Embryo culture and long-term consequences

Insight on cytotoxic NHC gold(I) halide complexes evaluated in multifaceted culture systems

Gold complexes can be a useful system in the fight against cancer. Although many studies have been carried out on in vitro 2D cell culture models embryotoxic assays are particularly lacking. Embryotoxicity and DNA damage are critical concerns in drug development. In this study, the effects of a new N-Heterocyclic carbene (NHC)-Au compound (Bromo[1,3-di-4-methoxybenzyl-4,5-bis(4-methoxyphenyl)imidazol-2-ylidene]gold(I)) at different concentrations were explored using multifaceted approach, encompassing 2D cancer cell cultures, in vivo zebrafish and in vitro bovine models, and compared with a consolidated similar complex (Bromo[1,3-diethyl-4,5-bis(4-methoxyphenyl)imidazol-2-ylidene]gold(I)). The results obtained from 2D cancer cell cultures revealed concentration-dependent effects of the gold compounds by estimating the cytotoxicity with MTT assay and cellular damage as indicated by LDH release. Selected concentrations of gold complexes demonstrated no adverse effects on zebrafish embryo development. However, in bovine embryos, these same concentrations led to significant impairments in the early developmental stages, triggering cell apoptosis and reducing blastocyst competence. These findings underscore the importance of evaluating drug effects across different model systems to comprehensively assess their safety and potential impact on embryonic development.

The uterine secretory cycle: recurring physiology of endometrial outputs that setup the uterine luminal microenvironment

Conserved in female reproduction across all mammalian species is the estrous cycle and its regulation by the hypothalamic-pituitary-gonadal (HPG) axis, a collective of intersected hormonal events that are crucial for ensuring uterine fertility. Nonetheless, knowledge of the direct mediators that synchronously shape the uterine microenvironment for successive yet distinct events, such as the transit of sperm and support for progressive stages of preimplantation embryo development, remain principally deficient. Toward understanding the timed endometrial outputs that permit luminal events as directed by the estrous cycle, we used Bovidae as a model system to uniquely surface sample and study temporal shifts to in vivo endometrial transcripts that encode for proteins destined to be secreted. The results revealed the full quantitative profile of endometrial components that shape the uterine luminal microenvironment at distinct phases of the estrous cycle (estrus, metestrus, diestrus, and proestrus). In interpreting this comprehensive log of stage-specific endometrial secretions, we define the "uterine secretory cycle" and extract a predictive understanding of recurring physiological actions regulated within the uterine lumen in anticipation of sperm and preimplantation embryonic stages. This repetitive microenvironmental preparedness to sequentially provide operative support was a stable intrinsic framework, with only limited responses to sperm or embryos if encountered in the lumen within the cyclic time period. In uncovering the secretory cycle and unraveling realistic biological processes, we present novel foundational knowledge of terminal effectors controlled by the HPG axis to direct a recurring sequence of vital functions within the uterine lumen.NEW & NOTEWORTHY This study unravels the recurring sequence of changes within the uterus that supports vital functions (sperm transit and development of preimplantation embryonic stages) during the reproductive cycle in female Ruminantia. These data present new systems knowledge in uterine reproductive physiology crucial for setting up in vitro biomimicry and artificial environments for assisted reproduction technologies for a range of mammalian species.

Assessing the influence of distinct culture media on human pre-implantation development using single-embryo transcriptomics

The use of assisted reproductive technologies is consistently rising across the world. However, making an informed choice on which embryo culture medium should be preferred to ensure satisfactory pregnancy rates and the health of future children critically lacks scientific background. In particular, embryos within their first days of development are highly sensitive to their micro-environment, and it is unknown how their transcriptome adapts to different embryo culture compositions. Here, we determined the impact of culture media composition on gene expression in human pre-implantation embryos. By employing single-embryo RNA-sequencing after 2 or 5 days of the post-fertilization culture in different commercially available media (Ferticult, Global, and SSM), we revealed medium-specific differences in gene expression changes. Embryos cultured pre-compaction until day 2 in Ferticult or Global media notably displayed 266 differentially expressed genes, which were related to essential developmental pathways. Herein, 19 of them could have a key role in early development, based on their previously described dynamic expression changes across development. When embryos were cultured after day 2 in the same media considered more suitable because of its amino acid enrichment, 18 differentially expressed genes thought to be involved in the transition from early to later embryonic stages were identified. Overall, the differences were reduced at the blastocyst stage, highlighting the ability of embryos conceived in a suboptimal in vitro culture medium to mitigate the transcriptomic profile acquired under different pre-compaction environments.

Effects of the addition of insulin-transferrin-selenium (ITS) and/or metformin to the in vitro maturation of porcine oocytes on cytoplasmic maturation and embryo development

CONTEXT

One of the main problems of porcine in vitro maturation (IVM) is incomplete cytoplasmatic maturation. Nuclear and cytoplasmic maturation will determine the future success of fertilisation and embryo development. Insulin-transferrin-selenium (ITS) has insulin-like and antioxidant effects, and metformin (M) is an insulin-sensitiser and antioxidant drug.

AIMS

To assess the effects of adding ITS and/or M in porcine IVM media on cytoplasmic maturation and early embryo development.

METHODS

Cumulus -oocyte complexes (COC) were IVM with M (10-4 M), ITS (0.1% v/v), M+ITS or no adding (Control).

KEY RESULTS

ITS increased glucose consumption compared to Control and M (P <0.01), and M+ITS did not differ from ITS or Control. Redox balance: M, ITS and M+ITS increased glutathione (P <0.01) and decreased lipid peroxidation (P <0.005). The viability of cumulus cells by flow cytometry increased with M (P <0.005) and decreased with ITS (P <0.001); M+ITS did not differ from Control. After IVF, M increased penetration and decreased male pronucleus (P <0.05). Embryo development: cleavage increased with M (P <0.05), and blastocysts increased with ITS and M+ITS (P <0.05). The number of blastocyst cells increased with ITS (P <0.05).

