Effects of prolonged exposure of mouse embryos to elevated temperatures on embryonic developmental competence

To investigate effects of heat stress on developmental competence, in-vitro fertilized zygotes were incubated at different temperatures until 96 h post human chorionic gonadotrophin (HCG). Under severe and moderate conditions (41°C and 40°C), most embryos did not overcome the 2-cell block. In long-term mild heat stress (39°C until 96 h post HCG), cleavage and blastocyst formation were comparable to non-heat-stress control, but the number of live pups per transferred embryo and mean litter size were significantly affected (P < 0.05) in the mild-heat-stress group (19.4%, and 5.1 ± 0.4, respectively), compared with control (41.7% and 8.3 ± 0.3, respectively). To elucidate the different competence, gene expression was examined and the numbers of inner cell mass (ICM) and trophectoderm (TE) cells were counted. Aberrant expression of genes for embryonic viability and trophoblast differentiation in the mild-heat-stressed blastocysts was found. Moreover, the expanded blastocysts in the heat-stressed group and the control had a ICM:TE ratio of 1:2.47 and 1:2.96 with average total cell numbers of 59.21 ± 2.38 and 72.79 ± 2.40, respectively (P < 0.05), indicating lower cell numbers in TE. These findings underscore that prevention of heat stress in early embryos is important for maintaining embryo viability embryos during pregnancy.

Developmental competence of 8?16-cell stage bison embryos produced by interspecies somatic cell nuclear transfer

Altered communication between nuclear and cytoplasmic components has been linked to impaired development in interspecies somatic cell nuclear transfer (iSCNT) embryos as a result of genetic divergence between the two species. This study investigated the developmental potential and mitochondrial function of cattle (Bos taurus), plains bison (Bison bison bison) and wood bison (Bison bison athabascae) embryos produced by iSCNT using domestic cattle oocytes as cytoplasts. Embryos in all groups were analysed for development, accumulation of ATP, apoptosis and gene expression of nuclear- and mitochondrial-encoded genes at the 8-16-cell stage. The results of this study showed no significant differences in the proportion of developed embryos at the 2-, 4- and 8-16-cell stages between groups. However, significantly higher ATP levels were observed in cattle SCNT embryos compared with bison iSCNT embryos. Significantly more condensed and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL)-positive nuclei were found in plains bison iSCNT embryos. No significant differences in the expression levels of nuclear respiratory factor 2 (NRF2) or mitochondrial subunit 2 of cytochrome c oxidase (mt-COX2) were found in any of the groups. However, mitochondrial transcription factor A (TFAM) expression significantly differed between groups. The results of this study provide insights into the potential causes that might lead to embryonic arrest in bison iSCNT embryos, including mitochondrial dysfunction, increased apoptosis and abnormal gene expression.

Reduction of Mitochondrial Function by FCCP During Mouse Cleavage Stage Embryo Culture Reduces Birth Weight and Impairs the Metabolic Health of Offspring

The periconceptual environment represents a critical window for programming fetal growth trajectories and susceptibility to disease; however, the underlying mechanism responsible for programming remains elusive. This study demonstrates a causal link between reduction of precompaction embryonic mitochondrial function and perturbed offspring growth trajectories and subsequent metabolic dysfunction. Incubation of embryos with carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP), which uncouples mitochondrial oxidative phosphorylation, significantly reduced mitochondrial membrane potential and ATP production in 8-cell embryos and the number of inner cell mass cells within blastocysts; however, blastocyst development was unchanged. This perturbed embryonic mitochondrial function was concomitant with reduced birth weight in female offspring following embryo transfer, which persisted until weaning. FCCP-treated females also exhibited increased adiposity at 4 wk, increased adiposity gain between 4 and 14 wk, glucose intolerance at 8 wk, and insulin resistance at 14 wk. Although FCCP-treated males also exhibited reduced glucose tolerance, but their insulin sensitivity and adiposity gain between 4 and 14 wk was unchanged. To our knowledge, this is one of the first studies to demonstrate that reducing mitochondrial function and, thus, decreasing ATP output in the precompacting embryo can influence offspring phenotype. This is of great significance as a large proportion of patients requiring assisted reproductive technologies are of advanced maternal age or have a high body mass index, both of which have been independently linked with perturbed early embryonic mitochondrial function.

