Effect of protein supplementation and presence of an antioxidant on the development of bovine zygotes in synthetic oviduct fluid medium under high or low oxygen tension

Mitochondria-targeted therapy rescues development and quality of embryos derived from oocytes matured under oxidative stress conditions: a bovine in vitro model

STUDY QUESTION

Can we use a mitochondrial-targeted antioxidant (Mitoquinone) during in vitro embryo culture to rescue developmental competence of oocytes matured under lipotoxic conditions, exhibiting mitochondrial dysfunction and oxidative stress?

SUMMARY ANSWER

Supplementation of embryo culture media with Mitoquinone reduced oxidative stress and prevented mitochondrial uncoupling in embryos derived from metabolically compromised oocytes in vitro, leading to higher blastocyst rates and lower blastomeric apoptosis.

WHAT IS KNOWN ALREADY

Maternal metabolic disorders, such as obesity and type-II diabetes are associated with hyperlipidemia and elevated free fatty acid (FFA) concentrations in the ovarian follicular fluid (FF). Oocyte maturation under these lipotoxic conditions results in increased oxidative stress levels, mitochondrial dysfunction, reduced developmental competence and disappointing IVF results.

STUDY DESIGN, SIZE, DURATION

A well-described bovine oocyte IVM model was used, where a pathophysiologically relevant elevated FF concentrations of palmitic acid (PA; 150 μM or 300 μM) were added to induce oxidative stress. After fertilization (Day 0, D0), zygotes were in vitro cultured (IVC, from D1 to D8) in standard fatty acid-free media in the presence or absence of Mitoquinone or its carrier triphenyl-phosphonium.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Embryo cleavage and fragmentation (D2) and blastocyst rates (D8) were recorded. Mitochondrial activity and oxidative stress in cleaved embryos at D2 were determined using specific fluorogenic probes and confocal microscopy. D8 blastocysts were used to (i) examine the expression of marker genes related to mitochondrial unfolded protein responses (UPRmt; HSPD1 and HSPE1), mitochondrial biogenesis (TFAM), endoplasmic reticulum (ER) UPR (ATF4, ATF6 and BiP) and oxidative stress (CAT, GPX1 and SOD2) using real time RT-PCR; (ii) determine cell differentiation and apoptosis using CDX-2 and cleaved caspase-3 immunostaining; and (iii) measure mtDNA copy numbers. This was tested in a series of experiments with at least three independent replicates for each, using a total of 2525 oocytes. Differences were considered significant if a P value was <0.05 after Bonferroni correction.

MAIN RESULTS AND THE ROLE OF CHANCE

Exposure to PA during IVM followed by culture under control conditions resulted in a significant increase in oxidative stress in embryos at D2. This was associated with a significant reduction in mitochondrial inner membrane potential (uncoupling) compared with solvent control (P < 0.05). The magnitude of these effects was PA-concentration dependent. Consequently, development to the blastocysts stage was significantly hampered. Surviving blastocysts exhibited high apoptotic cell indices and upregulated mRNA expression indicating persistent oxidative stress, mitochondrial and ER UPRs. In contrast, supplementation of PA-derived zygotes with Mitoquinone during IVC (i) prevented mitochondrial uncoupling and alleviated oxidative stress at D2; and (ii) rescued blastocyst quality; normalized oxidative stress and UPR related genes and apoptotic cell indices (P > 0.01 compared with solvent control). Mitoquinone also improved blastocyst rate in PA-exposed groups, an effect that was dependent on PA concentration.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This is a fundamental study performed using a bovine in vitro model using PA-induced lipotoxicity during oocyte maturation. PA is the most predominant FFA in the FF that is known to induce lipotoxicity; however, in vivo maturation in patients suffering from maternal metabolic disorders involve more factors that cannot be represented in one model. Nevertheless, focusing on the carryover oxidative stress as a known key factor affecting developmental competence, and considering the novel beneficial rescuing effects of Mitoquinone shown here, we believe this model is of high biological relevance.

WIDER IMPLICATIONS OF THE FINDINGS

Human oocytes collected for IVF treatments from patients with maternal metabolic disorders are vulnerable to lipotoxicity and oxidative stress during in vivo maturation. The results shown here suggest that mitochondrial targeted therapy, such as using Mitoquinone, during IVC may rescue the developmental competence and quality of these compromised oocytes. After further clinical trials, this may be a valuable approach to increase IVF success rates for infertile patients experiencing metabolic disorders.

STUDY FUNDING/COMPETING INTEREST(S)

This study was financially supported by a BOF/KP grant number 34399, from the University of Antwerp, Belgium. W.F.A.M. was supported by a postdoctoral fellowship from the Research Foundation-Flanders (FWO), grant number 12I1417N, Antwerp, Belgium. The Leica SP 8 confocal microscope used in this study was funded by the Hercules Foundation of the Flemish Government (Hercules grant AUHA.15.12). All authors have no financial or non-financial competing interests to declare.

Developmental potential of buffalo embryos cultured in serum free culture system

The presence of serum in embryo culture medium has been implicated for increased embryo's sensitivity to cryopreservation, compromised viability, abnormal embryo and fetal development. Hence, designing a serum free culture system is indispensable. The present study aims to compare the efficiency of the serum and granulosa cells monolayer free commercial culture system (SFCS) with the conventional serum supplemented co-culture system (SSCS) and optimized culture system (OCS). Generally, SFCS is designed explicitly for bovine oocyte maturation and embryo culture (SF-IVM and SF-IVC), and SSCS (based on M199, SS-IVM, and SS-IVC) is utilized for buffalo in vitro embryo production. However, OCS is a newly designed culture system in which oocyte maturation is performed in serum supplemented maturation medium, and the subsequent embryos are co-cultured with granulosa cells in serum free culture medium. To evaluate the effect of serum on buffalo embryo production, buffalo oocytes, and their subsequent embryos were cultured in SSCS, SFCS, and OCS, simultaneously. The percentage of cleaved embryos cultured in SSCS and OCS was approximately 4% higher as compared to SFCS. However, OCS significantly showed the maximum proportion of embryos that developed to the blastocyst stage (7d) and hatched (6d) as compared to the SFCS and SSCS. Additionally, OCS promoted the expression of developmentally important genes (BCL2-L1 and VEGF-A), cell number, and cryo-survival ability of blastocysts in comparison with SSCS. Taken together, OCS is more suitable for the oocyte maturation and culture of buffalo embryos. However, to design the serum free culture system, it is recommended to find suitable serum alternatives for in vitro oocyte maturation.

The Replacement of Fetal Bovine Serum with Bovine Serum Albumin During Oocyte Maturation and Embryo Culture Does Not Improve Blastocyst Quality After Slow Freezing Cryopreservation

In the present study, four experimental groups were used: fresh embryos, cultured during in vitro maturation and in vitro culture in media supplemented with bovine serum albumin (BSA) (fresh BSA) or fetal bovine serum (FBS) (fresh FBS); and two groups of cryopreserved and thawed embryos, produced under the same conditions (frozen BSA and frozen FBS). Experiment 1 evaluated the protein source effect on embryo development and response to cryopreservation. At day 7, half of the expanded blastocysts (Bx) from each group were cryopreserved and warmed and the other half were used as controls. After warming, embryos were incubated under the same conditions for 48 hours, and the hatching rate was measured at 24 and 48 hours. The total and the apoptotic cell numbers were measured in a subset of Bx after 24 hours. Experiment 2 used the Bx of experiment 1 to compare the expression of KRT8, PLAC8, FOSL1, HSP1A1, and HSPA5 genes in hatched blastocysts at 24 and 48 hours for all groups. The FBS group showed a higher percentage (p < 0.05) of embryos (42.8% vs. 27.9%) and higher rates of Bx (75.0% vs. 63.8%) on day 7, compared with the BSA group. At 24 hours postwarming, the fresh FBS group showed the highest hatching rate (p < 0.05) in comparison with other treatments. However, at 48 hours, the hatching rate was similar (p > 0.05) among groups: fresh FBS (68.1% ± 23.3%), fresh BSA (70.0% ± 31.0%), frozen FBS (39.2 ± 27.1), and frozen BSA (38.2 ± 23.9). After 24 hours, frozen BSA showed a higher number of cells compared with frozen FBS (p < 0.05). The expression of the PLAC8 gene was higher (p < 0.05) in fresh BSA embryos compared with frozen FBS embryos at 24 hours. In the present study, BSA replacement reduced embryo development, but did not affect the response to cryopreservation. However, upregulation of the PLAC8 gene suggests that embryos cultured in BSA might have better quality to support further development.

