Glucose transporter expression is developmentally regulated in in vitro derived bovine preimplantation embryos

Effect of IGFBP-4 during In Vitro Maturation on Developmental Competence of Bovine Cumulus Oocyte Complexes

Insulin-like growth factors (IGFs) are essential for oocyte maturation. Their bioavailability is regulated by their respective binding proteins (IGFBPs) and proteases. IGFBP-4 blocks the biological effects of IGFs. High IGFBP-4 expression has been associated with follicle atresia. We hypothesized that IGFBP-4 affects oocyte developmental competence during maturation. Therefore, the aim of this study was to examine the effect of IGFBP-4 on the developmental rate of bovine cumulus-oocyte complexes (COCs) during in vitro embryo production. Abattoir-derived COCs were matured with rbIGFBP-4 (2000, 540, and 54 ng/mL) compared to a control. Cumulus expansion, oocyte maturation, cleavage, blastocyst, and hatching rates were evaluated. Furthermore, blastocyst gene expression of SOCS2, STAT3, SLC2A1, SLCA3, BAX, and POU5F1 transcripts were quantified using RT-qPCR. No statistical differences were detected among the groups for cumulus expansion, maturation, cleavage, blastocyst rates, or all gene transcripts analyzed. However, at day 8 and 9, the number of total hatching and successfully hatched blastocysts was lower in 2000 ng/mL rbIGFBP-4 compared to the control (day 8: total hatching: 17.1 ± 0.21 vs. 31.2 ± 0.11%, p = 0.02 and hatched blastocyst 6.7 ± 0.31 vs. 21.5 ± 0.14%, p = 0.004; day 9 total hatching 36.4 ± 0.18 vs. 57.7 ± 0.10%, p = 0.009 and hatched blastocyst 18.2 ± 0.21 vs. 38.1 ± 0.11%, p = 0.004). We concluded that high concentrations of rbIGFBP-4 might negatively affect the subsequent ability of the embryo to hatch and possibly compromise further elongation.

Mitochondrial DNA content and developmental competence of blastocysts derived from pre-pubertal heifer oocytes

In the cattle-breeding industry, there is an increasing demand for in vitro embryo production from pre-pubertal heifers. In this study, we evaluated the differences in mitochondrial DNA content, oxidative stress, and developmental competence in blastocysts derived from pre-pubertal and pubertal heifers. We found higher mitochondrial DNA copy numbers in blastocysts produced from pre-pubertal heifers than from pubertal heifers. In the group of pre-pubertal animals, there was a significantly lower number of blastocysts produced in vitro from the same number of collected oocytes, and these blastocysts did not differ from those obtained from pubertal oocytes in terms of their morphological quality. The morphologically appropriate blastocysts derived from pre-pubertal heifers had higher concentrations of reactive oxygen species and glutathione. In blastocysts derived from pre-pubertal heifers, we found alterations in the expression of gene markers for developmental competence, which correlated with higher mitochondrial DNA content, suggesting a lower quality of blastocysts derived from pre-pubertal animals than from pubertal animals. The inadequate redox balance in blastocysts obtained from pre-pubertal females, along with higher mitochondrial DNA copy number, as well as differential gene expression of markers of developmental competence, elucidate the low quality of blastocysts derived from pre-pubertal animals, despite their unaltered morphology.

Human Granulosa Cells-Stemness Properties, Molecular Cross-Talk and Follicular Angiogenesis

The ovarian follicle is the basic functional unit of the ovary, comprising theca cells and granulosa cells (GCs). Two different types of GCs, mural GCs and cumulus cells (CCs), serve different functions during folliculogenesis. Mural GCs produce oestrogen during the follicular phase and progesterone after ovulation, while CCs surround the oocyte tightly and form the cumulus oophurus and corona radiata inner cell layer. CCs are also engaged in bi-directional metabolite exchange with the oocyte, as they form gap-junctions, which are crucial for both the oocyte’s proper maturation and GC proliferation. However, the function of both GCs and CCs is dependent on proper follicular angiogenesis. Aside from participating in complex molecular interplay with the oocyte, the ovarian follicular cells exhibit stem-like properties, characteristic of mesenchymal stem cells (MSCs). Both GCs and CCs remain under the influence of various miRNAs, and some of them may contribute to polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI) occurrence. Considering increasing female fertility problems worldwide, it is of interest to develop new strategies enhancing assisted reproductive techniques. Therefore, it is important to carefully consider GCs as ovarian stem cells in terms of the cellular features and molecular pathways involved in their development and interactions as well as outline their possible application in translational medicine.

Inhibiting diacylglycerol acyltransferase-1 reduces lipid biosynthesis in bovine blastocysts produced in vitro

Diacylglycerol acyltransferase-1 (DGAT1) is one of the DGAT enzymes that catalyzes the final step in the synthesis of triacylglycerol, which is a major component of the lipid droplets in embryos. Intracellular lipids accumulated in embryos produced in vitro have been associated with reduced cryotolerance and quality. The objective of the present study was to investigate the influence of DGAT1 inhibition on embryo development, quality, and post-vitrification survival, in addition to expression profiles of selected lipid metabolism-regulating and oxidative stress genes. Bovine cumulus-oocyte complexes were matured and fertilized in vitro and were cultured in synthetic oviduct fluid (SOF) supplemented with 5% fetal calf serum (FCS) alone (Control) or with 1, 5, 10 or 50 μM DGAT1 inhibitor (A922500®; D1, D5, D10, and D50, respectively) or 0.1% dimethyl sulfoxide (CDMSO: vehicle for DGAT1 inhibitor dilution) from 54 h post-insemination until Day 8 post insemination. No differences were found in blastocyst yield on days 7 and 8 in Control, CDMSO, D10, and D50 groups. Embryos cultured with 10 or 50 μM DGAT1 inhibitor had greater mitochondrial activity (P < 0.01), and increased number of cells (P < 0.05), while the cytoplasmic lipid content was reduced (P < 0.01), the latter associated with altered expression profiles of selected genes regulating lipid metabolism or genes related with oxidative stress (transcript abundance increased for SLC2A1 and SLC2A5 and decreased for DGAT1 and GPX1). Importantly, the survival rate of blastocysts produced with 10 μM DGAT1 was higher than that of Control, CDMSO and D50 groups at 72 h after vitrification and warming (73.8 vs 57.1, 55.9 and 56.1%, respectively, P < 0.001). In conclusion, inhibition of DGAT1 synthesis in bovine embryos produced in vitro abrogates the negative effect of FCS by decreasing their lipid content, increasing mitochondria activity and improving embryo cryotolerance, as well as favoring the expression of lipid metabolism regulating and oxidative stress-related transcripts.

Expression pattern of GLUT 1, 5, 8 and citrate synthase transcripts in buffalo (Bubalus bubalis) preimplantation embryos produced in vitro and derived in vivo

In vitro-produced (IVP) embryos are reported to be developmentally lesser competent than in vivo-derived (IVD) embryos and supposed to differ in the expression of genes related with glucose metabolism. So, the present study was conducted to analyse the expression pattern of GLUT 1, 5, 8 and citrate synthase (CS) in oocytes and embryos produced in vivo or in vitro in buffalo. IVD embryos were obtained from 18 superovulated buffaloes. IVP embryos were obtained from slaughterhouse-derived oocytes subsequently subjected to in vitro fertilization and culture. Total RNA was isolated from different stages of oocytes (immature and in vitro matured) and embryos (8-16 cell to blastocysts of IVP embryos and morula to blastocysts of IVD embryos). Results demonstrated that the expression of GLUT1, GLUT 8 increased from 8 to 16 cells to blastocyst and was significantly (p < .05) higher in IVP embryos. Expression of both genes was (p < .05) higher in IVD than in IVP blastocysts; though GLUT5 transcripts were not detected at 8- to 16-cell stage IVP embryos, significantly (p < .05) higher transcripts were found at morula and blastocyst stages irrespective of embryo source with significantly (p < .05) higher expression in IVD embryos compared to IVP embryos. No significant difference was observed in citrate synthase expression in embryos at morula stage irrespective of the embryo source while significantly (p < .05) higher transcript level was observed at blastocyst stage with no difference between in vivo and in vitro embryos. It can be concluded that expression of GLUTs and CS is upregulated with progression of embryonic stage and expression is higher in in vivo embryos than in vitro counter parts; thus, it can be said that in vivo-produced embryos are metabolically superior to in vitro embryos.