CONCLUSIONS

Adding ITS and M+ITS to porcine IVM media benefits embryo development to blastocysts, but ITS alone has better effects than M+ITS.

IMPLICATIONS

ITS is an excellent tool to improve IVM and embryo development after IVF in pigs.

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.

DMSO supplementation during in vitro maturation of bovine oocytes improves blastocyst rate and quality

The molecule Dimethyl sulfoxide is widely used as drug solvent. However, its antioxidant property was poorly explored. In this study, we evaluated the effect of DMSO supplementation during oocyte in vitro maturation (IVM) on embryo development and quality. Bovine oocytes were matured with different DMSO concentrations (0, 0.1, 0.25, 0.5, 0.75, 1 and 10% v:v) followed by in vitro fertilization. Subsequently, quality indicators such as gene expression of SOX2, OCT4, CDX2, SOD1, oocyte and embryo redox status and DNA damage were evaluated. Polar body extrusion and blastocyst rates increased with 0.5% v:v DMSO. Moreover, first polar body extrusion and blastocyst rates did not increase with 1%, and 10% of DMSO reduced polar body extrusion and did not produce blastocyst. Optimal concentration of DMSO for the use on the maturation was estimated at around 0.45% v:v. Supplementation with 0.5% v:v DMSO has not affected mRNA abundance of genes key in blastocyst, however 0.75% increased gene expression of OCT4 and SOX2. Oocytes matured with 0.5% v:v DMSO and blastocyst from DMSO group showed reduced lipid peroxidation respect control. Total Glutathione concentrations increased in blastocyst stage in DMSO group. DMSO increased the total cell number of blastocysts but not TUNEL positive cells. In conclusion, our results suggest that low DMSO concentrations used during bovine oocytes in vitro maturation increases the maturation, as well as the blastocyst rate and its quality, without demonstrating deleterious effect on embryo cells.

Use of Melatonin in the In Vitro Production of Bovine Embryos

ABSTRACT We aimed to assess the effects of melatonin in the in vitro production of bovine embryos. Our experiment was conducted at the Laboratório de Reprodução Animal of the Universidade Estadual do Maranhão. The cumulus-oocyte complexes (COCs) were distributed among treatments at concentrations of 0, 10-1, 10-3 and 10-5 µMol/L melatonin. Our experiment was further divided into two: the first was to assess the effect of different concentrations of melatonin (treatments) on the maturation rate of COCs, and the second was to assess the effects of melatonin treatments on the in vitro production of bovine embryos. The results from the first experiment demonstrated no significant difference between the in vitro maturation rate of the cultivated COCs in treatments with melatonin. In the second experiment, however, melatonin treatments yielded statistically higher cleavage, morula and blastocyst rates in the 10-5 µM group (52.9%, 52.9%, and 35.3%, respectively), and lower rates in the 10-1 µM group (19.5%, 19.5% and 7.8%, respectively), compared to the others. The control group (no melatonin) and the 10-3 µM group showed similar results. We concluded that supplementation of melatonin in the in vitro maturation medium resulted in no improvement in the oocyte maturation rate, but in the in vitro production of embryos at different concentrations, the 10-5 µM group displayed better results, but with no improvement in the variables (P < 0.05).

Glutamine supplementation enhances development of in vitro-produced porcine embryos and increases leucine consumption from the medium

Improper composition of culture medium contributes to reduced viability of in vitro-produced embryos. Glutamine (Gln) is a crucial amino acid for preimplantation embryos as it supports proliferation and is involved in many different biosynthetic pathways. Previous transcriptional profiling revealed several upregulated genes related to Gln transport and metabolism in in vitro-produced porcine blastocysts compared to in vivo-produced counterparts, indicating a potential deficiency in the culture medium. Therefore, the objective of this study was to determine the effects of Gln supplementation on in vitro-produced porcine embryo development, gene expression, and metabolism. Cleaved embryos were selected and cultured in MU2 medium supplemented with 1 mM Gln (control), 3.75 mM Gln (+Gln), 3.75 mM GlutaMAX (+Max), or 3.75 mM alanine (+Ala) until day 6. Embryos cultured with +Gln or +Max had increased development to the blastocyst stage and total number of nuclei compared to the control (P < 0.05). Moreover, expression of misregulated transcripts involved in glutamine and glutamate transport and metabolism was corrected when embryos were cultured with +Gln or +Max. Metabolomics analysis revealed increased production of glutamine and glutamate into the medium by embryos cultured with +Max and increased consumption of leucine by embryos cultured with +Gln or +Max. As an indicator of cellular health, mitochondrial membrane potential was increased when embryos were cultured with +Max which was coincident with decreased apoptosis in these blastocysts. Lastly, two embryo transfers by using embryos cultured with +Max resulted in viable piglets, confirming that this treatment is consistent with in vivo developmental competence.

Impacts of and interactions between environmental stress and epigenetic programming during early embryo development

The processes of assisted reproductive technologies (ART) involve a variety of interventions that impact on the oocyte and embryo. Critically, these interventions cause considerable stress and coincide with important imprinting events throughout gametogenesis, fertilisation and early embryonic development. It is now accepted that the IVM and in vitro development of gametes and embryos can perturb the natural course of development to varying degrees of severity. Altered gene expression and, more recently, imprinting disorders relating to ART have become a focused area of research. Although various hypotheses have been put forward, most research has been observational, with little attempt to discover the mechanisms and periods of sensitivity during embryo development that are influenced by the culture conditions following fertilisation. The embryo possesses innate survival factor signalling pathways, yet when an embryo is placed in culture, this signalling in response to in vitro stress becomes critically important in mitigating the effects of stresses caused by the in vitro environment. It is apparent that not all embryos possess this ability to adequately adapt to the stresses experienced in vitro, most probably due to an inadequate oocyte. It is speculated that it is important that embryos use their survival signalling mechanisms to maintain normal epigenetic programming. The seeming redundancy in the function of various survival signalling pathways would support this notion. Any invasion into the natural, highly orchestrated and dynamic process of sexual reproduction could perturb the normal progression of epigenetic programming. Therefore the source of gametes and the subsequent culture conditions of gametes and embryos are critically important and require careful attention. It is the aim of this review to highlight avenues of research to elucidate the effects of stress and the relationship with epigenetic programming. The short- and long-term health and viability of human and animal embryos derived in vitro will also be discussed.

