Glutamine and hypotaurine improves intracellular oxidative status and in vitro development of porcine preimplantation embryos

Dihydromyricetin supplementation during in vitro culture improves porcine oocyte developmental competence by regulating oxidative stress

Dihydromyricetin (DHM), a dihydroflavonoid compound, exhibits a variety of biological activities, including antitumor activity. However, the effects of DHM on mammalian reproductive processes, especially during early embryonic development, remain unclear. In this study, we added DHM to porcine zygotic medium to explore the influence and underlying mechanisms of DHM on the developmental competence of parthenogenetically activated porcine embryos. Supplementation with 5 μM DHM during in vitro culture (IVC) significantly improved blastocyst formation rate and increased the total number of cells in porcine embryos. Further, DHM supplementation also improved glutathione levels and mitochondrial membrane potential; reduced natural reactive oxygen species levels in blastomeres and apoptosis rate; upregulated Nanog, Oct4, SOD1, SOD2, Sirt1, and Bcl2 expression; and downregulated Beclin1, ATG12, and Bax expression. Collectively, DHM supplementation regulated oxidative stress during IVC and could act as a potential antioxidant during in vitro porcine oocytes maturation.

Effects of alpha lipoic acid treatment during in vitro maturation on the development of porcine somatic cell nuclear transfer embryos

Oxidative stress influences the embryo production efficiency in vitro. We investigated the effects of alpha lipoic acid (ALA) treatment during the in vitro maturation (IVM) period on the porcine somatic cell nuclear transfer (SCNT) embryo production. After IVM, maturation rates of the 12.5- and 25-μM ALA-treated groups were not significantly different from those of the 0-μM ALA-treated group. Compared to those in the 0-μM ALA-treated group, the reactive oxygen species and glutathione levels were significantly decreased and increased, respectively, in the cytoplasm of matured oocytes in the 12.5-50-μM ALA-treated groups. Apoptosis rate in cumulus cells after IVM was significantly lower in the 12.5-50-μM ALA-treated groups than in the 0-μM ALA-treated group. Blastocyst formation rate was significantly higher in parthenogenetic oocytes treated with 12.5-μM ALA than in the 0-, 25-, and 50-μM ALA-treated groups. Similarly, in SCNT embryos, the 12.5-μM ALA-treated group showed a significantly higher blastocyst formation rate than the 0-μM ALA-treated group. Apoptosis rate in SCNT blastocysts was significantly decreased by 12.5-μM ALA treatment. The results showed that treatment with 12.5-μM ALA during IVM improves porcine SCNT embryo development and partial quality.

The effects of temperature variation treatments on embryonic development: a mouse study

Since the development of ART, embryos have been cultured at 37 °C in an attempt to mimic the in vivo conditions and the average body temperature of an adult. However, a gradient of temperatures within the reproductive tract has been demonstrated in humans and several other mammalian species. Therefore, the aim of this study was to evaluate the effects of temperature variation treatments on mouse embryo quality through morphokinetic events, blastocyst morphology, the relative gene expression of Igf2, Bax, Bcl2 and Apaf1 and the metabolomics of individual culture media. Study groups consisted of 2 circadian treatments, T1 with embryos being cultured at 37 °C during the day and 35.5 °C during the night, T2 with 38.5 °C during the day and 37 °C during the night and a control group with constant 37 °C. Our main findings are that the lower-temperature group (T1) showed a consistent negative effect on mouse embryo development with “slow” cleaving embryos, poor-quality blastocysts, a higher expression of the apoptotic gene Apaf1, and a significantly different set of amino acids representing a more stressed metabolism. On the other hand, our higher-temperature group (T2) showed similar results to the control group, with no adverse effects on blastocyst viability.

Disrupting porcine glutaminase does not block preimplantation development and elongation nor decrease mTORC1 activation in conceptuses†