Glucose Metabolism and Dynamics of Facilitative Glucose Transporters (GLUTs) under the Influence of Heat Stress in Dairy Cattle

Heat stress is one of the main threats to dairy cow production; in order to resist heat stress, the animal exhibits a variety of physiological and hormonal responses driven by complex molecular mechanisms. Heat-stressed cows have high insulin activity, decreased non-esterified fatty acids, and increased glucose disposal. Glucose, as one of the important biochemical components of the energetic metabolism, is affected at multiple levels by the reciprocal changes in hormonal secretion and adipose metabolism under the influence of heat stress in dairy cattle. Therefore, alterations in glucose metabolism have negative consequences for the animal’s health, production, and reproduction under heat stress. Lactose is a major sugar of milk which is affected by the reshuffle of the whole-body energetic metabolism during heat stress, contributing towards milk production losses. Glucose homeostasis is maintained in the body by one of the glucose transporters’ family called facilitative glucose transporters (GLUTs encoded by SLC2A genes). Besides the glucose level, the GLUTs expression level is also significantly changed under the influence of heat stress. This review aims to describe the effect of heat stress on systemic glucose metabolism, facilitative glucose transporters, and its consequences on health and milk production.

Interaction between growing oocytes and granulosa cells in vitro

BACKGROUND

Oocyte growth is accompanied by follicular development in mammalian ovaries. Since the discovery of two oocyte-derived factors, growth differentiation factor 9 (GDF9), and bone morphogenetic protein 15 (BMP15), knowledge of the bidirectional communication between oocytes and granulosa cells for ovarian function and fertility has been accumulated. In addition, the growth culture system of oocytes has been improved, further promoting the studies on the communication between oocytes and granulosa cells in vitro.

METHODS

We provide an overview of the role of granulosa cells in oocyte growth and the role of oocytes in follicular development along with our recent findings in culture experiments of bovine growing oocytes.

MAIN FINDINGS

Granulosa cells supply nutrients and metabolites through gap junctions to oocytes and secrete paracrine signals to regulate oocytes. Oocytes regulate granulosa cell proliferation and differentiation and induce antrum formation via GDF9 and BMP15.

CONCLUSION

Oocytes actively participate in various aspects of follicular development, including antrum formation via the oocyte-derived factors GDF9 and BMP15, whose synthesis is probably regulated by granulosa cells. In vitro studies will reveal the precise communication loop between oocytes and granulosa cells that facilitates the coordinated development of oocytes and granulosa cells in the follicles.

Difference in Developmental Kinetics of Y-Specific Monoclonal Antibody Sorted Male and Female In Vitro Produced Bovine Embryos

Sex-related growth differences between male and female embryos remain an attractive subject for reproductive biologists. This study aimed to investigate the endogenous factors that play a crucial role in the pace of early development between male and female bovine embryos. Using sex pre-selected semen by Y-specific monoclonal antibodies for the production of bovine embryos, we characterized the critical endogenous factors that are responsible for creating the development differences, especially during the pre-implantation period between male and female embryos. Our results showed that at day seven, (57.8%) Y-sperm sorted in vitro cultured embryos reached the expanded blastocyst (BL) stage, whereas the X-sperm sorted group were only 25%. Y-BLs showed higher mRNA abundance of pluripotency and developmental competency regulators, such as Oct4 and IGF1-R. Interestingly, Y-sperm sorted BLs had a homogeneous mitochondrial distribution pattern, higher mitochondrial membrane potential (∆Ѱ_m), efficient OXPHOS (oxidative phosphorylation) system and well-encountered production of ROS (reactive oxygen species) level. Moreover, Y-blastocysts (BLs) showed less utilization of glucose metabolism relative to the X-BLs group. Importantly, both sexes showed differences in the timing of epigenetic events. All these factors directly or indirectly orchestrate the whole embryonic progression and may help in the faster and better quality yield of BL in the Y-sperm sorted group compared to the X counterpart group.

Treatment with cyclic adenosine monophosphate modulators prior to in vitro maturation alters the lipid composition and transcript profile of bovine cumulus-oocyte complexes and blastocysts

Mammalian oocytes resume meiosis spontaneously after removal from the ovarian follicle. We tested the effects of a 2-h prematuration treatment (Pre-IVM) with forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX) in bovine cumulus-oocyte complexes (COCs) on the lipid content of oocytes and blastocysts, on the membrane lipid composition of blastocysts and on the transcriptional profiling of cumulus cells and blastocysts in a high-throughput platform. Embryonic development rates to the morula (mean 56.1%) or blastocyst (mean 26.3%) stages were unaffected by treatment. Lipid content was not affected after Pre-IVM, but was increased after IVM in treated oocytes. Conversely, the lipid content was reduced in Pre-IVM blastocysts. Pre-IVM COCs generated blastocysts containing blastomeres with more unsaturated lipids in their membranes. Pre-IVM also altered the relative abundance of 31 gene transcripts after 2h and 16 transcripts after 24h in cumulus cells, while seven transcripts were altered in blastocysts. Our results suggest that the Pre-IVM treatment affected the lipid composition and transcriptional profiles of COCs and blastocysts. Therefore, Pre-IVM with FSK and IBMX could be used either to prevent spontaneous meiotic resumption during IVM or to modulate lipid composition in the membrane and cytoplasm of blastocysts, potentially improving bovine embryos.

Effect of butafosfan supplementation during oocyte maturation on bovine embryo development

Around 60-80% of oocytes maturated in vivo reached competence, while the proportion of maturation in vitro is rarely higher than 40%. In this sense, butafosfan has been used in vivo to improve metabolic condition of postpartum cows, and can represent an alternative to increase reproductive efficiency in cows. The aim of this study was to evaluate the addition of increasing doses of butafosfan during oocyte maturation in vitro on the initial embryo development in cattle. In total, 1400 cumulus-oocyte complexes (COCs) were distributed in four groups and maturated according to supplementation with increasing concentrations of butafosfan (0 mg/ml, 0.05 mg/ml, 0.1 mg/ml and 0.2 mg/ml). Then, 20 oocytes per group were collected to evaluate nuclear maturation and gene expression on cumulus cells and oocytes and the remaining oocytes were inseminated and cultured until day 7, when blastocysts were collected for gene expression analysis. A dose-dependent effect of butafosfan was observed, with decrease of cleavage rate and embryo development with higher doses. No difference between groups was observed in maturation rate and expression of genes related to oocyte quality. Our results suggest that butafosfan is prejudicial for oocytes, compromising cleavage and embryo development.

Effects of gonadotrophins and insulin on glucose uptake in the porcine cumulus-oocyte complex during IVM

The combination of gonadotrophins (LH and FSH) and insulin is frequently used in porcine oocyte IVM, but the individual effects of gonadotrophins and insulin have not been completely studied. The aim of this study was to investigate the mechanisms involved in glucose metabolism in the swine cumulus-oocyte complex (COC), analysing the effects of gonadotrophins (10IUmL-1 LH+10IUmL-1 FSH) and 0.4μUmL-1 insulin, during 44h of IVM, on glucose transport and consumption, as well as on nuclear maturation and sperm penetration. We evaluated the effects of gonadotrophins and insulin separately or in combination on glucose consumption, membrane permeability to the glucose fluorescent analogue 6-(N -(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-6-deoxyglucose (6-NBDG), the presence of GLUT-4 and oocyte maturation rates, after 44h of IVM. Nuclear maturation percentages increased significantly following the addition of gonadotrophins alone or in combination with insulin to the culture medium (P P P <0.0001). Although gonadotrophins and insulin increased GLUT-4 expression, neither modified 6-NBDG incorporation. In conclusion, gonadotrophins and insulin had different effects during IVM; although gonadotrophins increased maturation rates and glucose consumption, they had no effect on glucose transport, and insulin improved sperm penetration without affecting the parameters related to glucose utilisation. Therefore, glucose metabolism is likely to be primarily regulated by its consumption in metabolic pathways rather than by changes in membrane permeability.