Supplementation of bovine follicular fluid during in vitro maturation increases oocyte cumulus expansion, blastocyst developmental kinetics, and blastocyst cell number

Bovine follicular fluid (bFF) is the natural milieu for oocyte growth and development. However, its value as supplementation to in vitro maturation medium is still questioned due to inconsistent results. In this study we hypothesized that adding 10% of follicular fluid as well as heat treating it to inhibit the complement system, would produce higher quality embryos. To do so, experiments were conducted to compare the effect of bFF and heat-treated bFF (bFFin) on oocyte competence assessed by different parameters such as nuclear and cytoplasmic maturation, IVF efficiency, in vitro embryo development and embryo survivability post-vitrification. No differences on nuclear maturation nor cortical granules migration were observed but differences were found on oocyte's cumulus cell expansion, with bFF group having the highest increase (79.0 ± 3.7%). bFFin had a negative impact on IVF efficiency (58.6 ± 3.2%), but no differences were found between bFF (62.9 ± 3.2%) and control (72.8 ± 3.0%). Although the cleavage and blastocyst rate were similar between groups, the day 6 embryo development rate was higher in bFFin group, suggesting an accelerated developmental kinetics. Hatched blastocysts from the bFF group showed a higher cell count than the control group (241.3 ± 20.1 and 185.8 ± 10.0, respectively), and bFFin embryos showed values in between (214.9 ± 14.0). No difference on survivability post-vitrification was found between groups, although the blastocyst stage had a significant impact on the survival rate across all groups. In conclusion, using bFF as supplementation to maturation medium showed a higher benefit when comparing to the standard supplementation by having oocytes with higher cumulus expansion rate, faster development of embryos and higher number of cells per embryo. Inactivation of bFF lowered IVF efficiency but didn't compromise blastocyst development and quality.

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.

Improved Murine Blastocyst Quality and Development in a Single Culture Medium Compared to Sequential Culture Media

OBJECTIVE

Validate single versus sequential culture media for murine embryo development.

DESIGN

Prospective laboratory experiment.

SETTING

Assisted Reproduction Laboratory.

ANIMALS

Murine embryos.

INTERVENTIONS

Thawed murine zygotes cultured for 3 or 5 days (d3 or d5) in single or sequential embryo culture media developed for human in vitro fertilization.

MAIN OUTCOME MEASURES

On d3, zygotes developing to the 8 cell (8C) stage or greater were quantified using 4',6-diamidino-2-phenylindole (DAPI), and quality was assessed by morphological analysis. On d5, the number of embryos reaching the blastocyst stage was counted. DAPI was used to quantify total nuclei and inner cell mass nuclei. Localization of ubiquitin C-terminal hydrolase L1 (UCHL1) and ubiquitin C-terminal hydrolase L3 (UCHL3) was reference points for evaluating cell quality.

RESULTS

Comparing outcomes in single versus to sequential media, the odds of embryos developing to the 8C stage on d3 were 2.34 time greater (P = .06). On d5, more embryos reached the blastocyst stage (P = <.0001), hatched, and had significantly more trophoblast cells (P = .005) contributing to the increased total cell number. Also at d5, localization of distinct cytoplasmic UCHL1 and nuclear UCHL3 was found in high-quality hatching blastocysts. Localization of UCHL1 and UCHL3 was diffuse and inappropriately dispersed throughout the cytoplasm in low-quality nonhatching blastocysts.

CONCLUSIONS

Single medium yields greater cell numbers, an increased growth rate, and more hatching of murine embryos. Cytoplasmic UCHL1 and nuclear UHCL3 localization patterns were indicative of embryo quality. Our conclusions are limited to murine embryos but one might speculate that single medium may also be more beneficial for human embryo culture. Human embryo studies are needed.

R. Neto R, Andrade ES, Andrade EA. Toxicity of cryoprotectants on Prochilodus lineatus (Valenciennes, 1837) (curimba) embryos in an experimental incubator (Characiformes: Prochilodontidae)

This paper investigated the effect of cryoprotectant substances on Prochilodus lineatus embryos in an experimental incubator. The prospective study applied combinations of polyvinyl alcohol, hydroxyethyl cellulose, gelatin and fetal bovine serum with dimethyl sulfoxide and ethylene glycol in a new experimental incubator. The morphology of embryos, larval viability and the efficiency of experimental incubators in maintaining the quality of embryos were evaluated. This study demonstrates the efficient association between hydroxyethylcellulose and dimethyl sulfoxide as greater viability (p<0.05) was found for embryos (72.9 ± 23.9%). It should also be noted the permeation of cryoprotectants in embryos through the changes found in chorion diameter, embryo diameter and embryo volume comparing the treatments versus control group (water) (p<0.05), this results can help in future cryopreservation protocols. Although the temperature and oxygenation differed between the usual and experimental incubators (p<0.05), the results showed a high fertilization rate (79.6 ± 13.2%) for experimental incubators (p<0.05) which is sufficient for the maintenance of embryos in a cryoprotective environment and effectively allows experimentation for long periods with cryoprotectant substances. Cryopreservation of fish embryos has not been accomplished yet and new approaches are required for understanding the permeability of teleost embryos, especially in Brazilian native species.

Stability of reference genes for normalization of reverse transcription quantitative real-time PCR (RT-qPCR) data in bovine blastocysts produced by IVF, ICSI and SCNT

Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is a sensitive and accurate tool for quantitative estimation of gene transcription levels in preimplantation embryos. To control for possible experimental variations, gene expression data must be normalized using internal control genes commonly known as reference genes. However, the stability of reference genes can vary depending on the state of development and/or experimental conditions; hence the assessment of their stability is essential before initiating a gene expression analysis. In the present study, we used RT-qPCR to measure the transcript levels of 10 commonly used reference genes and analyzed their expression stability in bovine blastocysts produced by in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and somatic cell nuclear transfer (SCNT). Using the geNorm program, we found the best combination of genes to normalize gene expression data in bovine embryos at the blastocyst stage produced by IVF (HMBS, SF3A1, and HPRT1), ICSI (H2A, HMBS, and GAPDH), SCNT (ACTB, SF3A1, and SDHA) and/or between blastocysts produced by these methods (GAPDH, HMBS and EEF1A2). We also demonstrated that not only the culture conditions may affect the expression patterns in bovine blastocysts but also the choice of embryo production method may have an important effect.

Defined media optimization for in vitro culture of bovine somatic cell nuclear transfer (SCNT) embryos

The objective was to establish an efficient defined culture medium for bovine somatic cell nuclear transfer (SCNT) embryos. In this study, modified synthetic oviductal fluid (mSOF) without bovine serum albumin (BSA) was used as the basic culture medium (BCM), whereas the control medium was BCM with BSA. In Experiment 1, adding polyvinyl alcohol (PVA) to BCM supported development of SCNT embryos to blastocyst stage, but blastocyst formation rate and blastocyst cell number were both lower (P < 0.05) compared to the undefined group (6.1 vs. 32.6% and 67.3 ± 3.4 vs. 109.3 ± 4.5, respectively). In Experiment 2, myo-inositol, a combination of insulin, transferrin and selenium (ITS), and epidermal growth factor (EGF) were added separately to PVA-supplemented BCM. The blastocyst formation rate and blastocyst cell number of those three groups were dramatically improved compared with that of PVA-supplemented group in Experiment 1 (18.5, 23.0, 24.1 vs. 6.1% and 82.7 ± 2.0, 84.3 ± 4.2, 95.3 ± 3.8 vs. 67.3 ± 3.4, respectively, P < 0.05), but were still lower compared with that of undefined group (33.7% and 113.8 ± 3.4, P < 0.05). In Experiment 3, when a combination of myo-inositol, ITS and EGF were added to PVA-supplemented BCM, blastocyst formation rate and blastocyst cell number were similar to that of undefined group (30.4 vs. 31.1% and 109.3 ± 4.4 vs. 112.0 ± 3.6, P > 0.05). In Experiment 4, when blastocysts were cryopreserved and subsequently thawed, there were no significant differences between the optimized defined group (Experiment 3) and undefined group in survival rate and 24 and 48 h hatching blastocyst rates. Furthermore, there were no significant differences in expression levels of H19, HSP70 and BAX in blastocysts derived from optimized defined medium and undefined medium, although the relative expression abundance of IGF-2 was significantly decreased in the former. In conclusion, a defined culture medium containing PVA, myo-inositol, ITS, and EGF supported in vitro development of bovine SCNT embryos.

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

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

In vitro assessment of sperm from bulls of high and low field fertility

The aim of this study was to investigate the reasons for differences in field fertility of bulls following insemination with frozen-thawed semen. The study was carried out in two separate parts over two years and comparisons were made between 5 high and 4 low fertility Holstein Friesian bulls as determined by their either 90 day non-return rate (Year 1) or calving rate (Year 2). Two high fertility Limousin bulls were included in Year 1 for comparative purposes. The ability of sperm from each bull to penetrate artificial mucus was assessed (Year 1 = 7 replicates; Year 2 = 5 replicates). Glass capillary tubes (2 per bull per replicate) were filled with artificial mucus and incubated with sperm stained in 1% Hoechst 33342 for 30 min at 37 °C. The number of sperm were subsequently counted at 10 mm intervals along the tube between 40 and 80 mm markers. Sperm mitochondrial activity of each bull was assessed by the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay (4 replicates in each year). Sperm were incubated with MTT for 1 h at 37 °C following which the absorbance of formazan was read using a spectrophotometer. Sperm viability after thawing was assessed for each bull using a live/dead sperm viability kit (Year 1 = 3 replicates; Year 2 = 4 replicates). A minimum of 250 cells were assessed per bull in each replicate and classified as either live or dead. Finally, the ability of sperm to fertilize oocytes in vitro and their ability to develop to blastocyst stage embryos were assessed (5 replicates in each year involving 220 to 306 oocytes per bull). Data transformation to normalize residuals was required for mucus sperm penetration (square root) and IVF (cleavage and blastocyst rate) results (arcsin). The mean number of sperm counted at each 10 mm mark between 40 and 80 mm was higher in the high fertility (56.0; 95% CI 39.5 to 75.3) compared to the low fertility (42.9; 95% CI 29.3 to 59.1) Holstein Friesian bulls but the difference did not reach formal significance (P = 0.09). Fertility status had no effect on the ability of sperm to reduce MTT to formazan (mean absorbance 0.34 ± 0.051 and 0.30 ± 0.044) or on the percentage of live sperm per straw (mean 47.3 ± 5.47 and 32.4 ± 4.66) for high and low fertility Holstein Friesian bulls respectively. Oocyte cleavage rate following insemination with sperm from high fertility Holstein Friesian bulls was significantly higher than with sperm from low fertility Holstein Friesian bulls [76.7% (95% CI 60.9 to 89.4) and 55.3 (95% CI 40.4 to 69.7) respectively, P = 0.04]. There was no significant effect of bull fertility on blastocyst rate [34.7% (95% CI 21.1 to 49.6) and 24.2 % (95% CI 14.1 to 36.0) for the high and low fertility Holstein Friesian bulls, respectively; P = 0.2]. In conclusion, sperm from high fertility bulls tended to be more effective in penetrating artificial mucus and to have an increased ability to fertilize oocytes in vitro; however, once fertilization occurred subsequent embryo development was not significantly affected by fertility status.

