Cryo-survival and development of bovine blastocysts are enhanced by culture with recombinant albumin and hyaluronan

Mammalian embryo culture media: now and into the future

For over 70years, since the culture of the first mammalian embryo in vitro , scientists have undertaken studies to devise and optimise media to support the manipulation and culture of gametes and embryos. This area of research became especially active in the late 1970s onwards following the successful birth of the first human in vitro fertilised embryo. This review summarises some of the key advances in mammalian embryo culture media over time based on a greater understanding of the biochemical milieu of the reproductive tract. It highlights how learnings from studies in mice and agricultural species have informed human culture media compositions, in particular the inclusion of albumin, growth factors, cytokines, and antioxidants into contemporary culture media formulations, and how these advances may then in turn help to inform and guide development of in vitro culture systems used in other arenas, in particular agriculture. Additionally, it will highlight how the introduction of new technologies, such as timelapse, can influence current trends in media composition and usage that may see a return to a single step medium.

Non-Invasive Identification of Sex in Cultured Bovine Embryos by UHPLC-MS/MS Metabolomics

INTRODUCTION

Different gene expression between male and female bovine embryos leads to metabolic differences.

OBJECTIVE

We used UHPLC-MS/MS to identify sex metabolite biomarkers in embryo culture medium (CM).

METHODS

Embryos were produced in vitro under highly variable conditions, i.e., fertilized with 7 bulls, two breeds, and cultured with BSA or BSA + serum until Day-6. On Day-6, embryos were cultured individually for 24 h. CM of Day-7 embryos (86 female and 81 male) was collected, and Day-6 and Day-7 embryonic stages recorded.

RESULTS

A study by sample subsets with fixed factors (culture, bull breed, and Day-6 and Day-7 stages) tentatively identified 31 differentially accumulated metabolites through 182 subsets. Day-6 and Day-7 stage together affected 13 and 11 metabolites respectively, while 19 metabolites were affected by one or another stage and/or day. Culture supplements and individual bull changed 19 and 15 metabolites, respectively. Single bull exerted the highest influence (20 metabolites with the significantly highest p values). Lipid (93 subsets; 11 metabolites) and amino acid (55 subsets; 13 metabolites) were the most relevant classes for sex identification.

CONCLUSIONS

Single biomarker led to inefficient sex diagnosis, while metabolite combinations accurately identified sex. Our study is a first in non-invasive sex identification in cattle by overcoming factors that induce metabolic variation.

Absorption, distribution, metabolism and excretion of hyaluronic acid during pregnancy: a matter of molecular weight

INTRODUCTION

For many years hyaluronic acid (HA) was mainly used for its hydrating properties. However, new applications have recently arisen, considering the biological properties of HA and its molecular weight. Clinical application of low molecular weight HA (LMW-HA) initially was supported by specific absorption data. The identification of high molecular weight HA (HMW-HA) absorption pathways and the knowledge of its physiological role allowed to evaluate its clinical application. Based on the immunomodulatory properties of HMW-HA and its physiological involvement as signaling molecule, pregnancy represents an interesting context of application.

AREA COVERED

This expert opinion includes in-vitro, in-vivo, ex-vivo and clinical studies on gestational models. It provides an overview of the physiological and the therapeutic role of HMW-HA in pregnancy starting from its metabolism. Indeed, HMW-HA is widely involved in several physiological processes as implantation, immune response, uterine quiescence and cervical remodeling, and therefore is an essential molecule for a successful pregnancy.

EXPERT OPINION

Available evidence suggests that HMW-HA administration can support physiological pregnancy, favoring blastocyst adhesion and development, preventing miscarriage and pre-term birth. For this reason, supplementation in pregnancy should be evaluated.

Development of Decellularized Oviductal Hydrogels as a Support for Rabbit Embryo Culture

The oviducts (fallopian tubes in mammals) function as the site of fertilization and provide necessary support for early embryonic development, mainly via embryonic exposure to the tubal microenvironment. The main objective of this study was to create an oviduct-specific extracellular matrix (oviECM) hydrogel rich in bioactive components that mimics the native environment, thus optimizing the developmental trajectories of cultured embryos. Rabbit oviducts were decellularized through SDS treatment and enzymatic digestion, and the acellular tissue was converted into oviductal pre-gel extracellular matrix (ECM) solutions. Incubation of these solutions at 37 °C resulted in stable hydrogels with a fibrous structure based on scanning electron microscopy. Histological staining, DNA quantification and colorimetric assays confirmed that the decellularized tissue and hydrogels contained no cellular or nuclear components but retained important components of the ECM, e.g. hyaluronic acid, glycoproteins and collagens. To evaluate the ability of oviECM hydrogels to maintain early embryonic development, two-cell rabbit embryos were cultured on oviECM-coated surfaces and compared to those cultured with standard techniques. Embryo development was similar in both conditions, with 95.9% and 98% of the embryos reaching the late morula/early blastocyst stage by 48 h under standard culture and oviECM conditions, respectively. Metabolomic analysis of culture media in the presence or absence of embryos, however, revealed that the oviECM coating may include signalling molecules and release compounds beneficial to embryo metabolism.

Methodological approaches for vitrification of bovine oocytes

Numerous factors affect vitrification success and post-thaw development of oocytes after in vitro fertilization. Therefore, elaboration of an optimal methodology ensuring higher cryotolerance of oocytes and subsequent blastocyst yield is still of great interest. This paper describes and evaluates critical factors affecting the success of oocyte vitrification. In particular, an appropriate oocyte stage such as maturation status (germinal vesicle stage, metaphase II stage), presence/absence of cumulus cells before vitrification, and the effect of follicle size, as well as different culture systems and media for in vitro production of embryos, the types and concentrations of cryoprotectants, and cooling and warming rates at vitrification are considered. Special attention is paid to various cryocarriers used for low-volume vitrification, which ensures safe storage of oocytes/embryos in liquid nitrogen and their successful post-thaw recovery. At the end, we focussed on how age of oocyte donors (heifers, cows) influences post-thaw development. This review summarizes results of recently published studies describing different methodologies of cryopreservation and post-thaw oocyte development with the main focus on vitrification of bovine oocytes.

Hyaluronic acid in embryo transfer media for assisted reproductive technologies

BACKGROUND

This is an update of a Cochrane Review first published in the Cochrane Library (2010, Issue 7). To increase the success rate of assisted reproductive technologies (ARTs), adherence compounds such as hyaluronic acid (HA) have been introduced into subfertility management. Adherence compounds are added to the embryo transfer medium to increase the likelihood of embryo implantation, with the potential for higher clinical pregnancy and live birth rates.

