). Grade 3 oocytes cultured in OM + BSA/FBS also showed the greatest proportion of blastocyst formation. However, FBS supplementation throughout the IVC period reduced blastocyst number. The percentage of 2 pronuclei after fertilization as well as blastocyst cell number were significantly higher in Grade 1 and 2 than Grade 3 oocytes when cultured in OM + BSA/FBS (P<0.05). These results indicate that commercially available OM supplemented with BSA for the first 2 days of culture and FBS for the subsequent 5 days is suitable for feline embryo development until the blastocyst stage.

Randomized controlled trial of low (5%) versus ultralow (2%) oxygen for extended culture using bipronucleate and tripronucleate human preimplantation embryos

OBJECTIVE

To determine whether [1] exposure of embryos to 5% oxygen (O₂) from day 1 (D1) to D3, and then to 2% O₂ from D3 to D5, improves total blastocyst yield, as compared with continuous exposure to 5% O₂; and [2] extended culture in 2% O₂ alters key metabolic processes and O₂-regulated gene expression in human preimplantation embryos.

DESIGN

Randomized controlled trial.

SETTING

Academic medical center.

PATIENT(S)

Bipronucleate and tripronucleate embryos donated for research.

INTERVENTION(S)

On D1, sibling zygotes were randomized to culture in 5% O₂ from D1 to D5 (n = 102; "5% group") or 5% O₂ from D1 to D3, then 2% O₂ from D3 to D5 (n = 101, "2% group").

MAIN OUTCOME MEASURE(S)

Developmental stage and grade; D5 total cell counts; mass spectrometry of spent media; quantitative polymerase chain reaction of 21 genes in inner cell mass and trophectoderm.

RESULT(S)

Among cleaved embryos (n = 176, 87%), those in the 2% group were less likely to arrest at the cleavage stage on D5 (34 of 87, 39.1%) compared with the 5% group (52 of 89, 58.4%) (adjusted odds ratio 0.38, 95% confidence interval 0.18-0.80). Those in the 2% group were more likely to blastulate (35 of 87, 40.2%) than those in the 5% group (20 of 89, 22.5%) (adjusted odds ratio 2.55, 95% confidence interval 1.27-5.12). Culture in 2% O₂ was associated with significantly fewer cells in early and advanced blastocysts, alteration in relative abundances of anabolic amino acids and metabolites involved in redox homeostasis, and differential expression of MUC1 in trophectoderm.

CONCLUSION(S)

These findings provide foundational evidence for future investigation of 2% O₂ as the preferred O₂ tension for extended culture of human embryos.

Histone 3 lysine 9 acetylation is a biomarker of the effects of culture on zygotes

Acetylation of histone proteins is a major determinant of chromatin structure and function. Fertilisation triggers a round of chromatin remodelling that prepares the genome for the first round of transcription from the new embryonic genome. In this study we confirm that fertilisation leads to a marked progressive increase in the level of histone 3 lysine 9 acetylation in both the paternally and maternally derived genomes. The culture of zygotes in simple defined media caused a marked increase in the global level of acetylation and this affected the male pronucleus more than the female. The culture created a marked asymmetry in staining between the two pronuclei that was not readily detected in zygotes collected directly from the reproductive tract and was ameliorated to some extent by optimized culture media. The increased acetylation caused by culture resulted in increased transcription of Hspa1b, a marker of embryonic genome activation. Pharmacological analyses showed the hyperacetylation of H3K9 and the increased expression of Hspa1b caused by culture were due to the altered net activity of a range of histone acetylases and deacetylases. The marked hyperacetylation of histone 3 lysine 9 caused by culture of zygotes may serve as an early biomarker for the effects of culture on the normal function of the embryo. The results also provide further evidence for an effect of the stresses associated with assisted reproductive technologies on the normal patterns of epigenetic reprogramming in the early embryo.

Embryo development until blastocyst stage with and without renewal of single medium on day 3

Objective

This study aimed to assess the effects of using a single culture medium not renewed on day 3 on the development of the embryo up to the blastocyst stage.

Methods

The study was carried out in the Assisted Reproduction Laboratory of Clínica Miraflores in the period ranging from April to December of 2016. The study included 589 human embryos obtained from 82 couples submitted to IVF/ICSI with donor oocytes. The couples were randomly divided into two groups: group 1 (medium renewed on day 3) and group 2 (medium not renewed on day 3).

