Comparison of the efficacy of two commercially available media for culturing one-cell embryos in the in vitro fertilization mouse model

Exposure to urban ambient particles (PM2.5) before pregnancy affects the expression of endometrial receptive markers to embryo implantation in mice: Preliminary results

Air pollution (AP) is one of the main recent concerns in reproductive healthy due to its potential to promote negative outcomes during pregnancy and male and female fertility. Several studies have demonstrated that AP exposure has been linked to increased embryonic implantation failures, alterations in embryonic, fetal and placental development. For a well-succeeded implantation, both competent blastocyst and receptive endometrium are required. Based on the lack of data about the effect of AP in endometrial receptivity, this study aimed to evaluate he particulate matter (PM) exposure impact on uterine receptive markers in mice and associate the alterations to increased implantation failures due to AP. For this study, ten dams per group were exposed for 39 days to either filter (F) or polluted air (CAP). At fourth gestational day (GD4), females were euthanized. Morphological, ultrastructural, immunohistochemical and molecular analysis of uterine and ovarian samples were performed. CAP-exposed females presented a reduced number of corpus luteum; glands and epithelial cells were increased with pinopodes formation impairment. Immunohistochemistry analysis revealed decreased LIF protein levels. These preliminary data suggests that PM exposure may exert negative effects on endometrial receptivity by affecting crucial parameters to embryonic implantation as uterine morphological differentiation, corpus luteum quantity and LIF expression during implantation window.

Physiological, metabolic and transcriptional postnatal phenotypes of in vitro fertilization (IVF) in the mouse

Approximately 1-4% of children today are conceived using assisted reproductive technologies (ARTs), including in vitro fertilization (IVF). IVF is considered safe and the great majority of these children are healthy, yet there is increasing physiological and molecular evidence from animal models that ART is associated with postnatal metabolic and cardiovascular alterations. Understanding the mechanisms underlying these changes and determining whether they have biological significance is of paramount importance for optimizing the design of culture conditions and improving the health of ART children across the life course. In this review, we examine the evidence of molecular changes present in adult tissues of rodent offspring generated by preimplantation manipulation of gametes and embryos. Although embryo manipulation in vitro can induce common transcriptional effects in the blastocyst, transcriptional and metabolomic signatures in adult IVF tissues are largely tissue-specific. However, there is pervasive evidence of oxidative stress and metabolic dysfunction, indicating a lasting effect of IVF on molecular physiology.

Quantitative and qualitative trophectoderm grading allows for prediction of live birth and gender

PURPOSE

Prolonged in vitro culture is thought to affect pre- and postnatal development of the embryo. This prospective study was set up to determine whether quality/size of inner cell mass (ICM) (from which the fetus ultimately develops) and trophectoderm (TE) (from which the placenta ultimately develops) is reflected in birth and placental weight, healthy live-birth rate, and gender after fresh and frozen single blastocyst transfer.

METHODS

In 225 patients, qualitative scoring of blastocysts was done according to the criteria expansion, ICM, and TE appearance. In parallel, all three parameters were quantified semi-automatically.

RESULTS

TE quality and cell number were the only parameters that predicted treatment outcome. In detail, pregnancies that continued on to a live birth could be distinguished from those pregnancies that aborted on the basis of TE grade and cell number. Male blastocysts had a 2.53 higher chance of showing TE of quality A compared to female ones. There was no correlation between the appearance of both cell lineages and birth or placental weight, respectively.

CONCLUSIONS

The presented correlation of TE with outcome indicates that TE scoring could replace ICM scoring in terms of priority. This would automatically require a rethinking process in terms of blastocyst selection and cryopreservation strategy.

Why we should not select the faster embryo: lessons from mice and cattle

Many studies have shown that in vitro culture can negatively impact preimplantation development. This necessitates some selection criteria for identifying the best-suited embryos for transfer. That said, embryo selection after in vitro culture remains a subjective process in most mammalian species, including cows, mice and humans. General consensus in the field is that embryos that develop in a timely manner have the highest developmental competence and viability after transfer. Herein lies the key question: what is a timely manner? With emerging data in bovine and mouse supporting increased developmental competency in embryos with moderate rates of development, it is time to question whether the fastest developing embryos are the best embryos for transfer in the human clinic. This is especially relevant to epigenetic gene regulation, including genomic imprinting, where faster developing embryos exhibit loss of imprinted methylation, as well as to sex selection bias, where faster developmental rates of male embryos may lead to biased embryo transfer and, in turn, biased sex ratios. In this review, we explore evidence surrounding the question of developmental timing as it relates to bovine embryo quality, mouse embryo quality and genomic imprint maintenance, and embryo sex.

