Enrichment of in vitro maturation medium for buffalo (Bubalus bubalis) oocytes with thiol compounds: Effects of cystine on glutathione synthesis and embryo development

Salidroside Supplementation Affects In Vitro Maturation and Preimplantation Embryonic Development by Promoting Meiotic Resumption

Salidroside (Sal) possesses several pharmacological activities, such as antiaging, and anti-inflammatory, antioxidant, anticancer activities, and proliferation-promoting activities, but the effects of Sal on oocytes have rarely been reported. In the present study, we evaluated the beneficial effects of Sal, which is mainly found in the roots of Rhodiola. Porcine cumulus oocyte complexes were cultured in IVM medium supplemented (with 250 μmol/L) with Sal or not supplemented with Sal. The maturation rate in the Sal group increased from 88.34 ± 4.32% to 94.12 ± 2.29%, and the blastocyst rate in the Sal group increased from 30.35 ± 3.20% to 52.14 ± 7.32% compared with that in the control group. The experimental groups showed significant improvements in the cumulus expansion area. Sal reduced oocyte levels of reactive oxygen species (ROS) and enhanced intracellular GSH levels. Sal supplementation enhanced the mitochondrial membrane potential (MMP), ATP level, and mtDNA copy number, which shows that Sal enhances the cytoplasmic maturation of oocytes. Oocytes in the Sal group exhibited slowed apoptosis and reduced DNA breakage. Cell cycle signals and oocyte meiosis play important roles in oocyte maturation. The mRNA expressions of the MAPK pathway and MAPK phosphorylation increased significantly in the Sal group. The mRNA expression of the oocyte meiosis gene also increased significantly. These results show that Sal enhances the nuclear maturation of oocytes. Moreover, Sal increased the number of blastocyst cells, the proliferation of blastocysts, and the expressions of pluripotency genes. Sal down-regulated apoptosis-related genes and the apoptotic cell rate of blastocysts. In summary, our results demonstrate that Sal is helpful to improving the quality of porcine oocytes in vitro, and their subsequent embryonic development.

Review: Development, adoption, and impact of assisted reproduction in domestic buffaloes

The domestic buffalo (Bubalus bubalis), also known as water buffalo, comprises two sub-species the River buffalo (B. bubalis ssp. bubalis; 50 chromosomes) and the Swamp buffalo (ssp. carabanensis; 48 chromosomes). Domestic buffaloes are a globally significant livestock species. In South Asia, the River buffalo is a primary source of milk and meat and has a very important role in food security. The River buffalo also supports high-value, differentiated food production in Europe and the Americas. The Swamp buffalo is an important draft animal and a source of food in Southeast Asia and East Asia. The growing importance of buffaloes requires that they undergo an accelerated rate of genetic gain for efficiency of production, product quality, and sustainability. This will involve the increased use of assisted reproduction. The initial application of reproductive technology in buffaloes had variable success as it relied on the adoption of procedures developed for cattle. This included artificial insemination (AI), sperm cryopreservation, and embryo technologies such as cloning and in vitro embryo production (IVEP). Reproductive technology has been progressively refined in buffaloes, and today, the success of AI and IVEP is comparable to cattle. Ovarian follicular superstimulation (superovulation) combined with in vivo embryo production results in low embryo recovery in buffaloes and has limited practical application. The contribution of elite female buffaloes to future genetic improvement will therefore rely mainly on oocyte pickup and IVEP. This will include IVEP from females before puberty to reduce generation intervals. This review provides for the first time a clear chronology on the development, adoption, and impact, of assisted reproduction in domestic buffaloes.

Seasonal variations in the metabolomic profile of the ovarian follicle components in Italian Mediterranean Buffaloes

The aim of this work was to evaluate the seasonal effect on the metabolomic profile of the ovarian follicle in Italian Mediterranean buffalo to unravel the causes of the reduced competence during the non-breeding season (NBS). Samples of follicular fluid, follicular cells, cumulus cells and oocytes were collected from abattoir-derived ovaries during breeding season (BS) and NBS and analyzed by 1H Nuclear Magnetic Resonance. The Orthogonal Projections to Latent Structures of the Discriminant Analysis showed clear separation into seasonal classes and Variable Importance in Projection method identified differentially abundant metabolites between seasons. Seasonal differences were recorded in metabolite content in all analyzed components suggesting that the decreased oocyte competence during NBS may be linked to alteration of several metabolic pathways. The pathway enrichment analysis revealed that differences in the metabolites between the seasons were linked to glutathione, energy generating and amino acid metabolism and phospholipid biosynthesis. The current work allows the identification of potential positive competence markers in the follicular fluid as glutathione, glutamate, lactate and choline, and negative markers like leucine, isoleucine and β-hydroxybutyrate. These results form a major basis to develop potential strategies to optimize the follicular environment and the IVM medium to improve the competence of oocytes during the NBS.

Optimization of gonadotropin stimulation protocols for in vitro embryo production in prepubertal Mediterranean water buffalo

Embryos can be produced from prepubertal donor animals using laparoscopic ovum pickup and in vitro embryo production technologies (LOPU-IVEP). Together, these tools can shorten the interval between generations, rapidly accelerating the rate of genetic gain. Here, we assessed the impact of different gonadotropin stimulation protocols in Mediterranean water buffalo heifer calves aged between 2 and 6 months old. Following gonadotropin stimulation, LOPU was performed at two-week intervals, with animals receiving different protocols on subsequent LOPUs. After collection, the cumulus-oocyte complexes (COCs) were matured and fertilized in vitro, and embryos were cultured to the blastocyst stage followed by transfer into synchronized adult recipients. The number and size of follicles aspirated during LOPU, the number and quality of COCs recovered, as well as cleavage, embryo development and pregnancy rates were assessed. First, we evaluated the impact of using FSH with and without eCG (administered 24-h prior to LOPU) and found that a combination of FSH and eCG was able to significantly improve embryo development rates (20.6 ± 2.0% vs. 9.0 ± 3.6%; P < 0.05). Second, we compared this protocol to a slow-release formulation of FSH reconstituted in hyaluronan. In addition to requiring less work to prepare the animals for LOPU, this slow-release formulation yielded numerically higher, but not statistically different, average number of recovered COCs (14.4 ± 2.1 vs. 10.3 ± 2.0; P > 0.05) and embryo development rates (22.9 ± 4.7% vs. 14.1 ± 5.2%; P > 0.05) compared to FSH given every 12 h. Next, we compared the length of gonadotropin treatment over 3-, 4- and 5-days prior to LOPU and found that as the length of gonadotropin treatment increased, although the number of COCs recovered steadily decreased (14.1 ± 2.4 vs. 8.7 ± 1.0 vs. 6.9 ± 0.7; P < 0.05), the embryo development rates steadily increased (14.4 ± 3.9 vs. 27.3 ± 4.4 vs. 35.9 ± 7.0; P < 0.05), presumably due to an increase in the proportion of large follicles at the time of LOPU. Numerically, the 4-day treatment yielded more transferrable embryos per donor per LOPU (2.70 ± 0.5) than 3-day (1.94 ± 0.6) and 5-day (2.25 ± 0.5) treatments. Finally, following embryo transfer, 26 of 90 recipient females became pregnant (28.9%). Pregnancies were established from all treatments, which suggests that post-implantation development was not affected among the gonadotropin treatments assessed.