Blastocyst metabolism

The mammalian blastocyst exhibits an idiosyncratic metabolism, reflecting its unique physiology and its ability to undergo implantation. Glucose is the primary nutrient of the blastocyst, and is metabolised both oxidatively and through aerobic glycolysis. The production of significant quantities of lactate by the blastocyst reflects specific metabolic requirements and mitochondrial regulation; it is further proposed that lactate production serves to facilitate several key functions during implantation, including biosynthesis, endometrial tissue breakdown, the promotion of new blood vessel formation and induction of local immune-modulation of the uterine environment. Nutrient availability, oxygen concentration and the redox state of the blastocyst tightly regulate the relative activities of specific metabolic pathways. Notably, a loss of metabolic normality is associated with a reduction in implantation potential and subsequent fetal development. Even a transient metabolic stress at the blastocyst stage culminates in low fetal weights after transfer. Further, it is evident that there are differences between male and female embryos, with female embryos being characterised by higher glucose consumption and differences in their amino acid turnover, reflecting the presence of two active X-chromosomes before implantation, which results in differences in the proteomes between the sexes. In addition to the role of Hypoxia-Inducible Factors, the signalling pathways involved in regulating blastocyst metabolism are currently under intense analysis, with the roles of sirtuins, mTOR, AMP-activated protein kinase and specific amino acids being scrutinised. It is evident that blastocyst metabolism regulates more than the production of ATP; rather, it is apparent that metabolites and cofactors are important regulators of the epigenome, putting metabolism at centre stage when considering the interactions of the blastocyst with its environment.

Mdivi-1, mitochondrial fission inhibitor, impairs developmental competence and mitochondrial function of embryos and cells in pigs

Mitochondria are highly dynamic organelles that undergo constant fusion/fission as well as activities orchestrated by large dynamin-related GTPases. These dynamic mitochondrial processes influence mitochondrial morphology, size and function. Therefore, this study was conducted to evaluate the effects of mitochondrial fission inhibitor, mdivi-1, on developmental competence and mitochondrial function of porcine embryos and primary cells. Presumptive porcine embryos were cultured in PZM-3 medium supplemented with mdivi-1 (0, 10 and 50 μM) for 6 days. Porcine fibroblast cells were cultured in growth medium with mdivi-1 (0 and 50 μM) for 2 days. Our results showed that the rate of blastocyst production and cell growth in the mdivi-1 (50 μM) treated group was lower than that of the control group (P < 0.05). Moreover, loss of mitochondrial membrane potential in the mdivi-1 (50 μM) treated group was increased relative to the control group (P < 0.05). Subsequent evaluation revealed that the intracellular levels of reactive oxygen species (ROS) and the apoptotic index were increased by mdivi-1 (50 μM) treatment (P < 0.05). Finally, the expression of mitochondrial fission-related protein (Drp 1) was lower in the embryos and cells in the mdivi-1-treated group than the control group. Taken together, these results indicate that mdivi-1 treatment may inhibit developmental competence and mitochondrial function in porcine embryos and primary cells.

The impact of mitochondrial function/dysfunction on IVF and new treatment possibilities for infertility

Mitochondria play vital roles in oocyte functions and they are critical indicators of oocyte quality which is important for fertilization and development into viable offspring. Quality-compromised oocytes are correlated with infertility, developmental disorders, reduced blastocyst cell number and embryo loss in which mitochondrial dysfunctions play a significant role. Increasingly, women affected by metabolic disorders such as diabetes or obesity and oocyte aging are seeking treatment in IVF clinics to overcome the effects of adverse metabolic conditions on mitochondrial functions and new treatments have become available to restore oocyte quality. The past decade has seen enormous advances in potential therapies to restore oocyte quality and includes dietary components and transfer of mitochondria from cells with mitochondrial integrity into mitochondria-impaired oocytes. New technologies have opened up new possibilities for therapeutic advances which will increase the success rates for IVF of oocytes from women with compromised oocyte quality.