Results

Significant differences in pregnancy rates, implantation rates, and blastocyst formation were not observed.

Conclusion

No statistically significant difference was found between the groups with respect to the analyzed parameters. However, a non-significant trend was observed in favor of the group without medium renewal for clinical pregnancy and positive pregnancy rates (β-hCG).

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.

Quantitative and qualitative changes of mitochondria in human preimplantation embryos

PURPOSE

The oxygen consumption rates (OCRs) in mice and cattle have been reported to change during preimplantation embryogenesis. On the other hand, mitochondrial DNA (mtDNA) copy number has been shown to be unchanged in mice and changed in cattle and pigs. The interactions between mitochondrial functions and mtDNA copy numbers in human embryos during preimplantation development remain obscure.

METHODS

Sixteen oocytes and 100 embryos were used to assess mtDNA copy numbers and OCR. Three oocytes and 12 embryos were used to determine cytochrome c oxidase activity. All specimens were obtained between July 2004 and November 2014, and donated from couples after they had given informed consent. Mature oocytes and embryos at 2-14-cell, morula, and blastocyst stages were used to assess their OCR in the presence or absence of mitotoxins. The mtDNA copy number was determined using the samples after analysis of OCR. The relationships between developmental stages and OCR, and developmental stages and mtDNA copy number were analyzed. Furthermore, cytochrome c oxidase activity was determined in oocytes and 4-cell to blastocyst stage embryos.

RESULTS

The structure of inner mitochondrial membranes and their respiratory function developed with embryonic growth and the mtDNA copy numbers decreased transiently compared with those of oocytes. The undifferentiated state of inner cell mass cells appears to be associated with a low OCR. On the other hand, the mtDNA copy numbers increased and aerobic metabolism of mitochondria increased in trophectoderm cells.

CONCLUSIONS

The mitochondrial respiratory function of human embryos developed along with embryonic growth although the copy numbers of mtDNA decreased transiently before blastulation. OCRs increased toward the morula stage ahead of an increase of mtDNA at the time of blastulation. Data regarding changes in mitochondrial function and mtDNA copy number during preimplantation development of human embryos will be useful for the development of ideal culture media.

Blastocyst Development in a Single Medium Compared to Sequential Media: A Prospective Study With Sibling Oocytes

The aim of the present study was to compare blastocyst formation rates after embryo culture in a single medium (Global) as compared to sequential media (ISM1/BlastAssist). In this prospective trial with sibling oocytes, 542 metaphase II (ΜΙΙ) oocytes from 31 women were randomly and equally divided to be fertilized and cultured to the blastocyst stage in either sequential media (ISM1/BlastAssist; n = 271 MII oocytes) or a single medium (Global; n = 271 MII oocytes). In both groups, embryos were cultured in an interrupted fashion with media changes on day 3. Embryo transfer was performed on day 5. Blastocyst formation rates on day 5 (61.7% ± 19.9% vs 37.0% ± 25.5%, P < .001) were significantly higher following culture in Global as compared to ISM1/BlastAssist, respectively. Fertilization rates, cleavage rates, and percentage of good quality embryos on day 3 were similar between Global and ISM1/BlastAssist, respectively. The percentages of good quality blastocysts (63.0% ± 24.8% vs 32.1% ± 37.2%, P < .001), blastocysts selected for transfer (27.8% ± 19.2% vs 11.1% ± 14.4%, P = .005), and utilization rates (62.5% ± 24.8% vs 39.0% ± 25.2%, P < .001) were significantly higher in Global as compared to ISM1/BlastAssist, respectively. In conclusion, culture in Global was associated with higher blastocyst formation rates compared to ISM1/BlastAssist, suggesting that the single medium may provide better support to the developing embryo.

Building a model to increase live birth rate through patient-specific optimization of embryo transfer day

PURPOSE

Many practices are moving away from cleavage-stage transfer in favor of blastocyst transfer. The purpose of this study is to evaluate how the overall live birth rate for fresh IVF cycles may increase by optimizing the day of transfer for each patient.

METHODS

This is a retrospective cohort study of 1225 first fresh autologous IVF cycles performed between May 2012 and November 2013. Stepwise logistic regression was used to determine characteristics associated with live birth following cleavage-stage versus blastocyst transfer. The optimal transfer day (i.e., the day that maximized the odds of live birth) was determined for each patient, and the actual live birth rate was compared with the projected rate had each patient undergone transfer on her optimal day.