Mechanisms of action of non-enzymatic antioxidants to control oxidative stress during in vitro follicle growth, oocyte maturation, and embryo development

In vitro follicle growth and oocyte maturation still has a series of limitations, since not all oocytes matured in vitro have the potential to develop in viable embryos. One of the factors associated with low oocyte quality is the generation of reactive oxygen species (ROS) during in vitro culture. Therefore, this review aims to discuss the role of non-enzymatic antioxidants in the control of oxidative stress during in vitro follicular growth, oocyte maturation and embryonic development. A wide variety of non-enzymatic antioxidants (melatonin, resveratrol, L-ascorbic acid, L-carnitine, N-acetyl-cysteine, cysteamine, quercetin, nobiletin, lycopene, acteoside, mogroside V, phycocyanin and laminarin) have been used to supplement culture media. Some of them, like N-acetyl-cysteine, cysteamine, nobiletin and quercetin act by increasing the levels of glutathione (GSH), while melatonin and resveratrol increase the expression of antioxidant enzymes and minimize oocyte oxidative stress. L-ascorbic acid reduces free radicals and reactive oxygen species. Lycopene positively regulates the expression of many antioxidant genes. Additionally, L-carnitine protects DNA against ROS-induced damage, while acteoside and laminarin reduces the expression of proapoptotic genes. Mogrosides increases mitochondrial function and reduces intracellular ROS levels, phycocyanin reduces lipid peroxidation, and lycopene neutralizes the adverse effects of ROS. Thus, it is very important to know their mechanisms of actions, because the combination of two or more antioxidants with different activities has great potential to improve in vitro culture systems.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

In Vitro Production of Embryos from Prepubertal Holstein Cattle and Mediterranean Water Buffalo: Problems, Progress and Potential

Laparoscopic ovum pick-up (LOPU) coupled with in vitro embryo production (IVEP) in prepubertal cattle and buffalo accelerates genetic gain. This article reviews LOPU-IVEP technology in prepubertal Holstein Cattle and Mediterranean Water Buffalo. The recent expansion of genomic-assisted selection has renewed interest and demand for prepubertal LOPU-IVEP schemes; however, low blastocyst development rates has constrained its widespread implementation. Here, we present an overview of the current state of the technology, limitations that persist and suggest possible solutions to improve its efficiency, with a focus on gonadotropin stimulations strategies to prime oocytes prior to follicular aspiration, and IVEP procedures promoting growth factor metabolism and limiting oxidative and endoplasmic reticulum stress.

Asiatic acid protects oocytes against in vitro aging-induced deterioration and improves subsequent embryonic development in pigs

As a pentacyclic triterpene in Centella asiatica, asiatic acid (AA) is a powerful antioxidant with many bioactivities. In the present research, we investigated whether AA has the potential to rescue the decrease in porcine oocyte quality that occurs during in vitro aging (IVA). Mature porcine oocytes were collected and then continuously cultured for an additional 24 h or 48 h with or without AA in maturation medium as an IVA model. The results revealed that AA supplementation reduced the percentage of abnormal aged porcine oocytes during IVA. Furthermore, AA supplementation effectively maintained aged porcine oocyte developmental competence, both parthenogenetic activation and in vitro fertilization. The number of sperm that bound to the zona pellucida on aged porcine oocytes was higher in the AA-supplemented group than in the non-supplemented group. Moreover, AA supplementation not only blocked IVA-induced oxidative stress but also maintained intracellular GSH levels and reduced the percentage of early apoptosis aged porcine oocytes. Mitochondrial functions were disordered during the IVA process. The intracellular ATP levels and mitochondrial membrane potential in aged porcine oocytes were dramatically increased by AA supplementation. Therefore, AA has beneficial effects on porcine oocyte quality and developmental potential maintenance during IVA.

Effects of increasing lipopolysaccharide concentrations on in vitro developmental competence of ovine oocytes

Although a considerable number of studies have investigated the effects of lipopolysaccharide (LPS) on the reproductive performance of dairy cows, the response of ovine oocytes to LPS during their in vitro maturation and development is not well defined yet. Ewe’s ovaries were obtained from a slaughterhouse, the oocytes were collected and matured in the presence of increasing concentrations (0, 0.01, 0.1, 1 and 10 µg/mL) of LPS in order to evaluate the meiotic maturation by measuring the proportion of oocytes reaching the MII stage. The concentration of intracellular glutathione (GSH) was measured in oocytes following maturation in vitro. In addition, concentrations of selected metabolites including glucose, pyruvate, lactate and glutamine were quantified in the medium following maturation. A number of treated matured oocytes along with the control group were subsequently fertilized using frozen semen and assessed for the rate of cleavage and for the proportion reaching the blastocyst stage. The number of oocytes in MII stage was significantly reduced in response to the increasing concentrations of LPS (77.83%, 70.64%, 68.86%, 66.32%, respectively, in case of 0.01, 0.1, 1 and 10 µg/mL LPS when compared to the control group, 76.34%; P<0.05). There were no differences neither in the intracellular concentration of GSH in the oocytes nor in case of the metabolites in the maturation medium. Although the rate of cleaved oocytes was not affected by increasing levels of LPS, the blastocyst rate was reduced in a dose dependent manner (36.69%, 34.21%, 30.35%, 17.27% and 14.03% for the control, 0.01, 0.1, 1 and 10 µg/mL LPS, respectively (P<0.05). These results demonstrate that the developmental competence of ovine oocytes may be affected detrimentally by LPS and such deleterious effects could be related to the maturation process.