Elongation of pig conceptuses is a dynamic process, requiring adequate nutrient provisions. Glutamine is used as an energy substrate and is involved in the activation of mechanistic target of rapamycin complex 1 (mTORC1) during porcine preimplantation development. However, the roles of glutamine have not been extensively studied past the blastocyst stage. Therefore, the objective of the current study was to determine if glutaminase (GLS), which is the rate-limiting enzyme in glutamine metabolism, was necessary for conceptus elongation to proceed and was involved in mTORC1 activation. The CRISPR/Cas9 system was used to induce loss-of-function mutations in the GLS gene of porcine fetal fibroblasts. Wild type (GLS+/+) and knockout (GLS-/-) fibroblasts were used as donor cells for somatic cell nuclear transfer, and GLS+/+ and GLS-/- blastocyst-stage embryos were transferred into surrogates. On day 14 of gestation, GLS+/+ conceptuses primarily demonstrated filamentous morphologies, and GLS-/- conceptuses exhibited spherical, ovoid, tubular, and filamentous morphologies. Thus, GLS-/- embryos were able to elongate despite the absence of GLS protein and minimal enzyme activity. Furthermore, spherical GLS-/- conceptuses had increased abundance of transcripts related to glutamine and glutamate metabolism and transport compared to filamentous conceptuses of either genotype. Differences in phosphorylation of mTORC1 components and targets were not detected regarding conceptus genotype or morphology, but abundance of two transcriptional targets of mTORC1, cyclin D1, and peroxisome proliferator-activated receptor gamma coactivator 1-alpha was increased in spherical conceptuses. Therefore, porcine GLS is not essential for conceptus elongation and is not required for mTORC1 activation at this developmental timepoint.

Metabolomic fingerprinting of pig seminal plasma identifies in vivo fertility biomarkers

Background

Metabolomic approaches, which include the study of low molecular weight molecules, are an emerging -omics technology useful for identification of biomarkers. In this field, nuclear magnetic resonance (NMR) spectroscopy has already been used to uncover (in) fertility biomarkers in the seminal plasma (SP) of several mammalian species. However, NMR studies profiling the porcine SP metabolome to uncover in vivo fertility biomarkers are yet to be carried out. Thus, this study aimed to evaluate the putative relationship between SP-metabolites and in vivo fertility outcomes. To this end, 24 entire ejaculates (three ejaculates per boar) were collected from artificial insemination (AI)-boars throughout a year (one ejaculate every 4 months). Immediately after collection, ejaculates were centrifuged to obtain SP-samples, which were stored for subsequent metabolomic analysis by NMR spectroscopy. Fertility outcomes from 1525 inseminations were recorded over a year, including farrowing rate, litter size, stillbirths per litter and the duration of pregnancy.

Results

A total of 24 metabolites were identified and quantified in all SP-samples. Receiver operating characteristic (ROC) curve analysis showed that lactate levels in SP had discriminative capacity for farrowing rate (area under the curve [AUC] = 0.764) while carnitine (AUC = 0.847), hypotaurine (AUC = 0.819), sn-glycero-3-phosphocholine (AUC = 0.833), glutamate (AUC = 0.799) and glucose (AUC = 0.750) showed it for litter size. Similarly, citrate (AUC = 0.743), creatine (AUC = 0.812), phenylalanine (AUC = 0.750), tyrosine (AUC = 0.753) and malonate (AUC = 0.868) levels had discriminative capacity for stillbirths per litter; and malonate (AUC = 0.767) and fumarate (AUC = 0.868) levels for gestation length.

Conclusions

The assessment of selected SP-metabolites in ejaculates through NMR spectroscopy could be considered as a promising non-invasive tool to predict in vivo fertility outcomes in pigs. Moreover, supplementing AI-doses with specific metabolites should also be envisaged as a way to improve their fertility potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00636-5.

Redox Regulation and Oxidative Stress in Mammalian Oocytes and Embryos Developed In Vivo and In Vitro

Oocytes and preimplantation embryos require careful regulation of the redox environment for optimal development both in vivo and in vitro. Reactive oxygen species (ROS) are generated throughout development as a result of cellular metabolism and enzyme reactions. ROS production can result in (i) oxidative eustress, where ROS are helpful signalling molecules with beneficial physiological functions and where the redox state of the cell is maintained within homeostatic range by a closely coupled system of antioxidants and antioxidant enzymes, or (ii) oxidative distress, where excess ROS are deleterious and impair normal cellular function. in vitro culture of embryos exacerbates ROS production due to a range of issues including culture-medium composition and laboratory culture conditions. This increase in ROS can be detrimental not only to assisted reproductive success rates but can also result in epigenetic and genetic changes in the embryo, resulting in transgenerational effects. This review examines the effects of oxidative stress in the oocyte and preimplantation embryo in both the in vivo and in vitro environment, identifies mechanisms responsible for oxidative stress in the oocyte/embryo in culture and approaches to reduce these problems, and briefly examines the potential impacts on future generations.