Endothelial dysfunction and preeclampsia: role of oxidative stress

Preeclampsia (PE) is an often fatal pathology characterized by hypertension and proteinuria at the 20th week of gestation that affects 5-10% of the pregnancies. The problem is particularly important in developing countries in where the incidence of hypertensive disorders of pregnancy is higher and maternal mortality rates are 20 times higher than those reported in developed countries. Risk factors for the development of PE include obesity, insulin resistance and hyperlipidemia that stimulate inflammatory cytokine release and oxidative stress leading to endothelial dysfunction (ED). However, how all these clinical manifestations concur to develop PE is still not very well understood. The related poor trophoblast invasion and uteroplacental artery remodeling described in PE, increases reactive oxygen species (ROS), hypoxia and ED. Here we aim to review current literature from research showing the interplay between oxidative stress, ED and PE to the outcomes of current clinical trials aiming to prevent PE with antioxidant supplementation.

The prion protein family: a view from the placenta

Based on its developmental pattern of expression, early studies suggested the implication of the mammalian Prion protein PrP, a glycosylphosphatidylinositol-anchored ubiquitously expressed and evolutionary conserved glycoprotein encoded by the Prnp gene, in early embryogenesis. However, gene invalidation in several species did not result in obvious developmental abnormalities and it was only recently that it was associated in mice with intra-uterine growth retardation and placental dysfunction. A proposed explanation for this lack of easily detectable developmental-related phenotype is the existence in the genome of one or more gene (s) able to compensate for the absence of PrP. Indeed, two other members of the Prnp gene family have been recently described, Doppel and Shadoo, and the consequences of their invalidation alongside that of PrP tested in mice. No embryonic defect was observed in mice depleted for Doppel and PrP. Interestingly, the co-invalidation of PrP and Shadoo in two independent studies led to apparently conflicting observations, with no apparent consequences in one report and the observation of a developmental defect of the ectoplacental cone that leads to early embryonic lethality in the other. This short review aims at summarizing these recent, apparently conflicting data highlighting the related biological questions and associated implications in terms of animal and human health.

The effect of vitrification and in vitro culture on the adenosine triphosphate content and mitochondrial distribution of mouse pre-implantation embryos

BACKGROUND

The mitochondria are an important source of adenosine triphosphate (ATP) production in pre-implantation embryo. Therefore, the objective of this study was to investigate the effect of vitrification and in vitro culture of mouse embryos on their mitochondrial distribution and ATP content.

METHODS

The embryos at 2-PN, 4-cell and blastocyst stages were collected from the oviduct of stimulated pregnant mice and uterine horns. Then, the embryos were vitrified with the cryotop method using ethylene glycol and dimethylsulphoxide. After evaluating the survival rates of vitrified embryos, their development to hatching stages were assessed. The ATP content of collected in vivo and in vitro embryos at different stages was measured by luciferin-luciferase bioluminescence assay. The distribution of mitochondria was studied using Mito-tracker green staining under a fluorescent microscope.

RESULTS

The survival rates of vitrified embryos at 2-PN, 4-cell and early blastocyst stages were 84.3, 87.87 and 89.89%, respectively. The hatching rates in previous developmental stages in vitrified group were 57.44, 66.73 and 70.89% and in non-vitrified group were 66.32, 73.25 and 75.89%, respectively (P>0.05). The ATP content of in vivo or in vitro collected embryos was not significantly different in both vitrified and non-vitrified groups (P>0.05). Mitochondrial distribution of vitrified and non-vitrified 2-PN embryos was similar, but some clampings or large aggregation of mitochondria within the vitrified 4-cell embryos was prominent.

CONCLUSIONS

Vitrification method did not affect the mouse embryo ATP content. Also, the cellular stress was not induced by this procedure and the safety of vitrification was shown.

Placental mitochondrial content and function in intrauterine growth restriction and preeclampsia

Intrauterine growth restriction (IUGR) and pregnancy hypertensive disorders such as preeclampsia (PE) associated with IUGR share a common placental phenotype called "placental insufficiency", originating in early gestation when high availability of energy is required. Here, we assess mitochondrial content and the expression and activity of respiratory chain complexes (RCC) in placental cells of these pathologies. We measured mitochondrial (mt)DNA and nuclear respiratory factor 1 (NRF1) expression in placental tissue and cytotrophoblast cells, gene and protein expressions of RCC (real-time PCR and Western blotting) and their oxygen consumption, using the innovative technique of high-resolution respirometry. We analyzed eight IUGR, six PE, and eight uncomplicated human pregnancies delivered by elective cesarean section. We found lower mRNA levels of complex II, III, and IV in IUGR cytotrophoblast cells but no differences at the protein level, suggesting a posttranscriptional compensatory regulation. mtDNA was increased in IUGR placentas. Both mtDNA and NRF1 expression were instead significantly lower in their isolated cytotrophoblast cells. Finally, cytotrophoblast RCC activity was significantly increased in placentas of IUGR fetuses. No significant differences were found in PE placentas. This study provides genuine new data into the complex physiology of placental oxygenation in IUGR fetuses. The higher mitochondrial content in IUGR placental tissue is reversed in cytotrophoblast cells, which instead present higher mitochondrial functionality. This suggests different mitochondrial content and activity depending on the placental cell lineage. Increased placental oxygen consumption might represent a limiting step in fetal growth restriction, preventing adequate oxygen delivery to the fetus.