OBJECTIVES

To determine whether adding adherence compounds to embryo transfer media could improve pregnancy outcomes, including improving live birth and decreasing miscarriage, in women undergoing assisted reproduction.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Trials Register, CENTRAL, MEDLINE, Embase, and PsycINFO electronic databases on 7 January 2020 for randomised controlled trials that examined the effects of adherence compounds in embryo transfer media on pregnancy outcomes. Furthermore, we communicated with experts in the field, searched trials registries, checked reference lists of relevant studies, and conference abstracts were handsearched.

SELECTION CRITERIA

Only truly randomised controlled trials comparing embryo transfer media containing functional concentrations of adherence compounds to media with no or low adherence compound concentrations were included.

DATA COLLECTION AND ANALYSIS

Two review authors selected trials for inclusion according to the above criteria, after which the same two review authors independently extracted data for subsequent analysis. Statistical analysis was performed according to the guidelines developed by Cochrane. We combined data to calculate pooled risk ratios (RRs) and 95% confidence intervals (CIs). We assessed statistical heterogeneity using the I² statistic. We used GRADE methods to assess the overall quality of evidence for the main comparisons.

MAIN RESULTS

We analysed 26 studies with a total of 6704 participants. Overall, the certainty of evidence was low to moderate: the main limitations were imprecision and/or heterogeneity. Compared to embryos transferred in media containing no or low (0.125 mg/mL) HA, the addition of functional (0.5 mg/mL) HA concentrations to the transfer media probably increases the live birth rate (RR 1.21, 95% CI 1.1 to 1.31; 10 RCTs, N = 4066; I² = 33%; moderate-quality evidence). This suggests that if the chance of live birth following no HA addition in media is assumed to be 33%, the chance following HA addition would be between 37% and 44%. The addition of HA may slightly decrease miscarriage rates (RR 0.82, 95% CI 0.67 to 1.00; 7 RCTs, N = 3091; I² = 66%; low-quality evidence). Nevertheless, when only studies with low risk of bias were included in the analysis, there was no conclusive evidence of a difference in miscarriage rates (RR 0.96, 95% CI 0.75 to 1.23; N = 2219; I² = 36%). Adding HA to transfer media probably results in an increase in both clinical pregnancy (RR 1.16, 95% CI 1.09 to 1.23; 17 studies, N = 5247; I² = 40%; moderate-quality evidence) and multiple pregnancy rates (RR 1.45, 95% CI 1.24 to 1.70; 7 studies, N = 3337; I² = 36%; moderate-quality evidence). We are uncertain of the effect of HA added to transfer media on the rate of total adverse events (RR 0.86, 95% CI 0.40 to 1.84; 3 studies, N = 1487; I² = 0%; low-quality evidence).

AUTHORS' CONCLUSIONS

Moderate-quality evidence shows improved clinical pregnancy and live birth rates with the addition of HA as an adherence compound in embryo transfer media in ART. Low-quality evidence suggests that adding HA may slightly decrease miscarriage rates, but when only studies at low risk of bias were included in the analysis, the results were inconclusive. HA had no clear effect on the rate of total adverse events. The increase in multiple pregnancy rates may be due to combining an adherence compound and transferring more than one embryo. Further studies of adherence compounds with single embryo transfer need to be undertaken.

Investigating the role of CD44 and hyaluronate in embryo-epithelial interaction using an in vitro model

Implantation failure is an important impediment to increasing success rates in assisted reproductive technologies. Knowledge of the cascade of morphological and molecular events at implantation remains limited. Cell surface CD44 and hyaluronate (HA) have been reported in the uterus, but a role in intercellular interaction at implantation remains to be evaluated. Mouse embryos were co-cultured with human Ishikawa endometrial epithelial monolayers over 2 days. Attachment was tenuous during the first 24 h, after which it became stable, leading to breaching of the monolayer. The effects of enzymatically reducing the density of HA, or introducing a function-blocking antibody to CD44, were monitored during progression from weak to stable embryonic attachment. Hyaluronidase-mediated removal of surface HA from the epithelial cells enhanced the speed of attachment, while a similar treatment of embryos had no effect. The antibody to CD44 caused retardation of initial attachment. These results suggest that CD44-HA binding could be employed by embryos during initial docking, but the persistence of HA in epithelial cells might be detrimental to later stages of implantation by retarding attainment of stable attachment.

Recent progress in bovine in vitro-derived embryo cryotolerance: Impact of in vitro culture systems, advances in cryopreservation and future considerations

Cryopreservation of in vitro-derived bovine embryos is a crucial step for the widespread reproduction and conservation of valuable high-merit animals. Given the current popularity of bovine in vitro embryo production (IVP), there is a demand for a highly efficient ultra-low temperature storage method in order to maximize donor ovum pickup (OPU) turn-over, recipient availability/utilization and domestic/overseas commercial trading opportunities. However, IVP bovine embryos are still very sensitive to chilling and cryopreservation, and despite recent progress, a convenient (simple and robust) protocol has not yet been developed. At the moment, there are two methods for bovine IVP embryo cryopreservation: slow programmable freezing and vitrification. Both of the aforementioned techniques have pros and cons. While controlled-rate slow cooling can easily be adapted for direct transfer (DT), ice crystal formation remains an issue. On the other hand, vitrification solved this problem but the possibility of successful DT commercial incorporation remains to be determined. Moreover, simplification of the vitrification protocol (including warming) through the use of an in-straw dilution without the use of a microscope is a prerequisite for its use under farm conditions. This review summarizes the bovine IVP embryo cryopreservation achievements, strengths and limitations of both freezing systems and prospective improvements to enhance cryosurvival, as well as perspectives on future directions of this assisted reproductive technology.

Prevention of hatching of porcine morulae and blastocysts by liquid storage at 20 °C

Vitrification is the ideal method for long-lasting storage of porcine embryos. However, both strict airline regulations for transport of liquid nitrogen dewars and the technical problems experienced when vitrified embryos are transferred using non-surgical procedures have led to the introduction of alternative storage methods, such as preserving embryos in liquid state. This study evaluated whether a pH-stable medium containing high concentrations of either foetal calf serum (FCS; 50%) or BSA (4%) combined with storage at temperatures of 17 °C or 20 °C maintained in vivo-derived morulae and blastocysts alive and unhatched (a sanitary requirement for embryo transportation) during 72 h of storage. Neither FCS nor BSA supplements were able to counteract the negative effect of low temperatures (17 °C) on embryonic survival after storage. At 20 °C, the protective effect of FCS or BSA depended on embryo stage. While FCS successfully arrested embryo development of only blastocysts, BSA arrested the development of both morulae and blastocysts. Over 80% of BSA arrested embryos restarted development by conventional culture and progressed to further embryonic stages, including hatching. In conclusion, porcine morulae and blastocysts can survive and remain unhatched during at least 72 h when stored at 20 °C in a BSA-containing medium.