Glutaminolysis is involved in the activation of mTORC1 in in vitro-produced porcine embryos

Glutamine supplementation to porcine embryo culture medium improves development, increases leucine consumption, and enhances mitochondrial activity. In cancer cells, glutamine has been implicated in the activation of mechanistic target of rapamycin complex 1 (mTORC1) to support rapid proliferation. The objective of this study was to determine if glutamine metabolism, known as glutaminolysis, was involved in mTORC1 activation in porcine embryos. Culture with 3.75 mM GlutaMAX improved development to the blastocyst stage compared to culture with 1 mM GlutaMAX, and culture with 0 mM GlutaMAX decreased development compared to all groups with GlutaMAX. Ratios of phosphorylated to total MTOR were increased when embryos were cultured with 3.75 or 10 mM GlutaMAX, which was enhanced by the absence of leucine, but ratios for RPS6K were unchanged. As another indicator of mTORC1 activation, colocalization of MTOR and a lysosomal marker was increased in embryos cultured with 3.75 or 10 mM GlutaMAX in the absence of leucine. Culturing embryos with glutaminase inhibitors decreased development and the ratio of phosphorylated to total MTOR, indicating reduced activation of the complex. Therefore, glutaminolysis is involved in the activation of mTORC1 in porcine embryos, but further studies are needed to characterize downstream effects on development.

Iron Overload-Induced Ferroptosis Impairs Porcine Oocyte Maturation and Subsequent Embryonic Developmental Competence in vitro

Accumulating evidence indicates that ferroptosis is an iron-dependent form of regulated cell death. This type of iron-dependent programmed cell death is different from traditional forms of regulated cell death, such as apoptosis and autophagy. However, the role of ferroptosis in porcine oocyte maturation and the associated mechanism remain unclear. In the present research, we investigated the effects of ferric ammonium citrate (FAC), a specific ferroptosis inducer, on porcine oocyte meiotic maturation and quality and subsequent embryonic developmental competence. FAC treatment caused obvious accumulation of intracellular ferrous ions in porcine oocytes. At the end of the in vitro maturation (IVM) period, there was a significant decrease in the polar body (PB) extrusion rate and an increase in the percentage of abnormal oocytes in the FAC treatment groups, indicating that iron overload-induced ferroptosis may suppress the meiotic process during porcine oocyte maturation. We also found that after FAC treatment, the subsequent two-cell rate, four-cell rate and blastocyst formation rate were significantly decreased in porcine parthenogenetic activation (PA) embryos, indicating that iron overload-induced ferroptosis decreased porcine oocyte quality. Further analysis revealed that FAC treatment not only enhanced intracellular reactive oxygen species (ROS) generation, decreased intracellular free thiol levels and induced mitochondrial dysfunction but also triggered autophagy in porcine oocytes. Taken together, these findings suggest that iron overload-induced ferroptosis impairs porcine oocyte meiosis and decreases porcine oocyte quality, possibly by increasing oxidative stress, inducing mitochondrial dysfunction and triggering autophagy.

Removal of hypotaurine from porcine embryo culture medium does not impair development of in vitro-fertilized or somatic cell nuclear transfer-derived embryos at low oxygen tension

Hypotaurine (HT) is a routine component of porcine embryo culture medium, functioning as an antioxidant, but its requirement may be diminished as most embryo culture systems now use 5% O2 instead of atmospheric (20%) O2 . Our objective was to determine the effects of removing HT from the culture medium on porcine preimplantation embryo development. Embryos cultured in 20% O2 without HT had decreased blastocyst development compared to culture with HT or in 5% O2 with or without HT. Notably, differences in blastocyst development or total cell number were not detected between embryos cultured in 5% O2 with or without HT. After culture in 5% O2 without HT and embryo transfer, healthy fetuses were retrieved from two pregnancies on Day 42, confirming in vivo developmental competence. Transcript abundance of proapoptotic markers was decreased in embryos cultured without HT regardless of oxygen tension; however, assays for apoptosis did not demonstrate differences between groups. Additionally, no differences were observed in the development or apoptosis of somatic cell nuclear transfer-derived embryos cultured in 5% O2 with or without HT. With decreased utility in 5% O2 , removing HT from porcine embryo culture medium would also have economic advantages because it is undoubtedly the most expensive component.

Applications of omics and nanotechnology to improve pig embryo production in vitro

An appropriate environment to optimize porcine preimplantation embryo production in vitro is required as genetically modified pigs have become indispensable for biomedical research and agriculture. To provide suitable culture conditions, omics technologies have been applied to elucidate which metabolic substrates and pathways are involved during early developmental processes. Metabolomic profiling and transcriptional analysis comparing in vivo- and in vitro-derived embryos have demonstrated the important role of amino acids during preimplantation development. Transcriptional profiling studies have been helpful in assessing epigenetic reprogramming agents to allow for the correction of gene expression during the cloning process. Along with this, nanotechnology, which is a highly promising field, has allowed for the use of engineered nanoplatforms in reproductive biology. A growing number of studies have explored the use of nanoengineered materials for sorting, labeling, and targeting purposes; which demonstrates their potential to become one of the solutions for precise delivery of molecules into gametes and embryos. Considering the contributions of omics and the recent progress in nanoscience, in this review, we focused on their emerging applications for current in vitro pig embryo production systems to optimize the generation of genetically modified animals.