In vitro fertilization affects growth and glucose metabolism in a sex-specific manner in an outbred mouse model

The preimplantation period is a time of reprogramming that may be vulnerable to disruption. This question has wide clinical relevance since the number of children conceived by in vitro fertilization (IVF) is rising. To examine this question, outbred mice (CF1 × B6D2F1) conceived by IVF and cultured using Whitten medium and 20% O2 (IVFWM group, less optimal) or K simplex optimized medium with amino acids and 5% O2 (IVFKAA group, more optimal and similar to conditions used in human IVF) were studied postnatally. We found that flushed blastocysts transferred to recipient mice provided the best control group (FB group), as this accounted for the effects of superovulation, embryo transfer, and litter size. We observed that many physiological parameters were normal. Reassuringly, IVFKAA offspring did not differ significantly from FB offspring. However, male IVFWM mice (but not females) were larger during the first 19 wk of life and exhibited glucose intolerance. Male IVFWM mice also showed enlarged left heart despite normal blood pressure. Expression of candidate imprinted genes (H19, Igf2, and Slc38a4) in multiple adult tissues did not show differences among the groups; only Slc38a4 was down-regulated following IVF (in both culture conditions) in female adipose tissue. These studies demonstrate that adult metabolism is affected by the type of conditions encountered during the preimplantation stage. Further, the postnatal growth trajectory and glucose homeostasis following ex vivo manipulation may be sexual dimorphic. Future work on the long-term effects of IVF offspring should focus on glucose metabolism and the cardiovascular system.

Effects of embryo culture media do not persist after implantation: a histological study in mice

STUDY QUESTION

Is post-implantation embryonic development after blastocyst transfer affected by exposure to different assisted reproduction technology (ART) culture media?

SUMMARY ANSWER

Fetal development and placental histology of ART embryos cultured in vitro in different ART media was not impaired compared with embryos grown in vivo.

WHAT IS KNOWN ALREADY

The application of different in vitro culture (IVC) media for human ART has an effect on birthweight of newborns. In the mouse model, differences in blastocyst formation were reported after culture in different ART media. Moreover, abnormalities in the liver and heart have been detected as a result of suboptimal IVC conditions.

STUDY DESIGN, SIZE, DURATION

Fertilized oocytes from inbred and outbred breeding schemes were retrieved and either immediately transferred to foster mothers or incubated in control or human ART culture media up to the blastocyst stage prior to transfer. Placental and fetal anatomy and particularly bone development were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

B6C3F1 female mice were used as oocyte donors after ovulation induction. C57Bl/6 and CD1 males were used for mating and CD1 females as foster mothers for embryo transfer. Fertilized oocytes were recovered from mated females and incubated in sequential human ART media (ISM1/ISM2 and HTF/Multiblast), in control media [KSOM(aa) and Whitten's medium] or grown in utero without IVC (zygote control). As in vivo, control B6C3F1 females were superovulated and left untreated. Fetuses and placentae were isolated by Caesarean section and analysed at 18.5 days post-coitum (dpc) for placenta composition and at 15.5 dpc for body weight, crown-rump length (CRL), fetal organ development, morphological development, total bone length and extent of bone ossification.

MAIN RESULTS AND THE ROLE OF CHANCE

No major differences in the number of implantation sites or in histological appearance of the placentae were detected. CRL of KSOM(aa) fetuses was higher compared with zygote control and Whitten's medium. Histological analysis of tissue sections revealed no gross morphological differences compared with the in vitro groups or in vivo controls. Furthermore, no changes in skeletal development and degree of ossification were observed. However, fibula and tibia of ISM1/ISM2 fetuses were longer than the respective ones from in vivo fetuses.

LIMITATIONS, REASONS FOR CAUTION

Findings in the mouse embryo and fetus may not be fully transferable to humans. In addition to skeletal development and placentation, there may be other parameters, e.g. on the molecular level which respond to IVC in ART media. Some comparisons have limited statistical power.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that once implantation is achieved, subsequent post-implantation development unfolds normally, resulting in healthy fetuses. With mouse models, we gather information for the safety of human ART culture media. Our mouse study is reassuring for the safety of ART conditions on human embryonic development, given the lack of bold detrimental effects observed in the mouse model.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Deutsche Forschungsgemeinschaft (BO 2540/4-1 and SCHL 394/9-1) and by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (S.L.G.); Bilateral grant NWO-DFG 63-258. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

Effects of transfer of embryos independently cultured in essential and sequential culture media on pregnancy rates in assisted reproduction cycles

PURPOSE

Several culture media are available to be used in ART. However it is uncertain whether embryos would preferably benefit from one type of medium or the association of different media.