Appendix E: Rapid-iTM: Closed Vitrification Device by Vitrolife

Cryopreservation of gametes and embryos is a growing technique in numerous reproductive fields including human-assisted reproduction. With improved understanding of embryo physiology and optimized culture conditions, there are now more embryos than ever to vitrify for potential use in subsequent cycles. Many gametes and embryos have been cryopreserved in open systems, but there are concerns with regard to contamination from the liquid nitrogen and also cross-contamination between patients' germplasm. The development of the Rapid-i™, a closed vitrification device that does not use direct contact with liquid nitrogen during vitrification or subsequent storage, will be discussed as well as clinical protocols for human oocytes and embryos.

Applying metabolomic analyses to the practice of embryology: physiology, development and assisted reproductive technology

The advent of metabolomics technology and its application to small samples has allowed us to non-invasively monitor the metabolic activity of embryos in a complex culture environment. The aim of this study was to apply metabolomics technology to the analysis of individual embryos from several species during in vitro development to gain an insight into the metabolomics pathways used by embryos and their relationship with embryo quality. Alanine is produced by both in vivo- and in vitro-derived human, murine, bovine and porcine embryos. Glutamine is also produced by the embryos of these four species, but only those produced in vitro. Across species, blastocysts significantly consumed amino acids from the culture medium, whereas glucose was not significantly taken up. There are significant differences in the metabolic profile of in vivo- compared with in vitro-produced embryos at the blastocyst stage. For example, in vitro-produced murine embryos consume arginine, asparagine, glutamate and proline, whereas in vivo-produced embryos do not. Human embryos produce more alanine, glutamate and glutamine, and consume less pyruvate, at the blastocyst compared with cleavage stages. Glucose was consumed by human blastocysts, but not at a high enough level to reach significance. Consumption of tyrosine by cleavage stage human embryos is indicative of blastocyst development, although tyrosine consumption is not predictive of blastocyst quality. Similarly, although in vivo-produced murine blastocysts consumed less aspartate, lactate, taurine and tyrosine than those produced in vitro, consumption of these four amino acids by in vitro-derived embryos with high octamer-binding transcription factor 4 (Oct4) expression, indicative of high quality, did not differ from those with low Oct4 expression. Further application of metabolomic technologies to studies of the consumption and/or production of metabolites from individual embryos in a complete culture medium could transform our understanding of embryo physiology and improve our ability to produce developmentally competent embryos in vitro.

Regulation and roles of the hyaluronan system in mammalian reproduction

Hyaluronan (HA) is a non-sulphated glycosaminoglycan polymer naturally occurring in many tissues and fluids of mammals, including the reproductive system. Its biosynthesis by HA synthase (HAS1–3) and catabolism by hyaluronidases (HYALs) are affected by ovarian steroid hormones. Depending upon its molecular size, HA functions both as a structural component of tissues in the form of high-molecular-weight HA or as a signalling molecule in the form of small HA molecules or HA fragments with effects mediated through interaction with its specific cell-membrane receptors. HA is produced by oocytes and embryos and in various segments of the reproductive system. This review provides information about the expression and function of members of the HA system, including HAS, HYALs and HA receptors. We examine their role in various processes from folliculogenesis through oocyte maturation, fertilisation and early embryo development, to pregnancy and cervical dilation, as well as its application in assisted reproduction technologies. Particular emphasis has been placed upon the role of the HA system in pre-implantation embryo development and embryo implantation, for which we propose a hypothetical sequential model.

Appendix F: Quinn's Advantage Embryo Freeze Kit

Despite a large focus on the use of vitrification to cryopreserve embryos in recent years, there are still arguments for the use of slow freezing for the cleavage-stage embryo. Having said this, there are lessons to be learned from the process of vitrification that could be applied to slow freezing to improve post-thaw survival and ultimately clinical pregnancy rates. Specifically, increasing the concentration of sucrose in the freezing solution from 0.1 to 0.2 M and subsequently increasing the sucrose concentrations in thawing solutions could prove beneficial. The use of vitrification warming solutions in the thawing of slow-frozen embryos may also be an option that not only improves survival but also streamlines product purchasing and protocols within the laboratory.

Clinical evaluation of two formulations of slow-freezing solutions for cleavage stage embryos

PURPOSE

The aim was to investigate if improved survival rates could be achieved using a new formulation of solutions for slow freezing of human cleavage stage embryos.

METHODS

The evaluation was divided into two parts. The first part was a retrospective analysis of results obtained after freezing and thawing of day 3 embryos from 400 women using an old formulation of cryopreservation solutions compared to results from 108 women for which cryopreservation had been performed using new compositions of solutions. The second part was prospective, adding cycles until similar numbers of patients had been included in both groups. In total, 2274 embryos from 897 patients were thawed using the old formulation of solutions while 1273 embryos from 542 patients were frozen and thawed using the new solutions. The primary endpoint was survival rate.

RESULTS

With the new solutions, the survival rate increased from 82.1 to 94.4 % and the complete embryo survival rate increased from 54.9 to 81.3 %. The implantation rate, clinical pregnancy rate per embryo transfer, and per cycle were 28.2, 45.2, and 43.7 %, respectively, using the old formulations of cryosolutions. With the new solutions, the results reached 33.7, 54.1, and 54.1 %, respectively. All differences in results were statistically significant. The number of cancelled embryo transfers due to no survived embryos was 18 with the old solutions and 0 using the new solutions.

CONCLUSION

With the new composition of solutions for slow freezing and thawing of embryos, significantly improved results were obtained. Additionally, the number of cancelled embryo transfers was reduced.

Efficacy of hyaluronan-rich transfer medium on implantation and pregnancy rates in fresh and frozen-thawed blastocyst transfers in Korean women with previous implantation failure

Objective

To evaluate the effect of hyaluronan-rich transfer medium on pregnancy and implantation rates in fresh and frozen-thawed embryo transfers in Korean women with previous implantation failure.