RESULTS

With transfer on the optimal day for each patient, the overall birth rate would have increased from its actual value of 34.8 % to a projected 43.0 %, a 24 % increase. The majority of this increase (21 %) was due to optimization of patients who underwent cleavage-stage transfer but had a higher projected birth rate from blastocyst transfer. These patients were older (37.8 versus 36.0 years, p < 0.01) and had more follicles ≥18 mm than patients who should have remained with a cleavage-stage transfer.

CONCLUSIONS

A model can be built enabling patient-specific identification of optimal transfer day; within this discovery cohort, such optimization was estimated to increase live birth following a fresh transfer by 24 %. This study suggests blastocyst transfer should be more widely offered; however, there remain patients for whom a cleavage-stage transfer may yield better outcomes.

Time to take human embryo culture seriously

STUDY QUESTION

Is it important that end-users know the composition of human embryo culture media?

SUMMARY ANSWER

We argue that there is as strong case for full transparency concerning the composition of embryo culture media intended for human use.

WHAT IS KNOWN ALREADY

Published data suggest that the composition of embryo culture media may influence the phenotype of the offspring.

STUDY DESIGN, SIZE, DURATION

A review of the literature was carried out.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data concerning the potential effects on embryo development of culture media were assessed and recommendations for users made.

MAIN RESULTS AND THE ROLE OF CHANCE

The safety of ART procedures, especially with respect to the health of the offspring, is of major importance. There are reports from the literature indicating a possible effect of culture conditions, including culture media, on embryo and fetal development. Since the introduction of commercially available culture media, there has been a rapid development of different formulations, often not fully documented, disclosed or justified. There is now evidence that the environment the early embryo is exposed to can cause reprogramming of embryonic growth leading to alterations in fetal growth trajectory, birthweight, childhood growth and long-term disease including Type II diabetes and cardiovascular problems. The mechanism for this is likely to be epigenetic changes during the preimplantation period of development. In the present paper the ESHRE working group on culture media summarizes the present knowledge of potential effects on embryo development related to culture media, and makes recommendations.

LIMITATIONS, REASONS FOR CAUTION

There is still a need for large prospective randomized trials to further elucidate the link between the composition of embryo culture media used and the phenotype of the offspring. We do not presently know if the phenotypic changes induced by in vitro embryo culture represent a problem for long-term health of the offspring.

WIDER IMPLICATIONS OF THE FINDINGS

Published data indicate that there is a strong case for demanding full transparency concerning the compositions of and the scientific rationale behind the composition of embryo culture media.

STUDY FUNDING/COMPETING INTERESTS

This work was funded by The European Society for Human Reproduction and Embryology. No competing interests to declare.

Blastocyst culture using single versus sequential media in clinical IVF: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The purpose of this study was to undertake a review of the available evidence comparing the use of a single medium versus sequential media for embryo culture to the blastocyst stage in clinical IVF.

METHODS

We searched the Cochrane Central, PubMed, Scopus, ClinicalTrials.gov, Current Controlled Trials and WHO International Clinical Trials Registry Platform to identify randomized controlled trials comparing single versus sequential media for blastocyst culture and ongoing pregnancy rate. Included studies randomized either oocytes/zygotes or women. Eligible oocyte/zygote studies were analyzed to assess the risk difference (RD) and 95 % confidence intervals (CI) between the two media systems; eligible woman-based studies were analyzed to assess the risk ratio (RR) and 95 % CI for clinical pregnancy rate.

RESULTS

No differences were observed between single and sequential media for either ongoing pregnancy per randomized woman (relative risk (RR) = 0.9, 95 % CI = 0.7 to 1.3, two studies including 246 women, I ² = 0 %) or clinical pregnancy per randomized woman (RR = 1.0, 95 % CI = 0.7 to 1.4, one study including 100 women); or miscarriage per clinical pregnancy: RR = 1.3, 95 % CI = 0.4 to 4.3, two studies including 246 participants, I ² = 0 %). Single media use was associated with an increase blastocyst formation per randomized oocyte/zygote (relative distribution (RD) = +0.06, 95 % CI = +0.01 to +0.12, ten studies including 7455 oocytes/zygotes, I ² = 83 %) but not top/high blastocyst formation (RD = +0.05, 95 % CI = -0.01 to +0.11, five studies including 3879 oocytes/zygotes, I ² = 93 %). The overall quality of the evidence was very low for all these four outcomes.