The impact of exposure to serum lipids during in vitro culture on the transcriptome of bovine blastocysts

In vitro culture has a detrimental impact on early embryonic development, and serum addition to IVC is recognized to compromise blastocyst quality. Particularly, serum fatty acids affect embryonic lipid composition and reduce cryopreservation survival. To understand the molecular pathways of serum-induced embryonic stress, this study examined the early development of bovine embryos produced in different protein- or lipid-supplemented culture media: BSA alone (control), BSA + serum lipid fraction (SELF), delipidated serum and total serum. These protein-lipid treatments were applied from the eight to 16 cell stages to the blastocyst stage. As planned, SELF treatment increased the fatty acid concentration in the medium compared with control medium but did not induce embryo toxicity. However, microarray comparison between blastocysts cultured in BSA without or with SELF revealed differential transcriptomic profile associated with ceramide-induced oxidative stress and inflammation. Moreover, the SELF treatment had a significant impact on genes involved in cholesterol metabolism (LDLR, HMGCS1), with the potential upstream control of the transcription factors SREBP and PPARA, two major regulators of cholesterol metabolism. In addition, the expression of pluripotence-related genes (APEX, CLDN6) was downregulated in blastocysts subjected to either SELF or total serum. Taken together, these results illustrate how the early embryonic transcriptome responds to increased lipid exposure through an inflammatory and metabolic signature.

Does serum cause lipid-droplet accumulation in bovine embryos produced in vitro, during developmental days 1 to 4?

PURPOSE

Serum supplementation has shown to have beneficial effects on in vitro bovine embryo development. However, it is often assumed that serum supplementation may produce mitochondrial damage and this damage would generate lipid accumulation, a major obstacle for cryopreservation. The aim of the present study is to investigate the previous assumptions in early embryonic stages.

METHODS

We considered in vitro produced bovine embryos from day 1 to 4 of development, which were grown in presence of serum from days 1, 2 or 3 or in absence of it. Electron transmission micrographs allowed us to quantify the area occupied by lipid droplets and by the different mitochondrial types to evaluate serum effect. Using confocal microscopy we analyzed mitochondrial activity and location.

RESULTS

We found no evidence of lipid droplets accumulation or mitochondrial degeneration or reduction of mitochondrial area in serum supplemented media. Further, our results suggest that events of mitochondrial proliferation are taking place even in serum supplemented media.

CONCLUSIONS

Serum does not produce lipid accumulation or mitochondrial damage in bovine embryos from 2 to 16 cells. When serum was added to embryo culture medium on day 3 of development, there were ultrastructural signs of a beneficial effect for embryo development. The lack of serum until day 3 may also avoid the unnecessary exposure to potentially inhibitory factors present on it.

Comparative analysis of dynamic proteomic profiles between in vivo and in vitro produced mouse embryos during postimplantation period

Assisted reproductive technology (ART) increasingly is associated with long-term side-effects on postnatal development and behaviors. High-throughput gene expression analysis has been extensively used to explore mechanisms responsible for these disorders. Our study, for the first time, provides a comparative proteomic analysis between embryos after in vivo fertilization and development (IVO, control) and in vitro fertilization and culture (IVP). By comparing the dynamic proteome during the postimplantation period, we identified 300 and 262 differentially expressed proteins (DEPs) between IVO and IVP embryos at embryonic day 7.5 (E7.5) and E10.5, respectively. Bioinformatic analysis showed many DEPs functionally associated with post-transcriptional, translational, and post-translational regulation, and these observations were consistent with correlation analysis between mRNA and protein abundance. In addition to altered gene expression due to IVP procedures, our findings suggest that aberrant processes at these various levels also contributed to proteomic alterations. In addition, numerous DEPs were involved in energy and amino acid metabolism, as well as neural and sensory development. These DEPs are potential candidates for further exploring the mechanism(s) of ART-induced intrauterine growth restriction and neurodevelopmental disorders. Moreover, significant enrichment of DEPs in pathways of neurodegenerative diseases implies the potentially increased susceptibility of ART offspring to these conditions as adults.