Methods

This retrospective study included 283 blastocyst transfers in patients with previous embryo transfer failure at a private fertility clinic. In the study group (n=88), blastocyst transfers were performed using an hyaluronan-rich transfer medium prior to transfer, whereas blastocyst transfers without any treatment served as controls (n=195). According to the type of transfer (fresh elective or frozen-thawed), all the blastocyst transfers were divided into two study and two control groups.

Results

The patient's mean age, serum anti-Müllerian hormone level, causes of infertility, embryo quality, and the number of transferred embryos were comparable between the study and control groups. There were no significant differences in clinical pregnancy rate (45.5% vs. 43.1%), implantation rate (28.9% vs. 28.8%), and clinical abortion rate (10.0% vs. 8.3%) between the two groups, and these findings were not changed after subgroup analysis according to the type of transfer.

Conclusion

The use of hyaluronan-rich transfer medium in the blastocyst transfer does not appear to have any significant effect on the implantation and pregnancy rates in patients with previous implantation failure.

Hyaluronan and hyaluronidase, which is better for embryo development?

Our aim was to examine size-specific effects of Hyaluronan (HA) on preimplantation embryo development. We investigated the effects of Hyalovet (HA, 500-750 kDa; the size produced by HA synthase-3, which is abundant in the oviduct), or HA treated with Hyaluronidase-2 (Hyal2; also expressed in the oviduct that breaks down HA into 20 kDa fragments). In experiment 1 (in vivo), oviducts of synchronized and superovulated ewes (n = 20) were surgically exposed on Day 2 post-mating, ligated, and infused with either Hyalovet, Hyalovet + Hyal2, Hyal2, or PBS (control). Ewes were killed 5 days later for recovery of embryos and oviductal epithelial cells (OEC). Blastocyst rates were significantly higher in Hyal2 and Hyalovet + Hyal2 oviducts. Hyaluronidase-2 infusion resulted in higher blastocyst cell numbers and hatching rates. This was associated with increased HSP70 expression in OEC. In contrast, Hyalovet resulted in the lowest development to blastocyst stage and lowest hatching rates, and decreased IGF2 and IGFBP2 expression in OEC. IGF1 and IL1α expression were not affected. In experiment 2, to rule out indirect effects of oviductal factors, ovine embryos were produced and cultured with the same treatments in vitro from Day 2 to 8. Hyaluronidase-2, but not Hyalovet, enhanced blastocyst formation and reduced inner cell mass apoptosis. Hyalovet inhibited hatching. In conclusion, the presence of large-size HA (500-750 kDa) in the vicinity of developing embryos appears to disturb the oviductal environment and embryo development in vivo and in vitro. In contrast, we show evidence that breakdown of HA into smaller fragments is required to maximize embryo development and blastocyst quality.

The beneficial effects of reduced magnesium during the oocyte-to-embryo transition are conserved in mice, domestic cats and humans

In many cell types Mg2+ can antagonise Ca2+ -stimulated signalling pathways, but information regarding the effects of these ions on IVF and subsequent embryonic development is limited. Our objectives were to evaluate the effects of Mg2+ in the IVF medium on embryonic development in mice and then determine if similar effects occurred in domestic cats and humans. Oocytes from hybrid and outbred mice, domestic cats and humans were fertilised (IVF, mice and cats; intracytoplasmic sperm injection (ICSI), humans) in the presence of 0.2 or 1.2 (mouse and human) or 1.0 (cat) mM Mg2+ and the resulting embryos were cultured to the blastocyst stage. Decreased concentrations of Mg2+ during IVF increased (P<0.05) cleavage of oocytes from outbred mice (77.9 vs. 51.0%), development of embryos from hybrid mice (74.5 vs. 51.0% hatching blastocyst per cleaved embryo) and both cleavage (68.4 vs. 46.8%) and blastocyst development (53.0 vs. 26.2% per cleaved embryo) in cats. Development to the blastocyst stage (52.1 vs. 40.2%) was also improved (P<0.05) when ICSI was performed on human oocytes in the presence of 0.2 mM Mg2+, compared with a commercial culture medium. Sensitivity to increased (1.0 to 1.2 mM) concentrations of Mg2+ in the medium during the oocyte-to-embryo transition appears to be conserved in three different species.

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

BACKGROUND

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

METHODS

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

RESULTS AND CONCLUSIONS

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

Perinatal outcomes for transfer of blastocysts vitrified and warmed in defined solutions with recombinant human albumin: 374 babies born after 898 embryo transfers

PURPOSE

To assess the efficacy of a novel, defined vitrification procedure using recombinant human albumin (rHA) for cryopreservation of human blastocysts.

DESIGN

Retrospective study.

SETTING

Private IVF clinic.

PATIENTS

1,496 patients received vitrified/warmed embryo transfer (ET).

METHODS

Surplus blastocysts, and blastocysts from patients undergoing elective embryo cryopreservation, were vitrified/warmed using Cryotop carriers in homemade solutions containing either human serum albumin (HSA) or rHA.

MAIN OUTCOME MEASURES

Clinical and neonatal outcomes regarding the vitrified/warmed ET procedures.

RESULTS

The HSA and rHA groups had a total of 1,163 and 898 vitrified/warmed cycles, respectively. Embryo survival rates (98.7% vs. 98.9%, respectively) and the number of embryos transferred (1.08 ± 0.01 vs. 1.06 ± 0.01, respectively) were similar in the HSA and rHA groups. Clinical pregnancy rates/ET were higher (P < 0.05) in the rHA group (56.0%) than in the HSA group (51.5%). The HSA and rHA groups had similar live delivery rates/pregnancy (72.2% vs. 72.3%, respectively) and perinatal outcomes, including birth weight (2,988 ± 28 vs. 3,046 ± 26 g, respectively). Birth defects occurred in 0.9% and 1.6% of neonates in the HSA and rHA groups, respectively.

CONCLUSIONS

rHA effectively replaced HSA for human embryo vitrification procedures, and yielded high rates of pregnancy and live births after vitrified/warmed ET. This new approach will support the development of defined ART systems, which will eliminate the variation and risks associated with the use of blood-derived products.