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

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

Effect of PPARGC1A on the development and metabolism of early rabbit embryos in vitro

Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) is a central regulator of mitochondrial biogenesis and metabolism, and its expression is closely related to embryo development. To gain insights into the possible mechanisms of PPARGC1A during early embryogenesis, the development potential, mitochondrial biogenesis, and the culture medium metabolomics of embryos were evaluated when PPARGC1A overexpressed or suppressed in rabbit zygotes. Results showed that different PPARGC1A levels in rabbit zygotes could affect blastocyst percentage, and the expressions of mitochondrial biogenesis and metabolic-related genes, as well as the glutathione and adenosine triphosphate levels during early embryo development. In addition, compared with the controls, 12 and 10 different metabolites involved in carbohydrate, amino acid, and fatty acid metabolism were screened in the 5 day's spent culture medium of PPARGC1A overexpressed and suppressed embryos by gas chromatography-mass spectrometer, respectively. Consistent with these metabolite changes, the transcriptions of genes encoding glucose transporters and fatty acid biosynthetic proteins in the embryos from different groups were regulated by PPARGC1A during rabbit embryo development. Taken together, these data provide evidence that PPARGC1A may regulate early rabbit embryo development through mitochondrial biogenesis and metabolism.

Optimization of parthenogenetic activation of rabbit oocytes and development of rabbit embryo by somatic cell nuclear transfer

The present study explored a suitable parthenogenetic activation (PA) procedure for rabbit oocytes and investigated the developmental potential of somatic cell nuclear transfer (SCNT) embryos using rabbit foetal fibroblasts (RFFs). The electrical activation had the optimal rate of blastocyst (14.06%) when oocytes were activated by three direct current (DC) pulses (40 V/mm, 20 μs each) followed by 6-dimethylaminopurine (6-DMAP) and cycloheximide (CHX) treatment; the blastocyst rate of ionomycin (ION) + 6-DMAP + CHX (12.07%) activation was higher than that of ION + 6-DMAP (8.6%) activation or ION + CHX (1.24%) activation; there was no significant difference in blastocyst rate between ION + 6-DMAP + CHX and DC + 6-DMAP + CHX groups. The blastocyst rate of ION + 6-DMAP + CHX-activated oocytes in the basic rabbit culture medium (M-199) + 10% foetal bovine serum (FBS; 14.28%) was higher than that in buffalo conditioned medium (5.75%) or G1/G2 medium (0), and the blastocyst rate was increased when M-199 + 10% FBS was supplemented with amino acids. Refreshing culture medium every day or every other day significantly increased the blastocyst rate. Treatment of donor cells with 0.5% FBS for 3-5 days increased blastocyst rate of SCNT embryos (33.33%) than no serum starvation (22.47%) or 0.5% FBS treatment for 6-9 days (23.61%); the blastocyst rate of SCNT embryos derived from nontransgenic RFFs was higher than that derived from transgenic RFFs by electroporation. The blastocyst development ability of SCNT embryos derived from RFFs by electroporation (32.22%) was higher than that of liposome (19.11%) or calcium phosphate (20.00%) transfection, and only the embryos from electroporation group have the EGFP expression (24.44%). In conclusion, this study for the first time systematically optimized the conditions for yield of rabbit embryo by SCNT.

Dual effect of fetal bovine serum on early development depends on stage-specific reactive oxygen species demands in pigs

Despite the application of numerous supplements to improve in vitro culture (IVC) conditions of mammalian cells, studies regarding the effect of fetal bovine serum (FBS) on mammalian early embryogenesis, particularly in relation to redox homeostasis, are lacking. Herein, we demonstrated that early development of in vitro-produced (IVP) porcine embryos highly depends on the combination of FBS supplementation timing and embryonic reactive oxygen species (ROS) requirements. Interestingly, FBS significantly reduced intracellular ROS levels in parthenogenetically activated (PA) embryos regardless of the developmental stage. However, the beneficial effect of FBS on early embryogenesis was found only during the late phase (IVC 4-6 days) treatment group. In particular, developmental competence parameters, such as blastocyst formation rate, cellular survival, total cell number and trophectoderm proportion, were markedly increased by FBS supplementation during the late IVC phase. In addition, treatment with FBS elevated antioxidant transcript levels during the late IVC phase. In contrast, supplementation with FBS during the entire period (1-6 days) or during the early IVC phase (1-2 days) greatly impaired the developmental parameters. Consistent with the results from PA embryos, the developmental competence of in vitro fertilization (IVF) or somatic cell nuclear transfer (SCNT) embryos were markedly improved by treatment with FBS during the late IVC phase. Moreover, the embryonic stage-specific effects of FBS were reversed by the addition of an oxidant and were mimicked by treatment with an antioxidant. These findings may increase our understanding of redox-dependent early embryogenesis and contribute to the large-scale production of high-quality IVP embryos.