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

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

Ameliorating effect of vitamin E on in vitro development of preimplantation buffalo embryos

PURPOSE

Oxidative stress has been implicated in the etiology of defective embryo development. Vitamin E is an effective lipid-soluble antioxidant, protecting cell membranes from peroxidative damage. In this context, this study was undertaken to find if supplementation of vitamin E in culture medium could ameliorate the developmental competence of preimplantation buffalo embryos.

METHODS

Vitamin E was supplemented in maturation/embryo culture medium at concentrations of 0, 50, 100, 200 and 400 microM. The developmental competence of buffalo embryos was assessed by observing the cleavage, morulae, blastocyst rate, total cell count and comet assay.

RESULTS

Vitamin E had no significant effect in maturation medium. Vitamin E in embryo culture medium under 5% O(2) significantly reduced blastocyst formation in the 400 microM supplemented group. Culture under 20% O(2) enhanced the frequency of blastocyst formation, total cell count and significantly reduced comet tail in the 100 microM supplemented group (P < 0.001) when compared with the control. Vitamin E in ECM for the first 72 h of culture period enhanced blastocyst rate and total cell number in the 100 microM group (P < 0.001) when compared with the control.

CONCLUSION

Our results demonstrate that the addition of Vitamin E may enhance the developmental competence of buffalo embryos in vitro by protecting them from oxidative stress.

Effect of taurine and melatonin in the culture medium on buffalo in vitro embryo development

This study was carried out to investigate the effect of supplementing culture medium with different concentrations of taurine and melatonin, on buffalo oocyte in vitro meiotic maturation and embryo development. In experiment 1, oocytes were matured in vitro and the cleaved embryos were cultured in the same following seven culture medium; (i) control (TCM 199 + 10% SS); (ii) control + 0.5 mM taurine; (iii) control + 1 mM taurine; (iv) control + 3 mM taurine; (v) control + 5 microM melatonin; (vi) control + 10 microM melatonin and (vii) control + 50 microM melatonin. In experiment 2, based on the results of experiment 1, to examine the synergistic effect of antioxidants, the oocytes were matured in culture medium (TCM199 + 10% SS), supplemented with both taurine at 1 mM and melatonin at 10 microM concentration and the cleaved embryos were cultured in the same medium. Supplementation of taurine at 1 mM concentration in the culture medium resulted in a higher (p < 0.05) transferable embryo (TE) yield when compared with control (20.6% vs 14.1%). Supplementation of melatonin at 10 and 50 microM concentration in the culture medium resulted in a higher (p < 0.05) meiotic maturation rate (90.3% and 88.8% respectively) and TE yield (28.4% and 27.2% respectively), than the other treatments. In experiment 2, the TE yield did not improve by supplementing the culture medium with both taurine and melatonin, when compared with melatonin alone. In conclusion, the results of this study demonstrated that, enriching the culture medium with taurine and melatonin, improves in vitro embryo production efficiency in buffaloes. In particular, a high TE yield was obtained by enriching the culture medium with 10 microM melatonin.

Oxygen tension during in vitro culture of bovine embryos: Effect in production and expression of genes related to oxidative stress

In vitro bovine embryos production and quality was evaluated in two culture systems, which utilize different oxygen tension. After IVM/IVF presumptive zygotes were cultured in either one of the two systems. The culture systems evaluated were-high O2: SOFaaci medium and culture for 7 d under 5% CO2 in air, at 39 degrees C in the presence of cumulus cells (control); low O2: SOFaaci medium and culture for 7 d under 5% CO2 and 5% O2 at 39 degrees C. In low O2 system the zygotes were denuded by successive pipetting before being transferred to culture medium, while in the high O2 zygotes kept the cumulus cells that remained after IVF. Cleavage rates were evaluated 48 h post-insemination (hpi) and the blastocyst rates at D6 and D7 post-insemination (pi). From both groups a total of 94 expanded blastocysts, from D7 of culture, were fixed and stained with aceto-orcein to evaluate cell numbers. Seven pools of 15 embryos from each treatment were frozen for gene expression evaluation. The abundance of transcripts for genes related to oxidative stress, superoxide dismutase (Mn-SOD), catalase, gluthatione peroxidase (GPX) and for embryo quality, interferon-tau (IFN-tau) were determined using a semi-quantitative RT-PCR. Cleavage rate was similar (P>0.05) for both groups. The blastocyst rate at D6 pi was greater (P<0.05) in the group cultured under low O2 tension (37.4%) than in the high O2 tension (21.9%). However, blastocyst rate and total cell number at D7 were similar (P>0.05) between groups. No change (P>0.05) in transcript amount between treatments was observed for GPX, catalase and IFN-tau genes. However, the relative abundance of transcripts for Mn-SOD gene was greater (P<0.05) for embryos cultured in high O2 tension system. The results suggest that bovine embryos can be cultured either in SOFaaci medium under greater O2 tension in the presence of cumulus cells, or in SOFaaci medium under less O2 tension, without affecting embryo production or quality.

Human blastocyst morphological quality is significantly improved in embryos classified as fast on day 3 (≥10 cells), bringing into question current embryological dogma

OBJECTIVE

To evaluate developmental potential of fast cleaving day 3 embryos.

DESIGN

Retrospective analysis.

SETTING

Academic reproductive center.

PATIENT(S)

Three thousand five hundred twenty-nine embryos.

INTERVENTION(S)

Day 3 embryos were classified according to cell number: slow cleaving: <or=6 cells, intermediate cleaving: 7-9 cells, and fast cleaving: >or=10 cells, and further evaluated on day 5. The preimplantation genetic diagnosis (PGD) results of 43 fast cleaving embryos were correlated to blastocyst formation. Clinical outcomes of transfers involving only fast cleaving embryos (n = 4) were evaluated.

MAIN OUTCOME MEASURE(S)

Blastocyst morphology correlated to day 3 blastomere number. Relationship between euploidy and blastocyst formation of fast cleaving embryos. Implantation, pregnancy (PR), and birth rates resulting from fast embryo transfers.

RESULT(S)

Blastocyst formation rate was significantly greater in the intermediate cleaving (72.7%) and fast cleaving (54.2%) groups when compared to the slow cleaving group (38%). Highest quality blastocysts were formed significantly more often in the fast cleaving group. Twenty fast cleaving embryos that underwent PGD, formed blastocysts, of which 45% (9/20) were diagnosed as euploid. Aneuploidy was diagnosed in 82.6% (19/23) of arrested embryos. A 50% implantation and 100% PR and birth rate were achieved with embryo transfers involving fast cleaving embryos.

CONCLUSION(S)

Fast cleaving embryos not only reach the blastocyst stage at a similar rate to intermediate cleaving embryos, but also exceed morphological quality criteria on day 5. Fast cleaving embryo transfers demonstrated a high clinical potential.

Set up of a serum-free culture system for bovine embryos: embryo development and quality before and after transient transfer

It is well known that serum in culture medium negatively affects blastocyst quality. The objective of this work was to develop and test a serum-free culture medium which could improve embryo quality, measured by the resistance to freezing, lipid and glutathione content of the resulting blastocysts, as well as the ability of the blastocysts to elongate after transient transfer to recipient cows. In a first experiment we showed that adding a mixture of insulin, transferrin and selenium to serum-free Synthetic Oviduct Fluid medium (SOF-ITS) improved embryo development and quality. In the second experiment, the addition of BSA to SOF-ITS further improved blastocyst development. Moreover, a reduction in lipid content of morulae was observed in SOF-ITS-BSA by comparison with morulae cultured with serum (SOF-FCS). The resistance to freezing measured by hatching rates 24h post-thawing was also improved for blastocysts with a diameter between 160 and 180 microm cultured in SOF-ITS-BSA by comparison to those produced with serum. In order to evaluate the redox potential of the embryos, reduced glutathione content (GSH) was evaluated both before and after cryopreservation. A significant decrease in glutathione was observed after freezing, whatever the culture medium, but no difference was observed between culture conditions. Transient transfers were performed and elongated D-13 embryos were recovered. Elongation was more pronounced and the embryonic disk more often visible in embryos cultured in SOF-ITS-BSA than in embryos cultured with FCS. In conclusion, the serum-free system we developed to produce in vitro bovine embryos meets the developmental and qualitative requirements for a large-scale use.