Preimplantation embryo metabolism and culture systems: experience from domestic animals and clinical implications

Despite advantages of in vitro embryo production in many species, widespread use of this technology is limited by generally lower developmental competence of in vitro derived embryos compared to in vivo counterparts. Regardless, in vivo or in vitro gametes and embryos face and must adjust to multiple microenvironments especially at preimplantation stages. Moreover, the embryo has to be able to further adapt to environmental cues in utero to result in the birth of live and healthy offspring. Enormous strides have been made in understanding and meeting stage-specific requirements of preimplantation embryos, but interpretation of the data is made difficult due to the complexity of the wide array of culture systems and the remarkable plasticity of developing embryos that seem able to develop under a variety of conditions. Nevertheless, a primary objective remains meeting, as closely as possible, the preimplantation embryo requirements as provided in vivo. In general, oocytes and embryos develop more satisfactorily when cultured in groups. However, optimization of individual culture of oocytes and embryos is an important goal and area of intensive current research for both animal and human clinical application. Successful culture of individual embryos is of primary importance in order to avoid ovarian superstimulation and the associated physiological and psychological disadvantages for patients. This review emphasizes stage specific shifts in embryo metabolism and requirements and research to optimize in vitro embryo culture conditions and supplementation, with a view to optimizing embryo culture in general, and culture of single embryos in particular.

Ultrarapid vitrification of mouse oocytes and embryos

Cryopreservation facilitates long-term storage of gametes and embryos for numerous purposes. For example, cryobanking of unique mouse strains, particularly transgenic mice, offers important protection of valuable genetics. It also provides a practical solution for facilities trying to house large numbers of research animals or those looking to relocate without the risk of introducing an animal-derived pathogen. Furthermore, cryopreservation is currently being used for fertility preservation both in humans and as a safeguard for endangered animals. Ultrarapid vitrification offers an elegant, quick, and very reliable method for cryopreservation of mouse oocytes and embryos. Furthermore, research into the effects on mouse oocyte and embryo physiology has indicated that ultrarapid vitrification is superior to conventional slow freezing. High survival rates, embryo development, and viability are routinely achieved with the ultrarapid vitrification method described in this chapter.

Different in vitro culture systems affect the birth weight of lambs from vitrified ovine embryos

It has been reported that different in vitro culture systems affect the birth weight of lambs. The aim of this study was to test body weight and lambing rate of lambs born from five different in vitro culture systems after vitrification. Oocytes of Sarda sheep were matured in TCM-199 plus 0.4% bovine serum albumin (BSA) using systems: (i) 4 mg/ml fatty acid-free BSA (BSA4); (ii) 8 mg/ml fatty acid-free BSA (BSA8); (iii) BSA8–hyaluronan (BSA8–HA); (iv) BSA8–charcoal-stripped FBS (BSA8–CH); or (v) with 10% fetal bovine serum (FBS; serum) and fertilized with fresh semen. The presumptive zygotes were cultured up to the blastocyst stage with BSA8, BSA8-HA, BSA8-CH or serum or BSA4. In the third and fifth days of culture 5% charcoal-stripped FBS was added into BSA8-CH and serum, while 8 mg/ml or 4 mg/ml fatty acid-free BSA was added as BSA8, BSA8-HA and BSA4 respectively; 6 mg/ml HA was added to BSA8-HA. In total, 240 vitrified blastocysts were transferred into synchronized ewes. The lambing rate was not significant different between BSA groups or between serum groups (BSA8-CH and serum), while serum groups showed significant lower values when compared with BSA groups. Only BSA8 groups produced heavy lambs (≥4.5 kg) with a significant difference between BSA4 and BSA8 groups (P < 0.05).

Hyaluronan and synovial joint: function, distribution and healing

Synovial fluid is a viscous solution found in the cavities of synovial joints. The principal role of synovial fluid is to reduce friction between the articular cartilages of synovial joints during movement. The presence of high molar mass hyaluronan (HA) in this fluid gives it the required viscosity for its function as lubricant solution. Inflammation oxidation stress enhances normal degradation of hyaluronan causing several diseases related to joints. This review describes hyaluronan properties and distribution, applications and its function in synovial joints, with short review for using thiol compounds as antioxidants preventing HA degradations under inflammation conditions.

Oocyte cryopreservation: searching for novel improvement strategies

PURPOSE

To highlight emerging techniques aimed at improving oocyte cryopreservation.

METHODS

Review of available and relevant literature through Pubmed and Medline searches.

RESULTS

Oocyte cryopreservation is an increasingly common procedure utilized for assisted reproduction and may benefit several patient populations. Therefore, improving efficiency is paramount in realizing the tremendous promise of this approach. However, in addition to numerous studies looking to improve oocyte cryopreservation efficacy via examination of variables involved with protocol methodology, such as type/concentration of cryoprotectant (CPA), type of storage device, or cooling/warming rates, there are more novel approaches for improvement. These alternate approaches include utilizing different the stages of oocytes, examining alteration of basal media and buffer composition, optimizing CPA exchange protocols and device loading through use of automated technology, as well as examination/manipulation of oocyte cellular composition to improve cryotolerance. Finally, elucidating more accurate or insightful indicators of "success" is crucial for continued improvement of oocyte cryopreservation.

CONCLUSION

Oocyte cryopreservation has improved dramatically in recent years and is receiving widespread clinical use. Novel approaches to further improve success, as well as improved methods to assess this success will aid in continued improvement.

Variability in protein quality used for embryo culture: embryotoxicity of the stabilizer octanoic acid

OBJECTIVE

To screen human serum albumin (HSA) preparations for toxicity and investigate causes of variation.

DESIGN

Experimental laboratory study.

SETTING

University-based laboratory.

ANIMAL(S)

FVB and CF1 mice crossed to create embryos used in experiments.

INTERVENTION(S)

Mouse embryo assay performed with 5% or 15% HSA (100 mg/mL albumin) from three samples from three separate manufacturers (A, B, C).

MAIN OUTCOME MEASURE(S)

Blastocyst rates calculated at 96 hours of culture (experiments repeated in triplicate).

RESULT(S)

The HSA preparations were desalted to remove stabilizers added during HSA processing, then mass spectrometry was used to determine the relative variation in stabilizer concentrations; the effect of the stabilizer octanoic acid on embryo development was tested. At 5% HSA, all samples had blastocyst rates ≥ 70%; at 15% HSA, the blastocyst rates for samples B and C were <50%. Desalting did not affect sample B but did improve the blastocyst rates of sample C. Mass spectrometry revealed high levels of octanoic acid in sample C compared with sample A. The addition of octanoic acid to sample A produced toxicity similar to sample C.

CONCLUSION(S)

The stabilizer octanoic acid varies by lot and inhibits embryo development. Because octanoic acid is known to cause disruptions in mitochondrial bioenergetics, reduce intracellular pH, and induce oxidative damage in peripheral tissues, its use in embryo culture should be monitored and limited.