Antioxidant supplementation during in vitro culture improves mitochondrial function and development of embryos from aged female mice

Maternal aging results in reduced oocyte and blastocyst quality, thought to be due, in part, to mitochondrial dysfunction and accumulation of reactive oxygen species. To reduce oxidative stress, the antioxidants α-lipoic acid (ALA; 10µM), α-tocopherol (250µM), hypotaurine (1mM) and N-acetylcysteine (NAC; 1mM), and sirtuin (100ngmL(-1)) were added to embryo culture medium (AntiOX) and compared with a control (CON) without antioxidants to assess blastocyst development after in vitro maturation and fertilisation of oocytes from aged B6D2F1 female mice (13.5 months). Development to the blastocyst stage increased in the AntiOX compared with CON group (87.6% vs 72.7%, respectively; P<0.01), in addition to higher mitochondrial membrane potential and ATP levels in the AntiOX group. Expression of genes associated with oxidative stress (PI3K, FOXO3A and GLRX2) was upregulated in the CON compared with AntiOX group. In addition to AntiOX, a medium containing only NAC and ALA (rAntiOX) was used to culture embryos from young CF1 females (6-8 weeks). More blastocysts developed in the rAntiOX compared with CON group (64.1% vs 43.3%, respectively; P<0.01), although AntiOX (48.0% blastocysts) did not result in improved development in young mice. Antioxidants improved mitochondrial activity, gene expression and development in embryos of older female mice, whereas a reduced level of antioxidants during culture was beneficial to embryos from young mice.

Protective effect of quercetin on the development of preimplantation mouse embryos against hydrogen peroxide-induced oxidative injury

Quercetin, a plant-derived flavonoid in Chinese herbs, fruits and wine, displays antioxidant properties in many pathological processes associated with oxidative stress. However, the effect of quercetin on the development of preimplantation embryos under oxidative stress is unclear. The present study sought to determine the protective effect and underlying mechanism of action of quercetin against hydrogen peroxide (H₂O₂)-induced oxidative injury in mouse zygotes. H₂O₂ treatment impaired the development of mouse zygotes in vitro, decreasing the rates of blastocyst formation and hatched, and increasing the fragmentation, apoptosis and retardation in blastocysts. Quercetin strongly protected zygotes from H₂O₂-induced oxidative injury by decreasing the reactive oxygen species level, maintaining mitochondrial function and modulating total antioxidant capability, the activity of the enzymatic antioxidants, including glutathione peroxidase and catalase activity to keep the cellular redox environment. Additionally, quercetin had no effect on the level of glutathione, the main non-enzymatic antioxidant in embryos.

Effect of 7,8-dihydroxyflavone as an antioxidant on in vitro maturation of oocytes and development of parthenogenetic embryos in pigs

One of the factors that impairs in vitro produced porcine embryos is the oxidative stress that is mainly caused by the imbalance between reactive oxygen species (ROS) generation and antioxidants activity, especially that of glutathione (GSH). Here, we examined the effect of 7,8-dihydroxyflavone (7,8-DHF), a kind of flavonoid antioxidant, on porcine oocyte maturation and its developmental competence. Porcine oocytes were cultured in media supplemented with 0, 1, 5 and 10 μM 7,8-DHF during both in vitro maturation (IVM) and in vitro culture (IVC) after parthenogenetic activation. Maturation of oocytes was evaluated based on first polar body (PB) extrusion and intracellular GSH level, and developmental competence was assessed through observing cleavage and blastocyst formation. In each step, the levels of intracellular GSH and ROS were assessed by fluorescence intensity, and the apoptosis-related gene expression was examined using semiquantitative RT-PCR. The group treated with 1 μM 7,8-DHF during IVM and IVC showed increased cytoplasmic maturation and reached the blastocysts stage (36.1%) at a higher rate than the other groups (24.7, 16.0 and 10.3% for 0, 5 and 10 μM, P<0.05). In that group, the intracellular GSH level was significantly increased while ROS generation was significantly decreased after IVM and IVC (P<0.05). Moreover, it showed high expression of an anti-apoptotic gene (BCL2L1) and low expression of a pro-apoptotic gene (BAK1) (P<0.05). In conclusion, treatment with 1 μM 7,8-DHF during IVM and IVC showed an anti-apoptotic effect by increasing intracellular GSH synthesis and scavenging ROS and therefore improved the developmental competence of porcine embryos.