Inter-generational effects of the in vitro maturation technique on pregnancy outcomes, early development, and cognition of offspring in mouse model

In vitro maturation (IVM) of oocytes has been a highly successful method for avoiding the occurrence of severe ovarian hyperstimulation syndrome in some patients during in vitro fertilization. However, the safety of the protocol, especially the long-term effects, is still an issue of debate. The current study is to investigate the long-term effects of IVM on mice through two generations and reveal its inter-generational effects as well. The data indicate that the rates of embryo resorption and fetal death in the F1 generation were significantly increased while the newborn survival rate in the F1 and F2 generations were significantly decreased in the IVM group. Increased body weights in the F1 generation and mouse number per litter in the F2 generation were observed in both the IVM and VVM groups; however, no insulin resistance was detected. No significant differences were detected in birth defects, organ weights, testis histology and sperm motility, estrous cycle, and cognition among the IVM, VVM and N mice in either the F1 or F2 generations. Our results suggest that mouse IVM can affect pregnancy outcomes throughout two generations. IVM does not appear to influence the development and cognition of the offspring throughout two generations.

The ART of studying early embryo development: progress and challenges in ruminant embryo culture

The study of preimplantation mammalian embryo development is challenging due to difficulties in accessing in vivo-derived embryos in large numbers at the early stages and the inability to culture embryos in vitro much beyond the blastocyst stage. Nonetheless, embryos exhibit an amazing plasticity and tolerance when it comes to adapting to the environment in which they are cultured. They are capable of developing in media ranging in composition from simple balanced salt solutions to complex systems involving serum and somatic cells. At least a proportion of the blastocysts that develop in culture are developmentally competent as evidenced by the fact that live offspring have resulted following transfer. However, several studies using animal models have shown that such embryos are sensitive to environmental conditions that can affect future pre- and post-natal growth and developmental potential. This review summarises some key aspects of early embryo development and the approaches taken to study this important window in early life.

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.

Composition of commercial media used for human embryo culture

OBJECTIVE

To determine the composition of commercially available culture media and test whether differences in composition are biologically relevant in a murine model.

DESIGN

Experimental laboratory study.

SETTING

University-based laboratory.

ANIMAL(S)

Cryopreserved hybrid mouse one-cell embryos were used in experiments.

INTERVENTION(S)

Amino acid, organic acid, ions, and metal content were determined for two different lots of media from Cook, In Vitro Care, Origio, Sage, Vitrolife, Irvine CSC, and Global. To determine whether differences in the composition of these media are biologically relevant, mouse one-cell embryos were thawed and cultured for 120 hours in each culture media at 5% and 20% oxygen in the presence or absence of protein in an EmbryoScope time-lapse incubator.

MAIN OUTCOME MEASURE(S)

The compositions of seven culture media were analyzed for concentrations of 39 individual amino acids, organic acids, ions, and elements. Blastocyst rates and cell cycle timings were calculated at 96 hours of culture, and the experiments were repeated in triplicate.

RESULT(S)

Of the 39 analytes, concentrations of glucose, lactate, pyruvate, amino acids, phosphate, calcium, and magnesium were present in variable concentrations, likely reflecting differences in the interpretation of animal studies. Essential trace elements, such as copper and zinc, were not detected. Mouse embryos failed to develop in one culture medium and were differentially affected by oxygen in two other media.

CONCLUSION(S)

Culture media composition varies widely, with differences in pyruvate, lactate, and amino acids especially notable. Blastocyst development was culture media dependent and showed an interaction with oxygen concentration and presence of protein.

Effect of dexamethasone on development of in vitro-produced bovine embryos

Studies in somatic cells have shown that glucocorticoids such as dexamethasone (DEX) may trigger or prevent apoptosis depending on the cell type in culture. Because the dysregulation of apoptosis may lower in vitro embryo production efficiency, we sought to investigate the effects of supplementing IVC medium with DEX (0.1 μg/mL) on embryo morphology, development kinetics, and apoptosis rates of in vitro-produced bovine preimplantation embryos. Embryo morphology was graded on Day 7, and development rates were assessed on Days 4 and 7 of IVC. Apoptosis was evaluated via annexin/propidium iodide staining under fluorescence microscopy where a cell labeled with annexin, propidium iodide, or both would be considered apoptotic. An embryo was counted in the apoptosis rates, if it displayed at least one such labeled cell. Although DEX supplementation did not reduce apoptosis rates, it had a positive impact on developmental kinetics and cell number both on Days 4 and 7 of embryo culture. Presumably, such effect resulted from increased cell proliferation rather than a direct inhibition of apoptosis. Further studies may evaluate the mechanisms by which glucocorticoids may affect embryo development, as DEX supplementation could become a tool to improve in vitro embryo yield in mammalian species.