Defined media optimization for in vitro culture of bovine somatic cell nuclear transfer (SCNT) embryos

The objective was to establish an efficient defined culture medium for bovine somatic cell nuclear transfer (SCNT) embryos. In this study, modified synthetic oviductal fluid (mSOF) without bovine serum albumin (BSA) was used as the basic culture medium (BCM), whereas the control medium was BCM with BSA. In Experiment 1, adding polyvinyl alcohol (PVA) to BCM supported development of SCNT embryos to blastocyst stage, but blastocyst formation rate and blastocyst cell number were both lower (P < 0.05) compared to the undefined group (6.1 vs. 32.6% and 67.3 ± 3.4 vs. 109.3 ± 4.5, respectively). In Experiment 2, myo-inositol, a combination of insulin, transferrin and selenium (ITS), and epidermal growth factor (EGF) were added separately to PVA-supplemented BCM. The blastocyst formation rate and blastocyst cell number of those three groups were dramatically improved compared with that of PVA-supplemented group in Experiment 1 (18.5, 23.0, 24.1 vs. 6.1% and 82.7 ± 2.0, 84.3 ± 4.2, 95.3 ± 3.8 vs. 67.3 ± 3.4, respectively, P < 0.05), but were still lower compared with that of undefined group (33.7% and 113.8 ± 3.4, P < 0.05). In Experiment 3, when a combination of myo-inositol, ITS and EGF were added to PVA-supplemented BCM, blastocyst formation rate and blastocyst cell number were similar to that of undefined group (30.4 vs. 31.1% and 109.3 ± 4.4 vs. 112.0 ± 3.6, P > 0.05). In Experiment 4, when blastocysts were cryopreserved and subsequently thawed, there were no significant differences between the optimized defined group (Experiment 3) and undefined group in survival rate and 24 and 48 h hatching blastocyst rates. Furthermore, there were no significant differences in expression levels of H19, HSP70 and BAX in blastocysts derived from optimized defined medium and undefined medium, although the relative expression abundance of IGF-2 was significantly decreased in the former. In conclusion, a defined culture medium containing PVA, myo-inositol, ITS, and EGF supported in vitro development of bovine SCNT embryos.

A simple medium enables bovine embryos to be held for seven days at 4°C

Cryopreservation methods using liquid nitrogen (LN₂) for gametes and embryos are prevalent in mammalian artificial reproduction. However, the pregnancy rate from frozen embryos has not improved over the past two decades because freeze–thawing causes significant damage. The strict regulation of transportation of LN₂ containers by airlines also limits exchange between breeders. In this article, we introduce a medium that enabled bovine embryos to be held for up to 7 days at 4°C. A pregnancy rate of 75% (24/32) was obtained for embryos held for 7 days in this medium and transferred to primed recipients. Its constituents were medium 199, foetal bovine serum, and HEPES for buffering. This technique will enable LN₂-free storage and air transportation of embryos provided transplantation to recipients can be completed within 7 days.

The redox state of recombinant human serum albumin and its optimal concentration for mouse embryo culture

Albumin has multiple physiological functions in embryo culture, such as a chelator of heavy metals, free radical scavenger, pH and osmotic regulator, a stabilizer, growth factor carrier, a surfactant, and a nutrient. However, the commercially available human serum albumin (HSA) products may not be completely safe since they could be contaminated with viruses and prions. Recombinant human serum albumin (rHSA) has been reported to be as efficient as commercial HSA for fertilization and embryo development. Despite the possible benefits of rHSA, it has not been widely used for embryo culture due to its high cost of production. Our objective was to analyze the redox state of different types of HSA products and rHSA to define oxidative status batch variations of HSA and rHSA and to evaluate the optimal concentration of rHSA for mouse embryo culture. The redox state of the HSA and rHSA used in embryo culture media was found to vary widely. Redox variations were found among different HSA batches as well as among rHSA batches. The highest blastocyst development and hatching rates were obtained with rHSA used at a concentration of 0.05 mg/mL. We showed that very low concentrations of rHSA were most favorable for advanced mouse embryo development in culture.

Diet-induced paternal obesity in the absence of diabetes diminishes the reproductive health of two subsequent generations of mice

BACKGROUND

Obesity and related conditions, notably subfertility, are increasingly prevalent. Paternal influences are known to influence offspring health outcome, but the impact of paternal obesity and subfertility on the reproductive health of subsequent generations has been overlooked.

METHODS

A high-fat diet (HFD) was used to induce obesity but not diabetes in male C57Bl6 mice, which were subsequently mated to normal-weight females. First-generation offspring were raised on a control diet and their gametes were investigated for signs of subfertility. Second-generation offspring were generated from both first generation sexes and their gametes were similarly assessed.

RESULTS

We demonstrate a HFD-induced paternal initiation of subfertility in both male and female offspring of two generations of mice. Furthermore, we have shown that diminished reproductive and gamete functions are transmitted through the first generation paternal line to both sexes of the second generation and via the first generation maternal line to second-generation males. Our previous findings that founder male obesity alters the epigenome of sperm, could provide a basis for the developmental programming of subfertility in subsequent generations.

CONCLUSIONS

This is the first observation of paternal transmission of diminished reproductive health to future generations and could have significant implications for the transgenerational amplification of subfertility observed worldwide in humans.

Improving post-transfer survival of bovine embryos produced in vitro: actions of insulin-like growth factor-1, colony stimulating factor-2 and hyaluronan

Technologies for in vitro embryo production have the potential to enhance the efficiency of cattle production systems. However, utilization of in vitro-produced embryos for transfer remains limited throughout much of the world. Despite improvements over the past two decades, problems associated with the production of bovine embryos in vitro still exist which limit the widespread commercial application of this technology. In particular, bovine embryos produced in vitro have a reduced capacity to establish and maintain pregnancy as compared with their in vivo-derived counterparts. Embryo competence for survival following transfer is improved by in vivo culture in the sheep oviduct, thus indicating that standard embryo culture conditions are sub-optimal. Therefore, one strategy to improve post-transfer survival is to modify embryo culture media to more closely mimic the in vivo microenvironment. The maternal environment in which the bovine embryo develops in vivo contains various growth factors, cytokines, hormones, and other regulatory molecules. In addition to affecting bovine embryo development in vitro, recent research indicates that embryo competence for survival following transfer can also be improved when such molecules are added to embryo culture medium. Among the specific molecules that can increase post-transfer embryo survival are insulin-like growth factor-1 (IGF-1), colony stimulating factor-2 (CSF-2) and hyaluronan. This paper will review the effects IGF-1, CSF-2 and hyaluronan on post-culture embryo viability and discuss the potential mechanisms through which each of these molecules improves post-transfer survival.