Effective Oocyte Vitrification and Survival Techniques for Bovine Somatic Cell Nuclear Transfer

Bovine somatic cell nuclear transfer (SCNT) using vitrified-thawed (VT) oocytes has been studied; however, the cloning efficiency of these oocytes is not comparable with that of nonvitrified (non-V) fresh oocytes. This study sought to optimize the survival and cryopreservation of VT oocytes for SCNT. Co-culture with feeder cells that had been preincubated for 15 h significantly improved the survival of VT oocytes and their in vitro developmental potential following SCNT in comparison to co-culture with feeder cells that had been preincubated for 2, 5, or 24 h (p<0.05). Spindle assessment via the Oosight Microscopy Imaging System and microtubule staining revealed that vitrified metaphase II oocytes (VT group) were not suitable for SCNT. However, enucleating and/or activating oocytes prior to freezing enhanced their developmental potential and suitability for SCNT. The cloning efficiency of the enucleated-activated-vitrified-thawed (EAVT) group (21.6%) was better than that of the other vitrification groups [enucleated-vitrified-thawed (EVT) group, 13.7%; VT group, 15.0%; p<0.05] and was comparable with that of the non-V group (25.9%). The reactive oxygen species level was significantly lower in the EAVT group than in the other vitrification groups (p<0.05). mRNA levels of maternal genes (ZAR1, BMP15, and NLRP5) and a stress gene (HSF1) were lower in the vitrification groups than in the non-V group (p<0.05), whereas the level of phospho-p44/42 mitogen-activated protein kinase did not differ among the groups. Among the vitrification groups, blastocysts in the EAVT group had the best developmental potential, as judged by their high mRNA expression of developmental potential-related genes (POU5f1, Interferon-tau, and SLC2A5) and their low expression of proapoptotic (CASP3) and stress (Hsp70) genes. This study demonstrates that SCNT using bovine frozen-thawed oocytes can be successfully achieved using optimized vitrification and co-culture techniques.

The effect of lysophosphatidic acid during in vitro maturation of bovine cumulus-oocyte complexes: cumulus expansion, glucose metabolism and expression of genes involved in the ovulatory cascade, oocyte and blastocyst competence

BACKGROUND

In the cow, lysophosphatidic acid (LPA) acts as an auto-/paracrine factor, through its receptors LPAR1-4, on oocytes and cumulus cells during in vitro maturation (IVM). The aim of the present work was to determine the effect of LPA during IVM of bovine oocytes on: 1) oocyte maturation; 2) apoptosis of COCs; 3) expression of genes involved in developmental competence and apoptosis in bovine oocytes and subsequent blastocysts; 4) cumulus expansion and expression of genes involved in the ovulatory cascade in cumulus cells; 5) glucose metabolism and expression of genes involved in glucose utilization in cumulus cells; 6) cleavage and blastocyst rates on Day 2 and Day 7 of in vitro culture, respectively.

METHODS

Cumulus-oocyte complexes (COCs) were matured in vitro in the presence or absence of LPA (10(-5) M) for 24 h. Following maturation, we determined: oocyte maturation stage, cumulus expansion, COCs apoptosis and glucose and lactate levels in the maturation medium. Moreover, COCs were either used for gene expression analysis or fertilized in vitro. The embryos were cultured until Day 7 to assess cleavage and blastocyst rates. Oocytes, cumulus cells and blastocysts were used for gene expression analysis.

RESULTS

Supplementation of the maturation medium with LPA enhanced oocyte maturation rates and stimulated the expression of developmental competence-related factors (OCT4, SOX2, IGF2R) in oocytes and subsequent blastocysts. Moreover, LPA reduced the occurrence of apoptosis in COCs and promoted an antiapoptotic balance in the transcription of genes involved in apoptosis (BAX and BCL2) either in oocytes or blastocysts. LPA increased glucose uptake by COCs via augmentation of GLUT1 expression in cumulus cells as well as stimulating lactate production via the enhancement of PFKP expression in cumulus cells. LPA did not affect cumulus expansion as visually assessed, however, it stimulated upstream genes of cumulus expansion cascade, AREG and EREG.

CONCLUSIONS

Supplementation of the maturation medium with LPA improves oocyte maturation rates, decreases extent of apoptosis in COCs and sustains the expression of developmental competence related factors during oocyte maturation and subsequently affects gene expression profile at the blastocyst stage. We also demonstrate that LPA directs glucose metabolism toward the glycolytic pathway during IVM.

Effect of crotamine, a cell-penetrating peptide, on blastocyst production and gene expression of in vitro fertilized bovine embryos

The present study investigated the effects of crotamine, a cell-penetrating peptide from rattlesnake venom, at different exposure times and concentrations, on both developmental competence and gene expression (ATP1A1, AQP3, GLUT1 and GLUT3) of in vitro fertilized (IVF) bovine embryos. In Experiment 1, presumptive zygotes were exposed to 0.1 μM crotamine for 6, 12 or 24 h and control groups (vehicle and IVF) were included. In Experiment 2, presumptive zygotes were exposed to 0 (vehicle), 0.1, 1 and 10 μM crotamine for 24 h. Additionally, to visualize crotamine uptake, embryos were exposed to rhodamine B-labelled crotamine and subjected to confocal microscopy. In Experiment 1, no difference (P > 0.05) was observed among different exposure times and control groups for cleavage and blastocyst rates and total cells number per blastocyst. Within each exposure time, mRNA levels were similar (P > 0.05) in embryos cultured with or without crotamine. In Experiment 2, concentrations as high as 10 μM crotamine did not affect (P > 0.05) the blastocyst rate. Crotamine at 0.1 and 10 μM did not alter mRNA levels when compared with the control (P > 0.05). Remarkably, only 1 μM crotamine decreased both ATP1A1 and AQP3 expression levels relative to the control group (P < 0.05). Also, it was possible to visualize the intracellular localization of crotamine. These results indicate that crotamine can translocate intact IVF bovine embryos and its application in the culture medium is possible at concentrations from 0.1–10 μM for 6–24 h.

Metabolic control of oocyte development: linking maternal nutrition and reproductive outcomes

Obesity, diabetes, and related metabolic disorders are major health issues worldwide. As the epidemic of metabolic disorders continues, the associated medical co-morbidities, including the detrimental impact on reproduction, increase as well. Emerging evidence suggests that the effects of maternal nutrition on reproductive outcomes are likely to be mediated, at least in part, by oocyte metabolism. Well-balanced and timed energy metabolism is critical for optimal development of oocytes. To date, much of our understanding of oocyte metabolism comes from the effects of extrinsic nutrients on oocyte maturation. In contrast, intrinsic regulation of oocyte development by metabolic enzymes, intracellular mediators, and transport systems is less characterized. Specifically, decreased acid transport proteins levels, increased glucose/lipid content and elevated reactive oxygen species in oocytes have been implicated in meiotic defects, organelle dysfunction and epigenetic alteration. Therefore, metabolic disturbances in oocytes may contribute to the diminished reproductive potential experienced by women with metabolic disorders. In-depth research is needed to further explore the underlying mechanisms. This review also discusses several approaches for metabolic analysis. Metabolomic profiling of oocytes, the surrounding granulosa cells, and follicular fluid will uncover the metabolic networks regulating oocyte development, potentially leading to the identification of oocyte quality markers and prevention of reproductive disease and poor outcomes in offspring.

The adenosine salvage pathway as an alternative to mitochondrial production of ATP in maturing mammalian oocytes

Although the oocyte is the largest cell in the body and an unavoidable phase in life, its physiology is still poorly understood, and other cell types provide little insight into its unique nature. Even basic cellular functions in the oocyte such as energy metabolism are not yet fully understood. It is known that the mitochondria of the female gamete exhibit an immature form characterized by limited energy production from glucose and oxidative phosphorylation. We show that the bovine oocyte uses alternative means to maintain ATP production during maturation, namely, the adenosine salvage pathway. Meiosis resumption is triggered by destruction of cyclic AMP by phosphodiesterases producing adenosine monophosphate that is converted into ATP by adenylate kinases and creatine kinases. Inhibition of these enzymes decreased ATP production, and addition of their substrates restored ATP production in denuded oocytes. Addition of phosphocreatine to the oocyte maturation medium influenced the phenotype of the resulting blastocysts. We propose a model in which adenylate kinases and creatine kinases act as drivers of ATP production from added AMP during oocyte maturation.