CONCLUSIONS

Although using a single medium for extended culture has some practical advantages and blastocyst formation rates appear to be higher, there is insufficient evidence to recommend either sequential or single-step media as being superior for the culture of embryos to days 5/6. Future studies comparing these two media systems in well-designed trials should be performed.

Sequential versus Monophasic Media Impact Trial (SuMMIT): a paired randomized controlled trial comparing a sequential media system to a monophasic medium

OBJECTIVE

To determine whether sequential or monophasic media is the more optimal formulation for blastocyst development and sustained implantation rates (SIR) in IVF.

DESIGN

Paired randomized controlled trials.

SETTING

Academic.

PATIENT(S)

Infertile couples (N = 192) with female partner ≤42 years old and normal ovarian reserve.

INTERVENTION(S)

Fertilized zygotes from each patient were randomly divided into two groups: [1] cultured in sequential media and [2] cultured in monophasic medium. Sequential media consisted of Quinn's Advantage Cleavage Medium (SAGE) followed by Blast Assist (Origio). The monophasic medium used was Continuous Single Culture (Irvine Scientific). Paired ETs were accomplished by transferring the best euploid blastocyst from each media group. DNA fingerprinting was used to link outcomes.

MAIN OUTCOME MEASURE(S)

The primary outcome measure was the proportion of blastocysts suitable for clinical use. Secondary outcome measures included timing of blastulation, aneuploidy rates, and SIR. Sustained implantation rate is defined as the number fetal heart beats at 8-9 weeks of gestation, divided by the number of embryos transferred.

RESULT(S)

A total of 192 patients had their 2PN embryos (N = 2,257) randomized to each culture system. Sequential media had higher blastulation rate than monophasic medium (55.2% vs. 46.9%). No differences were found in the day of blastulation or aneuploidy rate. Of the 168 patients who had euploid blastocysts suitable for transfer, 126 completed a paired ET. Among the double ETs, there was no difference in implantation between groups.

CONCLUSION(S)

This is the first randomized controlled trial to examine paired euploid transfers of sibling zygotes cultured in sequential versus monophasic media. This study demonstrates that the usable blastocyst rate is greatest after culture in the sequential media tested in comparison with the monophasic formulation selected for study. However, no difference exists in timing of blastulation, aneuploidy, or SIR. Whether these observations are generalizable to other media systems remains to be determined.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01917240.

Blastocyst development in single medium with or without renewal on day 3: a prospective cohort study on sibling donor oocytes in a time-lapse incubator

OBJECTIVE

To evaluate the efficiency of using a continuous (one-step) protocol with a single medium for the culture of human embryos in a time-lapse incubator (TLI).

DESIGN

Prospective cohort study on sibling donor oocytes.

SETTING

University-affiliated in vitro fertilization (IVF) center.

PATIENT(S)

Embryos from 59 patients.

INTERVENTION(S)

Culture in a TLI in a single medium with or without renewal of the medium on day-3.

MAIN OUTCOME MEASURE(S)

Embryo morphology and morphokinetic parameters, clinical pregnancy, take-home baby rate, and perinatal outcomes.

RESULT(S)

The blastocyst rates (68.3 vs. 66.8%) and the proportion of good-quality blastocysts (transferred plus frozen) obtained with the two-step (80.0%) protocol were statistically significantly similar to those obtained in the one-step protocol (72.2%). Similarly, morphokinetic events from early cleavage until late blastocyst stages were statistically significantly equivalent between both groups. No differences were found either in clinical pregnancy rates when comparing pure transfers performed with embryos selected from the two-step (75.0%), one-step (70.0%, respectively), and mixed (57.1%) groups. A total of 55 out of 91 embryos transferred implanted successfully (60.4%), resulting in a total of 37 newborns with a comparable birth weight mean among groups.

CONCLUSION(S)

Our findings support the idea that in a TLI with a controlled air purification system, human embryos can be successfully cultured continuously from day 0 onward in single medium with no need to renew it on day-3. This strategy does not affect embryo morphokinetics or development to term and offers more stable culture conditions for embryos as well as practical advantages and reduced costs for the IVF laboratory.

Culture media for human pre-implantation embryos in assisted reproductive technology cycles

BACKGROUND

Many media are commercially available for culturing pre-implantation human embryos in assisted reproductive technology (ART) cycles. It is unknown which culture medium leads to the best success rates after ART.