Advances in embryo culture platforms: novel approaches to improve preimplantation embryo development through modifications of the microenvironment

BACKGROUND

The majority of research aimed at improving embryo development in vitro has focused on manipulation of the chemical environment, examining details such as energy substrate composition and impact of various growth factors or other supplements. In comparison, relatively little work has been done examining the physical requirements of preimplantation embryos and the role culture platforms or devices can play in influencing embryo development.

METHODS

Electronic searches were performed using keywords centered on embryo culture techniques using PUBMED through June 2010 and references were searched for additional research articles.

RESULTS

Various approaches to in vitro embryo culture that involve manipulations of the physical culture environment are emerging. Novel culture platforms being developed examine issues such as media volume and embryo spacing. Furthermore, methods to permit dynamic embryo culture with fluid flow and embryo movement are now available, and novel culture surfaces are being tested.

CONCLUSIONS

Although several factors remain to be studied to optimize efficiency, manipulations of the embryo culture microenvironment through novel culture devices may offer a means to improve embryo development in vitro. Reduced volume systems that reduce embryo spacing, such as the well-of-the-well approach, appear beneficial, although more work is needed to verify the source of their true benefit in human embryos. Emerging microfluidic technology appears to be a promising approach. However, along with the work on specialized culture surfaces, more information is required to determine the impact on human embryo development.

A prospective randomized sibling-oocyte study of two media systems for culturing cleavage-stage embryos-impact on fertilization rate

PURPOSE

Although several media systems have been developed, data from prospective randomised clinical studies are still lacking. In the present study we compared the effects of 2 different media systems on embryo morphology and development at days 2/3 using sibling oocytes.

METHODS

In this prospective sibling-split trial, 1206 oocytes from 110 women were divided via alternate allocation to fertilization and culture in media system A (G-IVF (TM) v5 PLUS/ G-1(TM) v5 PLUS) or for fertilization and culture in media system B (Universal IVF medium/EmbryoAssist (TM)).

RESULTS

The use of media system A significantly increased the normal fertilization rate (73.5% versus 67.2%; p = 0.030) and embryo utilization rate (55.5% versus 42.9%; p = 0.001), whereas polyploidy and embryo quality were similar in the two groups.

CONCLUSION

The different impacts on fertilization and early embryo development between the two commercially available and commonly used media systems show the importance of evaluation of the efficacy of existing sequential culture media and the need to further improve media for in vitro development of human embryos.

Embryo Culture Media, Culture Techniques and Embryo Selection: A Tribute to Wesley Kingston Whitten

This review article gives a brief history of the classical experiments that led to the development of the embryo culture medium and in vitro embryo culture. It proposes that, in view of the outstanding and significant pioneering contributions of Wesley Kingston Whitten to the development of embryo culture medium, he be considered the “Father of Embryo Culture Medium”. Furthermore, it describes the nutritional requirements of early embryos and how these requirements with specific references to carbohydrates, amino acids, phosphates, growth factors, etc, have been utilized to formulate increasingly more complex embryo culture media. This has led to the development of progressively more efficacious embryo culture media including the formulation of completely defined and synthetic protein-free embryo culture medium. The review also describes physical factors, growth factors, insemination methods for the fertilization of oocytes and culture methods affecting embryo growth, development, metabolism, oxygen embryotoxicity and survival. In procedural terms, the review also summarizes the evolution of embryo culture techniques from tube culture to, microdrop culture under oil to co-culture to ultra microdrop culture techniques. It includes techniques of in vitro maturation and for the selection of potentially viable embryos of various developmental stages.

Effects of gamete source and culture conditions on the competence of in vitro-produced embryos for post-transfer survival in cattle

One limitation to the use of in vitro-produced embryos in cattle production systems is the fact that pregnancy rates after transfer to recipients are typically lower than when embryos produced in vivo are transferred. Conceptually, the oocyte and spermatozoon from which the embryo is derived could affect competence for post-transfer survival. There are sire differences in embryonic survival after transfer, but there is little evidence that an embryo's ability to establish pregnancy is determined by sex sorting of spermatozoa by flow cytometry. The role of the source of the oocyte as a determinant of embryonic survival after transfer has not been examined carefully. Conditions for embryo culture after fertilisation can have an impact on the ability of the embryo to establish pregnancy following transfer. Among the specific molecules produced in the reproductive tract of the cow that have been shown to improve competence of in vitro-produced embryos for post-transfer survival are colony-stimulating factor 2, insulin-like growth factor-1 (for recipients exposed to heat stress) and hyaluronan (for less-advanced embryos). There is also a report that embryo competence for post-transfer survival can be improved by inclusion of a carbon-activated air filtration system in the incubator used to culture embryos. Progress in developing culture systems to improve embryonic competence for survival after transfer would be hastened by the development of in vitro assays that accurately predict the potential of an embryo to establish pregnancy after transfer. A group of 52 genes has been identified that are differentially expressed in embryos that developed to term v. embryos that did not establish pregnancy. Perhaps a gene microarray consisting of these genes, alone or in combination with other genes, could be used to screen embryos for competence to establish pregnancy.

Synthetic media for culture, freezing and vitrification of bovine embryos

Media designed for the recovery, holding and cryopreservation of bovine and equine embryos are available from several commercial sources. In years past, some of these media contained bovine serum, although inclusion of serum in embryo transfer media is now largely discontinued due to issues relating to storage and biosecurity. Currently, bovine serum albumin (BSA) is included in most commercially manufactured media intended for use in embryo transfer (ET). Although BSA poses less risk than serum for the transmission of infectious disease, its inclusion still entails risk of viral contamination. The present review briefly describes the various components of ET media and the development of efficacious ET media containing no products of animal origin. An evaluation of the efficacy of recovery, holding, slow controlled freezing and vitrification media in both research and commercial ET embryo transfer settings is also presented.