METHODS

We performed this study to evaluate the impact of simultaneous transfer of embryos independently cultured in two distinct culture media, on pregnancy outcome. A total of 722 couples who underwent infertility treatment were sequentially allocated into three groups: those who had half of the embryos individually cultured in MEM and the other half cultured in sequential media (MEM + Seq Group) (n = 243); those who had all embryos cultured only in sequential medium (Seq Group) (n = 239); and those who had all embryos cultured only in MEM (MEM Group) (n = 240).

RESULTS

The pregnancy rate was higher in the MEM + Seq group (51.8 %) than the Seq group (36.7 %) (p < 0.001). However the pregnancy rate observed in the MEM group was similar to the others (44.2 %). When a logistic regression test was applied it demonstrated that the number of transferred embryos did not interfere in the pregnancy rates.

CONCLUSIONS

Our results suggests that offering different culture conditions for sibling embryos with subsequent transfer of embryos that were kept in distinct culture media, might increase pregnancy rates in assisted reproduction cycles.

Impaired placental nutrient transport in mice generated by in vitro fertilization

More than 4.5 million children have been conceived by in vitro fertilization (IVF). Interestingly, singleton IVF offspring born at term have an increased incidence of low birth weight. The mechanism responsible for the lower birth weight is unknown, but alterations in placental function are possible. Hence, the goal of our study was to examine placental growth and function in mice generated in vivo or in vitro. To assess placental function, blastocysts were generated by IVF or produced by natural mating (control group); both IVF and control blastocysts were transferred to pseudopregnant recipients. Placental weights did not differ at embryonic d 15.5 (E15.5) but were increased at E18.5 in the IVF group (25.4%, P < 0.001) compared with control. Proliferation was increased in IVF placentae, whereas overall placental gross morphology and apoptosis were not affected. Both fetal weights (16.4% lower at E15.5 and 8.8% lower at E18.5, P < 0.05) and fetal to placental ratios were lower (P < 0.001) in the IVF compared with the control group at both time points, whereas birth weights did not differ. At E18.5, the mRNA for selected glucose, system A amino acid transporters, and imprinted genes were down-regulated in IVF placentae. GLUT3 protein level was decreased in the IVF group (P < 0.05). Importantly, intrajugular injections of (14)C-methyl-D-glucose or (14)C-MeAIB tracers (n = 6 litters per group) showed that placental transport of glucose and amino acids were 24.8% (not significant) and 58.1% (P < 0.05) lower in the IVF group. Fetal accumulation of glucose was not different, but amino acid accumulation was significantly (36 %) lower in IVF fetuses (P < 0.05). We conclude that IVF alters both fetal and placental growth and, importantly, decreases placental transport efficiency in mice conceived by IVF.

Superovulation, in vitro fertilization (IVF) and in vitro development (IVD) protocols for inbred BALB/cJ mice in comparison with outbred NMRI mice

Purpose

To study assisted reproductive technology (ART) protocols including superovulation, in vitro fertilization (IVF) and in vitro development (IVD) for BALB/cJ mice in comparison with a common ART protocol for NMRI mice.

Methods

Adult NMRI and BALB/cJ mice were superovulated using a 48 h G-interval. In order to find a more suitable G-interval for the BALB/cJ strain, G-intervals including 44, 46 and 50 h were also examined. Superovulation rates were recorded in all groups. IVF rate of BALB/c oocytes in T6 and mHTF media were compared. IVD rates of BALB/cJ zygotes in mHTF, T6 and G1V₅/G2V₅ media were compared. In addition, IVF and IVD rates of BALB/cJ and NMRI oocytes were compared in T6 medium during IVF-IVD procedures.

Results

In BALB/cJ mice the highest superovulation rates were observed with 44-46 h G-intervals. However, with a 48 h G-interval, superovulation rates were significantly lower in BALB/cJ compared to NMRI mice (p < 0.05). mHTF medium significantly increased in vitro fertilization of BALB/cJ oocytes compared to T6 medium (p < 0.05). Fertilization rate of NMRI oocytes was significantly higher than BALB/cJ oocytes in T6 medium (p < 0.05). The BALB/cJ embryo IVD was significantly higher in G1/G2 medium compared to mHTF and T6 media (p < 0.01).

Conclusions

Superovulation with 48 h G-interval and using T6 during all in vitro procedures produces embryos more efficiently for NMRI mice than for BALB/cJ mice. For BALB/cJ mice, a protocol including superovulation with a 44-46 h G-interval, using mHTF during IVF and G1V₅/G2V₅ medium during IVD, may improve in vitro embryo production.