OBJECTIVES

To evaluate the safety and effectiveness of different human pre-implantation embryo culture media in used for in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) cycles.

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group's Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, the National Research Register, the Medical Research Council's Clinical Trials Register and the NHS Center for Reviews and Dissemination databases from January 1985 to March 2015. We also examined the reference lists of all known primary studies, review articles, citation lists of relevant publications and abstracts of major scientific meetings.

SELECTION CRITERIA

We included all randomised controlled trials which randomised women, oocytes or embryos and compared any two commercially available culture media for human pre-implantation embryos in an IVF or ICSI programme.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected the studies, assessed their risk of bias and extracted data. We sought additional information from the authors if necessary. We assessed the quality of the evidence using Grades of Recommendation, Assessment, Development and Evaluation (GRADE) methods. The primary review outcome was live birth or ongoing pregnancy.

MAIN RESULTS

We included 32 studies in this review. Seventeen studies randomised women (total 3666), three randomised cycles (total 1018) and twelve randomised oocytes (over 15,230). It was not possible to pool any of the data because each study compared different culture media.Only seven studies reported live birth or ongoing pregnancy. Four of these studies found no evidence of a difference between the media compared, for either day three or day five embryo transfer. The data from the fifth study did not appear reliable.Six studies reported clinical pregnancy rate. One of these found a difference between the media compared, suggesting that for cleavage-stage embryo transfer, Quinn's Advantage was associated with higher clinical pregnancy rates than G5 (odds ratio (OR) 1.56; 95% confidence interval (CI) 1.12 to 2.16; 692 women). This study was available only as an abstract and the quality of the evidence was low.With regards to adverse effects, three studies reported multiple pregnancies and six studies reported miscarriage. None of them found any evidence of a difference between the culture media used. None of the studies reported on the health of offspring.Most studies (22/32) failed to report their source of funding and none described their methodology in adequate detail. The overall quality of the evidence was rated as very low for nearly all comparisons, the main limitations being imprecision and poor reporting of study methods.

AUTHORS' CONCLUSIONS

An optimal embryo culture medium is important for embryonic development and subsequently the success of IVF or ICSI treatment. There has been much controversy about the most appropriate embryo culture medium. Numerous studies have been performed, but no two studies compared the same culture media and none of them found any evidence of a difference between the culture media used. We conclude that there is insufficient evidence to support or refute the use of any specific culture medium. Properly designed and executed randomised trials are necessary.

Abnormal early cleavage events predict early embryo demise: sperm oxidative stress and early abnormal cleavage

Human embryos resulting from abnormal early cleavage can result in aneuploidy and failure to develop normally to the blastocyst stage. The nature of paternal influence on early embryo development has not been directly demonstrated although many studies have suggested effects from spermatozoal chromatin packaging, DNA damage, centriolar and mitotic spindle integrity, and plasma membrane integrity. The goal of this study was to determine whether early developmental events were affected by oxidative damage to the fertilizing sperm. Survival analysis was used to compare patterns of blastocyst formation based on P2 duration. Kaplan-Meier survival curves demonstrate that relatively few embryos with short (<1 hr) P2 times reached blastocysts, and the two curves diverged beginning on day 4, with nearly all of the embryos with longer P2 times reaching blastocysts by day 6 (p < .01). We determined that duration of the 2nd to 3rd mitoses were sensitive periods in the presence of spermatozoal oxidative stress. Embryos that displayed either too long or too short cytokineses demonstrated an increased failure to reach blastocyst stage and therefore survive for further development. Although paternal-derived gene expression occurs later in development, this study suggests a specific role in early mitosis that is highly influenced by paternal factors.

ACE consensus meeting report: culture systems

The UK Association of Clinical Embryologists held a workshop on Culture Systems for assisted conception in Sheffield on 22 May 2013. The meeting was organised in the light of the availability of numerous commercial products for the culture of human preimplantation embryos in vitro and the absence of data comparing the performance of these products. Expert opinions were presented, along with survey data provided by participating IVF Centres. The workshop highlighted the lack of a sound evidence base to support the selection of any one commercial product over another, and raised concerns over the lack of information defining precisely the composition of media, and the potential for adverse long-term effects of such products following their use in assisted conception.

The importance of the cleavage stage morphology evaluation for blastocyst transfer in patients with good prognosis

PURPOSE

To evaluate: (i) the influence of morphology at cleavage stage on blastocyst formation and implantation, and (ii) whether the transfer of low-quality embryos on day-three would be a better approach than the transfer at blastocyst stage.