Differential immunoregulation in successful oocyte donation pregnancies compared with naturally conceived pregnancies

In oocyte donation (OD) pregnancies, there is a higher level of antigenic dissimilarity between mother and fetus compared with naturally conceived (NC) pregnancies. We hypothesize that a higher degree and/or a different type of immunoregulation is necessary to maintain an uncomplicated OD pregnancy. Different immunological aspects of successful OD pregnancies (n=28) were compared with those of NC pregnancies (n=51), and non-donor IVF (n=20) pregnancies. Maternal peripheral blood mononuclear cells (mPBMCs) were characterized by flow cytometry; the outcome correlated with the number of mother-child HLA mismatches. The fetus-specific alloreactivity of mPBMCs was measured in a mixed lymphocyte reaction. The percentages of CD4(+)CD25(bright) and CD4(+)CD25(dim) cells were higher in mPBMCs of OD and IVF pregnancies compared with NC pregnancies. The percentage of CD4(+)CD25(dim) cells in mPBMCs of OD pregnancies correlated positively with the number of HLA mismatches. Functional studies showed a lower proliferative response to umbilical cord blood by mPBMCs in OD pregnancies. In conclusion, we found a higher degree of peripheral immunoregulation in OD and IVF pregnancies compared with NC pregnancies. A higher number of HLA mismatches in successful OD pregnancies leads to increased percentages of activated T cells in peripheral blood, but not to a higher alloreactivity to the fetus. These studies show that immunoregulation in OD pregnancy is different from that in NC pregnancies. The antigenic dissimilarity in OD pregnancies may play a role in the pathophysiology of preeclampsia.

Changing expression of chloride channels during preimplantation mouse development

Plasma membrane chloride channels (ClCs) play important roles in a broad range of cellular processes including cell volume regulation, proliferation, and transepithelial transport, all of which are critical during preimplantation embryonic development. In this study, the molecular and functional expression of voltage-gated ClCs was analyzed throughout preimplantation development of the mouse conceptus. mRNA transcripts for allClcngenes were detected. OnlyClcn1mRNA showed differential expression in the blastocyst, being detected in the trophectoderm but not in the inner cell mass. CLCN3 protein was detected at low levels in the cytoplasm and plasma membrane in 4-cell embryos and was localized to the apical plasma membrane of the trophoblasts in the blastocyst. Whole-cell patch-clamp recordings demonstrated the presence of a DIDS-sensitive, outwardly rectifying Cl−current throughout development, with this conductance being large at the 1-cell, morula and blastocyst stages. A second DIDS-insensitive Cl−current, which was inactivated by membrane depolarization, was present in cells differentiating into the trophoblast lineage and during blastocyst expansion. Inhibition of the DIDS-sensitive current and the DIDS-insensitive current, with 9-AC, prevented blastocyst expansion.

Metabolic induction and early responses of mouse blastocyst developmental programming following maternal low protein diet affecting life-long health

Previously, we have shown that a maternal low protein diet, fed exclusively during the preimplantation period of mouse development (Emb-LPD), is sufficient to induce by the blastocyst stage a compensatory growth phenotype in late gestation and postnatally, correlating with increased risk of adult onset cardiovascular disease and behavioural dysfunction. Here, we examine mechanisms of induction of maternal Emb-LPD programming and early compensatory responses by the embryo. Emb-LPD induced changes in maternal serum metabolites at the time of blastocyst formation (E3.5), notably reduced insulin and increased glucose, together with reduced levels of free amino acids (AAs) including branched chain AAs leucine, isoleucine and valine. Emb-LPD also caused reduction in the branched chain AAs within uterine fluid at the blastocyst stage. These maternal changes coincided with an altered content of blastocyst AAs and reduced mTORC1 signalling within blastocysts evident in reduced phosphorylation of effector S6 ribosomal protein and its ratio to total S6 protein but no change in effector 4E-BP1 phosphorylated and total pools. These changes were accompanied by increased proliferation of blastocyst trophectoderm and total cells and subsequent increased spreading of trophoblast cells in blastocyst outgrowths. We propose that induction of metabolic programming following Emb-LPD is achieved through mTORC1signalling which acts as a sensor for preimplantation embryos to detect maternal nutrient levels via branched chain AAs and/or insulin availability. Moreover, this induction step associates with changes in extra-embryonic trophectoderm behaviour occurring as early compensatory responses leading to later nutrient recovery.

Using cell banks as a tool in conservation programmes of native domestic breeds: the production of the first cloned Anatolian Grey cattle

The aim of this study was to clone native Anatolian Grey cattle by using different donor cell types, such as fibroblast, cartilage and granulosa cells cryopreserved in a gene bank and oocytes aspirated from ovaries of Holstein cows as the recipient cytoplasm source. One male calf from fibroblast, three female calves from granulosa cells and one female calf from cartilage cells were born healthy and at normal birthweights. No calves were lost after birth. The results demonstrated that the cloned calves had the same microsatellite alleles at 11 loci as their nuclear donors. However, the mtDNAs of the five Anatolian Grey cloned calves had different haplotypes from their donor cells and mtDNA heteroplasmy could not be detected in any of the clones. The birth of healthy clones suggests that the haplotype difference between the cell and oocyte donor did not affect the pre- or post-implantation development of the bovine nuclear transfer derived embryos in our study. The results showed that well established nuclear transfer protocols could be useful in conserving endangered species. In conclusion, somatic cell banking can be suggested as a tool in conservation programmes of animal genetic resources.