Is it possible to alter the embryo lipid accumulation with reduction of fetal bovine serum and use of l-carnitine for in vitro maturation of bubaline oocytes?

In vitro embryo production (IVEP) is a procedure that can promote genetic improvement in a short time frame. However, the success rates obtained with this biotechnology in water buffaloes are still inconsistent, and can be associated with the high concentration of lipids in the cytoplasm of oocytes and embryos. The objective of this study was to evaluate the effects of reduced concentration of fetal bovine serum (FBS) and/or use of l-carnitine during in vitro maturation (IVM) on the preimplantation development and lipid accumulation in bubaline embryos. In a first experiment, the lowest concentration of FBS in the IVM medium (0%, 2.5%, 5% or 10%) was determined, and the lowest concentration that maintained good embryo development rates was 5%. In a second experiment, the addition of 5 mM of l-carnitine into the maturation medium was evaluated. The blastocysts produced were submitted to lipid evaluation involving staining followed by observation using optical (Oil Red O) and confocal (BODIPY 493/503) microscopy. No difference was observed between the 5% and 10% FBS groups, which were superior to the 0% and 2.5% groups. Furthermore, the performance of the groups treated with 5% and 10% FBS was better than the groups supplemented with l-carnitine. There was no difference regarding embryo lipid accumulation. The results indicated that it is possible to reduce the FBS concentration to 5% in in vitro maturation medium for production of bubaline embryos, and supplementation with 5 mM l-carnitine does not increase embryo production.

Proteomics Analysis Reveals that Warburg Effect along with Modification in Lipid Metabolism Improves In Vitro Embryo Development under Low Oxygen

The molecular mechanism regulating embryo development under reduced oxygen tension remains elusive. This study aimed to identify the molecular mechanism impacting embryo development under low oxygen conditions. Buffalo embryos were cultured under 5% or 20% oxygen and were evaluated according to their morphological parameters related to embryo development. The protein profiles of these embryos were compared using iTRAQ-based quantitative proteomics. Physiological O2 (5%) significantly promoted blastocyst yield, hatching rate, embryo quality and cell count as compared to atmospheric O2 (20%). The embryos in the 5% O2 group had an improved hatching rate of cryopreserved blastocysts post-warming (p < 0.05). Comparative proteome profiles of hatched blastocysts cultured under 5% vs. 20% O2 levels identified 43 differentially expressed proteins (DEPs). Functional analysis indicated that DEPs were mainly associated with glycolysis, fatty acid degradation, inositol phosphate metabolism and terpenoid backbone synthesis. Our results suggest that embryos under physiological oxygen had greater developmental potential due to the pronounced Warburg Effect (aerobic glycolysis). Moreover, our proteomic data suggested that higher lipid degradation, an elevated cholesterol level and a higher unsaturated to saturated fatty acid ratio might be involved in the better cryo-survival ability reported in embryos cultured under low oxygen. These data provide new information on the early embryo protein repertoire and general molecular mechanisms of embryo development under varying oxygen levels.

Effect of cysteine, glutamate and glycine supplementation to in vitro fertilization medium during bovine early embryo development

Glutathione (GSH) is an antioxidant synthesized from three constitutive amino acids (CAA): cysteine (Cys), glycine (Gly) and glutamate (Glu). Glutathione plays an important role in oocyte maturation, fertilization and early embryo development. This study aimed to investigate the effect of Cys (0.6 mM), Gly (0.6 mM) and Glu (0.9 mM) supplementation during in vitro fertilization (IVF) of cattle oocytes. In a Pilot Experiment, de novo synthesis of GSH in bovine zygote was evaluated using a modified TALP medium prepared without MEM-essential and MEM-non-essential amino acids (mTALP): mTALP + CAA (constitutive amino acids); mTALP + CAA+5 mMBSO (buthionine sulfoximide); mTALP + Cys + Gly; mTALP + Cys + Glu and mTALP + Gly + Glu. This evidence led us to investigate the impact of CAA supplementation to TALP medium (with essential and non-essential amino acids) on zygote viability, lipid peroxidation, total intracellular GSH content (include reduced and oxidized form; GSH-GSSG), pronuclear formation in zygotes and subsequent embryo development. IVF media contained a) TALP; b) TALP + Cys + Gly + Glu (TALP + CAA); c) TALP + Cys + Gly; d) TALP + Cys + Glu; e) TALP + Gly + Glu, were used. Total GSH-GSSG concentration was increased in TALP, TALP + CAA, and TALP + Cys + Gly. The viability of zygote was similar among treatments. Lipid peroxidation was increased in zygote fertilized with TALP + Cys + Gly; TALP + Cys + Glu; TALP + Gly + Glu and TALP + CAA. The percentage of penetrated oocytes decreased in TALP + CAA and TALP + Cys + Gly. The cleavage rate was lower in TALP + CAA and TALP + Gly + Glu. The percentage of embryos developing to the blastocyst stage was lower in TALP + Cys + Glu and TALP + CAA. In conclusion, we have demonstrated the synthesis of GSH during IVF. However, Cys, Gly and Glu supplementation to TALP medium had negative effects on embryonic development.

In vitro embryo production in buffaloes: from the laboratory to the farm

Transvaginal follicular aspiration technique together with in vitro embryo production are the biotechnological alternatives currently available to support genetic improvement breeding programs in buffalo species. However, aspects related to animal management, lack of knowledge of the metabolic needs and biochemical peculiarities of gametes and embryos, as well as the reproductive physiology characteristics have hampered progress in the results. Despite the low availability of good quality oocytes collected after OPU in donors as a physiological characteristic of buffalo species, high rates of oocyte maturation, modest embryo cleavage, blastocyst production and pregnancy rates after transvaginal embryo transfer in recipients could be obtained in buffalo in vitro embryo production programs. The results of implementing an in vitro embryo production program in buffaloes in the northern region of Pará state, Brazil, and results published by other groups demonstrate the feasibility of implementing this biotechnology in the routine of breeding programs. Nevertheless, in order to achieve better and consistent results, it is necessary to deepen the knowledge on the peculiarities of reproductive biology in this specie. Selection of donor animals based on ovarian size and ovarian follicular reserve and on the rate of blastocyst production is presented as an effective alternative to increase the efficiency of the in vitro embryo production technique applied to the buffalo species.