Replacement of glutamine with the dipeptide derivative alanyl-glutamine enhances in vitro maturation of porcine oocytes and development of embryos

The presence of glutamine (Gln) in in vitro maturation (IVM) and in vitro culture (IVC) medium is a more potent factor for improving porcine oocyte and embryo development than other amino acids. However Gln is inherently unstable and spontaneously breaks down into ammonia, and therefore interferes with proper development. To avoid this adverse effect, Gln was replaced in the present study with its stable dipeptide derivative alanyl-glutamine (Ala-Gln) and the effects of this replacement on porcine IVM and IVC were evaluated. Replacement of Gln with Ala-Gln during IVM did not improve nuclear maturation, however numbers of early cleaved embryos were significantly increased after activation. Blastocyst formation rates were also significantly improved by using Ala-Gln during IVM. Replacement of Gln with Ala-Gln during IVC significantly increased total cell numbers in blastocysts. Blastocyst formation rate was also significantly higher when Ala-Gln was used in both IVM and IVC. In conclusion, the use of Ala-Gln rather than Gln gives better results for development in both porcine IVM and IVC.

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

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

Ascorbic acid improves the developmental competence of porcine oocytes after parthenogenetic activation and somatic cell nuclear transplantation

In this study, a dose-response assessment was performed to understand the relation between supplementation of media with L-ascorbic acid or vitamin C and porcine oocyte maturation and the in vitro development of parthenotes (PA) and handmade cloned (HMC) embryos. Various concentrations (0, 25, 50 and 100 µg/ml) of vitamin C supplemented in in vitro maturation (IVM) and culture (IVC) media were tested. None of these vitamin C additions affected nuclear maturation of oocytes, yet supplementation at 50 µg/ml led to significantly increased intracellular glutathione (GSH) levels and reduced reactive oxygen species (ROS). When cultured in IVM- and/or IVC-supplemented media, the group supplemented with 50 µg/ml of vitamin C showed improved cleavage rates, blastocyst rates and total cell numbers per blastocyst (P<0.05) compared with other groups (control, 25 µg/ml and 100 µg/ml). In contrast, supplementation with 50 µg/ml vitamin C decreased (P<0.05) the apoptosis index as compared with the groups supplemented with 100 µg/ml. In addition, even with a lower blastocyst rate to start with (37.6 vs. 50.3%, P<0.05), supplementation of HMC embryos with vitamin C ameliorated their blastocyst quality to the extent of PA embryos as indicated by their total cell numbers (61.2 vs. 59.1). Taken together, an optimized concentration of vitamin C supplementation in the medium not only improves blastocyst rates and total cell numbers but also reduces apoptotic indices, whereas overdosages compromise various aspects of the development of parthenotes and cloned porcine embryos.

Involvement of N-glycosylation of zona glycoproteins during meiotic maturation in sperm-zona pellucida interactions of porcine denuded oocytes

The present study was conducted to delineate whether N-glycosylation of zona pellucida (ZP) glycoproteins occurred during meiotic maturation and whether this N-glycosylation played a role in sperm-ZP interactions of porcine cumulus denuded oocytes (DOs). After mechanical removal of cumulus cells from cumulus oocyte complexes (COCs), DOs were cultured for 44 h in in vitro maturation (IVM) culture. The experiments were carried out to determine the effects of tunicamycin, a specific N-glycosylation inhibitor, for various intervals during IVM on sperm-ZP interactions in porcine DOs. The results determined that DOs could induce meiotic maturation, although the maturation rate of DOs was earlier than that of COCs. In addition, N-glycosylation of ZP glycoproteins occurred during meiotic maturation and was crucial in sperm-ZP interactions, was responsible for sperm penetration, sperm binding to ZP and induction of acrosome reaction in ZP-bound sperm. However, the inhibition of N-glycosylation by tunicamycin during IVM did not influence ZP hardness and male pronuclear formation, indicating that this N-glycosylation was involved in the initial stage of fertilization. We conclude that 24-44 h of N-glycosylation of ZP glycoproteins during meiotic maturation was crucial in sperm penetration and sperm binding to ZP and the induction of acrosome reaction in sperm bound to ZP of porcine DOs.