The role of mitochondria from mature oocyte to viable blastocyst

The oocyte requires a vast supply of energy after fertilization to support critical events such as spindle formation, chromatid separation, and cell division. Until blastocyst implantation, the developing zygote is dependent on the existing pool of mitochondria. That pool size within each cell decreases with each cell division. Mitochondria obtained from oocytes of women of advanced reproductive age harbor DNA deletions and nucleotide variations that impair function. The combination of lower number and increased frequency of mutations and deletions may result in inadequate mitochondrial activity necessary for continued embryo development and cause pregnancy failure. Previous reports suggested that mitochondrial activity within oocytes may be supplemented by donor cytoplasmic transfer at the time of intracytoplasmic sperm injection (ICSI). Those reports showed success; however, safety concerns arose due to the potential of two distinct populations of mitochondrial genomes in the offspring. Mitochondrial augmentation of oocytes is now reconsidered in light of our current understanding of mitochondrial function and the publication of a number of animal studies. With a better understanding of the role of this organelle in oocytes immediately after fertilization, blastocyst and offspring, mitochondrial augmentation may be reconsidered as a method to improve oocyte quality.

Analysis of metabolism to select viable human embryos for transfer

As we move to reducing the number of embryos transferred in a given IVF cycle, ideally down to one, there is an ever-increasing need for noninvasive quantitative markers of embryo viability. Although stage-specific morphologic markers and grading systems have been developed, such an approach is unable to assess the physiological status of the embryo. Analysis of metabolism has proved to be a valuable marker of embryo viability after transfer in animal models. We therefore reviewed what is known about human embryo metabolism, how media systems can affect the patterns of nutrient utilization and the activities of metabolic pathways, and how this relates to the developmental competence of the embryo. It is proposed that a unifying hypothesis of metabolism for the entire preimplantation period is not realistic, given the dramatic changes in embryo physiology that occur from fertilization to blastocyst development, and that the concept of a "quiet metabolism" can be interpreted as stress induced by the presence of high oxygen in the embryo culture/analysis system. Further research is required to fully understand the origins of metabolic stress in embryos for it to be alleviated and to develop a comprehensive range of markers that not only reflect embryo viability, but also sex-specific differences in physiology.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Maternal calorie restriction modulates placental mitochondrial biogenesis and bioenergetic efficiency: putative involvement in fetoplacental growth defects in rats

Low birth weight is associated with an increased risk for developing type 2 diabetes and metabolic diseases. The placental capacity to supply nutrients and oxygen to the fetus represents the main determiner of fetal growth. However, few studies have investigated the effects of maternal diet on the placenta. We explored placental adaptive proteomic processes implicated in response to maternal undernutrition. Rat term placentas from 70% food-restricted (FR30) mothers were used for a proteomic screen. Placental mitochondrial functions were evaluated using molecular and functional approaches, and ATP production was measured. FR30 drastically reduced placental and fetal weights. FR30 placentas displayed 14 proteins that were differentially expressed, including several mitochondrial proteins. FR30 induced a marked increase in placental mtDNA content and changes in mitochondrial functions, including modulation of the expression of genes implicated in biogenesis and bioenergetic pathways. FR30 mitochondria showed higher oxygen consumption but failed to maintain their ATP production. Maternal undernutrition induces placental mitochondrial abnormalities. Although an increase in biogenesis and bioenergetic efficiency was noted, placental ATP level was reduced. Our data suggest that placental mitochondrial defects may be implicated in fetoplacental pathologies.

