Does glucose affect fertilization, development and pregnancy rates of human in-vitro fertilized oocytes?

A method to improve embryo development potential when fertilization is delayed in mice

The purpose of this study was to explore the application of glucose to improve embryo development potential when fertilization is delayed in mice. After recovery, mouse oocytes were cultured alone for 6 h before fertilization in three fertilization media: G-IVF PLUS, G-IVF PLUS with 5 mM and 10 mM glucose. G-IVF PLUS group was used as the control group. Then, in vitro fertilization (IVF) was performed and blastocysts were transferred at Day 4. To compare the effects of different glucose concentrations on embryo development and birth outcomes, conventional IVF and embryo transfer were carried out in G-IVF PLUS, G-IVF PLUS with 5 mM and 10 mM glucose. The results indicated that G-IVF PLUS with 5 mM glucose significantly increased blastocyst rate (p < 0.05) and birth rate (p < 0.05) when fertilization was delayed 6 h compared with G-IVF PLUS groups. In conventional IVF without delayed fertilization, embryo development was not significantly affected by G-IVF PLUS with 5 mM or 10 mM glucose. There were no significant differences in terms of birth rate, fetal weight, crown-rump length, tail length and birth defect rate among the three groups. In conclusion, 5 mM glucose could significantly improve embryo developmental potential and birth outcomes when fertilization was delayed 6 h and did not have adverse effects on embryo quality and birth outcomes for normal IVF. It might have a good prospect of clinical application in assisted reproductive technology (ART). Abbreviations: ART: assisted reproductive technology; IVF: in vitro fertilization; ICSI: intracytoplasmic sperm injection; TFF: total fertilization failure; TESA: testicular sperm aspiration.

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.

IVF culture media: past, present and future

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

A physiological replacement for polyvinylpyrrolidone (PVP) in assisted reproductive technology

The technique of intracytoplasmic sperm injection (ICSI) requires mechanical immobilization of the sperm that are to be injected; damage thus caused to the sperm membrane is considered to be necessary to activate the sperm for fertilization. Mechanical immobilization and the injection procedure are facilitated by introducing the sperm into a viscous medium that will hinder motility: a solution of polyvinylpyrrolidone (PVP) has been used successfully for this purpose. PVP is an artificial polymer, which has been regarded as chemically inert, although adverse effects have been reported as a result of its use both in vivo and in vitro. Therefore, the use of hyaluronate, the natural component of the extracellular matrix of the cumulus-oocyte complex, was investigated as a replacement for PVP during ICSI. A solution of hyaluronate was found to be as effective as PVP in facilitating the injection procedure, its effect on sperm motility was readily reversible, and its use did not affect the outcome of the treatment cycles in terms of fertilization, pregnancy and live birth rates. Every attempt should be made to eliminate artificial factors in assisted reproductive procedures. Hyaluronate, a natural and readily degradable glycosaminoglycan can be used as a substitute for the artificial PVP polymer without jeopardising the outcome of the treatment cycle.

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.

Moving to the beat: a review of mammalian sperm motility regulation

Because it is generally accepted that a high percentage of poorly motile or immotile sperm will adversely affect male fertility, analysis of sperm motility is a central part of the evaluation of male fertility. In spite of its importance to fertility, poor sperm motility remains only a description of a pathology whose underlying cause is typically poorly understood. The present review is designed to bring the clinician up to date with the most current understanding of the mechanisms that regulate sperm motility and to raise questions about how aberrations in these mechanisms could be the underlying causes of this pathology.

Human embryonic stem cell methyl cycle enzyme expression: modelling epigenetic programming in assisted reproduction?