Bovine in vitro oocyte maturation as a model for manipulation of the γ-glutamyl cycle and intraoocyte glutathione

Glutathione (GSH) is the main non-enzymatic defence against oxidative stress and is a critical intracellular component required for oocyte maturation. In the present study, several modulators of intracellular GSH were assessed for their effect on the in vitro maturation (IVM) and intracellular GSH content of bovine metaphase (MII) oocytes. Of the five GSH modulators tested, only the cell-permeable GSH donor glutathione ethyl ester (GSH-OEt) significantly increased the GSH content of IVM MII oocytes in a concentration-dependent manner without adversely affecting oocyte maturation rate. The GSH level in IVM MII oocytes was greatly influenced by the presence or absence of cumulus cells and severely restricted when oocytes were cultured in the presence of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. The addition of GSH-OEt to cumulus-denuded or BSO-treated oocytes increased the GSH content of bovine MII oocytes. Supplementation of the maturation medium with bovine serum albumin (BSA) or fetal calf serum (FCS) affected the GSH content of IVM MII oocytes, with greater levels attained under BSA culture conditions. The addition of GSH-OEt to the maturation medium increased the GSH content of IVM MII oocytes, irrespective of protein source. Spindle morphology, as assessed by immunocytochemistry and confocal microscopy, displayed distinct alterations in response to changes in oocyte GSH levels. GSH depletion caused by BSO treatment tended to widen spindle poles and significantly increased spindle area. Supplementation of the IVM medium with GSH-OEt increased spindle length, but did not significantly alter spindle area or spindle morphology. GSH-OEt represents a novel oocyte-permeable and cumulus cell-independent approach for effective elevation of mammalian oocyte GSH levels.

Melatonin effect on bovine embryo development in vitro in relation to oxygen concentration

Melatonin promotes mouse embryo development in vitro. An effect of melatonin on bovine embryo development is described here. Slaughterhouse derived oocytes were subjected to standard in vitro maturation and fertilization procedures. Presumptive zygotes were cultured for 2 days in CR1aaLA medium supplemented with melatonin (10(-4) m) or without melatonin (control). Culture was performed under two different gas atmospheres containing physiological (7%) or atmospheric (20%) oxygen concentrations (2x2 factorial analysis). After day 2, embryos from each treatment group developed to at least four-cell stage, were cultured without melatonin until day 10 at optimum 7% O2 atmosphere. Blastocyst formation rates of presumptive zygotes and of four-cell embryos were calculated for each group. Significant interactions between oxygen tension and the melatonin treatment were found. Out of four-cell embryos put into in vitro culture after initial incubation in medium containing melatonin, decreased blastocyst rate was observed in melatonin group (47.7%) compared with control (67.7%; P=0.0327) when lower oxygen concentration was applied. A beneficial effect of melatonin was observed in 20% O2: out of 61 embryos, 42 (68.9%) developed to the blastocyst stage after treatment in melatonin versus 32 of 63 (50.8%; P=0.0458) blastocysts that developed in control group. In conclusion, beneficial or harmful effects of melatonin on bovine embryo development in vitro were observed, depending on the oxygen tension during the treatment.

Temporal expression of transcripts related to embryo quality in bovine embryos cultured from the two-cell to blastocyst stage in vitro or in vivo

The post-fertilization embryo culture environment can have a dramatic effect on the pattern of gene expression in the embryo and it is widely acknowledged that bovine embryos derived from in vitro culture are of inferior quality to those derived in vivo. The objective of this study was to examine temporal variation in the mRNA abundance of several transcription and translation factors known to differ between blastocysts produced following culture in vitro and in vivo. Embryos were recovered from two in vitro culture systems SOF1 or SOF2 at five developmental stages: 2- to 4-cell, 8-cell, 16-cell, morula, and blastocyst. In vivo embryos were produced from superovulated and artificially inseminated heifers and recovered at approximately 40 hr or 3, 4, 5, and 7 days postinsemination. Blastocysts were also produced following in vitro maturation, in vitro fertilization and culture in the ewe oviduct. Analysis of relative transcript abundance for FOXO3A, EEF1G, HMG2, and REA was performed using quantitative real-time PCR. Irrespective of culture environment each transcript followed, approximately the same general pattern of expression where relative abundance decreased dramatically from the 2- to 4-cell stage to 8-cell stage and increased from the morula to blastocyst stage (P < 0.05). Transcripts for GNBL2 were not observed between the 2- and 16-cell stage of development. Relatively high expression at the 2- to 4-cell indicated that these transcripts are most likely of maternal origin produced in the oocyte during growth and final maturation. A culture-induced change in mRNA abundance of transcription and translation factors was evident in embryos that were produced not only between in vivo and in vitro culture environments but also between different in vitro culture systems.

Selenium improves the developmental ability and reduces the apoptosis in porcine parthenotes

Selenium is an essential trace element in conventional tissue culture media to guarantee adequate biosynthesis of selenoprotein in cellular antioxidant system to protect the cells from oxidative damage and apoptosis. This study investigated the effect of selenium, in the form of sodium selenite (SS), on developmental ability and quality of in vitro produced porcine parthenotes. For this, parthenogenetic presumptive diploid zygotes were produced by electroactivation and cultured in the absence or presence of SS at different concentrations (0, 2.5, 25, 250 ng/ml) in a serum-free defined culture medium supplemented with polyvinyl alcohol (PVA) or bovine serum albumin (BSA). Results showed that, development rate of 2-4 cell stage parthenotes to blastocyst and their cell number was increased while TUNEL index was decreased, in a dose-dependent manner, when SS was supplemented to NCSU23 + PVA. Interestingly, the blastocyst rate and their quality approached to those cultured in NCSU23 + BSA (P < 0.05), thereby suggesting PVA + 25 ng/ml SS to be a partial replacement of BSA. In the presence of PVA, supplementation of SS at a concentration of 25 ng/ml did not improve the cleavage rate of in vitro matured oocytes but there was significant improvement in the blastocyst rate (45.4 +/- 8.8% vs. 12.7 +/- 4.8%), total nuclei number (42.1 +/- 3.5 vs. 31.3 +/- 2.9) and inner cell mass (ICM) rate (29.4 +/- 1.5% vs. 21.3 +/- 1.2%) and decrease in TUNEL index (5.6 +/- 0.5 vs. 12.9 +/- 1.3) compared to nonsupplemented controls. The SS supplementation also decreased the BAX:BCL-xL transcript ratio, increased the expression of ERK1/2 and glutathione peroxidase (GPX) and reduced the level of Caspase 3 proteins (P < 0.05). These data thus suggest that SS improves the development rate and quality of porcine parthenotes by preventing oxidative damage and apoptosis.

Developmental potential of bovine oocytes cultured in different maturation and culture conditions

Diverse groups of chemicals in culture media are needed for successful bovine oocyte maturation and embryo development during which dramatic cytoplasmic and nuclear reprogramming events take place. In vitro embryo production (IVP) procedures frequently include supplements such as serum and/or co-culture with various types of somatic cells. However, the presence of undefined serum in culture media introduces a variation from batch to batch, increases viral or prion contamination risk, and leads to problems during fetal development. The aim of the present study was to investigate the possibility of using chemically defined-synthetic serum substitute (SSS) in place of fetal calf serum (FCS) during maturation and long-term culture to stimulate in vitro maturation (IVM), fertilization (IVF) and subsequent embryo development. In Experiment I, the effect of the protein source on in vitro maturation was tested by maturing oocytes in culture media supplemented with 10% FCS (Control Group), 10% SSS (Group I) and 10% SSS+10 ng/ml epidermal growth factor (EGF) (Group II). In Experiment II, effects of SSS on both oocyte maturation and embryo development during in vitro culture (IVC) were tested by maturing oocytes in media supplemented with 10% FCS (FCS Group) or 10% SSS+10 ng/ml EGF (SSS Group), followed by IVF and IVC in SOF media supplemented with 10% FCS and 10% SSS on day 4 for FCS and SSS Groups, respectively. Even though rates for cleavage and development to blastocyst stage were not different, blastocyst cell numbers were higher in Group II containing SSS and EGF. The SSS supplementation group had higher apoptotic nuclei as compared to the FCS Group in Experiment II. Transcripts for heat shock protein 70 (Hsp70), interferon tau (IF-tau), DNA methyltransferase 3a (Dnmt3a), desmosomal glycoprotein desmocollin III (DcIII) and insulin-like growth factor II receptor (Igf-2r) were altered in different culture conditions in Experiment I. However, only glucose transporter-1 (Glut-1) mRNA was different in the SSS and FCS Groups in the second experiment. In summary, SSS and EGF in maturation medium and replacement of FCS with SSS alone in culture medium on day 4 of IVC support oocyte maturation and embryo development in vitro. However, significance of culture condition induced changes on the genome-wide abundance of messenger ribonucleic acid and the significance of the apoptotic nuclei during fetal development still remain to be determined.