Post-hatching development of in vitro bovine embryos from day 7 to 14 in vivo versus in vitro

This study evaluates the post-hatching development of in vitro-produced (IVP) embryos until Day 14. On Day 7, IVP embryos were either transferred to recipient uteruses or placed in a post-hatching development (PHD) system. As a control group, in vivo-produced (IVV), Day-7 embryos were also transferred to recipient uteruses. All groups were collected on Day 14 and were morphologically evaluated. Day-7 and Day-14 IVV and IVP embryos were used for quantification of eight genes (PLAC8, CD9, SLC2A1, SLC2A3, KRT8, SOD2, HSP1A1, and IFNT2) by reverse transcriptase qPCR. Day-14 embryos from the PHD system were smaller (2.92 ± 0.45 mm) and had a lower embryonic disk diameter (0.14 ± 0.00 mm) than those produced by IVV (24.18 ± 3.71; 0.29 ± 0.03 mm, respectively) or IVP (19.06 ± 2.43; 0.28 ± 0.01 mm) culture and transferred to the uterus (P > 0.05). Day-7 IVP embryos had a higher expression of the HSP1A1, SCL2A1, and SCL2A3 genes than IVV embryos. When these embryos were cultured in the uterus, no differences in gene expression were observed on Day 14. Conversely, Day-14 IVP embryos cultured in the PHD system showed a higher expression of PLAC8, SOD2, and SLC2A3 genes. It is concluded that Day-7 IVP embryos are different from IVV embryos in regards to gene expression, although exposure to the uterine environment during the elongation period allowed the IVP embryos to overcome this difference. In contrast, IVP embryos cultured in the PHD system were morphologically and molecularly different, being of poorer quality than those cultured in the uterus.

Effect of physiologically relevant heat shock on development, apoptosis and expression of some genes in buffalo (Bubalus bubalis) embryos produced in vitro

For investigating the effects of physiologically relevant heat shock, buffalo oocytes/embryos were cultured at 38.5°C (control) or were exposed to 39.5°C (Group II) or 40.5°C (Group III) for 2 h once every day throughout in vitro maturation (IVM), fertilization (IVF) and culture (IVC). Percentage of oocytes that developed to 8-cell, 16-cell or blastocyst stage was lower (p < 0.05) and the number of apoptotic nuclei was higher (p < 0.05) for Group III > Group II > controls. At both 8-16-cell and blastocyst stages, relative mRNA abundance of stress-related genes HSP 70.1 and HSP 70.2 and pro-apoptotic genes CASPASE-3, BID and BAX was higher (p < 0.05) in Groups III and II than that in controls with the exception of stress-related gene HSF1. Expression level of anti-apoptotic genes BCL-XL and MCL-1 was also higher (p < 0.05) in Groups III and II than that in controls at both 8-16-cell and blastocyst stages. Among the genes related to embryonic development, at 8-16-cell stage, the expression level of GDF9 was higher (p < 0.05) in Group III than that in controls, whereas that of GLUT1, ZAR1 and BMP15 was not significantly different among the three groups. At the blastocyst stage, relative mRNA abundance of GLUT1 and GDF9 was higher (p < 0.05) in Group II than that in controls, whereas that of ZAR-1 and BMP15 was not affected. The results of this study demonstrate that exposure of buffalo oocytes and embryos to elevated temperatures for duration of time that is physiologically relevant severely compromises their developmental competence, increases apoptosis and affects stress-, apoptosis- and development-related genes.

Histone modifications and mRNA expression in the inner cell mass and trophectoderm of bovine blastocysts

Normal development depends on the precise sequence of changes in the configuration of chromatin; these are primarily related to specific biochemical modifications such as acetylation or methylation of histones and DNA methylation. While the role of DNA methylation during preimplantation development has been studied extensively, little is known about histone modifications related to early embryonic development. Here, we investigated gene-specific histone modifications in in vitro produced bovine blastocysts. Selected genes thought to be critical for bovine preimplantation development were examined and included POU5F1 (OCT4), NANOG, INFT, GAPDH, SLC2A3 and IGF1. We used chromatin immunoprecipitation from pools of bovine blastocysts to unravel several modifications of histone H3 in relation to mRNA expression profiles. We focused on the two cell compartments of the blastocyst, the inner cell mass (ICM) and the trophectoderm (TE). We show that gene expression patterns in the ICM and TE of the bovine blastocyst are consistent with histone modification patterns on the promoter of the corresponding genes. The data show a complex epigenetic pattern of promoter occupancy by transcriptionally permissive and repressive H3 modifications. These results pave the way to in-depth epigenetic studies of preimplantation embryos that are crucial to gain a better understanding of the epigenetic changes frequently observed after use of assisted reproductive technologies.

Loss of genomic imprinting in mouse embryos with fast rates of preimplantation development in culture

Currently, the stage of embryo development has been proposed as one of many criteria for identifying healthy embryos in infertility clinics with the fastest embryos being highlighted as the healthiest. However the validity of this as an accurate criterion with respect to genomic imprinting is unknown. Given that embryo development in culture generally requires an extra day compared to in vivo development, we hypothesized that loss of imprinting correlates with slower rates of embryonic development. To evaluate this, embryos were recovered at the 2-cell stage, separated into four groups based on morphological stage at two predetermined time points, and cultured to blastocysts. We examined cell number, embryo volume, embryo sex, imprinted Snrpn and H19 methylation, imprinted Snrpn, H19, and Cdkn1c expression, and expression of genes involved in embryo metabolism-Atp1a1, Slc2a1, and Mapk14-all within the same individual embryo. Contrary to our hypothesis, we observed that faster developing embryos exhibited greater cell numbers and embryo volumes as well as greater perturbations in genomic imprinting and metabolic marker expression. Embryos with slower rates of preimplantation development were most similar to in vivo derived embryos, displaying similar cell numbers, embryo volumes, Snrpn and H19 imprinted methylation, H19 imprinted expression, and Atp1a1 and Slc2a1 expression. We conclude that faster development rates in vitro are correlated with loss of genomic imprinting and aberrant metabolic marker expression. Importantly, we identified a subset of in vitro cultured embryos that, according to the parameters evaluated, are very similar to in vivo derived embryos and thus are likely most suitable for embryo transfer.

In vivo oocyte IGF-1 priming increases inner cell mass proliferation of in vitro-formed bovine blastocysts

Studies addressing the effects of supraphysiological levels of IGF-1 on oocyte developmental competence are relevant for unravelling conditions resulting in high bioavailability of IGF-1, such as the polycystic ovary syndrome (PCOS). This study investigated the effects of supraphysiological levels of IGF-1 during in vivo folliculogenesis on the morula-blastocyst transition in bovine embryos. Compacted morulae were non-surgically collected and frozen for subsequent mRNA expression analysis (IGF1R, IGBP3, TP53, AKT1, SLC2A1, SLC2A3, and SLC2A8), or underwent confocal microscopy analysis for protein localization (IGF1R and TP53), or were cultured in vitro for 24 h. In vitro-formed blastocysts were subjected to differential cell staining. The mRNA expression of SLC2A8 was higher in morulae collected from cows treated with IGF-1. Both IGF1R and TP53 protein were present in the plasma membrane and cytoplasm. IGF-1 treatment did not affect protein localization of both IGF1R and TP53. In vitro-formed blastocysts derived from morulae recovered from IGF-1-treated cows displayed a higher number of cells in the inner cell mass (ICM). Total cell number (TCN) of in vitro-formed blastocysts was not affected. A higher mean ICM/TCN proportion was observed in in vitro-formed blastocysts derived from morulae collected from cows treated with IGF-1. The percentage of in vitro-formed blastocysts displaying a low ICM/TCN proportion was decreased by IGF-1 treatment. In vitro-formed blastocysts with a high ICM/TCN proportion were only detected in IGF-1 treated cows. Results show that even a short in vivo exposure of oocytes to a supraphysiological IGF-1 microenvironment can increase ICM cell proliferation in vitro during the morula to blastocyst transition.