Bovine OPU-derived oocytes can be matured in vitro for 16-28 h with similar developmental capacity

The aim of this study was to determine the optimal maturation culture period of ovum pick up (OPU)-derived cumulus oocytes complexes (COCs) in relation to their developmental capacity. Embryo production, embryo cryotolerance, post-transfer embryonic survival and calf characteristics such as gestation length, birthweight and sex ratio were investigated. This retrospective study covers the analyses of ovum pick up -in vitro production and calving results from a commercial programme that took place between March 1994 and September 2004. Donors were both heifers (of which approximately 90% pregnant) and cows (of which approximately 10% pregnant). Embryo production analyses were based on 7800 OPU sessions conducted from January 1995 until January 1999. Analyses of calving rate were based on 13 468 embryo transfers performed during January 1995 until May 2002. Analyses on calf characteristics were based on 2162 calves born between March 1994 and September 2004. The in vitro maturation culture period ranged from 16 to 28 h. The mean production rate of transferable embryos was 16.5% (1.2 embryos per OPU session). Length of maturation culture period did not affect the production of transferable embryos. Mean calving rate was 40.9% and 38.7% for fresh and frozen/thawed embryos, respectively. Calving rate was not affected by the maturation culture period. Mean birthweight, gestation length and proportion of male calves were 46 kg, 281.9 days and 52.8%, respectively. Maturation culture period did not affect these variables. In conclusion, this study shows that the in vitro maturation culture period within the range of 16-28 h does not affect in vitro embryo production, embryo cryotolerance, post-transfer embryonic survival and calf characteristics, suggesting that all COC batches collected by OPU on the same day, can be fertilized in one IVF session without a significant loss in the production from oocyte to calf.

Media composition: growth factors

Despite the fact that the fundamental principle underlying the most common method of culture media constitution is that of mimicking the natural environment of the preimplantation embryo, one major difference that remains between current embryo culture media and in vivo conditions is the absence of growth factors in vitro. Numerous growth factors are known to be present in the in vivo environment of human and nonhuman preimplantation embryos, often with peak concentrations corresponding to when fertilization and preimplantation embryo growth would occur. Although these growth factors are found in very small concentrations, they have a profound effect on tissue growth and differentiation through attachment to factor-specific receptors on cell surfaces. Receptors for many different growth factors have also been detected in human preimplantation embryos. Preimplantation embryos themselves express many growth factors. The growth factors and receptors are metabolically costly to produce, and thus their presence in the environment of the preimplantation embryo and in the embryo respectively strongly implies that embryos are designed to encounter and respond to the corresponding factors. Studies of embryo coculture also indirectly suggest that growth factors can improve in vitro development. Several animal and human studies attest to a probable beneficial effect of addition of growth factors to culture media. However, there is still ambiguity regarding the exact role of growth factors in embryonic development, the optimal dose of growth factors to be added to culture media, the combinatorial effect and endocrine of growth factors in embryonic development.

Culture systems: embryo density

Embryo density is defined as the embryo-to-volume ratio achieved during in vitro culture; in other words, it is the number of embryos in a defined volume of culture medium. The same density can be achieved by manipulating either the number of embryos in a given volume of medium, or manipulating the volume of the medium for a given number of embryos: for example, a microdrop with five embryos in a 50 μl volume under oil has the same embryo-to-volume ratio (1:10 μl) as a microdrop with one embryo in a 10 μl volume under oil (1:10 μl). Increased embryo density can improve mammalian embryo development in vitro; however, the mechanism(s) responsible for this effect may be different with respect to which method is used to increase embryo density.Standard, flat sterile plastic petri dishes are the most common, traditional platform for embryo culture. Microdrops under a mineral oil overlay can be prepared to control embryo density, but it is critical that dish preparation is consistent, where appropriate techniques are applied to prevent microdrop dehydration during preparation, and results of any data collection are reliable, and repeatable. There are newer dishes available from several manufacturers that are specifically designed for embryo culture; most are readily available for use with human embryos. The concept behind these newer dishes relies on fabrication of conical and smaller volume wells into the dish design, so that embryos rest at the lowest point in the wells, and where putative embryotrophic factors may concentrate.Embryo density is not usually considered by the embryologist as a technique in and of itself; rather, the decision to culture embryos in groups or individually is protocol-driven, and is based more on convenience or the need to collect data on individual embryos. Embryo density can be controlled, and as such, it can be utilized as a simple, yet effective tool to improve in vitro development of human embryos.

Adaptive responses of the embryo to maternal diet and consequences for post-implantation development

Maternal periconceptional (PC) nutrition, coupled with maternal physiological condition, can impact on reproductive performance and potential across mammalian species. Oocyte quality and embryo development are affected adversely by either nutrient restriction or excess. Moreover, the quality of maternal PC nutrition can have lasting effects through fetal development and postnatally into adulthood. Chronic disease, notably cardiovascular and metabolic disease, and abnormal behaviour have been identified in adult offspring in small and large animal models of PC nutrient restriction. These long-term effects associate with compensatory responses that begin from the time of early embryo development. This review assesses the field of PC nutrition in vivo on short- and long-term developmental consequences in rodent and ruminant models and considers the implications for human health.

Inclusion of bovine lipoproteins and the vitamin E analogue, Trolox, during in vitro culture of bovine embryos changes both embryo and fetal development

This experiment investigated effects of lipoproteins and Trolox (vitamin E analogue) on bovine embryo and fetal development. The treatments were: in vitro culture (IVC) in synthetic oviducal fluid alone (SOF); with bovine lipoproteins (2% v/v; SOFLP); with Trolox (100 μM; SOFT); and with lipoproteins and Trolox (SOFLPT). In vitro culture with lipoproteins increased fatty acid content of blastocysts (P < 0.001) whereas inclusion of Trolox had no effect (P > 0.05). Whereas lipoproteins reduced zygote development to blastocysts (P = 0.03), Trolox facilitated increased development (P < 0.001) and counteracted the reduction observed with lipoproteins (interaction, P = 0.009). Lipoproteins also compromised (P < 0.001) but presence of Trolox (P > 0.05) had no effect on blastocyst morphological grade. Pregnancy rates resulting from synchronous transfer of IVP embryos were not affected by IVC treatment. At Day 70 of pregnancy, compared with SOF, fetal weight was lower in SOFLP but not SOFLPT (interaction, P < 0.001). Liver weight (g kg–1 fetal weight) was greater (P = 0.03) in treatments containing Trolox. Placentome numbers were greater in SOF and SOFLPT compared with SOFLP and SOFT (interaction, P = 0.002); superior embryo grades were also associated with increased numbers of placentomes (P = 0.024). In conclusion, the interactive effects of lipoprotein and Trolox inclusion on in vitro embryo development were also evident in fetal development at Day 70.