In Vitro Embryo Production in Buffalo Species (Bubalus bubalis)

In the last years there has been a growing attention in the world regarding buffalo (Bubalus bubalis) breeding. In tropical countries, climatic and environmental conditions make buffalo an irreplaceable milk producer. Since cattle cannot express their own productive potential in these conditions, buffaloes are best suited to satisfy animal protein demand, as they are easy to maintain, long-lived, and parasite resistant. Here we describe how to produce buffalo embryos from slaughterhouse oocytes, with protocols for media formulation, oocyte selection, semen capacitation, and in the end embryo evaluation.

Evaluation of factors involved in the failure of ovum capture in superovulated buffaloes

The aim of this work was to evaluate factors affecting ovum capture in superovulated buffaloes, by comparing the morphological features of pre-ovulatory follicles and oocytes, the intrafollicular and plasmatic steroid profile, as well as the expression of genes involved in cumulus expansion and steroid cascade in granulosa cells (GCs) and that of genes involved in contraction-relaxation of the oviduct between superovulated and synchronized buffaloes. Italian Mediterranean Buffalo cows were either synchronized by Ovsynch (n = 25) and superovulated (n = 10) with conventional FSH protocol and sacrificed 18 h after last GnRH. Antral follicular count, recovery rate and oocyte quality were recorded, and plasma and follicular fluid were collected for steroid profile determination. In addition, in 10 animals (5/group), GCs were collected to analyse the mRNA expression of gonadotropin receptors (LHR and FSHR) and genes involved in steroid synthesis, as the cytochrome P450 family 19 (CYP19A1) and the steroidogenic acute regulatory protein (STAR). Moreover, oviducts were collected to evaluate the mRNA expression of estrogen receptor 1 (ER1) and the progesterone receptor (PGR), the vascular endothelial growth factor (VEGF) and the VEGF receptors, i.e. the kinase insert domain receptor (FLK1) and the fms related tyrosine kinase 1 (FLT1). No differences were recorded in steroids plasma concentration between synchronized and superovulated animals whereas intrafollicular E₂ and P₄ concentrations decreased in superovulated group (63.2 ± 10.6 vs 30.3 ± 5.9 ng/mL of E₂ and 130.1 ± 19.8 vs 71.6 ± 8.5 ng/mL of P₄, respectively in synchronized and superovulated animals; P < 0.05). Interestingly, both the recovery rate (85.7% vs 56.6%, respectively in synchronized and in superovulated animals; P < 0.05) and the percentage of oocytes exhibiting proper cumulus expansion (75% vs 28.1%, respectively in synchronized and in superovulated animals; P < 0.01) decreased in superovulated animals. In addition, the expression of FSHR and CYP19A1 increased while the expression of STAR in GCs decreased (P < 0.05). Finally, in superovulated buffaloes a decreased expression of PGR, ER1, VEGF and its receptor FLK1 in the oviduct was observed. The results suggest that the exogenous FSH treatment impairs steroidogenesis, affecting both the oviduct and the ovarian function, accounting for the failure of ovum capture in superovulated buffaloes.

The effects of canthaxanthin on porcine oocyte maturation and embryo development in vitro after parthenogenetic activation and somatic cell nuclear transfer

The objective of this study was to examine the effects of canthaxanthin (Cx) treatment during in vitro maturation (IVM) of porcine oocytes on embryonic development after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT), on intracellular glutathione (GSH) and reactive oxygen species (ROS) levels in mature oocytes, and on gene expression in both PA- and SCNT-derived blastocysts. To determine the optimal effective concentration of Cx, porcine oocytes were cultured in IVM medium supplemented with various concentrations (0, 20, 40 and 80 μM) of Cx for 22 hr. Compared to other groups, supplementation with 40 μM Cx significantly improved blastocyst formation rates after PA (p < .05), but no significant differences were observed among groups in total blastocyst cell numbers. Subsequently, oocytes were cultured in IVM medium supplemented with or without 40 μM Cx. Oocytes treated with 40 μM Cx showed significantly increased cleavage and blastocyst formation rates after SCNT compared to the control group (p < .05). Moreover, significantly increased intracellular GSH and reduced ROS levels were observed in the Cx-treated group (p < .05). In addition, both PA- and SCNT-derived blastocysts from the 40 μM Cx-treated group showed significantly increased mRNA expression of Bcl2 and Oct4 and decreased Caspase3 expression level (p < .05), when compared with the control group. PA-derived blastocysts from the 40 μM Cx-treated group also exhibited significantly decreased expression of Bax (p < .05). Our results demonstrated that treatment with 40 μM Cx during IVM improves the developmental competence of PA and SCNT embryos. Improvement of embryo development by Cx is most likely due to increased intracellular GSH synthesis, which reduces ROS levels in oocytes, and it may also positively regulate apoptosis- and development-related genes.

Using cysteine/cystine to overcome oxidative stress in goat oocytes and embryos cultured in vitro

Assisted reproductive techniques expose gametes to excessive concentrations of reactive oxygen species. The present study aimed to evaluate the effects of oxidative stress on apoptosis in goat oocytes and embryonic development. The results demonstrated that the addition of 100 µM hydrogen peroxide (H2O2) into media produces an oxidative environment during oocyte maturation. The number of cumulus cells positive for terminal deoxynucleotidyl transferase UTP nick end labeling, and the activity of caspase 3 in mature oocytes were increased, compared with the control group (P<0.05). In addition, the expression levels of mitochondrial regulators, including peroxisome proliferator‑activated receptor γ coactivator-1 α (PGC-1α) and nuclear respiratory factor‑1 (NRF‑1) were increased in the oxidative oocytes, compared with those in the control group (P<0.05). The ratio of the proapoptotic gene, B cell lymphoma (Bcl-2)-associated X protein (BAX), to the anti‑apoptotic gene, BCL‑2, was higher in the H2O2 group, compared with the control group (P<0.05). To overcome oxidative stress in oocytes and embryos cultured in vitro, 200 µM cysteine and 200 µM cystine were added to the media, thereby increasing the concentration of intracellular glutathione (GSH) and assisting in maintaining the redox state of the cells. In conclusion, cysteine and cystine reduced the oxygen tension caused by H2O2, thereby providing a novel strategy for optimizing in vitro embryonic development systems.