Acute fasting decreases the expression of GLUT1 and glucose utilisation involved in mouse oocyte maturation and cumulus cell expansion

Acute fasting impairs meiotic resumption and glucose consumption in mouse cumulus cell and oocyte complexes (COCs). This study examines the effects of acute fasting on the regulation of glucose transporter 1 (GLUT1) expression and glucose consumption in oocyte maturation. Our results indicate that the restriction of glucose utilisation by 2-deoxyglucose (2-DG) mimicked the inhibitory effects of acute fasting on oocyte meiotic resumption and cumulus cell expansion, effects that were rescued by high glucose concentrations in the culture medium. GLUT1 protein levels were higher in cumulus cells compared with oocytes, and GLUT1 expression in COCs increased with FSH treatment in vitro. However, under acute fasting conditions, GLUT1 expression in COCs decreased and the response to FSH disappeared. Exposure to high glucose conditions (27.5 mM and 55 mM), significantly increased both glucose consumption and GLUT1 levels in COCs. Inhibition of GLUT1 function using an anti-GLUT1 antibody significantly inhibited FSH-induced oocyte meiotic resumption. Taken together, these results suggest that acute fasting decreases GLUT1 expression and glucose utilisation, inhibiting the processes of oocyte maturation and cumulus cell expansion.

Adiponectin and its receptors in preimplantation embryo development

Adiponectin can play an important role in regulating the female reproductive function and embryo development and can affect the embryo at very early stages of pregnancy--during the preimplantation period. Disturbances in the maternal adiponectin system are associated with several diseases, including diabetes type 2, obesity, and some female reproductive disorders. Adiponectin receptors are expressed in oocytes and preimplantation embryos and can be activated by adiponectin produced by maternal adipose tissue or organs of the female reproductive tract. Adiponectin can affect proliferation and survival of cells in preimplantation embryos, and these effects are isoform dependent. Experimental results suggest involvement of various protein kinases, including mitogen-activated protein kinases, in the regulation of these processes by adiponectin. Actions of adiponectin on lipid and glucose metabolism can increase the energy supply to the embryo, and final targets of adiponectin signaling are metabolic enzymes, glucose transporters, and fatty acid transporters. The involvement of several signaling molecules, such as AMPK/PRKA, PI3K, or AKT/PKB, in the regulation of metabolic processes by adiponectin has been demonstrated in preimplantation embryos. In summary, adiponectin produced in an endocrine/paracrine/autocrine manner can significantly influence preimplantation embryo development, uterine receptivity, and embryo implantation.

The ability to achieve meiotic maturation in the dog oocyte is linked to glycolysis and glutamine oxidation

We tested the hypothesis that meiotic competence of dog oocytes is tightly linked with donor follicle size and energy metabolism. Oocytes were recovered from small (<1 mm diameter, n = 327), medium (1-<2 mm, n = 292) or large (≥2 mm, n = 102) follicles, cultured for 0, 24, or 48 hr, and then assessed for glycolysis, glucose oxidation, pyruvate uptake, glutamine oxidation, and nuclear status. More oocytes (P < 0.05) from large follicles (37%) reached the metaphase-II (MII) stage than from the small group (11%), with the medium-sized class being intermediate (18%; P > 0.05). Glycolytic rate increased (P < 0.05) as oocytes progressed from the germinal vesicle (GV) to MII stage. After 48 hr of culture, oocytes completing nuclear maturation had higher (P < 0.05) glycolytic rates than those arrested at earlier stages. GV oocytes recovered from large follicle oocytes had higher (P < 0.05) metabolism than those from smaller counterparts at culture onset. MII oocytes from large follicles oxidized more (P < 0.05) glutamine than the same stage gametes recovered from smaller counterparts. In summary, larger-sized dog follicles contain a more metabolically active oocyte with a greater chance of achieving nuclear maturation in vitro. These findings demonstrate a significant role for energy metabolism in promoting dog oocyte maturation, information that will be useful for improving culture systems for rescuing intraovarian genetic material.

Post-hatching development of bovine embryos in vitro: the effects of tunnel preparation and gender

The objective of this study was to compare morphological characteristics, kinetics of development, and gene expression of male and female IVP embryos that were cultured until day (D)15 (fertilization = D0), using either phosphate-buffered saline (PBS) or Milli-Q water (MQW) to dilute the agarose gel used for tunnel construction. On D11, embryos (n = 286) were placed in agarose gel tunnels diluted in PBS and MQW. Embryos were evaluated for morphology, and embryo size was recorded on D11, D12.5, D14 and D15. Then, embryos were sexed and used for gene expression analyses (G6PD, GLUT1, GLUT3, PGK1, PLAC8, KRT8, HSF1 and IFNT). The percentage of elongated embryos at D15 was higher (p < 0.05) in the PBS (54%) than in the MQW (42%) gel. However, embryos produced in MQW were bigger (p < 0.05) and had a lower expression of GLUT1 (p = 0.08) than those cultured in PBS. There was a higher proportion of male than female embryos at D15 in both treatments, MQW (65% vs. 35%; p < 0.05) and PBS (67% vs. 33%; p < 0.05); however, embryo size was not significantly different between genders. Moreover, D15 female embryos had greater expression of G6PD (p = 0.05) and KRT8 (p = 0.03) than male embryos. In conclusion, the diluent used for tunnel construction affected embryo development in the post-hatching development (PHD) system, and the use of MQW was the most indicative measure for the evaluation of embryo quality. Male and female embryos cultured from D11 to D15, either in an MQW or PBS agarose gel, demonstrated similar development but different gene expression.

The use of embryonic stem cell derived bioactive material as a new protein supplement for the in vitro culture of bovine embryos

Embryonic stem (ES) cells are expanded versions of the inner cell mass cells that compose the early mammalian blastocyst. Components derived from ES cells may contain various bioactive materials (BM) helpful for early preimplantation embryo growth. In this study, we examined the effect of human ES cell derived BM (hES-BM) on in vitro culture of bovine embryos. When bovine parthenogenetic day 2 embryos were cultured in 10% hES-BM, a significantly higher embryo development rate (44.3%) and increased cell numbers were observed relative to control medium containing 3 mg/ml BSA (19.5%; P<0.01). Among the various concentrations (5, 10 and 15%) and days of treatment (2 or 4 days) tested, 10% hES-BM treatment for 4 days provided the best culture environment to support the growth of bovine embryos in vitro (P<0.05). Little difference was observed between 10% hES-BM and 10% FBS treatment in the examined parthenogenetic or in vitro fertilized embryos, although the hES-BM group developed at a slightly better rate. However, the ICM cell numbers were significantly higher in the hES-BM group in irrespective of embryo origin (P<0.05). In addition, the relative levels of pluripotency (Oct4, × 1.8 fold; Nanog. × 3.3 fold), embryogenesis (Stat3, × 2.8 fold; FGF4, × 18.8 fold; E-cad, × 2.0 fold) and growth (Glut5, × 2.6 fold) genes were significantly higher in the 10% hES-BM group than in the 10% FBS group (P<0.05), while the levels of other genes (Bax, Bcl2, MnSOD and Connexin43) were not different. This is the first report examining the positive effects of hES-BM on bovine embryo development in vitro. Based on our results, we conclude that hES-BM can be used as a new protein supplement for bovine preimplantation embryo development.