Development, freezability and amino acid consumption of bovine embryos cultured in synthetic oviductal fluid (SOF) medium containing amino acids at oviductal or uterine-fluid concentrations

In this study, we examined the development, freezability and amino acid consumption of in vitro produced bovine embryos cultured in a chemically defined medium (SOF+polyvinyl alcohol), supplemented with 24 amino acids at concentrations measured in bovine oviductal or uterine fluid. Amino acids at concentrations in oviductal fluid tested by Elhanssan (EOAA) significantly improved development to the hatched blastocyst stage, compared to Sigma amino acid solutions BME and MEM (SAA). Amino acids at concentrations in uterine fluid tested by Li (LUAA) were not compared to SAA, and development in LUAA was not significantly different from development in EOAA. Amino acids at concentrations in uterine fluid tested by Elhanssan (EUAA) significantly reduced cleavage rate and blocked further embryo development. When the IVF embryos were cultured in EOAA for 48, 72, 96, or 120 h and then transferred to LUAA, blastocyst and hatched blastocyst rates were not significantly affected. The freezability of blastocysts cultured in EOAA for the first 72 h and then moved to LUAA was improved compared to that in SAA. During the 1-8-cell stages, embryos secreted all 23 amino acids (total, 6,368 pmol/embryo). During the 8-cell to morula stages, embryos continued to secrete 21 amino acids (total, 2,495 pmol/embryo), meanwhile embryos began to absorb Arg (70 pmol/embryo) and Gln (18 pmol/embryo). After the morula stage, embryos began to absorb 15 amino acids including Glu, Gly, Arg, and Gln (total, 2,742 pmol/embryo) and secreted eight amino acids (total, 1,616 pmol/embryo). Embryos absorbed only Arg (183 pmol/embryo) and secreted the other 22 amino acids (total, 3,697 pmol/embryo) when the culture medium was not changed during the entire culture period (zygote to blastocyst).

Gene Expression and Developmental Competence of Bovine Embryos Produced In Vitro with Different Serum Concentrations

The objective of this study was to determine the developmental rates and relative abundance of Hsp 70.1 and Glut-1 transcripts in in vivo- and in vitro-produced (IVP) bovine embryos in media supplemented with bovine serum albumin (BSA) or different oestrous cow serum concentrations. In experiment 1, in vitro maturation and culture media were supplemented with 0.4% BSA or 1, 5, 10 or 20% of oestrous cow serum (ECS). The analysis of the expression of Hsp 70.1 and Glut-1 was carried out in individual days 7 and 8 embryos by a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay. In experiment 2, in vivo-produced morulae were collected on day 7 of the oestrous cycle and employed for the comparison of the relative abundances of Hsp 70.1 and Glut-1 transcripts with IVP morulae produced using two protein sources (10% ECS or 0.4% BSA). No differences were observed in cleavage rate among groups, but blastocyst formation (27%) and hatching rates (78%) were significantly higher in IVP embryos produced with 20% ECS than the other groups (p<0.05). No significant differences were observed in the relative abundances of Hsp 70.1 and Glut-1 mRNA in days 7 and 8 blastocysts expanded blastocysts between groups. The abundances of mRNA for those genes were similar between IVP and in vivo-produced morulae. In spite of the alterations observed in embryonic development, the presence of serum at distinct concentrations did not appear to alter the relative abundance profiles of Hsp 70.1 and Glut-1 compared with controls or the BSA supplementation to the IVP media.

Bovine blastocyst development rate in vitro is influenced by selection of oocytes by brillant cresyl blue staining before IVM as indicator for glucose-6-phosphate dehydrogenase activity

The aim of this present study was to increase the efficiency of blastocyst production from cows after in vitro maturation/fertilization (IVM/IVF) by oocyte selection before maturation. Oocytes were selected on the basis of brillant cresyl blue (BCB) staining, used to indicate glucose-6-phosphate dehydrogenase (G6PDH) activity. To re-valuate the hypothesis that growing oocytes are expected to have a high level of active G6PDH, while mature oocytes have low G6PDH activity, cumulus oocyte complexes (COCs) were recovered from slaughterhouse ovaries by slicing the surface of the ovary. Only oocytes with a compact cumulus investment were used. Oocytes were placed into three groups: (1) control--placed immediately into culture; (2) holding control--COCs kept in PBS containing 0.4% BSA for 90 min before placement into culture; and (3) treatment--incubation with BCB for 90 min before culture. Treated oocytes were then divided into BCB- (colorless cytoplasm, increased G6PDH) and BCB+ (colored cytoplasm, low G6PDH) on their ability to metabolize the stain. Activity of G6PDH was determined via measurement of NADP reduction induced by G6P as substrate oxidized by G6PDH in the cytosol of control, BCB- and BCB+ groups; G6PDH activity was significant higher in BCB- COCs than in control and BCB+ COCs. After IVM, oocytes were fertilized in vitro. Embryos were cultured to day 8. The rate of maturation to metaphase II was significantly higher for control and BCB+ oocytes than for BCB- oocytes. The BCB+ oocytes yielded a significantly higher proportion of blastocysts (34.1%) than did control or holding control oocytes (18.3 and 19.2%); and both controls and BCB+ oocytes had significantly higher blastocyst development than did BCB- oocytes (3.9%). These results show that the staining of bovine cumulus oocyte complexes with BCB before in vitro maturation may be used to select developmentally competent oocytes for IVF. In addition, G6PDH activity may be useful as a marker for oocyte quality in future studies on factors affecting developmental competence.

Stereomicroscopic and histological examination of bovine embryos following extended in vitro culture

Attempts to support survival of mammalian embryos after hatching have met with limited success, although some mouse studies have reported growth at the post-implantation stage. The aim of the present research was to establish and characterise an in vitro culture system that could support extended growth and differentiation of bovine embryos. Abattoir-derived oocytes were matured and fertilised in vitro. Presumptive zygotes were cultured in modified synthetic oviduct fluid (SOFaaci) medium supplemented with 5% cow serum (CS). On Day 9, single hatched blastocysts (n = 160) were randomly allocated to SOFaaci supplemented with either 5% bovine serum albumin, 5% CS, 5% fetal calf serum (FCS) or SOF only and cultured on a collagen gel substrate for up to 45 days. Embryos were evaluated at various time-points until complete disaggregation or the total disappearance of embryonic cells. Blastocyst viability post hatching was severely compromised in protein-free SOFaaci medium. Addition of FCS generated increased embryonic growth for the longest time period (Day 45) when compared to the other groups. Long-term survival of embryonic cells was observed stereomicroscopically by the proliferation and development of three-dimensional tubular structures to 85% confluence in culture. Haematoxylin and eosin staining of morphological structures obtained from all treatment groups revealed embryos displaying trophoblast, inner cell mass and hypoblast development to varying degrees. Regardless of treatment, extended in vitro culture did not result in development comparable with that described for in vivo embryos. In the present work, however, there was evidence of extended culture of bovine embryos beyond that achieved previously. However, further research is required to identify the exact requirements for extended in vitro culture for bovine embryos.

High oxygen tension during in vitro oocyte maturation improves in vitro development of porcine oocytes after fertilization

This study was conducted to evaluate the effect of oxygen tension during IVM and/or IVC on developmental competence of porcine follicular oocytes. Prospective, randomized experiments were designed, and oocytes were matured, inseminated and cultured in vitro in the designated condition. In experiment 1, either high (20%) or low (7%) oxygen tension was used for IVM. The high oxygen significantly improved blastocyst formation (23% versus 13%; P<0.01) after IVF than the low oxygen. Such treatment, however, did not significantly (P>0.05) improve the rates of nuclear maturation (89% in each treatment), sperm penetration (62-72%), monospermic fertilization (56-67%), pronuclear formation (90-96%), cleavage (49-53%) and blastocyst cell number (31-32 cells). In experiment 2, the combined effect of oxygen tension during IVM and IVC of embryos was evaluated by a 2 x 2 factorial arrangement. Again, the high oxygen tension during IVM supported blastocyst formation more efficiently (P<0.01) than the low oxygen, and this was independent of oxygen tension during IVC (26-28% versus 15-16%). In oocytes matured under the high oxygen, a tendency to increase blastomere number (P=0.0630) was found, when the low oxygen was used for IVC after insemination (39-45 cells/blastocyst). In conclusion, the use of high oxygen tension (20% maintained by exposure to 5% CO2 in air) for IVM of porcine oocytes promoted blastocyst formation in vitro.

Early embryo development is an indicator of implantation potential

To maximize the chances of pregnancy during assisted reproduction treatment, it is important to be able to identify embryos with high implantation potential. Embryos which divide more quickly following insemination have been shown to produce higher pregnancy and implantation rates than those which divide later. The aim of this study was to compare the developmental potential of early cleaving embryos with those in which the pronuclear membranes had broken down at the time of scoring. Normally fertilized zygotes (n = 2447) were assessed 25-27 h post-insemination and categorized according to developmental stage (pronuclei visible, no pronuclei, or early cleavage to two cells). Pregnancy and implantation rates were assessed in cycles where embryos selected for transfer were at an equivalent stage 25-27 h post-insemination. A significantly higher implantation rate was achieved following transfer of either early cleavage embryos or those which had no pronuclei compared with embryos with intact pronuclei when assessed 25-27 h post-insemination/microinjection. The correlation between early cleavage and an improved pregnancy and implantation rate was confirmed. Scoring for the presence of early cleavage or status of pronuclei is quick and objective and provides information that may be used to discriminate between morphologically equivalent embryos at a later stage in development.