High hydrostatic pressure influences the in vitro response to xenobiotics in Dicentrarchus labrax liver

Hydrostatic pressure (HP) increases by about 1 atmosphere (0.1MPa) for each ten-meter depth increase in the water column. This thermodynamical parameter could well influence the response to and effects of xenobiotics in the deep-sea biota, but this possibility remains largely overlooked. To grasp the extent of HP adaptation in deep-sea fish, comparative studies with living cells of surface species exposed to chemicals at high HP are required. We initially conducted experiments with precision-cut liver slices of a deep-sea fish (Coryphaenoides rupestris), co-exposed for 15h to the aryl hydrocarbon receptor (AhR) agonist 3-methylcholanthrene at HP levels representative of the surface (0.1MPa) and deep-sea (5-15MPa; i.e., 500-1500m depth) environments. The transcript levels of a suite of stress-responsive genes, such as the AhR battery CYP1A, were subsequently measured (Lemaire et al., 2012; Environ. Sci. Technol. 46, 10310-10316). Strikingly, the AhR agonist-mediated increase of CYP1A mRNA content was pressure-dependently reduced in C. rupestris. Here, the same co-exposure scenario was applied for 6 or 15h to liver slices of a surface fish, Dicentrarchus labrax, a coastal species presumably not adapted to high HP. Precision-cut liver slices of D. labrax were also used in 1h co-exposure studies with the pro-oxidant tert-butylhydroperoxide (tBHP) as to investigate the pressure-dependence of the oxidative stress response (i.e., reactive oxygen production, glutathione and lipid peroxidation status). Liver cells remained viable in all experiments (adenosine triphosphate content). High HP precluded the AhR agonist-mediated increase of CYP1A mRNA expression in D. labrax, as well as that of glutathione peroxidase, and significantly reduced that of heat shock protein 70. High HP (1h) also tended per se to increase the level of oxidative stress in liver cells of the surface fish. Trends to an increased resistance to tBHP were also noted. Whether the latter observation truly reflects a protective response to oxidative stress will be addressed in future co-exposure studies with both surface and deep-sea fish liver cells, using additional pro-oxidant chemicals. Altogether, data on CYP1A inducibility with D. labrax and C. rupestris support the view that high HP represses AhR signaling in marine fishes, and that only species adapted to thrive in the deep-sea have evolved the molecular adaptations necessary to counteract to some extent this inhibition.

The effect of temperature during liquid storage of in vitro-matured bovine oocytes on subsequent embryo development

The aim of the present study was to optimize the temperature for the temporal storage of matured bovine oocytes. In vitro-matured bovine oocytes were preserved in HEPES-buffered TCM199 medium supplemented with 10% newborn calf serum at different temperatures (4 °C, 15 °C, 25 °C, and 38.5 °C) for 20 hours. Embryo development and blastocyst quality after in vitro fertilization, cytoplasmic ATP and glutathione levels in oocytes, and the frequency of apoptotic oocytes were compared among storage groups and a control group without storage. Among the storage groups, those at 25 °C and 38.5 °C showed the highest rates of blastocyst development (19.3% and 24.5%, respectively) compared with those stored at 4 °C and 15 °C (8.5% and 14.9%, respectively); however, blastocyst formation rates in all storage groups were lower than that in the control group (39.8%; P < 0.05). Storage at 38.5 °C and 15 °C was associated with reduced cell numbers in resultant blastocysts compared with the control and the 25 °C storage groups. Storage at 4 °C reduced metabolic activity of oocytes characterized by their lower ATP levels compared with the other groups. Storage for 20 hours significantly reduced the glutathione content in oocytes in all groups in a similar manner, irrespective of the temperature. Storage at 4 °C or 15 °C but not at 25 °C and 38.5 °C significantly increased the percentage of apoptotic oocytes compared with the control group. In conclusion, 25 °C was found to be the most suitable temperature for the temporal storage of matured bovine oocytes regarding both the developmental competence of oocytes and the quality of resultant blastocysts.

Paradoxical effects of bovine somatotropin treatment on the ovarian follicular population and in vitro embryo production of lactating buffalo donors submitted to ovum pick-up

The aim of the present study was to evaluate the effect of bovine somatotropin (bST; 500mg) administration on lactating buffalo donors submitted to two different ovum pick-up (OPU) and in vitro embryo production schemes with a 7 or 14d intersession OPU interval. A total of 16 lactating buffalo cows were randomly assigned into one of four experimental groups according to the bST treatment (bST or No-bST) and the OPU intersession interval (7 or 14d) in a 2×2 factorial design (16 weeks of OPU sessions). The females submitted to OPU every 14d had a larger (P<0.001) number of ovarian follicles suitable for puncture (15.6±0.7 vs. 12.8±0.4) and an increased (P=0.004) number of cumulus-oocyte complexes (COCs) recovered (10.0±0.5 vs. 8.5±0.3) compared to the 7d interval group. However, a 7 or 14d interval between OPU sessions had no effect (P=0.34) on the number of blastocysts produced per OPU (1.0±0.1 vs. 1.3±0.2, respectively). In addition, bST treatment increased (P<0.001) the number of ovarian follicles suitable for puncture (15.3±0.5 vs. 12.1±0.4) but reduced the percentage (18.9% vs. 10.9%; P=0.009) and the number (1.4±0.2 vs. 0.8±0.1; P=0.003) of blastocysts produced per OPU session compared with the non-bST-treated buffaloes. In conclusion, the 14d interval between OPU sessions and bST treatment efficiently increased the number of ovarian follicles suitable for puncture. However, the OPU session interval had no effect on embryo production, and bST treatment reduced the in vitro blastocyst outcomes in lactating buffalo donors.

Ultrastructural changes in oocytes during folliculogenesis in domestic mammals

The ultrastructural analysis of oocytes and ovarian follicles has been used to evaluate the effects of assisted reproductive techniques, such as cryopreservation or in vitro oocyte maturation. It also benefits the understanding of such complex mechanisms that occur during folliculogenesis. From the beginning of primordial follicles growth until oocyte maturation in preovulatory follicles oocyte cytoplasmic organelles undergo dynamic alterations that reflect physiological changes and development. This review aims to make a retrospective survey of the relevant features of follicles and oocytes ultrastructure, highlighting the differences between mammalian species, specially the domestic ones.