Prepartum maternal plasma glucose concentrations and placental glucose transporter mRNA expression in cows carrying somatic cell clone fetuses

In this study, the plasma glucose concentrations of cows carrying a somatic cell clone fetus during late pregnancy and placental glucose transporter (GLUT) mRNA levels at parturition were examined. Parturition was induced using dexamethasone, prostaglandin F(2α) and estriol in cows bearing a clone (Clone) or a fetus fertilized in vivo as a control (DEX). Plasma glucose concentrations were measured in the cows (days 257 and 271 of pregnancy and at parturition) and newborn calves. Cotyledon and caruncle tissues removed just after parturition were used for mRNA extraction. Expression of mRNA was also analyzed in control cows that were induced to undergo parturition without dexamethasone (PG) or that spontaneously delivered (SP). The glucose concentrations of the Clone group were significantly low at all points examined, but those of the calves were normal. The increase in the maternal glucose concentration from day 257 to parturition was significantly lower in the Clone group. Glucose concentrations were negatively correlated with birth weight for clones (day 257; r=-0.584, day 271; r=-0.286, parturition; r=-0.549). There was no difference in mRNA levels in the cotyledons among the animals examined. In the caruncles, the Clone and PG groups showed significantly higher GLUT1 and GLUT3 mRNA levels than the SP group, and the GLUT3 mRNA level was significantly higher in the Clone group than in the DEX group. The glucocorticoid receptor α mRNA level was significantly lower in the SP group than in the DEX group. Although spontaneous parturition and administration of dexamethasone suppressed the placental GLUT mRNA levels, the action was not observed in clone pregnancy. These results raise the possibility of facilitation of glucose transportation through the placenta to meet increased nutritional requirements of overgrown clone fetuses.

Developmental competence and mRNA expression of preimplantation in vitro-produced embryos from prepubertal and postpubertal cattle and their relationship with apoptosis after intraovarian administration of IGF-1

Recombinant human Insulin-like growth factor-I (hIGF-1) was administered to one ovary of prepubertal and postpubertal cattle to determine its effects on (1) oocyte developmental competence, (2) the expression pattern of six developmentally important genes (GLUT3, GLUT8, AKT1, BCL-XL, BAD, and BAX), and (3) its relationship with apoptosis (female Holstein-Friesian). Oocytes were retrieved from 7- to 10-mo-old prepubertal dairy calves (preP), 11- to 18-mo-old postpubertal heifers (postP), and cows via ultrasound-guided follicular aspiration. Immature oocytes were matured in vitro then fertilized and cultured up to the blastocyst stage. Apoptosis was determined by terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) in 8-d blastocysts. Similar low blastocyst yields were observed in the IGF-1-treated preP group (11.2+/-2.4%), the control preP group (10.4+/-3.0%), and in the IGF-1 postP group (10.9+/-2.3%). These were lower (P<or=0.01) compared with the control postP group (21.2+/-3.8%) and with cows (23+/-3.7%). The expression profile of the six genes was partly affected by age and IGF-1 treatment. Apoptosis was correlated with the age of the oocyte donors and was increased in blastocysts derived from prepubertal heifers. Results show that apoptosis is a critical feature of the acquisition of developmental competence of oocytes from prepubertal cattle and that IGF-1 did not beneficially affect oocyte developmental competence.

The pivotal role of glucose metabolism in determining oocyte developmental competence

The environment that the cumulus oocyte complex (COC) is exposed to during either in vivo or in vitro maturation (IVM) can have profound effects on the success of fertilisation and subsequent embryo development. Glucose is a pivotal metabolite for the COC and is metabolised by glycolysis, the pentose phosphate pathway (PPP), the hexosamine biosynthesis pathway (HBP) and the polyol pathway. Over the course of oocyte maturation, a large proportion of total glucose is metabolised via the glycolytic pathway to provide substrates such as pyruvate for energy production. Glucose is also the substrate for many cellular functions during oocyte maturation, including regulation of nuclear maturation and redox state via the PPP and for the synthesis of substrates of extracellular matrices (cumulus expansion) and O-linked glycosylation (cell signalling) via the HBP. However, the oocyte is susceptible to glucose concentration-dependent perturbations in nuclear and cytoplasmic maturation, leading to poor embryonic development post-fertilisation. For example, glucose concentrations either too high or too low result in precocious resumption of nuclear maturation. This review will discuss the relevant pathways of glucose metabolism by COCs during in vivo maturation and IVM, including the relative contribution of the somatic and gamete compartments of the COC to glucose metabolism. The consequences of exposing COCs to abnormal glucose concentrations will also be examined, either during IVM or by altered maternal environments, such as during hyperglycaemia induced by diabetes and obesity.

Mechanisms contributing to the reduced developmental competence of glucosamine-exposed mouse oocytes

Glucosamine (GlcN) is a widely used hyperglycaemia mimetic because of its ability to upregulate the ‘energy-sensing’ hexosamine biosynthesis pathway in a dose-dependent manner. A previous study demonstrated that addition of GlcN (2.5–5 mM) during IVM of cattle and pig cumulus–oocyte complexes (COC) inhibited development following fertilisation and early cleavage. In the present study, we demonstrate that the addition of 2.5 mM GlcN during IVM of mouse COCs similarly inhibits embryo development, with the degree of inhibition dependent upon the availability of glucose in the maturation medium. Furthermore, we determined that the effect of GlcN is likely mediated by the cumulus cell vestment, because we failed to observe inhibitory effects of GlcN following maturation of denuded (and therefore already developmentally compromised) oocytes. As with cattle oocytes, inhibition of O-linked glycosylation of unknown proteins within mouse cumulus cells significantly reversed the effects of GlcN. Finally, we also provide preliminary evidence that GlcN may inhibit the pentose phosphate metabolic pathway within the oocyte, an effect possibly mediated by cumulus cells in intact COCs. Collectively, our results demonstrate that GlcN inhibits the developmental competence of IVM mouse oocytes and suggest that this occurs via cumulus cell-mediated mechanisms. Therefore, the in vitro addition of GlcN is a useful experimental tool to determine the mechanisms of hyperglycaemic responses within COCs.

Gene expression in early expanded parthenogenetic and in vitro fertilized bovine blastocysts

Mammalian oocytes can undergo artificial parthenogenesis in vitro and develop to the blastocyst stage. In this study, using real-time PCR, we analyzed the expression of genes representative of essential events in development. In vitro matured oocytes were either fertilized or activated with ionomycin + 6-DMAP and cultured in simple medium. The pluripotency-related gene Oct3/4 was downregulated in parthenotes, while the de novo methylation DNMT3A gene was unchanged. Among the pregnancy recognition genes, IFN-t was upregulated, PGRMC1 was downregulated and PLAC8 was unchanged in parthenotes. Among the metabolism genes, SLC2A1 was downregulated, while AKR1B1, COX2, H6PD and TXN were upregulated in parthenotes; there was no difference in SLC2A5. Among the genes involved in compaction/blastulation, GJA1 expression increased in parthenotes, but no differences were detected within ATP1A1 and CDH1. Expression of p66(shc) and the Bax/Bcl2 ratio were higher in parthenotes, and there was no difference in p53. Parthenotes and embryos may differ in the way they stimulate apoptosis, with a preponderant role for p66(shc) within parthenotes. Differentially affected functions may also include pluripotency, de novo methylation and early embryonic signalling.

Expression of glucose transporter isoforms and the insulin receptor during hamster preimplantation embryo development

During preimplantation development, embryos of many species are known to express up to five isoforms of the facilitative glucose transporter proteins (GLUT). Development of hamster blastocysts is inhibited by glucose. We therefore investigated GLUT isoform and insulin receptor (IR) expression in hamster preimplantation embryos cultured in glucose-free medium from the 8-cell stage onwards. We show that GLUT1, 3 and 8 mRNA are constitutively expressed from the 8-cell to the blastocyst stage. The IR is expressed from the morula stage onwards. Messenger RNA of the insulin-responsive GLUT4 was not detected at any stage. GLUT1 and 3 were localised by immunocytochemistry. GLUT1 was expressed in both embryoblast and trophoblast, in the latter, mainly in basal and lateral membranes directed towards the blastocoel and embryoblast. GLUT3 was exclusively localised in the apical membrane of trophoblast cells. We show that hamster preimplantation embryos express several GLUT isoforms thus closely resembling embryos of other mammalian species. Despite endogenous IR expression, the insulin-sensitive isoform GLUT4 was not expressed, indicating that the insulin-mediated glucose uptake known from classical insulin target cells may not be relevant for hamster blastocysts.