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 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.

Biological effects and dose-response assessment of diesel exhaust particles on in vitro early embryo development in mice

An increased risk of early pregnancy loss in women briefly exposed to high levels of ambient particulate matter during the preconceptional period was recently observed. The effects of this exposure on early embryo development are unknown. This study was designed to assess the dose-response and biological effects of diesel exhaust particles (DEP) on in vitro embryo development using the in vitro fertilization (IVF) mouse model. Zygotes obtained from superovulated mice after IVF were randomly cultured in different DEP concentrations (0, 0.2, 2, and 20 microg/cm(2)) for 5 days and observed for their capacity to attach and develop on a fibronectin matrix until day 8. Main outcome measures included blastocyst rates 96 and 120 h after insemination, hatching discriminatory score, total cell count, proportion of cell allocation to inner cell mass (ICM) and trophectoderm (TE), ICM morphology, attachment rate and outgrowth area, apoptosis and necrosis rates, and Oct-4 and Cdx-2 expression. Multivariate analysis showed a negative dose-dependent effect on early embryo development and hatching process, blastocyst cell allocation, and ICM morphology. Although blastocyst attachment and outgrowth were not affected by DEP, a significant impairment of ICM integrity was observed in day 8 blastocysts. Cell death through apoptosis was significantly higher after DEP exposure. Oct-4 expression and the Oct-4/Cdx-2 ratio were significantly decreased in day 5 blastocysts irrespective of DEP concentration. Results suggest that DEP appear to play an important role in disrupting cell lineage segregation and ICM morphological integrity even at lower concentrations, compromising future growth and viability of the blastocyst.

Dynamic microfunnel culture enhances mouse embryo development and pregnancy rates

BACKGROUND

Despite advances in in vitro manipulation of preimplantation embryos, there is still a reduction in the quality of embryos produced leading to lower pregnancy rates compared with embryos produced in vivo. We hypothesized that a dynamic microfunnel embryo culture system would enhance outcomes by better mimicking the fluid-mechanical and biochemical stimulation embryos experience in vivo from ciliary currents and oviductal contractions.

METHODS AND RESULTS

Mouse embryos were cultured in microdrop-static control, microfunnel-static control or microfunnel-dynamic conditions with microfluidics. All groups tested had greater than 90% total blastocyst development from zygotes after 96 h culture. Blastocyst developmental stage was significantly enhanced (P < 0.01) under dynamic microfunnel culture conditions as evidenced by an increased percentage of hatching or hatched blastocysts (Microdrop-control 31%; Microfunnel-control 23%; Microfunnel-pulsatile 71%) and significantly higher (P < 0.01) average number of cells per blastocyst (Microdrop-control 67 +/- 3; Microfunnel-control 60 +/- 3; Microfunnel-pulsatile 109 +/- 5). Blastocyst cell numbers in dynamic microfunnel cultures (109 +/- 5) more closely matched numbers obtained from in vivo grown blastocysts (144 +/- 9). Importantly, dynamic microfunnel culture significantly improved embryo implantation and ongoing pregnancy rates over static culture to levels approaching that of in utero derived preimplantation embryos.

CONCLUSIONS

The improved pregnancy outcomes along with the simple and user-friendly design of the microfluidic/microfunnel system has potential to alleviate many inefficiencies in embryo production for biomedical research, genetic gain in domestic species and assisted reproductive technologies in humans.

Choosing a culture medium: making informed choices

OBJECTIVE

To analyze critically the reasons justifying the choice of two-step protocols requiring two media for the culture of human preimplantation embryos from the zygote to the blastocyst.

DESIGN

Literature review.

RESULT(S)

Two types of protocol are used for the culture of human preimplantation embryos from the zygote to the blastocyst, using either one medium (one-step protocol) or two media of different composition (two-step protocol). Two-step protocols are the most widely used, largely because all but one of the commercially available protocols are of this type. The reasons for the adoption of two-step protocols are described and critically analyzed. They are based on considerations of the functions of glucose, ethylenediaminetetraacetic acid (EDTA), glutamine, and amino acids that are included in the media. A reappraisal of the reasons for selecting two-step protocols is important because recent animal experiments and clinical observations have raised doubts as to whether the more complex, two-step protocols have any advantage over one-step protocols. The analyses show that all of conclusions reached should be considered equivocal.

CONCLUSION(S)

Clinical embryologists should evaluate the justification for selecting two-step protocols for the culture of human preimplantation embryos from the zygote to the blastocyst.