A review: alteration of in vitro reproduction processes by thiols -emphasis on 2-mercaptoethanol

Descriptions of organosulfurs altering biologically relevant cellular functions began some 40 years ago when murine in vitro cell mediated and humoral immune responses were shown to be dramatically enhanced by any of four xenobiotic, sulfhydryl compounds-2-mercaptoethanol (2ME), dithiothreitol (DTT), glutathione, and L-cysteine; the most effective were 2ME and DTT. These findings triggered a plethora of reports defining 2ME benefits for a multitude of immunological processes. This in turn led to investigations on 2ME alterations of (a) immune functions in other species, (b) activities of other cell-types, and (c) in vivo diseases. In addition, these early findings preceded the identification of previously undefined anticarcinogenic chemicals in specific foods as organosulfurs. Taken all together, there is little doubt that organosulfur compounds have enormous benefits for cellular functions and for a multitude of diseases. Issues of importance still to be resolved are (a) clarification of mechanisms that underlie alteration of in vitro and in vivo processes and perhaps more importantly, (b) which if any in vitro alterations are relevant for (i) alteration of in vivo diseases and (ii) identification of other diseases that might therapeutically benefit from organosulfurs. As one means to address these questions, reviews of different processes impacted by thiols could be informative. Therefore, the present review on alterations of in vitro fertilization processes by thiols (mainly 2ME, since cysteamine alterations have been reviewed) was undertaken. Alterations found to occur in medium supplemented with 2ME were enhancement, no effect, or inhibition. Parameters associated with which are discussed as they relate to postulated thiol mechanisms.

Melatonin enhances the in vitro maturation and developmental potential of bovine oocytes denuded of the cumulus oophorus

This study was designed to determine the effect of melatonin on the in vitro maturation (IVM) and developmental potential of bovine oocytes denuded of the cumulus oophorus (DOs). DOs were cultured alone (DOs) or with 10-9 M melatonin (DOs + MT), cumulus-oocyte complexes (COCs) were cultured without melatonin as the control. After IVM, meiosis II (MII) rates of DOs, and reactive oxygen species (ROS) levels, apoptotic rates and parthenogenetic blastocyst rates of MII oocytes were determined. The relative expression of ATP synthase F0 Subunit 6 and 8 (ATP6 and ATP8), bone morphogenetic protein 15 (BMP-15) and growth differentiation factor 9 (GDF-9) mRNA in MII oocytes and IFN-tau (IFN-τ), Na+/K+-ATPase, catenin-beta like 1 (CTNNBL1) and AQP3 mRNA in parthenogenetic blastocysts were quantified using real-time polymerase chain reaction (PCR). The results showed that: (1) melatonin significantly increased the MII rate of DOs (65.67 ± 3.59 % vs. 82.29 ± 3.92%; P < 0.05), decreased the ROS level (4.83 ± 0.42 counts per second (c.p.s) vs. 3.78 ± 0.29 c.p.s; P < 0.05) and apoptotic rate (36.99 ± 3.62 % vs. 21.88 ± 2.08 %; P < 0.05) and moderated the reduction of relative mRNA levels of ATP6, ATP8, BMP-15 and GDF-9 caused by oocyte denudation; (2) melatonin significantly increased the developmental rate (24.17 ± 3.54 % vs. 35.26 ± 4.87%; P < 0.05), and expression levels of IFN-τ, Na+/K+-ATPase, CTNNBL1 and AQP3 mRNA of blastocyst. These results indicated that melatonin significantly improved the IVM quality of DOs, leading to an increased parthenogenetic blastocyst formation rate and quality.

Influence of oocyte donor on in vitro embryo production in buffalo

The aim of this research was to estimate the variability between buffalo as oocyte donors. In Experiment 1, reproductive variables were retrospectively analyzed in buffalo (n=40) that underwent repeated ovum pick up (OPU), over 16 puncture sessions (PS). The follicular recruitment among individuals and the relationship between follicular population and oocyte production were evaluated. In Experiment 2, eight buffalo underwent OPU for 28 PS and the oocytes were processed separately to correlate follicular and oocyte population at the first PS to blastocyst (BL) production. In Experiment 1, the average number of total follicles (TFL), small follicles (SFL), cumulus-oocyte complexes (COC) and Grade A+B COC recorded in each 4-PS period had great repeatability (r=0.52, 0.54, 0.60 and 0.57, respectively). The average number of Grade A+B COC recovered during the subsequent 15 PS was positively correlated with the first PS number of TFL (r=0.60; P<0.001), SFL (r=0.68; P<0.001), COC (r=0.48; P<0.01) and Grade A+B COC (r=0.40; P<0.05). In Experiment 2, a large variability among animals was observed in blastocyst yields. When animals were grouped according to the BL yield, the greatest BL yield group had a greater (P<0.05) number of TFL (8.3 ± 0.9 compared with 5.6 ± 0.7) and SFL (7.3 ± 0.3 compared with 3.8 ± 0.7) at the first PS than the lesser BL yield group. The average number of BL produced over the subsequent sessions was correlated with the number of TFL (r=0.80; P<0.05) and COC (r=0.76; P<0.05) observed at the first PS. These results demonstrated a donor influence on the oocyte and BL production, suggesting a preliminary screening to select the donors with greater potential.

Kinetics of GDF9 expression in buffalo oocytes during in vitro maturation and their associated development ability

The capacity of fully grown oocytes to regulate their own microenvironment by secreted paracrine factors contribute to their developmental competence. In spite of growing evidence about the vital role of Growth Differentiation Factor 9 (GDF9) in determination of oocyte developmental competence, there is insufficient information about time dependent behavior of its expression during in vitro maturation (IVM) to have definite understanding about at what time point during IVM it plays most crucial role. The study reports the kinetics of GDF9 expression under four different IVM supplement conditions in buffalo oocytes and their concomitant development rate up to blastocyst. Oocytes matured under an ideal media condition with all supplements and those cultured with only FSH resulted in significantly higher cumulus expansion, nuclear maturation, cleavage and blastocyst rates. GDF9 expression at both mRNA and protein levels at different time points of IVM revealed that magnitude of mRNA abundance at 8h of IVM was most important towards imparting development competence to buffalo oocytes. Appearance of GDF9 protein in maturing oocytes was found asynchronous with mRNA appearance in the time course of IVM suggesting possible posttranscriptional regulation of this gene under dynamic oocyte cumulus cell communication process. Abundance of mature GDF9 protein at 16 h was most consistently related with all oocyte development parameters.