METHODS

This study included 8,444 embryos obtained from 1,125 patients undergoing ICSI cycles between January/2011 and September/2013. The influence of the quality of the embryo on days-two and -three on blastocyst formation and implantation success was evaluated. Moreover, the implantation potential of low-quality embryos, at cleavage stage, transferred on day-three was compared with the implantation potential of low-quality embryos, at cleavage stage, transferred on day-five.

RESULTS

Low-quality embryos on day-two had an approximate 20 % decreased chance of achieving the blastocyst stage, and blastocysts derived from low-quality embryos on day-two had a nearly 40 % decrease in the implantation chance. Low-quality embryos on day-three had a 30 % decreased chance of achieving the blastocyst stage, and blastocysts derived from low-quality embryos on day-three had an almost 40 % decreased implantation chance. The implantation rate didn't differ when low-quality embryos on the cleavage stage were transferred on day-three or left in culture and transferred on day-five.

CONCLUSIONS

The transfer of low-quality embryos on day-three is a better approach than transfer at the blastocyst stage. In addition, the embryo morphology evaluation at the cleavage stage is still needed for the selection of the embryo with the best implantation potential in extended embryo culture programmes.

Human preimplantation embryo development in vitro: a morphological assessment of sibling zygotes cultured in a single medium or in sequential media

A comparison was made of the development of human zygotes in either a one-step (Global® medium) or two-step culture system (Quinn's Advantage®). A total of 257 normally fertilized 2PN zygotes from 28 patients were used in the study. The study was broken down into two parts: the first concerned the development of embryos from Days 1 to 3 in Global® medium and Quinn's Advantage® cleavage medium; the second consisted of a comparison of the development of embryos from Day 3 to 5/6 in Global® medium and Quinn's Advantage® blastocyst medium. There were no significant differences between the two culture media with respect to embryo quality throughout the preimplantation phase of human embryo development as determined by the extent and variability of the cell counts, fragmentation, and nucleation. A difference was noted in the blastomere symmetry of Day 2 embryos in the two media, but was no longer apparent on examination of Day 3 embryos. No differences were noted in the rates of blastocyst development, inner cell mass (ICM), and trophectoderm (TE) scores in the two culture media. Finally, no significant differences were noted with either the proportion of blastocysts chosen for transfer or cryopreservation (vitrification). The findings support the view that two-step sequential media protocols are sufficient but not necessary to support the complete in vitro development of human preimplantation embryos.

Historical background of gamete and embryo culture

The first tissue culture media were developed nearly 150 years ago by Ludwig and Ringer. These were simple salt solutions, which were initially based on the chemical properties of blood serum. The second generation of culture media was developed more than a century later, in the 1970s, aiming to mimic the reproductive environment. In the 1990s, simplex optimization was used to design the third group of media, to some extent ignoring existing formulations and principles. Simultaneous with the development of culture media, it became evident that it was necessary to carefully control the culture conditions, including temperature, pH, osmolarity, and air quality. Equally important was the development of instruments and tools specifically designed for cell tissue culture such as the inverted microscope, the incubator, the Petri dish, sterile plasticware, the laminar flow cabinet, and air filtration equipment.

Patient selection criteria for blastocyst transfers in extended embryo culture programs

PURPOSE

To identify the correlation between different cycles, patient factors and blastocyst characteristics.

METHODS

The study included 420 patients undergoing ICSI cycles and 2781 graded blastocysts, which took into account the blastocyst quality. The correlations between the blastocyst parameters and the patient and cycle characteristics were assessed.

RESULTS

The blastocyst development was negatively correlated with the maternal age, BMI and dose of FSH. The ICM was negatively correlated with the FSH dose, whereas the TE quality was influenced by the FSH dose, the maternal age and the number of retrieved oocytes. The embryo morphology on days two and three may predict the blastocyst developmental competence.

CONCLUSIONS

Older patients and patients with high BMI should not be included in extended embryo culture programmes. The extended culture may not favour embryos with poor morphology on days two and three of development. Additionally, a lower ovarian stimulation and decreased oocyte yields may lead to the development of high-quality blastocysts.