To investigate a possible mechanism for inducing epigenetic defects in the preimplantation embryo, a human embryonic stem cell model was developed, and gene expression of the key methyl cycle enzymes, MAT2A, MAT2B, GNMT, SAHH, CBS, CGL, MTR, MTRR, BHMT, BHMT2, mSHMT, cSHMT and MTHFR was demonstrated, while MAT1 was barely detectable. Several potential acceptors of cycle-generated methyl groups, the DNA methyltransferases (DNMT1, DNMT3A, DNMT3B and DNMT3L), glycine methyltransferase and the polyamine biosynthetic enzymes, SAM decarboxylase and ornithine decarboxylase, were also expressed. Expression of folate receptor alpha suggests a propensity for folate metabolism. Methotrexate-induced depletion of folate resulted in elevated intracellular homocysteine concentration after 7 days in culture and a concomitant increase in cysteine and glutathione, indicating clearance of homocysteine through the transulphuration pathway. These studies indicate that altered methyl group metabolism provides a potential mechanism for inducing epigenetic changes in the preimplantation embryo.

A randomized control comparison study of culture media (HTF versus P1) for human in vitro fertilization

OBJECTIVE

It is now widely accepted that increasing the number of replacement embryos (>3 embryos per embryo transfer [ET]) is associated with an increased risk of multiple pregnancies. While embryo reduction is often proposed when there is a high risk of multiple pregnancies, it is a difficult decision for the couple. For this reason, different studies have focused on single embryo transfer, more precisely blastocyst transfer. The aim of the study is to confirm that phosphate-free culture media can be used to generate greater quality embryos.

METHODS AND RESULTS

We carried out a study to compare the efficacy of human tubal fluid (HTF) versus preimplantation stage one (P1) as culture media for assisted reproductive therapy (ART). In 109 nonselected patients, we obtained an embryo fertilization rate with HTF and P1 culture media of 58.6 and 62.5% (P = 0.003), respectively. After 48 and 72 h, the morphology was similar for both P1 and HTF embryos in most patients. However, in the same patients, when HTF embryo quality was low (15.4%), P1 embryo quality was significantly higher 68.7% (P = 0.002). Some embryos were transferred at 48 h and some at 72 h after retrieval, in a randomized manner. We transferred a maximum of up to three embryos per ET. The implantation rate was significantly different; at 48 h, it was 6.8 and 12.2% for HTF and P1, respectively (P = 0.02). The pregnancy rate was 17.1% for HTF embryos and 23.7% for P1 embryos (P = 0.02).

CONCLUSIONS

Therefore, we observed a significant difference between P1 and HTF in the fertilization rate, in embryo quality, in implantation rate and in pregnancy rate. But the most important difference between this study and others is that every patient was the control of herself, so we eliminated every variable.

Requirements for glucose beyond sperm capacitation during in vitro fertilization in the mouse

In both the mouse and the human, it is a point of controversy whether glucose is necessary for in vitro fertilization. Some of this controversy has resulted from a failure to distinguish between requirements for glucose during sperm capacitation versus requirements during the multistage process of fertilization. Using the mouse as a model, we performed a series of experiments designed to identify specific processes that might require glucose. We observed a positive correlation between increasing glucose concentrations during capacitation and fertilization, and increasing fertilization of zona pellucida (ZP)-intact eggs. These data supported a requirement for glucose in the fertilization medium even when sperm were first capacitated in the presence of 5.5 mM glucose. This glucose requirement was observed for both ZP-intact and ZP-free eggs. During ZP-free in vitro fertilization, some binding and fusion between the plasma membrane of the sperm and egg occurred in the absence of glucose and at concentrations less than 1 mM, suggesting that this substrate is not absolutely required. However, glucose concentrations of 1 mM or higher greatly facilitated both binding and fusion under these conditions. These subtle distinctions suggest that during ZP-free in vitro fertilization, 1 mM glucose represents a threshold level that facilitates binding and fusion. Taken as a whole, the data suggest requirements for glucose during both capacitation and fertilization under normal physiologic conditions.