Characterization of oocyte-expressed GDF9 gene in buffalo and mapping of its TSS and putative regulatory elements

Summary In spite of emerging evidence about the vital role of GDF9 in determination of oocyte competence, there is insufficient information about its regulation of oocyte-specific expression, particularly in livestock animals. Because of the distinct prominence of buffalo as a dairy animal, the present study was undertaken to isolate and characterize GDF9 cDNA using orthologous primers based on the bovine GDF9 sequence. GDF9 transcripts were found to be expressed in oocytes irrespective of their follicular origin, and shared a single transcription start site (TSS) at -57 base pairs (bp) upstream of ATG. Assignment of the TSS is consistent with the presence of a TATA element at -23 of the TSS mapped in this study. Localization of a buffalo-specific minimal promoter within 320 bp upstream of ATG was consolidated by identification of an E-box element at -113bp. Presence of putative transcription factor binding sites and other cis regulatory elements were analyzed at ~5 kb upstream of TSS. Various germ cell-specific cis-acting regulatory elements (BNCF, BRNF, NR2F, SORY, Foxh1, OCT1, LHXF etc.) have been identified in the 5' flanking region of the buffalo GDF9 gene, including NOBOX DNA binding elements and consensuses E-boxes (CANNTG). Presence of two conserved E-boxes found on buffalo sequence at -520 and -718 positions deserves attention in view of its sequence deviation from other species. Two NOBOX binding elements (NBE) were detected at the -3471 and -203 positions. The fall of the NBE within the putative minimal promoter territory of buffalo GDF9 and its unique non-core binding sequence could have a possible role in the control of the core promoter activity.

Coculturing denuded oocytes during the in vitro maturation of bovine cumulus oocyte complexes exerts a synergistic effect on embryo development

The present study examined the effect of coculturing cumulus oocyte complexes (COCs) and denuded oocytes (DOs) during in vitro maturation (IVM) on nuclear and cytoplasmic maturation, zona pellucida (ZP) hardening, the pattern of fertilization and glutathione peroxidase 1 (GPX1) gene expression in the oocyte. Furthermore, the rate of embryonic development and the quality of blastocysts were examined for both COCs and DOs. Three IVM conditions were studied: 1) the coculture of 12 COCs and 60 DOs, 2) COC control with 12 COCs, and 3) DO control with 60 DOs. The IVM was performed in a 120-μl droplet of TCM199-based IVM medium. Following IVM, in vitro fertilization (IVF) and in vitro culture (IVC) were conducted separately for the COCs and DOs (DO coculture) from the IVM coculture group. Coculturing COCs and DOs increased the percentage of oocytes reaching the blastocyst stage and the total number of cells per blastocyst in both the COC coculture (44.4 ± 8.6 vs 26.7 ± 9.7%, P < 0.01, and 137.9 ± 24.9 vs 121.7 ± 21.1, P < 0.05) and the DO coculture (20.5 ± 5.0 vs 11.1 ± 2.5%, P < 0.01, and 121.9 ± 27.5 vs 112.3 ± 33.2, P < 0.05) compared to their respective control groups. The synergistic effects of coculturing were detected as increased nuclear and cytoplasmic maturation, the prevention of ZP hardening, increased monospermic fertilization and increased expression of GPX1 in the oocytes in response to endogenous oocyte-secreted factors. In conclusion, coculturing COCs and DOs may be an effective culture system for both intact COCs and immature DOs.

Mitochondrial distribution, ATP-GSH contents, calcium [Ca2+] oscillation during in vitro maturation of dromedary camel oocytes

Dromedary camel oocytes have the ability to spontaneous parthenogenetic activation and development in vivo and in vitro. The present study was conducted to investigate changes in mitochondrial distribution, adenosine triphosphate (ATP), and glutathione (GSH) contents and [Ca(2+)] oscillation during in vitro maturation and spontaneous parthenogentic activation of dromedary camel oocytes. Dromedary camel cumulus-oocyte complexes (COCs) were matured in TCM199 medium supplemented with 10% FCS + 10 μg/mL FSH + 10 IU hCG + 10 IU eCG + 10 ng/mL EGF and 50 μg/mL gentamycine. Maturation was performed at 38.5 °C under 5% CO(2) in humidified air for 40 h. After maturation and removal of cumulus cells, oocytes were classified into: immature cultured (Group 1); metaphase II (M II, Group 2); and spontaneously parthenogenetically activated (with 2 polar bodies, Group 3); cleaved embryos (Group 4); and immature oocytes served as a control (Group 5). Cytoplasmic mitochondrial distribution, ATP-GSH contents, calcium [Ca(2+)] oscillation were determined. Results indicated that M II and spontaneously parthenogenetically activated oocytes represent 37.53% and 32.67% of the cultured oocytes, respectively, and 3.3% cleaved and developed to 2-16-cell stage embryos. Mitochondrial distribution, ATP-GSH contents and [Ca(2+)] oscillation were significantly (P < 0.01) differ between immature and matured dromedary camel oocytes. Mitochondrial distribution showed clustering form in matured oocytes without polar body. High polarized mitochondrial distribution (HPM) was detected in M II and spontaneously parthenogenetically activated oocytes, and the intensity of MitoTracker Red was higher in spontaneously parthenogenetically activated than M II. ATP-GSH contents and the duration of [Ca(2+)] oscillation were significantly (P < 0.01) higher in spontaneously parthenogenetically activated than M II oocytes or that matured without polar body. In conclusion, the higher incidence of spontaneously parthenogenetically activated in vitro matured dromedary camel oocytes could be attributed to the high polarized mitochondrial distribution associated with significantly higher ATP-GSH contents and duration of [Ca(2+)] oscillation.

Short-term preservation of porcine oocytes in ambient temperature: novel approaches

The objective of this study was to evaluate the feasibility of preserving porcine oocytes without freezing. To optimize preservation conditions, porcine cumulus-oocyte complexes (COCs) were preserved in TCM-199, porcine follicular fluid (pFF) and FCS at different temperatures (4°C, 20°C, 25°C, 27.5°C, 30°C and 38.5°C) for 1 day, 2 days or 3 days. After preservation, oocyte morphology, germinal vesicle (GV) rate, actin cytoskeleton organization, cortical granule distribution, mitochondrial translocation and intracellular glutathione level were evaluated. Oocyte maturation was indicated by first polar body emission and spindle morphology after in vitro culture. Strikingly, when COCs were stored at 27.5°C for 3 days in pFF or FCS, more than 60% oocytes were still arrested at the GV stage and more than 50% oocytes matured into MII stages after culture. Almost 80% oocytes showed normal actin organization and cortical granule relocation to the cortex, and approximately 50% oocytes showed diffused mitochondria distribution patterns and normal spindle configurations. While stored in TCM-199, all these criteria decreased significantly. Glutathione (GSH) level in the pFF or FCS group was higher than in the TCM-199 group, but lower than in the non-preserved control group. The preserved oocytes could be fertilized and developed to blastocysts (about 10%) with normal cell number, which is clear evidence for their retaining the developmental potentiality after 3d preservation. Thus, we have developed a simple method for preserving immature pig oocytes at an ambient temperature for several days without evident damage of cytoplasm and keeping oocyte developmental competence.