Effect of the Post-Fertilization Culture Environment on the Incidence of Chromosome Aberrations in Bovine Blastocysts1

We have previously shown that the postfertilization embryo culture environment has a significant influence on the quality of the resulting bovine blastocyst measured in terms of its cryotolerance and relative abundance for several developmentally important gene transcripts. Using three different culture conditions known to produce blastocysts of differing quality, the objective of this study was to examine whether the postfertilization culture environment had an effect on the incidence of mixoploidy in bovine blastocysts. Presumptive zygotes, produced by in vitro maturation and fertilization, were cultured in vitro in synthetic oviduct fluid (SOF) medium in the absence or presence of fetal calf serum (FCS), or in vivo in the ewe oviduct. Blastocysts were recovered from the three systems at Day 7 and the incidence of mixoploidy was assessed using fluorescence in situ hybridization with chromosome 6- and chromosome 7-specific probes. A total of 10 025 nuclei were scored in 122 blastocysts. The frequency of normal, diploid, blastocysts was 8.8%, 21.4%, and 34.8% in embryos derived from culture in SOF+FCS, SOF, and the ewe oviduct, respectively, the remainder showing some degree of mixoploidy. The incidence of mixoploidy was apparently not related to the presence of serum; omission of serum from SOF resulted in a reduction in the incidence of mixoploidy (91.2% vs. 78.6%), although this difference was not significant. Culture in vivo, however, resulted in a significant (P < 0.01) reduction in the incidence of mixoploidy compared with culture in vitro in the presence of serum (65.2% vs. 91.2%, respectively). Among the mixoploid blastocysts, the majority contained less than 10% polyploid cells, irrespective of culture group (SOF, 69.7%; SOF+FCS, 64.5%; ewe oviduct, 60.0%). More than one type of polyploidy was frequently observed in mixoploid blastocysts. Overall, diploidy-triploidy was the most frequent abnormality, but diploid-tetraploid and diploid-triploid-tetraploid mosaics were also observed. A significantly higher proportion (P < 0.05) of blastocysts derived from SOF+FCS had more than one type of abnormality (80.6%, 25/ 31) compared with those derived from SOF (45.4%, 15/33) or in vivo culture (53.3%, 16/30). In conclusion, the postfertilization culture environment of the developing embryo can affect the incidence and severity of mixoploidy in the resulting blastocyst.

Improved in vitro development of porcine embryos with different energy substrates and serum

The effect of replacing 5.5 mM glucose in North Carolina State University (NCSU)-23 medium with 0.5 mM pyruvate/5.0 mM lactate on porcine IVF embryo development was investigated in Experiment 1. Culturing embryos with pyruvate/lactate for 7 days or with pyruvate/lactate from Days 0 to 2, and then glucose from Days 2 to 7 improved cleavage rates. In Experiment 2, embryos were cultured for 7 days in pyruvate/lactate containing NCSU-23 medium supplemented with 0.05% PVA, 0.4% BSA or 10% fetal bovine serum (FBS). The BSA supplement increased the rates of cleavage, blastocyst formation, and the number of total cells in blastocysts. In Experiment 3, embryos were cultured in pyruvate/lactate containing NCSU-23 medium supplemented with 0.4% BSA for 7 days (BSA-PL), 0.4% BSA from Days 0 to 4 and then 10% FBS from Days 4 to 7 (BSA-PL-->F ) or 0.4% BSA from Days 0 to 7 with addition of 10% FBS (BSA-PL + F ) at Day 4. More blastocysts in BSA-PL--> F and hatching or hatched blastocysts in BSA-PL-->F and BSA-PL+F were obtained. Total cell number in blastocysts derived from BSA-PL-->F and BSA-PL+F were increased. Our results demonstrated that supplementing pyruvate/lactate containing NCSU-23 medium with 0.4% BSA for 4 days and replacing it with 10% FBS for another 3 days improved porcine IVF embryo development.

Global gene expression analysis comparing bovine blastocysts flushed on day 7 or produced in vitro

In vitro produced (IVP) bovine embryos have darker cytoplasm, reduced buoyant density, fragile zonae pellucidae, chromosomal abnormalities, higher pregnancy failure rates, and altered gene expression compared to embryos produced in vivo. Characterization of early deviations in gene expression would enable us to better understand the biology of early embryo development and improve in vitro culture systems. Here we compared gene expression between Day 7 blastocysts generated in TCM199 with 5% FBS and Day 7 in vivo derived blastocysts and using suppression-subtractive hybridization (SSH). Pools of 25 embryos for both driver and tester were used in the RNA extraction process. The subtracted products were cloned and subjected to differential hybridization screening analysis. cDNAs were isolated, single-pass sequenced, and subjected to BLAST search. Of 32 in vivo ESTs (expressed sequence tags) that provided sequence information, 30 matched homologous sequences in GenBank. Of 32 in vitro ESTs, 22 provided specific matches while the remaining ten represented novel transcripts. Two in vivo ESTs, galectin-1 and fibronectin, and one in vitro EST, filamin A, were further characterized using real-time quantitative PCR. To further examine the reproducibility of the SSH data, three different pools of embryos with each pool containing ten embryos produced from each of the following production systems, namely, in vivo, IVP in TCM199 with 5% FBS and CR1aa with 5% FBS were used for real-time reverse transcription-polymerase chain reaction (RT-PCR) confirmation studies. Significant increases in the expression level of galectin-1 and fibronectin were observed in the in vivo derived blastocysts compared to blastocysts produced in TCM199 with 5% FBS and CR1aa cultures. No significant difference in filamin A expression was found between blastocysts produced in vivo and those derived from either of the in vitro production systems. We conclude that these techniques are useful to characterize the transcriptome of the early preattachment embryo and observed deviations in mRNA expression may partially explain the differences in quality between in vivo and IVP embryos.

Quantitative expression analysis of blastocyst-derived gene transcripts in preimplantation developmental stages of in vitro-produced bovine embryos using real-time polymerase chain reaction technology

The main objective of the present study was to analyse the quantitative expression pattern of genes from a subtracted blastocyst transcriptome throughout the preimplantation developmental stages of in vitro-produced bovine oocytes and embryos. For this purpose, Day 5 morula (M) cDNAs were subtracted from Day 7 blastocyst (B) cDNAs (B–M) and used to establish a B–M subtracted cDNA library, as reported previously. From the total generated clones, 19 were analysed quantitatively. The mRNA samples isolated from pools of immature oocytes (n = 150), mature oocytes (n = 150) and two-cell (n = 80), four-cell (n = 40), eight-cell (n = 20), morula (n = 6) and blastocyst (n = 3) embryos were reverse transcribed and subjected to real-time polymerase chain reaction (PCR) using sequence-specific primers and SYBR green as the DNA dye. A relative standard curve method was used to analyse the real-time data taking the morula stage as a calibrator. Applying suppression subtractive hybridisation (SSH), a total of 71 clones, which represent 33 different expressed sequence tags, were generated and available for analysis. Most transcripts were analysed for the first time in bovine embryogenesis. The real-time PCR has validated the results of SSH positively for 84% (16/19) of transcripts, whereas 16% (3/19) showed deviation in the expression pattern from the one seen during SSH. Several transcript-specific expression patterns were observed for genes that play decisive roles in bovine embryogenesis. In addition to identification, accurately quantifying the expression profiles of transcripts during development will pave the way towards understanding the molecular mechanisms of embryogenesis and their potential role in early embryo development. Most importantly, the present study has contributed to the enrichment of bovine embryo gene collection by generating new transcripts involved in bovine embryo development.

Amino acid metabolism of preimplantation bovine embryos cultured with bovine serum albumin or polyvinyl alcohol

Bovine serum albumin (BSA) is an embryotrophic macromolecule used in embryo culture media, which is commonly replaced with synthetic compounds, such as polyvinyl alcohol (PVA). This study compared the effect of BSA and PVA on the development, blastocyst cell number and amino acid metabolism of preimplantation bovine embryos in vitro. Embryos were produced by in vitro maturation and fertilization of immature oocytes from abattoir-derived ovaries. Zygotes were cultured in synthetic oviduct fluid with either 4 mg/ml BSA (SOFaaBSA) or 1 mg/ml PVA (SOFaaPVA) in microdrops with a mineral oil overlay at 39 degrees C under a 5% O2/5% CO2/90% N2 atmosphere. Blastocyst rate and cell numbers were determined after 123 h of culture. In parallel, single expanding blastocysts grown in either medium were incubated in microdrops for 12 h. Amino acid profile of spent drops was determined by high performance liquid chromatography. Replacing BSA with PVA depressed blastocyst rate and cell numbers, and led to quantitative and qualitative differences in amino acid appearance, disappearance and turnover. These differences could partly be due to an increase in free intracellular amino acid concentration in SOFaaBSA embryos derived from hydrolysis of endocytosed BSA, and argue against the inclusion of PVA in bovine embryo culture media.