Culture systems: physiological and environmental factors that can affect the outcome of human ART

Many aspects of the embryo culture environment have been shown to affect embryo development and the subsequent outcomes of human ART. It is now becoming increasingly evident that embryo and later development can be affected by events and conditions that occur before, perhaps long before, the oocytes and sperm are collected and brought together in the ART laboratory. These include diet and metabolic disorders, general health and disease, physical and psychological stress, exposure to environmental estrogens and other toxins, pharmaceuticals, alcohol, smoking, and drug abuse. This paper discusses the known and potential effects of season of the year (or temperature) and environmental air pollution on the outcomes of human ART. It may be useful to advise ART patients to avoid high environmental temperature and air pollution. In addition, it is important for clinical embryologists to recognize that adverse outcomes may result from such exposures, and to incorporate this into the analysis of clinic data for the purposes of quality management.

Components of oviduct physiology in eutherian mammals

Recalling the evolutionary sequence of development first of gonad and subsequently of oviducts, ovarian endocrine regulation of all known components of oviduct physiology is reviewed. Ovaries not only influence oviducts via the systemic blood circulation, but also locally by counter-current transfer of relatively high concentrations of steroid hormones and prostaglandins between the ovarian vein and oviduct branch of the ovarian artery. The efficiency and impact of such counter-current transfer is greatest around the time of ovulation, the transfer process receiving further inputs from hormones present in peritoneal fluid. Classical oviduct physiology is summarised, and the potential molecular consequences of temperature gradients within the duct lumen examined. At ovulation, an oocyte-cumulus complex is displaced in minutes from the follicular surface to the site of fertilisation at the ampullary-isthmic junction of the oviduct. This rapid initial phase is contrasted with the subsequent slow progression of embryos to the uterus in days, still encompassed within a zona pellucida. Regarding transport of spermatozoa, the formation of a pre-ovulatory reservoir in the caudal portion of the oviduct isthmus is noted, with suppression of motility and sperm-head binding to epithelial organelles acting to maintain fertilising ability. Completion of capacitation is prompted shortly before ovulation, predominantly by Ca(2+) influx into bound spermatozoa. A controlled release of spermatozoa coupled with their hyperactivation results in initial sperm:egg ratios at the site of fertilisation close to unity, thereby avoiding the pathological condition of polyspermy. Both the oviduct milieu and embryonic development are influenced by paracrine activity of follicular granulosa cells released at ovulation and remaining in suspension in the vicinity of the oocyte or embryo. These cells may amplify early pregnancy signals from a zygote to the endosalpinx. Beneficial effects of the oviduct on domestic animal embryos are contrasted with anomalies arising as a consequence of in vitro culture. Primate embryos do not require exposure to an oviduct for normal development, perhaps due to overlapping compositions of endosalpingeal and endometrial secretions. Additionally, primate endometrial secretions may be modified by viable gametes or an embryo in the presence of a cumulus cell suspension.

Reproductive medicine and inheritance of infertility by offspring: the role of fetal programming

OBJECTIVE

To summarize the molecular processes involved in fetal programming, to describe how assisted reproduction technologies (ART) may affect the epigenetic pattern of the embryo, and to highlight the current knowledge of the role of perinatal events in the subsequent development of reproductive pathology affecting infertile patients.

DESIGN

A literature review of fetal programming of adulthood gynecologic diseases and ART. A Medline search was performed with the following keywords: (fetal programming OR epigenetics OR methylation OR acetylation) AND (IVF OR ART) AND (gynecology). Articles up to October 2010 were selected. Articles and recent reviews were classified by human and animals studies and also according to their experimental or observational design.

SETTING

University hospital research center.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

None.

RESULT(S)

Data from experimental animal models and case-control studies support the potential effect of ART in changing methylation patterns in gametes and embryos. However, these findings are not supported by population studies or experimental studies performed in human gametes/embryos. Experimental and epidemiologic studies support the hypothesis that some adult gynecologic diseases causing infertility may have a fetal origin.

CONCLUSION(S)

Although it seems clear that some adult gynecologic diseases causing infertility may have a fetal origin, there is insufficient evidence to confirm that ART is the origin of later onset, adulthood diseases. Further research in this field must be conducted.

Culture system and long-term storage of culture media in the in vitro production of bovine embryos

The optimum culture system for in vitro matured and fertilised oocytes still remains to be clarified. Culture media (CM) for mammalian embryos are routinely prepared fresh for use and preserved under refrigeration during one or two weeks. The purposes of this work were (1) to compare the efficiency of a synthetic oviduct fluid (SOF) with two different bovine serum albumin (BSA) concentrations (3 and 8 g/L) for the in vitro production of bovine blastocysts, (2) to test the effect of timing on adding fetal calf serum (FCS) to the SOF, and (3) to evaluate the effects on bovine embryo development of freezing and lyophilisation as procedures for preserving the SOF. Supplementation of SOF with 3 g/L BSA increased Day-7 blastocyst expansion rates (18.3 ± 1.6 vs. 14.4 ± 0.7; P < 0.05), although no differences in hatching rates were found. Addition of FCS to SOFaa (SOF with amino acids) medium supplemented with sodium citrate (SOFaaci) at 48 and at 72 h post-insemination (PI) allowed obtaining higher Day-6 embryo development rates than when FCS was added at 18 or 96 h PI (Day-6 morulae + blastocyst rate: 30.0 ± 1.1, 40.8 ± 1.1, 43.9 ± 2.3 and 39.3 ± 0.5 for FCS addition at 18, 48, 72 and 96 h, respectively). Hatching rates were significantly improved when serum was added at 72 h PI. Finally, both refrigeration and lyophilisation appeared as useful cryopreservation procedures for SOFaaci, although a significant loss of its ability to support embryo development, compared to the control fresh culture medium, was observed.