Paternal diet-induced obesity retards early mouse embryo development, mitochondrial activity and pregnancy health

Worldwide, 48% of adult males are overweight or obese. An association between infertility and excessive body weight is now accepted, although focus remains primarily on females. It has been shown that parental obesity results in compromised embryo development, disproportionate changes in embryo metabolism and reduced blastocyst cell number. The aim of this study was to determine whether paternal obesity has negative effects on the resultant embryo. Specifically, using in vitro fertilisation (IVF), we wanted to isolate the functional effects of obesity on sperm by examining the subsequent embryo both pre- and post-implantation. Epididymal sperm was collected from age matched normal and obese C57BL/6 mice and cryopreserved for subsequent IVF with oocytes collected from Swiss females (normal diet/weight). Obesity was induced in male mice by feeding a high fat diet of 22% fat for 10 weeks. Resultant embryos were cultured individually and development monitored using time-lapse microscopy. Paternal obesity resulted in a significant delay in preimplantation embryo development as early as syngamy (P<0.05). Metabolic parameters were measured across key developmental stages, demonstrating significant reduction in mitochondrial membrane potential (P<0.01). Blastocysts were stained to determine trophectoderm (TE) and inner cell mass (ICM) cell numbers, revealing significant differences in the ratio of cell allocation to TE and ICM lineages (P<0.01). Functional studies examining blastocyst attachment, growth and implantation demonstrated that blastocysts derived from sperm of obese males displayed significantly reduced outgrowth on fibronectin in vitro (P<0.05) and retarded fetal development in vivo following embryo transfer (P<0.05). Taken together, these data clearly demonstrate that paternal obesity has significant negative effects on the embryo at a variety of key early developmental stages, resulting in delayed development, reduced placental size and smaller offspring.

Environmental regulation of placental phenotype: implications for fetal growth

Environmental conditions during pregnancy determine birthweight, neonatal viability and adult phenotype in human and other animals. In part, these effects may be mediated by the placenta, the principal source of nutrients for fetal development. However, little is known about the environmental regulation of placental phenotype. Generally, placental weight is reduced during suboptimal conditions like maternal malnutrition or hypoxaemia but compensatory adaptations can occur in placental nutrient transport capacity to help maintain fetal growth. In vivo studies show that transplacental glucose and amino acid transfer adapt to the prevailing conditions induced by manipulating maternal calorie intake, dietary composition and hormone exposure. These adaptations are due to changes in placental morphology, metabolism and/or abundance of specific nutrient transporters. This review examines environmental programming of placental phenotype with particular emphasis on placental nutrient transport capacity and its implications for fetal growth, mainly in rodents. It also considers the systemic, cellular and molecular mechanisms involved in signalling environmental cues to the placenta. Ultimately, the ability of the placenta to balance the competing interests of mother and fetus in resource allocation may determine not only the success of pregnancy in producing viable neonates but also the long-term health of the offspring.

Estrogen-related receptor gamma modulates energy metabolism target genes in human trophoblast

Placenta growth and functions depend on correct trophoblast migration, proliferation, and differentiation. The placenta has a critical role in gas and nutrient transport. To accomplish these numerous functions, the placenta depends on a highly efficient energy metabolism control. Recent studies showed that the orphan nuclear receptor Estrogen-Related Receptor gamma (ERRγ) is highly expressed in human placentas. As ERRγ has been described as a major energy metabolism regulator, we investigated ERRγ expression and putative roles on energy homeostasis in human trophoblast from first trimester placentas. First, we showed that ERRγ expression level increased during pregnancy and that ERRγ was more abundant in villous than in extravillous trophoblasts. We also observed that ERRγ expression increased during trophoblast differentiation. Second, we demonstrated that mitochondrial biogenesis and expression of some energy metabolism target genes decreased when ERRγ expression was impaired. Altogether, these results suggest that ERRγ could be implicated in the energy metabolism regulation of human trophoblasts.

Promising system for selecting healthy in vitro-fertilized embryos in cattle

Conventionally, in vitro–fertilized (IVF) bovine embryos are morphologically evaluated at the time of embryo transfer to select those that are likely to establish a pregnancy. This method is, however, subjective and results in unreliable selection. Here we describe a novel selection system for IVF bovine blastocysts for transfer that traces the development of individual embryos with time-lapse cinematography in our developed microwell culture dish and analyzes embryonic metabolism. The system can noninvasively identify prognostic factors that reflect not only blastocyst qualities detected with histological, cytogenetic, and molecular analysis but also viability after transfer. By assessing a combination of identified prognostic factors—(i) timing of the first cleavage; (ii) number of blastomeres at the end of the first cleavage; (iii) presence or absence of multiple fragments at the end of the first cleavage; (iv) number of blastomeres at the onset of lag-phase, which results in temporary developmental arrest during the fourth or fifth cell cycle; and (v) oxygen consumption at the blastocyst stage—pregnancy success could be accurately predicted (78.9%). The conventional method or individual prognostic factors could not accurately predict pregnancy. No newborn calves showed neonatal overgrowth or death. Our results demonstrate that these five predictors and our system could provide objective and reliable selection of healthy IVF bovine embryos.