Addition of β-mercaptoethanol or Trolox® at the morula/blastocyst stage improves the quality of bovine blastocysts and prevents induction of apoptosis and degeneration by prooxidant agents

This study was conducted to evaluate the effect of beta-mercaptoethanol (a stimulator of glutathione synthesis) and Trolox (an hydrosoluble analogue of Vitamin E) on bovine embryos cultured from the morula stage (Day 5 post-insemination; pi) under oxidative stress conditions. Culture of embryos with increased doses of Trolox showed a dose-dependent embryotoxicity on Day 8 pi. The use of 400 microM Trolox as well as beta-mercaptoethanol at 100 microM prevented at least partly (P < 0.05) the prooxidant-induced blastocyst degeneration on Day 8. Hatching rates of surviving blastocysts were significantly increased by both antioxidants and beta-mercaptoethanol alone improved their mean cell numbers, which was significant in the ICM (P < 0.05). Analysis of their effect on Day 7 pi showed that both the antioxidants significantly reduced the prooxidant-induced apoptosis and beta-mercaptoethanol diminished the physiological level of apoptosis as well as it stimulated the glutathione synthesis (P < 0.05). In addition, a comparison between in vitro- and in vivo-produced embryos showed that the levels of apoptosis were similar at the same age post-insemination (morulae and blastocysts) but increased steadily with the embryonic age in in vitro ones. In conclusion, beta-mercaptoethanol and Trolox added separately from the morula stage protected embryos against oxidative stress and improved the quality of the resulting blastocysts.

Species-related differences in blastocyst quality are associated with differences in relative mRNA transcription

The objective of this study was to compare the relative transcript abundance of several important candidate genes between ovine and bovine blastocysts. Blastocysts were produced by in vitro maturation, fertilization, and subsequent culture in one of two formulations of synthetic oviduct fluid medium (SOF1 and SOF2). From each IVF replicate groups of 10 bovine and 10 ovine blastocysts from each of the two media were used for analysis of mRNA relative abundance. Transcript levels for mitochondrial Mn-superoxide dismutase (MnSOD), survivin, and glucose transport 5 (Glut-5) were significantly higher in ovine blastocysts than bovine (P < 0.05), while transcripts for Connexin 31 (Cx31), interferon tau (IFN-tau), and sarcosine oxidase (SOX) were significantly more abundant in bovine blastocysts (P < 0.01). For the two remaining transcripts, E-cadherin (E-cad) and Na/K ATPase (Na/K), there was no difference. Culture of bovine embryos in SOF2 resulted in a significant increase in the level of expression of MnSOD and Glut-5 (P < 0.05) compared to those bovine embryos cultured in SOF1. For all the other transcripts, except survivin, there was a significant decrease in the relative abundance. Culture of sheep embryos in either SOF1 or SOF2 did not have a major influence on transcript abundance; of the eight transcripts examined, the relative abundance of only one, SOX, was significantly altered. Bovine blastocysts produced in SOF2 had significantly higher survival rates at 24, 48, and 72 hr and significantly higher hatching rates following vitrification and warming than those cultured in SOF1 (P < 0.001). In conclusion, we have quantified for the first time the mRNA expression of a set of important developmental genes in sheep blastocysts and we have demonstrated that these differences between species in their adaptability to culture conditions, manifested in differences in embryo morphology and cryotolerance, are related to differences in mRNA relative abundance. The results also highlight the usefulness of transcript analysis as a marker of embryo quality.

Cell cycle duration at the time of maternal zygotic transition for in vitro produced bovine embryos: effect of oxygen tension and transcription inhibition

Early embryonic cleavages are mostly regulated by maternal components then control of development progressively depends on newly synthesized zygotic products. The timing of the first cleavages is a way to assess embryo quality. The goal of this study was to evaluate the duration of the fourth cell cycle, at the time of maternal-to-zygotic transition (MZT) in in vitro-produced bovine embryos by means of cinematographic analysis. We found that 75% of the embryos displayed a long fourth cycle (43.5 +/- 5.4 h) whereas the remaining embryos had a very short fourth cell cycle (8.9 +/- 2.9 h). Both groups did not differ in cleavage rhythm up to the eight-cell stage and timing of cavitation and blastocyst expansion was identical. However, embryos with a short fourth cell cycle had a better blastocyst rate than embryos with a long cycle (59% versus 38%, P < 0.01). Total cell number, inner cell mass (ICM):total cell ratio, and hatching rate were identical for blastocysts produced from embryos with either a long or a short fourth cell cycle. In a second experiment, we showed that increasing the oxygen tension, from 5% to 20%, decreased the percentage of embryos with a short fourth cell cycle, from 25% to 11% (P < 0.01), indicating that suboptimal culture conditions can influence the length of this cycle. Finally, we investigated whether fourth cell cycle duration could be influenced by transcription inhibition. With alpha-amanitin added at 18 h postinsemination (HPI), cleavage was reduced (66% versus 79%) and, at 70 HPI, the 9- to 16-cell rate increased (50% versus 25%) concomitantly with a 5- to 8-cell rate decrease (16% versus 47%). A similar pattern was observed when the drug was added at 6 HPI or 42 HPI but not at 0 HPI. Cinematographic analysis revealed that alpha-amanitin increased the first cell cycle duration whereas the second and third cell cycles were not affected. With the drug, one third of the embryos could develop up to the 9- to 16-cell stage and they all had a short fourth cell cycle (11.2 +/- 3.7 h) with a good synchrony of cleavage between blastomeres. These results suggest that duration of the fourth cell cycle of bovine embryo, during the MZT, is under a zygotic transcriptional control that can be affected by oxidative conditions.

Effects of gas conditions, time of medium change, and ratio of medium to embryo on in vitro development of horse oocytes fertilized by intracytoplasmic sperm injection

This study was conducted to evaluate the effects of two different gas conditions (5% CO(2) in air or 5% CO(2), 5% O(2), 90% N(2), mixed gas), time of medium change (Day 3 or 4) and ratio of medium to embryo (2, 5 or 10 microl per presumptive zygote) on the development of horse oocytes fertilized by intracytoplasmic sperm injection and cultured in G1.2/2.2 medium. Oocytes from slaughterhouse-derived ovaries were matured in vitro for 24 h and fertilized by injection of frozen-thawed sperm using micromanipulation with a Piezo drill. Presumptive zygotes were randomly assigned to 5% CO(2) in air or mixed gas and fixed after 96 h of culture. Cleavage rates between two gas conditions were similar (67 and 63%), but the mean nucleus number of embryos in the mixed gas treatment was significantly (P<0.05) higher than that of embryos cultured in 5% CO(2) in air (15.2 versus 7.0, respectively). Further experiments were done with mixed gas incubation. Development of embryos was compared after change from G1.2 to G2.2 medium at Day 3 or 4. There was no significant difference in cleavage rate (56 and 65%, respectively) or development to the blastocyst stage after 7 days of culture (5% and 46%, respectively) between embryos changed on different days. To evaluate the effect of the ratio of medium to embryo, zygotes were cultured at a ratio of 2, 5 or 10 microl medium per zygote. There were no significant differences among ratio treatments in rates of cleavage or development to blastocyst.

Effects of thioredoxin on the preimplantation development of bovine embryos

Thioredoxin (TRX) is an ubiquitous protein disulfide reductase, which is known to be involved in the implantation development of mouse embryos. In the present study, recombinant human TRX was used to evaluate its effect on the promotion of preimplantation development of bovine embryos derived from in vitro maturation and fertilization. Supplementation of the medium 24h post insemination with TRX significantly (P<0.05) enhanced the frequency of development to the blastocyst stage in 5% O(2) concentration. The optimal concentration was 0.5 microg/ml (P<0.05, compared with 0, 0.1 and 1.0 microg/ml). This effect of TRX was evident only when added around the time of the first cleavage stage (24 h post insemination); no promotion was found with treatment at 6h (one-cell) or 44 h (six- to eight-cell) after insemination. Moreover, it is of interest that even with the best combination of the dose and timing of TRX treatment (0.5 microg/ml, at 24 h post insemination), no promotion of development was observed when embryos were cultured under 20% O(2). However, a preincubation of TRX in the culture medium under 20% oxygen for 24h did not diminish the promoting effect in the subsequent TRX treatment under optimal conditions, thus suggesting that the possible oxidation of TRX alone may not be the reason for the disappearance of the effect under a high oxygen concentration. These results indicate that TRX does improve the development of bovine embryos in vitro, though unlike the general reducing reagents such as beta-mercaptoethanol or cysteamine, TRX may have to exert its effect at specific times and in more physiologic oxygen environments.