The beneficial effect of fructose and glucose on in vitro maturation and the fertilization of porcine oocytes

Purpose

This study was conducted to investigate the effects of supplementing fructose in the culture medium on in vitro maturation (IVM), in vitro fertilization (IVF), and metabolism of porcine oocytes.

Methods

Porcine oocytes were matured in vitro in modified North Carolina State University 37 medium (NCSU-37) and then supplemented with either glucose (5.5 mM), fructose (5.5 mM), or glucose (2.75 mM) plus fructose (2.75 mM). The maturation and fertilization of oocytes, and the incorporation and oxidation of ¹⁴C-glucose, ¹⁴C-fructose, and ¹⁴C-methionine in oocytes at different stages of development were examined.

Results

The supplementation of glucose plus fructose significantly promoted (P < 0.05) oocytes germinal vesicle break down (GVBD), maturation to metaphase II (MII), penetration by spermatozoa, and male pronuclear formation compared with glucose. The incorporation and oxidation of ¹⁴C-methionine into the oocyte significantly increased (P < 0.05) with glucose plus fructose supplementation than glucose. A significantly higher (P < 0.05) rate of incorporation and oxidation was achieved with ¹⁴C-fructose compared to ¹⁴C-glucose.

Conclusions

Glucose plus fructose supplementation improved maturation, penetration by spermatozoa, male pronuclear formation, and energy metabolism by porcine oocytes.

Biological differences between in vitro produced bovine embryos and parthenotes

Parthenotes may represent an alternate ethical source of stem cells, once biological differences between parthenotes and embryos can be understood. In this study, we analyzed development, trophectoderm (TE) differentiation, apoptosis/necrosis, and ploidy in parthenotes and in vitro produced bovine embryos. Subsequently, using real-time PCR, we analyzed the expression of genes expected to underlie the observed differences at the blastocyst stage. In vitro matured oocytes were either fertilized or activated with ionomycin +6-DMAP and cultured in simple medium. Parthenotes showed enhanced blastocyst development and diploidy and reduced TE cell counts. Apoptotic and necrotic indexes did not vary, but parthenotes evidenced a higher relative proportion of apoptotic cells between inner cell mass and TE. The pluripotence-related POU5F1 and the methylation DNMT3A genes were downregulated in parthenotes. Among pregnancy recognition genes, TP-1 was upregulated in parthenotes, while PGRMC1 and PLAC8 did not change. Expression of p66(shc) and BAX/BCL2 ratio were higher, and p53 lower, in parthenotes. Among metabolism genes, SLC2A1 was downregulated, while AKR1B1, PTGS2, H6PD, and TXN were upregulated in parthenotes, and SLC2A5 did not differ. Among genes involved in compaction/blastulation, GJA1 was downregulated in parthenotes, but no differences were detected within ATP1A1 and CDH1. Within parthenotes, the expression levels of SLC2A1, TP-1, and H6PD, and possibly AKR1B1, resemble patterns described in female embryos. The pro-apoptotic profile is more pronounced in parthenotes than in embryos, which may differ in their way to channel apoptotic stimuli, through p66(shc) and p53 respectively, and in their mechanisms to control pluripotency and de novo methylation.

Effects of pre-mating nutrition on mRNA levels of developmentally relevant genes in sheep oocytes and granulosa cells

The present study was designed to investigate the relationship between pre-mating nutrition and the relative amounts of a panel of developmentally relevant genes in ovine oocytes and granulosa cells. Cast age ewes were fed a ration providing 0.5x (0.5 M) or 1.5x (1.5 M) live weight maintenance requirements for 2 weeks before slaughter. The ewes were synchronized and superovulated with FSH and pregnant mares serum gonadotropin. At slaughter, oocytes and granulosa cells were aspirated from follicles >2 mm in diameter and the relative abundance of 8 and 17 transcripts in oocytes and granulosa cells respectively were analyzed by semi-quantitative RT-PCR. In the oocytes, no differences between groups were observed for five transcripts (GDF9, BMP15, c-kit, glucose transporter 1 (SLC2A1), and hexokinase 1), but a lower amount of glucose transporter 3 (SLC2A3), sodium/glucose cotransporter 1 (SLC5A1), and Na(+)/K(+) ATPase mRNAs was detected in the 0.5 M group. Increased expression of PTGS2, HAS2, and the leptin receptor long form was observed in granulosa cells from the 0.5 M group. No differences between groups were observed for the other transcripts (early growth response factor-1, estrogen receptor-alpha, LH and FSH receptors, gremlin 1, pentraxin 3, KIT ligand, glucose transporters 1, 3, and 8, IGF1, IGF1 receptor, leptin receptor, and tumor necrosis factor-stimulated gene 6). Expression of leptin and sodium/glucose cotransporter 1 was not detected in both groups. The present data indicate that pre-mating nutrition is associated with alteration in the mRNA content in oocytes and surrounding follicle cells in ewes, which may account for the reduced reproductive performance typical of ewes that are fed a restricted ration for a short period of time before mating.

Regulation of blastocyst stage gene expression and outgrowth interferon tau activity of somatic cell clone aggregates

The inefficiency of mammalian somatic cell cloning is associated with abnormal gene expression presumably caused by errors in reprogramming of the transplanted genome. In the mouse, aggregation of four-cell stage clones leads to an improvement of both gene expression and development. To determine whether clone-clone aggregation at postgenomic activation stages influences gene expression in bovine clones, we profiled, in single and aggregated embryos at the blastocyst stage, expression of developmentally relevant genes namely Oct4, Dnmt1, Dnmt3, Glut1, Glut3, and a housekeeping gene, Poly(A) polymerase (PolyA) by real-time RT-PCR. Compared to embryos generated by in vitro fertilization (IVF), individual clones more frequently exhibited transcript levels that were more than twofold higher or lower than the average value of IVF embryos. This was observed less often in clone aggregates for Oct4, Dnmt1, Dnmt3, and PolyA, but not for Glut1 and Glut3. The analysis of interferon tau bioactivity as a marker of trophectoderm function in blastocyst outgrowths showed that both single clones and clone aggregates have less extraembryonic potential in vitro compared to IVF embryos, with no apparent consequence of aggregation. These findings indicate that aggregation of bovine clones with each other at later cleavage stages can change gene expression patterns at preimplantation stages, but does not rescue trophectoderm function in vitro.

Effects of either glucose or fructose and metabolic regulators on bovine embryo development and lipid accumulation in vitro

Our objective was to determine if replacing glucose with fructose would decrease cytoplasmic lipid accumulation during culture of embryos with or without regulators of metabolism. In vitro-produced bovine zygotes were cultured 60 hr in chemically defined medium-1 (CDM-1) plus 0.5% BSA and 0.5 mM fructose or glucose in Experiment 1, and glucose in Experiment 2. In both experiments, 8-cell embryos were next cultured 135 hr in CDM-2 plus 2 mM fructose or glucose in factorial combination with five treatments: (Experiment 1: control, 10% fetal calf serum (FCS), 0.3 microM phenazine ethosulfate (PES), 30 microM dinitrophenol (DNP), and PES + DNP), and (Experiment 2: control, PES, PES + DNP, and 1 and 3 microg/ml cerulenin (C1 and C3)). Day 7.5 blastocysts were stained with Sudan Black B to quantify cytoplasmic lipid droplets as small (SD, <2 microm), medium (MD, 2-6 microm), or large (LD, >6 microm). Blastocyst rates per oocyte were 22% (Experiment 1) and 15% (Experiment 2) higher (P < 0.05) for fructose than glucose. For Experiment 1, numbers of MD were lower for PES, DNP, and PES + DNP than control and FCS (P < 0.05). LD were lower for PES and DNP than control, and higher for FCS than all other treatments (P < 0.05). For Experiment 2, MD were lower (P < 0.05) for PES, and PES + DNP than C1, C3, and control. For LD, PES was lower (P < 0.05) than control, C1, and C3, but not different from PES + DNP. The only effect of hexose on lipids was that fructose resulted in fewer MD (P < 0.01) in Experiment 2. In conclusion, fructose produced more blastocysts than glucose, and PES reduced lipid accumulation.