Cysteine sulfinic acid decarboxylase activity of Aedes aegypti aspartate 1-decarboxylase: the structural basis of its substrate selectivity

Insect aspartate 1-decarboxylase (ADC) catalyzes the decarboxylation of aspartate to β-alanine. Insect ADC proteins share high sequence identity to mammalian cysteine sulfinic acid decarboxylase (CSADC), but there have been no reports indicating any CSADC activity in insect ADC or any ADC activity in mammalian CSADC. Substrate screening of Aedes aegypti ADC (AeADC), however, demonstrates that other than its activity to aspartate, the mosquito enzyme catalyzes the decarboxylation of cysteine sulfinic acid and cysteic acid as efficiently as those of mammalian CSADC under the same testing conditions. Further analysis of Drosophila melanogaster ADC also demonstrated its CSADC activity, suggesting that all insect ADC likely has CSADC activity. This represents the first identification of CSADC activity of insect ADC. On the other hand, HuCSADC displayed no detectable activity to aspartate. Homology modeling of AeADC and substrate docking suggest that residue Q377, localized at the active site of AeADC, could better interact with aspartate through hydrogen bonding, which may play a role in aspartate selectivity. A leucine residue in mammalian CSADC occupies the same position. A mutation at position 377 from glutamine to leucine in AeADC diminished its decarboxylation activity to aspartate with no major effect on its CSADC activity. Comparison of insect ADC sequences revealed that Q377 is stringently conserved among the available insect ADC sequences. Our data clearly established the CSADC activity of mosquito and Drosophila ADC and revealed the primary role Q377 plays in aspartate selectivity in insect ADC.

Vitamin C enhances in vitro and in vivo development of porcine somatic cell nuclear transfer embryos

The reprogramming of differentiated cells into a totipotent embryonic state through somatic cell nuclear transfer (SCNT) is still an inefficient process. Previous studies revealed that the generation of induced pluripotent stem (iPS) cells from mouse and human fibroblasts could be significantly enhanced with vitamin C treatment. Here, we investigated the effects of vitamin C, to our knowledge for the first time, on the in vitro and in vivo development of porcine SCNT embryos. The rate of blastocyst development in SCNT embryos treated with 50μg/mL vitamin C 15h after activation (36.0%) was significantly higher than that of untreated SCNT embryos (11.5%). The enhanced in vitro development rate of vitamin C-treated embryos was associated with an increased acetylation level of histone H4 lysine 5 and higher Oct4, Sox2 and Klf4 expression levels in blastocysts, as determined by real-time PCR. In addition, treatment with vitamin C resulted in an increased pregnancy rate in pigs. These findings suggest that treatment with vitamin C is beneficial for enhancement of the in vitro and in vivo development of porcine SCNT embryos.

L-carnitine enhances oocyte maturation and development of parthenogenetic embryos in pigs

The objective was to determine whether adding L-carnitine in IVM/IVC medium enhanced maturation and developmental competence of porcine oocytes in vitro. Oocyte maturation rates did not differ significantly among groups supplemented with 0, 0.25, 0.5, or 1 mg/mL of L-carnitine added during IVM (although 2 mg/mL of L-carnitine reduced maturation rate). Compared with control oocytes, those treated with 0.5 mg/mL of L-carnitine during IVM had greater (P < 0.05) rates of blastocyst formation after parthenogenetic activation, and these blastocysts had less (P < 0.05) apoptosis. Adding 0.5 mg/mL of L-carnitine during IVM also significantly reduced intracellular reactive oxygen species (ROS), and increased glutathione (GSH) concentrations. With or without glucose supplementation, 0.5 mg/mL of L-carnitine in the IVM medium significantly hastened nuclear maturation of oocytes. Moreover, supplementing the IVM medium with either glucose or L-carnitine increased (P < 0.05) percentages of oocytes that reached the metaphase II (MII) stage, relative to a control group. Final maturation rates in IVM medium containing either glucose or L-carnitine were not significantly different. Adding L-carnitine (0 to 2 mg/mL) to IVC medium for activated porcine oocytes did not significantly affect development. However, 0.5 mg/mL of L-carnitine in IVC medium significantly reduced reactive oxygen species levels and apoptosis in activated blastocysts, although glutathione concentrations were not significantly altered. In conclusion, adding L-carnitine during IVM/IVC improved developmental potential of porcine oocytes, and also the quality of parthenogenetic embryos, probably by accelerating nuclear maturation, and preventing oxidative damage and apoptosis.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Oxidative parameters of embryo culture media may predict treatment outcome in in vitro fertilization: a novel applicable tool for improving embryo selection

OBJECTIVE

To examine whether the oxidative status of an individual embryo before transfer may predict chances of implantation.

DESIGN

A prospective laboratory study.

SETTING

An IVF unit in a university-affiliated hospital.