Mitochondrial inhibition during preimplantation embryogenesis shifts the transcriptional profile of fetal mouse brain

Environmental stress results in perturbations to mitochondrial function in the preimplantation embryo and hinders subsequent embryo and possibly offspring development. Global gene expression in fetal mouse brain was investigated following targeted mitochondrial inhibition by amino-oxyacetate (AOA) from the 2-cell to the blastocyst stage. Blastocysts were transferred to pseudopregnant recipients and RNA extracted from Day 18 fetal brains for microarray interrogation. Exposure to 5 μM AOA during preimplantation embryo development induced differential expression of 166 genes (>1.25 fold) in the fetal brain, relative to control medium-cultured embryos. Altered expression pathways included carbohydrate metabolism, neurological development, cellular proliferation and death, DNA replication, recombination and repair. Of 28 genes exhibiting the greatest change in expression, qPCR confirmed that 16 were significantly altered. Targeted qPCR assessment of a further 20 genes associated with methylation, acetylation and mitochondrial dysfunction revealed that three were significantly altered (Immp1l, Nars2, Sat2) and Dmap1 exhibited a sex-specific response to AOA exposure. Only 2/48 genes had significantly altered expression by qPCR (Nola3, Timm8b) in fetal brains exposed to 50 μM AOA embryo culture, excluding an AOA dose-dependent response. It was concluded that perturbation of mitochondrial function induced by 5 μM AOA during preimplantation embryo development alters gene expression in the neonatal brain in a manner that suggests that proper brain development may be compromised.

Maternal pre-pregnancy obesity and risk for inattention and negative emotionality in children

OBJECTIVE

This study aimed to replicate and extend previous work showing an association between maternal pre-pregnancy adiposity and risk for attention deficit hyperactivity disorder (ADHD) symptoms in children.

METHODS

A Swedish population-based prospective pregnancy-offspring cohort was followed up when children were 5 years old (N = 1,714). Mothers and kindergarten teachers rated children's ADHD symptoms, presence and duration of problems, and emotionality. Dichotomized outcomes examined difficulties of clinical relevance (top 15% of the distribution). Analyses adjusted for pregnancy (maternal smoking, depressive symptoms, life events, education, age, family structure), birth outcomes (birth weight, gestational age, infant sex) and concurrent variables (family structure, maternal depressive symptoms, parental ADHD symptoms, and child overweight) in an attempt to rule out confounding.

RESULTS

Maternal pre-pregnancy overweight and obesity predicted high inattention symptom scores and obesity was associated with a two-fold increase in risk of difficulties with emotion intensity and emotion regulation according to teacher reports. Means of maternal ratings were unrelated to pre-pregnancy body mass index (BMI). Presence and duration of problems were associated with both maternal over and underweight according to teachers.

CONCLUSIONS

Despite discrepancies between maternal and teacher reports, these results provide further evidence that maternal pre-pregnancy overweight and obesity are associated with child inattention symptoms and extend previous work by establishing a link between obesity and emotional difficulties. Maternal adiposity at the time of conception may be instrumental in programming child mental health, as prenatal brain development depends on maternal energy supply. Possible mechanisms include disturbed maternal metabolic function. If maternal pre-pregnancy obesity is a causal risk factor, the potential for prevention is great.

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.

Embryo culture: can we perform better than nature?

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

Blastocyst environment and its influence on offspring cardiovascular health: the heart of the matter

The development of adult-onset diseases such as type II diabetes, obesity and cardiovascular disease is traditionally attributed to adult lifestyle characteristics such as a lack of physical exercise, poor diet and smoking. However, evidence from both human and animal model studies has demonstrated that environmental factors such as an imbalance or reduction in maternal nutrition during gestation can have adverse effects on offspring metabolism and cardiovascular health. The severity and nature of the phenotypic changes induced in offspring is influenced by the period of gestation manipulated. In particular, the mammalian preimplantation embryo in different animal models displays particular sensitivity to environmental factors, either in vivo (maternal diet) or in vitro (embryo culture) that is associated with the onset of cardiovascular dysfunction in adult life. The detailed mechanisms by which environmental conditions can alter postnatal cardiovascular physiology are poorly understood. However, various factors including endothelial function, vascular responsiveness, the renin-angiotensin system, kidney structure and early postnatal growth dynamics have all been recognize as potential contributors. Here, we review the relationship between preimplantation embryo environment and postnatal cardiovascular disease risk, and consider biochemical, molecular, genetic and physiological pathways implicated in this association.

Effect of in vitro maturation of mouse oocytes on the health and lifespan of adult offspring

BACKGROUND

In vitro maturation of oocytes can, in some circumstances, provide an alternative approach to gonadotrophin-induced maturation in clinical settings. However, the consequences of these protocols on the long-term health of offspring are unknown. Here, the long-term health status and lifespans of offspring produced by in vitro maturation of mouse oocytes was compared with that of oocytes induced to mature in vivo using gonadotrophin treatment.

METHODS

Mouse oocytes were matured in vitro using both an established optimized system and in the absence of amino acids to produce a suboptimal condition for maturation. Oocytes induced to mature in vivo with gonadotrophins constituted the control group. All metaphase II oocytes were fertilized in vitro and transferred at the 2-cell stage to the oviducts of pseudo-pregnant foster mothers for development to term. Offspring were subjected to a wide variety of physiological and behavioral tests for the first year of life and natural lifespan determined.