The effect of bovine embryo culture without proteins supplements until day 4 on transcription level of hyaluronan synthases, receptors and mtDNA content

The effect of bovine embryo culture on a flat surface, (without a surface-active compound) on the level of mRNA expression of hyaluronan (HA) synthases (Has1, Has2 and Has3), Ha receptors RHAMM and C44 receptors was evaluated by mitochondrial DNA concentration and in vitro development. Cultures were evaluated up to 96 h post-insemination (hpi) using SOFaa medium. Of the three Has isoforms, Has2 expression only increased in the bovine serum albumin (BSA)-only supplemented groups regardless of time of BSA addition. Expression of RHAMM receptors was highly dependent on the addition of HA, irrespective of the presence of BSA in the medium. In contrast, expression of the CD44 receptor gene was not affected by any treatment. The cleavage rates and number of embryos that developed to <or=8-cell stage by day 4 were not affected by lack of BSA in the medium, but increased numbers of blastocysts developed in medium supplemented with BSA from days 1 or 4 with or without HA than in medium that had HA only. Addition of both HA and BSA at day 4 increased mtDNA copy numbers at the blastocyst stage. Data suggest that the addition of BSA and/or HA at 96 hpi increased expression of RHAMM and Has2 genes, but not CD44, Has1 or Has3 genes. Higher expression levels of Has2 than Has1 and the three isoforms indicate that high- rather than low-molecular-weight HA should be used for preimplantation bovine embryo culture.

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

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Several aspects of animal embryo cryopreservation: anti-freeze protein (AFP) as a potential cryoprotectant

With the development of embryo technologies, such as in vitro fertilization, cloning and transgenesis, cryopreservation of mammalian gametes and embryos has acquired a particular interest. Despite a certain success, various cryopreservation techniques often cause significant morphological and biochemical alterations, which lead to the disruption of cell organelles, cytoskeleton damages, cell death and loss of embryo viability. Ultrastructural studies confirm high sensitivity of the cell membrane and organelle membrane to freezing and thawing. It was found that many substances with low molecular weights have a protective action against cold-induced damage. In this concern, an anti-freeze protein (AFP) and anti-freeze glycoproteins (AFGPs), which occur at extremely high concentrations in fish that live in Arctic waters and protect them against freezing, may be of potential interest for cryostorage of animal embryos at ultra-low temperatures. This mini-review briefly describes several models of AFP/AFGP action to preserve cells against chilling-induced damages and indicates several ways to improve post-thaw developmental potential of the embryo.

Plant protein hydrolysates (plant peptones) as substitutes for animal proteins in embryo culture medium

The aim of the present study was to improve the sanitary quality of in vitro-produced bovine embryos by using plant protein hydrolysates (plant peptones) as substitutes for animal proteins. Peptones were compared with bovine serum albumin (BSA) as the protein source in synthetic oviduct fluid medium and the quality of the resulting embryos was determined. Two batches of peptones (wheat and cotton) were selected on the basis of their anti-oxidant properties. When added to the culture medium, both peptones (at 0.56 mg mL–1 for cotton peptone and at 0.18 mg mL–1 for wheat peptone) led to similar developmental and hatching rates compared with 4 mg mL–1 BSA and embryos were equally resistant to freezing and able to elongate after transfer. Surprisingly, a significant decrease in reduced glutathione (GSH) content was observed when embryos were produced with plant peptone instead of BSA. Supplementation of the culture medium with precursors of GSH (cysteine and β-mercaptoethanol) significantly increased the GSH content. A shift of the sex ratio towards male embryos was seen for Day 8 embryos cultured with wheat peptone, whereas no shift was observed for embryos cultured in the presence of BSA or polyvinylpyrrolidone. In conclusion, culture with plant peptones enables embryos to be obtained at a similar rate and of similar quality to that seen following the use of BSA. The use of the plant peptones increased the sanitary quality of the embryos and decreased the cost of embryo production.

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

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

Development, molecular composition and freeze tolerance of bovine embryos cultured in TCM-199 supplemented with hyaluronan

Hyaluronan (HA) is glycosaminoglycan that is present from the start of embryonic development and its role and concentration increases with embryo development. The objective of this study was to evaluate if the presence of HA in TCM-199 culture medium had an effect on the development and quality of bovine embryos. There was no effect of HA on the total number of zygotes developing to blastocysts on day 7, however more expanded and hatched blastocyst stages were observed on days 8 and 9 in the group supplemented with HA (p< 0.05). Following freeze/thawing, significantly more (p< 0.05) embryos cultured in medium supplemented with HA hatched than those cultured in TCM-199 alone or those with BSA. Medium supplemented with HA and BSA significantly increased the level of expression of glucose metabolismGlut-1gene and embryo compactionCx43gene (p< 0.05), and had no effect onGlut-5andIGF-IIexpression. In addition, HA presence in culture decreased the level of expression of apoptosisBaxand oxidative stressSOXgenes (p< 0.05). There was significant difference in total number of nuclei between TCM-199 medium only and the remaining media containing BSA or HA plus BSA, between which there was no difference. In summary, our results indicate that the addition of high molecular weight HA to TCM-199 medium that contains BSA on day 4 of culture improved embryo development to hatching and hatched blastocysts and the quality of produced embryos, which were superior to embryos cultured without HA addition.

Set up of a serum-free culture system for bovine embryos: embryo development and quality before and after transient transfer

It is well known that serum in culture medium negatively affects blastocyst quality. The objective of this work was to develop and test a serum-free culture medium which could improve embryo quality, measured by the resistance to freezing, lipid and glutathione content of the resulting blastocysts, as well as the ability of the blastocysts to elongate after transient transfer to recipient cows. In a first experiment we showed that adding a mixture of insulin, transferrin and selenium to serum-free Synthetic Oviduct Fluid medium (SOF-ITS) improved embryo development and quality. In the second experiment, the addition of BSA to SOF-ITS further improved blastocyst development. Moreover, a reduction in lipid content of morulae was observed in SOF-ITS-BSA by comparison with morulae cultured with serum (SOF-FCS). The resistance to freezing measured by hatching rates 24h post-thawing was also improved for blastocysts with a diameter between 160 and 180 microm cultured in SOF-ITS-BSA by comparison to those produced with serum. In order to evaluate the redox potential of the embryos, reduced glutathione content (GSH) was evaluated both before and after cryopreservation. A significant decrease in glutathione was observed after freezing, whatever the culture medium, but no difference was observed between culture conditions. Transient transfers were performed and elongated D-13 embryos were recovered. Elongation was more pronounced and the embryonic disk more often visible in embryos cultured in SOF-ITS-BSA than in embryos cultured with FCS. In conclusion, the serum-free system we developed to produce in vitro bovine embryos meets the developmental and qualitative requirements for a large-scale use.