[In utero fetal programming and its impact on health in adulthood]

Adverse events during intrauterine life may program organ growth and favor disease later in life. This is the usually called 'Barker's hypothesis'. Increasing evidence suggests that conditions like vascular disease, hypertension, metabolic syndrome, and type 2 diabetes mellitus are programmed during the early stages of fetal development and become manifest in late stages of life, when there is an added impact of lifestyle and other conventional acquired environmental risk factors that interact with genetic factors. The aim of this review was to provide additional, updated evidence to support the association between intrauterine fetal health and increased prevalence of chronic non-communicable diseases in adulthood. Various potential cellular and molecular mechanisms proposed to be related to the above hypothesis are discussed, including endothelial function, oxidative stress, insulin resistance, and mitochondrial function.

Metabolism of the preimplantation embryo: 40 years on

This review considers how our understanding of preimplantation embryo metabolism has progressed since the pioneering work on this topic in the late 1960s and early 1970s. Research has been stimulated by a desire to understand how metabolic events contribute to the development of the zygote into the blastocyst, the need for biomarkers of embryo health with which to improve the success of assisted conception technologies, and latterly by the ‘Developmental Origins of Health and Disease’ (DOHaD) concept. However, arguably, progress has not been as great as it might have been due to methodological difficulties in working with tiny amounts of tissue and the low priority assigned to fundamental research on fertility and infertility, with developments driven more by technical than scientific advances. Nevertheless, considerable progress has been made in defining the roles of the traditional nutrients: pyruvate, glucose, lactate, and amino acids; originally considered as energy sources and biosynthetic precursors, but now recognized as having multiple, overlapping functions. Other nutrients; notably lipids, are beginning to attract the attention they deserve. The pivotal role of mitochondria in early embryo development and the DOHaD concept, and in providing a cellular focus for metabolic events is now recognized. Some unifying ideas are discussed; namely ‘stress–response models’ and the ‘quiet embryo hypothesis’; the latter aiming to relate the metabolism of individual preimplantation embryos to their subsequent viability. The review concludes by updating the state of knowledge of preimplantation embryo metabolism in the early 1970s and listing some future research questions.

Diet and exercise in an obese mouse fed a high-fat diet improve metabolic health and reverse perturbed sperm function

Male obesity is associated with reduced sperm motility and morphology and increased sperm DNA damage and oxidative stress; however, the reversibility of these phenotypes has never been studied. Therefore, the aim of this study was to assess the reversibility of obesity and its associated sperm physiology and function in mice in response to weight loss through diet and exercise. C57BL6 male mice (n = 40) were fed either a control diet (CD; 6% fat) or a high-fat diet (HFD; 21% fat) for 10 wk before allocation to either diet and/or swimming exercise interventions for 8 wk. Diet alone reduced adiposity (1.6-fold) and serum cholesterol levels (1.7-fold, P < 0.05), while exercise alone did not alter these, but exercise plus diet also improved glucose tolerance (1.3-fold, P < 0.05). Diet and/or exercise improved sperm motility (1.2-fold) and morphology (1.1-fold, P < 0.05), and reduced sperm DNA damage (1.5-fold), reactive oxygen species (1.1-fold), and mitochondrial membrane potential (1.2-fold, P < 0.05) and increased sperm binding (1.4-fold) (P < 0.05). Sperm parameters were highly correlated with measures of glycemia, insulin action, and serum cholesterol (all P < 0.05) regardless of adiposity or intervention, suggesting a link between systemic metabolic status and sperm function. This is the first study to show that the abnormal sperm physiology resulting from obesity can be reversed through diet and exercise, even in the presence of ongoing obesity, suggesting that diet and lifestyle interventions could be a combined approach to target subfertility in overweight and obese men.