RESULTS

There was no difference among the groups in lifespan or in most of the physiological and behavioral analyses. However, the pulse rate and cardiac output were slightly, but significantly, reduced in the optimized in vitro matured group compared with the in vivo matured group (P = 0.0119 and P = 0.0197, respectively). Surprisingly, these decreases were largely abrogated in the in vitro group matured without amino acids.

CONCLUSIONS

Evidence presented here using a mouse model suggests that the in vitro maturation of oocytes has minimal effects on the long-term health of offspring. However, a finding of slight reductions in pulse rate and cardiac output may focus future clinical attention.

The prevalence of embryonic remnants following the recovery of post-hatching bovine embryos produced in vitro or by somatic cell nuclear transfer

The reliable collection of peri-implantation embryos in the bovine has important ramifications to post-transfer consequences, particularly in the elucidation of mechanisms associated with post-hatching embryo development and to perturbations in developmental growth following transfer. This study analyzed both in vitro produced (IVP) and somatic cell nuclear transfer (SCNT) embryo-like structures (ELS) recovered at Day (D) 14 and D21. The recovered ELS were subsequently processed for histological examination. At D14 and D21, many of the embryos recovered in the IVP group conformed to the appropriate stage of development. However, a significant number of anomalies were present in the SCNT groups when examined in more detail. Histological examination revealed that irrespective of whether these embryos had undergone trophoblast expansion to an ovoid, tubular or filamentous morphology, many had a degenerated hypoblast layer and a large proportion did not possess an epiblast and therefore could not differentiate into any of the three germ layers as would be expected at the neural groove or somite stage. The prevalence of this developmental pattern was random and did not correlate with treatment (IVP or SCNT) or with types of structures recovered. The rapid embryo elongation period also coincides with the time of greatest embryonic loss and these observations could have important implications for assessing the recovery of embryos post-transfer where incorrect morphological assessment could lead to false implantation and pregnancy determination rates. The implementation of additional methodology is required to adequately characterize the quality of IVP and SCNT-derived embryos collected post-transfer.

The culture of zygotes to the blastocyst stage changes the postnatal expression of an epigentically labile allele, agouti viable yellow, in mice

Restricting the growth of the embryo can cause adverse whole-of-life changes in an organism's homeostasis. Such adverse long-term consequences may occur even when growth restriction occurs only during the preimplantation period. The molecular basis for these long-term effects has not been defined, although an epigenetic mechanism is suspected. Some loci seem to be more sensitive to epigenetic perturbation than others, and the agouti viable yellow allele (A(vy)) is the best studied example of this. It has active (hypomethylated) and inactive (hypermethylated) epialleles. This study used the A(vy) model to show that growth restriction of preimplantation embryos, as provided by culture of zygotes, induced persistent epigenetic changes that resulted in altered postnatal phenotype. C57BL/6 A(vy)/a males were mated to ovulation-induced FVB/N females, and then either zygotes were collected and cultured for 96 h and the resulting blastocysts were transferred to pseudopregnant recipient females, blastocysts were collected from females and transferred without embryo culture, or pregnancy was allowed to proceed after mating without intervention. Culture was in a commercial human in vitro fertilization media. The proportion of pups expressing the active (hypomethylated) epiallele and yellow coat was significantly higher following zygote culture compared to embryos that were transferred without culture (P = 0.014) or natural matings (P < 0.001). There was no difference in expression of the active epiallele in pups resulting from embryo transfer (without culture) compared to natural matings. These results show for the first time that the preimplantation embryo's growth environment can affect the postnatal expression of a defined epigenetically sensitive allele.

Adaptive responses by mouse early embryos to maternal diet protect fetal growth but predispose to adult onset disease

Poor maternal nutrition during pregnancy can alter postnatal phenotype and increase susceptibility to adult cardiovascular and metabolic diseases. However, underlying mechanisms are largely unknown. Here, we show that maternal low protein diet (LPD), fed exclusively during mouse preimplantation development, leads to offspring with increased weight from birth, sustained hypertension, and abnormal anxiety-related behavior, especially in females. These adverse outcomes were interrelated with increased perinatal weight being predictive of later adult overweight and hypertension. Embryo transfer experiments revealed that the increase in perinatal weight was induced within blastocysts responding to preimplantation LPD, independent of subsequent maternal environment during later pregnancy. We further identified the embryo-derived visceral yolk sac endoderm (VYSE) as one mediator of this response. VYSE contributes to fetal growth through endocytosis of maternal proteins, mainly via the multiligand megalin (LRP2) receptor and supply of liberated amino acids. Thus, LPD maintained throughout gestation stimulated VYSE nutrient transport capacity and megalin expression in late pregnancy, with enhanced megalin expression evident even when LPD was limited to the preimplantation period. Our results demonstrate that in a nutrient-restricted environment, the preimplantation embryo activates physiological mechanisms of developmental plasticity to stablize conceptus growth and enhance postnatal fitness. However, activation of such responses may also lead to adult excess growth and cardiovascular and behavioral diseases.

Interferons and the maternal-conceptus dialog in mammals

Two-way communication between the conceptus and the mother during early pregnancy is essential if the pregnancy is to survive. In this review, our primary focus is on biochemical communication between the conceptus and mother in the ruminant ungulate species. We emphasize, in particular, the role played by interferon-tau (IFNT) in triggering maternal responses in cattle and sheep and how maternal factors intervene to up-regulate IFNT gene (IFNT) expression in trophoblast. However, we also consider the possibility that different signaling cytokines or the physical presence of trophoblast may induce a partial IFN response in endometrium of those species where there is no evidence for large scale trophoblast IFN production. Conceivably, disparate signaling mechanisms trigger common downstream events necessary to secure a successful pregnancy.