In vitro developmental potential of macaque oocytes, derived from unstimulated ovaries, following maturation in the presence of glutathione ethyl ester

BACKGROUND

The inadequacies of oocyte in vitro maturation (IVM) systems for both non-human primates and humans are evidenced by reduced fertilization and poor embryonic development, and may be partly explained by significantly lower glutathione (GSH) contents compared with in vivo matured (IVO) oocytes. As this influence has not been fully explored, this study investigated the effect of the GSH donor, glutathione ethyl ester (GSH-OEt), on the IVM and development of macaque oocytes as a model of human oocyte IVM.

METHODS

Macaque oocytes derived from unstimulated ovaries were cultured in mCMRL-1066 alone or supplemented with 3 or 5 mM GSH-OEt. In vitro matured oocytes were subjected to the GSH assay, fixed for the assessment of spindle morphology or prepared ICSI. Embryo development of zygotes cultured in mHECM-9 was assessed up to Day 9 post-ICSI. RESULTS Supplementation of the maturation medium with GSH-OEt significantly increased oocyte maturation and normal fertilization rates compared with control oocytes, but only 5 mM GSH-OEt significantly increased the oocyte and cumulus cell GSH content. Confocal microscopy revealed significant differences in the spindle morphology between IVO and control in vitro matured metaphase II oocytes. Oocytes matured with 5 mM GSH-OEt exhibited spindle area and spindle pole width similar to that seen in the IVO oocyte. While no significant differences were observed in blastocyst rates, addition of 3 mM GSH-OEt during IVM significantly increased the proportion of embryos developing to the 5-8 cell stage while 5 mM GSH-OEt significantly increased the proportion of morula-stage embryos compared with controls.

CONCLUSIONS

Supplementation of the IVM medium with GSH-OEt promotes better maturation and normal fertilization of macaque oocytes compared with non-supplemented medium. However, further improvement of the primate oocyte IVM culture system is required to support better blastocyst development of oocytes derived from unstimulated ovaries.

Ultrastructure of in vitro oocyte maturation in buffalo (Bubalus bubalis)

The objective of the present study was to describe ultrastructural changes in the nucleus and cytoplasmic organelles during in vitro maturation (IVM) of buffalo cumulus–oocyte complexes (COCs). The structures were collected by ovum pick-up (OPU). Some COCs, removed from maturation medium at 0, 6, 12, 18 and 24 h, were processed for transmission electron microscopy. The average number of COCs collected by OPU/animal/session was 6.4, and 44% of them were viable. Immature oocytes had a peripherally located nucleus, Golgi complex and mitochondrial clusters, as well as a large number of coalescent lipid vacuoles. After 6 h of IVM, the oocyte nucleus morphology changed from round to a flatter shape, and the granulosa cells (GC) lost most of their contact with zona pellucida (ZP). At 12 h the first polar body was extruded and the aspect of lipid droplet changed to dark, probably denoting lipid oxidation. Cortical granules were clearly visible at 18 h of maturation, always located along the oocyte periphery. At 24 h of IVM the number of cortical granules increased. Ultrastructure studies revealed that: (1) immature oocytes have a high lipid content; (2) the perivitelline space (PS) increases during IVM; (3) Golgi complexes and mitochondrial clusters migrate to oocyte periphery during IVM; (4) 6 h of IVM are enough to lose contact between GC and ZP; (5) the oocyte lipid droplets’ appearance changes between 6 and 12 h of IVM.

Factors affecting laboratory production of buffalo embryos: a meta-analysis

In vitro fertilization (IVF) provides an excellent and inexpensive source of embryos for carrying out basic research on developmental physiology, farm animal breeding, and for commercial applications. Meta-analysis of the results from different publications rather than a narrative review may provide a current status of this technology in buffalo (Bubalus bubalis). In order to gain an idea of the factors affecting the IVF in buffalo, a review of the various studies conducted on buffalo IVF and a meta-analysis of their findings was undertaken. More than 100 articles published from 1991 to 2008 were searched, and results were subjected to meta-analysis to determine the treatment variations without any bias. Thirty factors affecting in vitro embryo production in buffalo were considered. Initially, both fixed- and random-effect models were used. We did not observe any heterogeneity between the studies. Thereafter, all the studies were pooled using the fixed-effect model for analysis. Our analysis suggested that good buffalo oocytes with more than three to five cumulus layers recovered from large-sized follicles in cold seasons when cultured in TCM-199 supplemented with serum, follicle-stimulating hormone, and cysteamine resulted in maximum maturation rate and subsequent embryonic development after insemination. The values obtained in the current study may be considered for a simulation model in establishing a cost-effective suitable method for buffalo IVF in further planned research.

Developmental competence of porcine oocytes selected by brilliant cresyl blue and matured individually in a chemically defined culture medium

The objective of this study was to investigate the effects of oocyte selection using brilliant cresyl blue (BCB) and culture density during individual in vitro maturation (IVM) on porcine oocyte maturity and subsequent embryo development using a chemically defined medium. Cumulus-oocyte complexes (COCs) were classified as BCB-positive or BCB-negative after exposure to a BCB solution for 90 min. The classified COCs were matured in a group (15 COCs per 100-microL droplet) or individually (1 COC per 1-, 2.5-, 5-, or 10-microL droplet). Meiotic competence, intraoocyte glutathione concentration, and developmental competence after intracytoplasmic sperm injection were monitored. The BCB selected oocytes competent for nuclear and cytoplasmic maturation. Furthermore, meiotic competence for oocytes matured individually in a 5-microL droplet was superior (P<0.05) to that of oocytes matured in a 1-microL droplet. Also, the culture density in a 5-microL droplet during IVM resulted in a higher (P<0.05) rate of cleaved embryos than that in a 1-microL droplet and produced a similar rate of blastocysts compared with that of a group culture system. Conversely, BCB selection did not improve cleavage and blastocyst formation. In conclusion, it was possible to predict porcine oocytes competent for maturation using oocyte selection with BCB. Moreover, a 5-microL droplet during the individual IVM culture was most suitable for oocyte maturation and subsequent embryo development, although every culture density used in this study supported development up to the blastocyst stage.