Intrafollicular conditions as a major link between maternal metabolism and oocyte quality: a focus on dairy cow fertility

Reduced oocyte and embryo quality are recognised as major factors in the problem of disappointing fertility in high producing dairy cows. This review aims to shed more light on the importance of the intrafollicular environment in the subfertility problem in dairy cows. Metabolic disturbances associated with negative energy balance (NEB) early postpartum are associated with ovarian dysfunction. Changes in the growth pattern of the ovarian follicle during a period of NEB can indirectly affect oocyte quality. Furthermore, a maternal metabolic disorder (linked with NEB or nutritionally induced) may alter the endocrine and biochemical composition of the follicular fluid, the micro-environment of the growing and maturing female gamete. The maturing oocyte is very sensitive to any perturbation in its direct environment and in vitro maturation models revealed that some of these metabolic changes reduce the oocyte’s developmental competence. Also, embryo quality is significantly reduced due to maturation in adverse conditions. Well balanced and timed oocyte metabolism and gene expression are crucial to safeguard an optimal oocyte development. In that perspective, metabolome and transcriptome parameters of the oocyte may serve to predict reproductive success rates. Finally, there is growing evidence that adverse conditions for oocyte growth and maturation may also jeopardise the health and performance of the offspring.

Follicular growth-stimulated cows provide favorable oocytes for producing cloned embryos

We examined the influence of recipient oocytes on in vitro development, oxygen consumption, and gene expression in the resulting cloned bovine embryos. Oocytes derived from slaughterhouse ovaries and ovum pickup (OPU)-derived oocytes were used as recipient cytoplasts for the production of cloned embryos. A series of OPU sessions was conducted on Holstein cows without follicular growth treatment (FGT). In the same cows, we then performed dominant follicle ablation and subsequently administered follicle-stimulating hormone and prostaglandin F(2α) with controlled internal drug release device before a second series of OPU. Cumulus cells collected from single Holstein cows were used as donor cells. After measurement of oxygen consumption at the blastocyst stage with modified scanning electrochemical microscopy, analysis of 10 genes (CDX2, IFN-tau, PLAC8, OCT4, SOX2, NANOG, ATP5A1, GLUT1, AKR1B1, and IGF2R) was performed with real-time RT-PCR. Rates of fusion, cleavage, and blastocyst formation were not different among the treatment groups. Levels of oxygen consumption in cloned blastocysts derived from slaughterhouse ovaries or OPU without FGT were significantly lower than in blastocysts derived from artificial insemination (AI). However, oxygen consumption was increased in cloned blastocysts derived from OPU with FGT, depending on the individual oocyte donor. Furthermore, gene expression of IFN-tau and OCT4 in cloned blastocysts derived from OPU with FGT was similar to that in AI-derived blastocysts, whereas expression of those genes in cloned blastocysts derived from slaughterhouse ovaries or OPU without FGT was significantly different from that in AI-derived blastocysts. Thus, recipient oocytes collected by OPU in combination with manipulation of follicular growth in donor cows are suitable for producing cloned embryos.

Paternal cyclophosphamide exposure induces the formation of functional micronuclei during the first zygotic division

Paternal exposures to cancer chemotherapeutics or environmental chemicals may have adverse effects on progeny outcome that are manifested in the preimplantation embryo. The objectives of this study were to determine the impact of paternal exposure to cyclophosphamide, an anticancer alkylating agent, on the formation, chromatin origin and function of micronuclei in cleavage stage rat embryos. Male Sprague-Dawley rats were gavaged with saline or cyclophosphamide (6 mg/kg/day) for 4 weeks and mated to naturally cycling females to collect pronuclear zygotes and 2 to 8 cell embryos. Micronuclear chromatin structure was characterized using confocal microscopy to detect immunoreactivities for H3K9me3, a marker for maternal chromatin, and lamin B, a nuclear membrane marker. DNA synthesis was monitored using EdU (5-ethynyl-2′-deoxyuridine) incorporation. Fertilization by cyclophosphamide-exposed spermatozoa led to a dramatic elevation in micronuclei in cleavage stage embryos (control embryos: 1% to 5%; embryos sired by treated males: 70%). The formation of micronuclei occurred during the first zygotic division and was associated with a subsequent developmental delay. The absence of H3K9me3 indicated that these micronuclei were of paternal origin. The micronuclei had incomplete peri-nuclear and peri-nucleolar lamin B1 membrane formation but incorporated EdU into DNA to the same extent as the main nucleus. The formation of micronuclei in response to the presence of a damaged paternal genome may play a role in increasing the rate of embryo loss that is associated with the use of assisted reproductive technologies, parenthood among cancer survivors, and paternal aging.

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.