Bovine embryo culture in the presence or absence of serum: implications for blastocyst development, cryotolerance, and messenger RNA expression

We have previously shown that, while the intrinsic quality of the oocyte is the main factor affecting blastocyst yield during bovine embryo development in vitro, the main factor affecting the quality of the blastocyst is the postfertilization culture conditions. Therefore, any improvement in the quality of blastocysts produced in vitro is likely to derive from the modification of the postfertilization culture conditions. The objective of this study was to examine the effect of the presence or absence of serum and the concentration of BSA during the period of embryo culture in vitro on 1) cleavage rate, 2) the kinetics of embryo development, 3) blastocyst yield, and 4) blastocyst quality, as assessed by cryotolerance and gene expression patterns. The quantification of all gene transcripts was carried out by real-time quantitative reverse transcription-polymerase chain reaction. Bovine blastocysts from four sources were used: 1) in vitro culture in synthetic oviduct fluid (SOF) supplemented with 3 mg/ml BSA and 10% fetal calf serum (FCS), 2) in vitro culture in SOF + 3 mg/ml BSA in the absence of serum, 3) in vitro culture in SOF + 16 mg/ml BSA in the absence of serum, and 4) in vivo blastocysts. There was no difference in overall blastocyst yield at Day 9 between the groups. However, significantly more blastocysts were present by Day 6 in the presence of 10% serum (20.0%) compared with 3 mg/ml BSA (4.6%, P < 0.001) or 16 mg/ml BSA (11.6%, P < 0.01). By Day 7, however, this difference had disappeared. Following vitrification, there was no difference in survival between blastocysts produced in the presence of 16 mg/ml BSA or those produced in the presence of 10% FCS; the survival of both groups was significantly lower than the in vivo controls at all time points and in terms of hatching rate. In contrast, survival of blastocysts produced in SOF + 3 mg/ml BSA in the absence of serum was intermediate, with no difference remaining at 72 h when compared with in vivo embryos. Differences in relative mRNA abundance among the two groups of blastocysts analyzed were found for genes related to apoptosis (Bax), oxidative stress (MnSOD, CuZnSOD, and SOX), communication through gap junctions (Cx31 and Cx43), maternal recognition of pregnancy (IFN-tau), and differentiation and implantation (LIF and LR-beta). The presence of serum during the culture period resulted in a significant increase in the level of expression of MnSOD, SOX, Bax, LIF, and LR-beta. The level of expression of Cx31 and Cu/ZnSOD also tended to be increased, although the difference was not significant. In contrast, the level of expression of Cx43 and IFN-tau was decreased in the presence of serum. In conclusion, using a combination of measures of developmental competence (cleavage and blastocyst rates) and qualitative measures such as cryotolerance and relative mRNA abundance to give a more complete picture of the consequences of modifying medium composition on the embryo, we have shown that conditions of postfertilization culture, in particular, the presence of serum in the medium, can affect the speed of embryo development and the quality of the resulting blastocysts. The reduced cryotolerance of blastocysts generated in the presence of serum is accompanied by deviations in the relative abundance of developmentally important gene transcripts. Omission of serum during the postfertilization culture period can significantly improve the cryotolerance of the blastocysts to a level intermediate between serum-generated blastocysts and those derived in vivo. The challenge now is to try and bridge this gap.

Optimization of culture medium for cloned bovine embryos and its influence on pregnancy and delivery outcome

This study was conducted to establish an effective culture system for supporting in vitro development of cloned bovine embryos and to evaluate whether improved development in the optimal culture system could contribute to enhancing pregnancy and delivery outcomes after transfer. Enucleated oocytes at the metaphase II stage were reconstructed with serum-starved ear fibroblasts and cloned embryos were subsequently cultured for 168 h in vitro. In Experiment 1, cloned embryos were cultured in either modified Charles Rosenkrans 2 amino acid medium (mCR2aa) or modified synthetic oviduct fluid medium (mSOF). More (P < 0.05) 2-cell embryos (78% versus 92%), morulae (51% versus 69%) and blastocysts (2% versus 39%) were obtained after culture in mSOF than after culture in mCR2aa. In Experiment 2, cloned embryos were successively cultured in mSOF supplemented with various macromolecules during different periods of culture. A successive culture of oocytes in BSA-containing medium for 72 h and then in FBS-containing medium for the next 96 h yielded a higher rate of blastocyst formation (49% versus 25-36%) than other combinations (BSA to BSA or PVA to PVA, BSA or FBS). This macromolecule supplementation also significantly increased the number of total blastomeres (117.3 cells/blastocyst) and inner cell mass cells (ICM, 49.7 cells/blastocyst), and the ratio of ICM cells to trophoblast cells (TB, 0.98). In Experiment 3, a total of 85 blastocysts obtained from each 2-step culture were transferred individually to recipient cows at the end of the culture period and 32 pregnancies (38%) were diagnosed on Day 60 after transfer. However, no (P > 0.05) significant differences due to culture were apparent in the pregnancy outcome. Although six calves were produced using the 2-step culture regime of either BSA-BSA or PVA-FBS, no calves were produced using the successive culture of BSA then FBS, which optimized preimplantation development. In conclusion, mSOF has more potential to support the development of clone embryos than mCR2aa, and successive supplementation of BSA and FBS to mSOF further promotes blastocyst formation. However, enhanced development in vitro might not directly contribute to improving pregnancy outcomes.

Different factors affect developmental competence and cryotolerance in in vitro produced bovine embryo

The present study was conducted to examine the effects of culture systems and culture media on developmental competence and freezability of bovine embryos obtained by in vitro culture of in vitro matured and fertilized (IVM-IVF) oocytes. No significant difference was observed in the proportions of oocytes developed to blastocysts, the speed at which the oocytes reached the blastocyst stage and the number of cells, when the IVM-IVF oocytes were cultured in CR1aa with or without cumulus cells. Nevertheless, more of the IVM-IVF oocytes cultured either with or without cumulus cells in CR1aa were seen to reach the blastocyst stage much sooner than those cultured with cumulus cells in TCM199 (P<0.05). The proportion of embryos developed to the blastocyst stage by day 7 in CR1aa culture was significantly higher than embryos cultured in TCM199. Viability after frozen-thawed blastocysts were obtained in vitro, was seen in a significantly higher percentage of embryos cultured in TCM199 and developed to the hatched blastocysts than in those cultured in CR1aa (P<0.05). These results indicate that CR1aa was superior to TCM199 for the potential developmental of IVM-IVF oocytes to blastocysts during in vitro culture regardless of co-culture with or without cumulus cells. But the freezability of blastocysts developed in CR1aa was inferior to those developed in TCM199.

Taurina no desenvolvimento de embriões bovinos fecundados in vitro

O objetivo deste trabalho foi avaliar o efeito de diferentes concentrações de taurina no desenvolvimento de embriões bovinos fecundados in vitro em meio de cultivo com diferentes fontes de soro. No experimento 1, zigotos (n=440) fecundados in vitro foram distribuídos aleatoriamente nos tratamentos com 0, 3, 7 ou 14 mM de taurina em meio de cultivo acrescido de 10% de soro fetal bovino (SFB) e 3g/l de albumina sérica bovina (BSA). No experimento 2, os zigotos (n=940) foram divididos nos tratamentos com 0, 3 ou 14 mM de taurina em meio acrescido de 10% de SFB ou 3g/l de BSA. No experimento 3, os zigotos (n=191) foram divididos nos tratamentos com 0 ou 3 mM de taurina em meio de cultivo sem fonte de soro, porém adicionado de 3 g/l de álcool polivinil. Nos experimentos 1 e 2 não se observou diferença (P>0,05) na taxa de clivagem, na produção de blastocistos e no número de células entre as concentrações de taurina avaliadas. No experimento 3 encontraram-se maior (P<0,05) taxa de clivagem (68,5% vs. 16,9%) e produção de blastocistos (8,3% vs. 0%) na presença de taurina. O cultivo de zigotos em meio adicionado de SFB produziu maior (P<0,01) taxa de blastocistos no sétimo (25,6% vs. 6,7%) e oitavo (30,8% vs. 13,9%) dia pós-fecundação e número de células/blastocistos (104,8± 2,63 vs. 84,7± 3,86) do que no cultivo com BSA, apesar de menor (P<0,01) taxa de clivagem (58,1% vs. 71,3%). Conclui-se que o efeito benéfico da taurina no desenvolvimento embrionário somente é observado na ausência de SFB e BSA. O SFB produz menor taxa de clivagem mas melhora o desenvolvimento embrionário após as primeiras divisões celulares.

Prevalence of apoptosis and inner cell allocation in bovine embryos cultured under different oxygen tensions with or without cysteine addition

Supraphysiological oxygen tension during embryo culture can generate reactive oxygen species (ROS), which can induce apoptosis. Antioxidants such as thiol compounds (cysteine, cysteamine) can be used to prevent ROS damage to the embryo. The purpose of this study was to evaluate the prevalence of apoptosis during bovine embryo development and to evaluate the effect of the presence or absence of cysteine 0.6 mM in modified synthetic oviduct fluid (mSOF) on in vitro produced cattle embryos cultured under two different oxygen tensions (5% O2 versus 20% O2). Effects were assessed by checking embryo development at Days 7, 8 and 9 and by evaluating Day 9 hatched blastocysts for differentiation by means of differential staining and for apoptosis by means of TUNEL-assay. Apoptotic cells were present in 94% of Day 7 blastocysts and in 100% of Days 8 and 9 blastocysts. Cysteine addition affected Day 8 blastocyst rates in a negative way (P < 0.05) regardless of the oxygen tension. In fact, cysteine addition to the mSOF culture medium had a negative effect upon embryo development in terms of blastocyst rates, hatching rates and apoptotic cell ratio. Embryos cultured under 5% O2 in the presence of cysteine, however, possessed significantly higher numbers of ICM cells. This finding corroborates the theoretical assumption that antioxidants are beneficial for ICM development.