PATIENT(S)

One hundred thirty-three women undergoing IVF-ET treatment cycles.

INTERVENTION(S)

Before ET, 10 μL of embryo culture medium was retrieved individually from each embryo and the oxidative status assessed by the thermochemiluminescence (TCL) analyzer.

MAIN OUTCOME MEASURE(S)

The occurrence of pregnancy. Two parameters were recorded: the TCL amplitude after 50 seconds (H1) and the TCL ratio. These were compared with demographic, clinical, and laboratory parameters and treatment outcome. All data underwent statistical analysis.

RESULT(S)

Altogether 284 embryos were transferred in 133 ET cycles. Forty-one pregnancies occurred (31%). For embryos transferred after 72 hours (77 transfers), the highest H1 levels in each group of transferred embryos correlated with the occurrence of pregnancy. The combination of maximal intracohort H1 level <210 counts per second with a TCL ratio of ≤ 80% had a positive predictive value of 70.6% for the occurrence of pregnancy.

CONCLUSION(S)

The oxidative status of the early embryo in IVF is associated with the chances of implantation. Assessment of the oxidative status of embryos in culture media before transfer may serve as an applicable tool for improving embryo selection in light of the legal limitations of the number of transferred embryos allowed.

Correlation of the mitochondrial activity of two-cell embryos produced in vitro and the two-cell block in Kunming and B6C3F1 mice

The correlation between the early embryonic block to development and mitochondrial activity was investigated comparing two-cell embryos produced in vitro from Kunming (KM) and B6C3F1 mice. One-cell embryos were obtained from two species of hybrids (female KM mice mated with KM males and female B6C3F1 mice mated with KM males) and cultured for 84 hr in M16 media. The mitochondrial membrane potential, ATP content, and reactive oxygen species levels were measured in the resulting KM and B6C3F1 two-cell embryos. Mitochondrial membrane potential and ATP content were also determined in KM and B6C3F1 metaphase II eggs. The results showed that the two-cell block was observed in cultured KM embryos but not in B6C3F1 embryos. Mitochondrial membrane potential and ATP content of KM two-cell embryos were significantly lower than in B6C3F1 two-cell embryos (P < 0.01). Interestingly, the reactive oxygen species levels of KM two-cell embryos were significantly lower than their B6C3F1 counterparts (P < 0.01). There was no difference in mitochondrial membrane potential and ATP content between KM and B6C3F1 metaphase II eggs. It is concluded that KM mice have an early two-cell embryo block and that a possible "blocking" mechanism is the lower mitochondrial membrane potential and ATP content in these embryos. The results suggest a new approach for overcoming early embryonic development block, that of manipulating mitochondrial activity.

Adding essential amino acids at a low concentration improves the development of in vitro fertilized porcine embryos

The aims of this study were to investigate improvements to the pig preimplantation embryo culture system using in vitro produced embryos. For experiment 1, the optimum time to change the medium from NCSU23 containing 0.6 mM glucose, 0.2 mM pyruvate, 5.7 mM lactate and nonessential amino acids to NCSU23 containing 5.6 mM glucose and both essential and nonessential amino acids was examined. There were no statistically significant differences in blastocyst rates or cell number when the medium was changed at 48, 72 or 96 h, although there was a consistent trend for the 96 h treatment to produce fewer blastocysts with fewer cells. For experiment 2, the addition of essential amino acids at either a 1:50 or a 1:100 dilution of the purchased stock solution for day 1 to 6 or for days 3 to 6 only was investigated. Adding essential amino acids at a 1:50 dilution for day 3 to 6 significantly reduced the blastocyst rate and adding them at a 1:50 dilution from day 1 to 6 significantly reduced both the blastocyst rate and blastocyst cell number compared to when it was added at a 1:100 dilution. Embryos were produced by IVF, cultured for 6 days and good quality blastocysts were transferred into 6 synchronized pseudopregnant recipients (24 to 35 blastocysts per recipient) resulting in 4 pregnancies and 21 live birth piglets. These results show that adding essential amino acids at a 1:100 dilution provided the best culture conditions and the blastocysts produced were able to attain full term development after transfer.

Symposium: innovative techniques in human embryo viability assessment. Assessing embryo viability by measurement of amino acid turnover

This review assesses the ability of non-invasive 'amino acid profiling' to predict early embryo viability. The history of amino acid supplementation of embryo culture media and the role of amino acids in early embryo development are first considered and these are followed by a review of methods to quantify amino acid depletion and production by single embryos. Data on amino acid profiling of embryos from a number of species are then discussed. It is concluded that this technology has excellent potential to improve the selection of single embryos for transfer in clinical IVF.