Supplementation of fructose in chemically defined protein-free medium enhances the in vitro development of bovine transgenic cloned embryos

The present study evaluated the possible embryotrophic role of fructose supplementation in chemically defined protein-free KSOM on in vitro development of bovine transgenic cloned embryos. Bovine fetal fibroblasts transfected with expression plasmids for bovine prion protein (PrP) mutant gene with GFP marker gene were used as donor nuclei for reconstruction of slaughterhouse-derived in vitro matured oocytes. The reconstructed oocytes were cultured in KSOM supplemented with 0.01% PVA (KSOM-PVA) at 39 degrees C in a humidified atmosphere of 5% CO2, 5% O2 and 90% N2 for 192 h. In Experiment 1, when reconstructed oocytes were cultured in KSOM-PVA supplemented with glucose (0.2 mM), fructose (1.5 mM) or combined glucose and fructose (0.2 and 1.5 mM, respectively), significantly (p < 0.05) higher blastocyst (19.2%) and hatching/hatched blastocyst (13.1%) formation rates were obtained in combined fructose and glucose supplemented medium than glucose supplemented counterpart (10.0% and 5.7%, respectively). In Experiment 2, when reconstructed oocytes were cultured in KSOM-PVA supplemented with 0.0, 0.2, 1.5, 3.0 and 5.6 mM fructose in combination with 0.2 mM glucose, the blastocyst formation rate was significantly higher (17.6%) in 1.5 mM fructose supplemented group than that of no fructose supplemented counterpart (9.7%; p > 0.05). In conclusion, supplementation of combined fructose (1.5 mM) and glucose (0.2 mM) in chemically defined protein-free KSOM enhances the in vitro development of bovine transgenic cloned embryos.

Respiration rates correlate with mRNA expression of G6PD and GLUT1 genes in individual bovine in vitro-produced blastocysts

Quantification of embryo respiration is a promising procedure to assess embryonic metabolism and possibly select viable embryos. At the blastocyst stage, ATP is produced by glycolysis and oxidative phosphorylation, processes that require uptake of oxygen and glucose, which is regulated by the expression of GLUT1 and G6PD. The purpose of the present study was to investigate the relationship between respiration rates and relative abundances of G6PD and GLUT1 transcripts in individual bovine blastocysts produced in vitro. Respiration rates of 104 bovine in vitro-produced blastocysts were measured individually using the nanorespirometer technology. Real-time RT-PCR was employed to determine the relative abundance of G6PD and GLUT1 mRNA in individual embryos. The mean respiration rates were similar for male and female blastocysts of the same developmental stage, but the sex ratio was skewed towards males. GLUT1 expression was down-regulated in female versus male embryos. In contrast, a approximately 1.8-fold increase in the expression of G6PD mRNA was observed in female blastocysts when compared to male blastocysts, indicating that dosage compensation for this gene had not yet occurred. Both GLUT1 and G6PD expression levels were affected by morphological quality and stage of development. Expression of GLUT1 and G6PD mRNAs was correlated with respiration rates, indicating that, in metabolically active blastocysts, uptake of oxygen and glucose are jointly increased. These findings suggest that expression of genes for oxidative phosphorylation and glycolysis are both involved in oxygen demanding ATP production.

Conserved molecular portraits of bovine and human blastocysts as a consequence of the transition from maternal to embryonic control of gene expression

The present study investigated mRNA expression profiles of bovine oocytes and blastocysts by using a cross-species hybridization approach employing an array consisting of 15,529 human cDNAs as probe, thus enabling the identification of conserved genes during human and bovine preimplantation development. Our analysis revealed 419 genes that were expressed in both oocytes and blastocysts. The expression of 1,324 genes was detected exclusively in the blastocyst, in contrast to 164 in the oocyte including a significant number of novel genes. Genes indicative for transcriptional and translational control (ELAVL4, TACC3) were overexpressed in the oocyte, whereas cellular trafficking (SLC2A14, SLC1A3), proteasome (PSMA1, PSMB3), cell cycle (BUB3, CCNE1, GSPT1), and protein modification and turnover (TNK1, UBE3A) genes were found to be overexpressed in blastocysts. Transcripts implicated in chromatin remodeling were found in both oocytes (NASP, SMARCA2) and blastocysts (H2AFY, HDAC7A). The trophectodermal markers PSG2 and KRT18 were enriched 5- and 50-fold in the blastocyst. Pathway analysis revealed differential expression of genes involved in 107 distinct signaling and metabolic pathways. For example, phosphatidylinositol signaling and gluconeogenesis were prominent pathways identified in the blastocyst. Expression patterns in bovine and human blastocysts were to a large extent identical. This analysis compared the transcriptomes of bovine oocytes and blastocysts and provides a solid foundation for future studies on the first major differentiation events in blastocysts and identification of a set of markers indicative for regular mammalian development.

Expression pattern of oxygen and stress-responsive gene transcripts at various developmental stages of in vitro and in vivo preimplantation bovine embryos

The present study examined the expression pattern of oxygen (O(2)) and stress-responsive gene transcripts at various preimplantation developmental stages of in vitro produced (IVP) and in vivo derived (IVD) bovine embryos. Embryos were produced in vitro from oocytes matured, fertilized and cultured in synthetic oviductal fluid (SOF) medium under low (5%) and high (20%) O(2) concentrations. In vivo embryos were derived from 18 superovulated and artificially inseminated cows. In IVP and IVD groups, embryos were collected at 2-, 4-, 8-, 16-cell morula and blastocyst stages at specific time points for gene expression analysis. The cleavage rates (69.8+/-4.8%) did not differ significantly, but blastocyst rates were significantly higher (28.5+/-3.7%) in low O(2) than those in high O(2) group (18.7+/-3.9%). Mean cell number in low O(2) (145+/-12) and high O(2) (121+/-73) IVP blastocyst were lower (P<0.05) than those of IVD blastocyst (223+/-25). The ICM ratio of IVD blastocyst (26+/-4) was lower (P<0.05) than that of IVP embryos under 5% O(2) (33+/-5) and 20% O(2) (34+/-4) concentrations, respectively. Using real time PCR, for the set of target transcripts (Glut1, Glut5, Sox, G6PD, MnSOD, PRDX5, NADH and Hsp 70.1) analyzed, there were differences in the mRNA expression pattern at 2-, 4-, 8-, 16-cell morula and Day 7 blastocyst stages between the two embryo sources. It can be concluded that, although in vitro bovine embryo culture in SOF medium under low (5%) O(2) concentration provided a more conducive environment in terms of blastocyst formation; differences in the total cell number and gene expression pattern between the IVP and IVD embryos reflected the effect of O(2) concentration.

Effects of in vitro oocyte maturation and embryo culture on the expression of glucose transporters, glucose metabolism and insulin signaling genes in rhesus monkey oocytes and preimplantation embryos

Glucose plays a fundamental role during oogenesis and embryogenesis, satisfying the metabolic demands of oocytes and embryos, providing for stored energy reserves in the form of glycogen and supporting nucleotide biosynthesis via the pentose phosphate pathway. Glucose also contributes to the production of amino acids, glycosylated proteins and extracellular components. A detailed understanding of the molecular mechanisms that mediate and regulate glucose uptake and metabolism at different stages of oogenesis and preimplantation embryogenesis could greatly benefit the development of improved methods for in vitro oocyte maturation and in vitro embryo production. Although these processes have been examined in a variety of rodent and agricultural species, detailed information has not yet been described for non-human primates. In this study, we examined the expression of the genes encoding glucose transporters, glucose metabolism enzymes and potential regulators of glucose metabolism in rhesus monkey oocytes and embryos. The data reveal stage-specific regulation of expression of specific types of glucose transporters, stage-specific changes in expression of genes related to different pathways of glucose metabolism and temporal changes in the expression of mRNAs related to insulin signaling. Additionally, the data reveal significant differences in expression of some of these genes in cultured embryos as compared with flushed embryos and between oocytes and embryos obtained following different hormonal stimulation and oocyte maturation protocols.