Localization of tyrosine phosphorylated proteins in human sperm and relation to capacitation and zona pellucida binding

Mammalian sperm must undergo a process known as capacitation before fertilization can take place. A key intracellular event that occurs during capacitation is protein tyrosine phosphorylation. The objective of this study was to investigate and visualize protein tyrosine phosphorylation patterns in human sperm during capacitation and interaction with the zona pellucida. The presence of specific patterns was also assessed in relation to the fertilizing capacity of the spermatozoa after in vitro fertilization. Protein tyrosine phosphorylation was investigated by immunofluorescence. Phosphorylation increased significantly with capacitation and was localized mainly to the principal piece of human sperm. Following binding to the zona pellucida, the percentage of sperm with phosphotyrosine residues localized to both the neck and the principal piece was significantly higher in bound sperm than in capacitated sperm in suspension. When the percentage of principal piece-positive sperm present after capacitation was <7%, fertilization rates after in vitro fertilization were reduced. Different compartments of human spermatozoa undergo a specific sequence of phosphorylation during both capacitation and upon binding to the zona pellucida. Tyrosine phosphorylation in the principal and neck piece may be considered a prerequisite for fertilization in humans.

Growth of human preimplantation embryos in vitro

The human oocyte fertilizes and develops into embryos in the Fallopian tube and reaches the uterus only after compaction. However, for several years embryos that were developed following in-vitro fertilization (IVF) were transferred into the uterus on day 2 or 3 at the 4-8 cell stage in contrast to the in-vivo situation where they would be present in the Fallopian tube. Earlier attempts to grow embryos in vitro for 5 to 6 days were not always successful. Attempts were therefore made to understand the in-vivo environment of the Fallopian tube where the early embryonic development occurs. This article reviews the studies carried out to understand the composition of fluids in the Fallopian tube specifically with reference to the energy metabolites - lactate, pyruvate and glucose; it also covers how the formulation of culture media for human IVF and embryonic development were modified over the years based on some classical work done on embryo culture in laboratory animals.

Nutritional and metabolic requirements of early cleavage stage embryos and blastocysts

During preimplantation human embryo development there is an increase in the synthesis of macromolecules and a demand for energy. Consequently, the metabolic requirements of the human embryo change as development proceeds from the zygote to the blastocyst stage. Evidence from a number of species indicates that before activation of the embryonic genome, human and other mammalian embryos have a preference for oxidizable energy substrates, particularly pyruvate, non-essential amino acids and glutamine. After embryonic genome activation, glucose and essential amino acids become increasingly important. As such, there is a switch in energy metabolism during preimplantation development from one based principally on aerobic respiration, to another based on oxidative metabolism and aerobic glycolysis.

Comparison of G1.2/G2.2 and Sydney IVF cleavage/blastocyst sequential media for the culture of human embryos: a prospective, randomized, comparative study

OBJECTIVE

To compare two commercially available sequential media, G1.2/G2.2 and Sydney IVF cleavage/blastocyst media, as supports for human embryo culture.

DESIGN

Prospective randomized study.

SETTING

University-based IVF clinic.

PATIENT(S)

Two hundred forty-nine patients undergoing IVF treatment for the first or second time, randomly allocated at the time of oocyte retrieval, to either culture in G1.2/G2.2 or Sydney IVF media.

INTERVENTION(S)

Oocyte recovery, IVF or intracytoplasmic sperm injection, embryo culture, transfer on day 3 or day 5/6.

MAIN OUTCOME MEASURE(S)

Developmental stage on day 3, blastocyst rate, pregnancy outcome as assessed by beta hCG positive test, implantation rates, and ongoing pregnancies.

RESULT(S)

Embryos cultured in G1.2/G2.2 media displayed a faster kinetics of cleavage, compaction, blastulation, and hatching, but a lower day 3 embryo quality than those grown in Sydney IVF media. For patients with at least five embryos, G1.2/G2.2 media yielded higher implantation rates (26.2%) in our day 3 embryo transfer program when compared to Sydney IVF medium (15.5%), whereas similar implantation rates were obtained for day 5/6 embryo transfer for both media (43.1% and 36.1%, respectively).

CONCLUSION(S)

In our day 3 embryo transfer program, G1.2/G2.2 media were superior to Sydney IVF media, whereas both media yielded similar outcomes in our blastocyst transfer program.