Media composition: antioxidants/chelators and cellular function

Protection of embryos against oxidative insults during culture is necessary to maintain viability. Generation of excessive levels of reactive oxygen species (ROS) is triggered by various components of the in vitro environment, most of which embryos do not normally encounter in vivo. To compensate for these deficiencies in the culture environment, antioxidants and chelators are often used to control or suppress ROS levels as embryos develop. However, there is no consensus regarding dosage, time of exposure, or appropriate combinations of antioxidants and chelators in embryo culture. In order to elucidate this aspect of an embryo's chemical surroundings in vitro, we present the current knowledge on the function and effect of each antioxidant or chelator that is often included in an embryo culture medium.

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.

Utility of animal models for human embryo culture development: rodents

Advancements in clinical human embryo culture over the last 30-40 years have been supported by research conducted with embryos from rodent and domestic species. The mouse has been the primary rodent species that has contributed to improved embryo culture outcomes. Numerous parameters applied in the beginning of experiments, during progress of experiments, and as end-point measures provide varying degrees of rigor and interpretive strength and/or complexity. A nonexhaustive discussion of these parameters is presented with important emphasis on experimental design to obtain the greatest power of intraexperimental interpretation of inferior, equivalent, or improved culture conditions in the mouse model. Additionally, data are presented demonstrating the inherent flaw of overinterpretation of interexperimental outcome comparisons and caution of expectations of data translation from the mouse to the human embryo culture scenario. Finally, a materials, methods, and notes discussion enumerates important steps in use of mouse embryos as a bioassay tool, independent of whether they are being used in an experiment focused on quality control or improving culture conditions.

Embryo culture media for human IVF: which possibilities exist?

The last three decades have seen considerable progress in the development of culture media for ART and infertility treatment. Basic research on the metabolism of mammalian preimplantation embryos demonstrated the specific needs in the evolving stage of the embryo growing in vitro. Two different philosophies led to two different culture strategies for human preimplantation embryos: the 'back-to-nature' or sequential culture principle, and 'let-the-embryo-choose' or one-step culture principle. Both systems are commercially available and the discussion between the different groups of scientists is ongoing. As a matter of fact, all ART culture media currently used are not optimal for the growing human preimplantation embryo. However, further research is needed to reduce stress to the human preimplantation embryo and determine how many embryos from a treatment cycle are capable of producing a live birth.

A potential use of embryonic stem cell medium for the in vitro culture of preimplantation embryos

PURPOSE

To assess the impact of embryonic stem cell culture medium (ESCM) on the pre- and post-implantation development of the mouse embryo, as a mammalian model, in comparison with the conventional culture medium, a potassium simplex optimized medium (KSOM).

METHODS

Development in ESCM versus KSOM was compared in terms of embryo morphology, cleavage, cavitation, hatching, cell number, expression of TE and ICM transcription factors (Cdx2 and Oct4, respectively), implantation, and development in utero.

RESULTS

An enriched medium like ESCM can be beneficial for in vitro embryo development when cultured from the 8-cell stage, as evidenced by promotion of blastocyst development with respect to cavity expansion, hatching, and cell division. Such benefits were not observed when embryos were cultured from the 2-cell stage.

CONCLUSIONS

ESCM may augment in vitro embryo development from the 8-cell stage. Using different culture media at different stages may be beneficial to achieve more effective human in vitro fertilization.

In vitro and in vivo viability of human blastocysts collapsed by laser pulse or osmotic shock prior to vitrification

PURPOSE

This study was designed to investigate whether artificial shrinkage, induced by a laser pulse or hyperosmotic sucrose solutions, improves in vitro survival and/or implantation of vitrified-warmed human expanded blastocysts.

METHODS

Before Cryotop vitrification, the blastocoelic cavity was collapsed either by a laser pulse or sucrose solutions. Non-treated blastocysts were used as control. Post-warm blastocyst survival and implantation after transfer were examined. Implantation rate outcome was retrospectively analyzed by morphological grading and developmental kinetics of post-warm blastocysts.

RESULTS

Survival rates in the three groups were high. Implantation rates in the laser-pulse group (59.7%) were comparable with those in the sucrose group (49.3%), and were significantly higher than those in the control group (34.2%). The proportion of blastocysts showing fast development tended to be higher when the blastocysts underwent artificial shrinkage treatment before vitrification. There was no clear correlation between morphology of post-warm blastocysts and implantation rate.

CONCLUSION

Artificial shrinkage treatment before vitrification is associated with an increased probability of fast-developing embryos, resulting in higher implantation rates.