Factors affecting bovine embryo development in synthetic oviduct fluid following oocyte maturation and fertilization in vitro

A retrospective analysis of sheep generated by somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is one of the primary methods for production of genetically engineered sheep, which allows for gene editing or transgene introduction in somatic cells. The use of SCNT eliminates the risk of genetic mosaicism in embryos and animals that is commonly observed after zygote micromanipulations. This retrospective analysis of SCNT in sheep performed at Utah State University, spanning from 2016 to 2021, examined parameters that may impact pregnancy and full-term development, including donor oocytes (donor age), donor cell lines, SCNT parameters (time of oocyte activation following SCNT, number of transferred embryos, in vitro maturation and culture conditions), and recipients (surgical number and ovulatory status), as well as factors that may correlate with large offspring syndrome or abnormal offspring syndrome (LOS/AOS) in the fetuses and lambs. Our findings indicated that compared to prepubertal oocytes, the SCNT embryos produced from adult sheep oocytes had comparable in vitro maturation rates, pregnancy and full-term development rates, as well as SCNT efficiency. In addition, earlier activation time of SCNT embryos (e.g. 24-26 h post maturation) was correlated to the early pregnancy loss rate, full-term rate, and SCNT efficiency. Compared to our standard serum-containing medium, commercial serum-free culture medium showed a positive correlation with the full-term development of sheep SCNT embryos. Transferring 15-30 embryos per recipient resulted in consistently good pregnancy rates. Surgical numbers and ovulatory status (having at least one follicle between 6 and 12 mm in size or a corpus hemorrhagicum (CH)) of recipients did not affect pregnancy and full-term development rates. In summary, this retrospective analysis identified parameters for improving pregnancy and full-term development of SCNT embryos in sheep.

Programming of postnatal phenotype caused by exposure of cultured embryos from Brahman cattle to colony-stimulating factor 2 and serum

Alterations in the environment of the preimplantation embryo can affect competence to establish pregnancy and phenotype of resultant calves. In this study, the bovine embryo produced in vitro was used to evaluate postnatal programming actions of the embryokine colony-stimulating factor 2 (CSF2) and serum, which is a common additive of culture media. Oocytes were collected by ovum pick up from Brahman donors and fertilized with semen from Brahman bulls. Embryos were randomly assigned to one of the three treatments: vehicle, CSF2 10 ng/mL, or 1% (v/v) serum. Treatments were added to the culture medium from day 5 to 7 after fertilization. Blastocysts were harvested on day 7 and transferred into crossbred recipients. Postnatal body growth and Longissimus dorsi muscle characteristics of the resultant calves were measured. The percent of cleaved embryos becoming blastocysts was increased by serum and, to a lesser extent, CSF2. Treatment did not affect survival after embryo transfer but gestation length was shortest for pregnancies established with serum-treated embryos. Treatment did not significantly affect postnatal body weight or growth. At 3 mo of age, CSF2 calves had lower fat content in the Longissimus dorsi muscle and less subcutaneous fat over the muscle than vehicle calves. There was a tendency for cross-sectional area of the muscle to be smaller for serum calves than vehicle calves. Results confirm the importance of the preimplantation period as a window to modulate postnatal phenotype of resultant calves. In particular, CSF2 exerted actions during the preimplantation period to program characteristics of accumulation of intramuscular and subcutaneous fat of resultant calves. The use of a low serum concentration in culture medium from day 5 to 7 of development can increase the yield of transferrable embryos without causing serious negative consequences for the offspring.

Porcine oocyte preincubation in oviductal fluid flush before in vitro fertilization in the presence of oviductal epithelial cells improves monospermic zygote production

The present study was designed to evaluate the effect of the combination of oviduct fluid flush (OFF) and oviduct epithelial cells (OEC) in modulating the incidence of polyspermy in pigs. Therefore, for in vitro fertilization (IVF), oocyte and sperm were co-cultured in Tris-buffered medium (TBM) either supplemented with 10% OFF (OFFD group), or in the presence of a bovine OEC monolayer (OEC group), or the oocytes were exposed to OFF for 30 min before IVF (OFFB group), or in the presence of an OEC monolayer (OFFB + OEC group). Regardless of sperm concentration used (0.5, 1.5, and 4.5 × 105 cells/ml), supplementation of IVF medium with 10% OFF led to an increased (P < 0.05) monospermy rate, without alteration (P > 0.05) of the penetration rate in comparison with the control and OEC groups. When the IVF medium was supplemented with heparin, an overall increase (P < 0.05) of the final output of the IVF system in terms of zygotes with two pronuclei (2PN) was observed in the OFFD group, compared with the control and OEC groups, at a sperm concentration of 4.5 × 105 cells/ml. At this concentration, OFFB improved the monospermy rate but decreased the penetration rate, resulting in low efficiency of monospermic zygotes production. Despite this, no major effect was observed in the developmental competence of the presumed zygotes up to the blastocyst stage. The combination of OFFB with OEC improved the penetration rate, while maintaining the high monospermic rate induced by OFFB. In conclusion, the combination of treatment of oocytes by diluted OFF 30 min before IVF, followed by IVF in the presence of OEC, improved monospermic zygote production without reducing the penetration rate, when the IVF medium was supplemented with heparin.

Methodological approaches for vitrification of bovine oocytes

Numerous factors affect vitrification success and post-thaw development of oocytes after in vitro fertilization. Therefore, elaboration of an optimal methodology ensuring higher cryotolerance of oocytes and subsequent blastocyst yield is still of great interest. This paper describes and evaluates critical factors affecting the success of oocyte vitrification. In particular, an appropriate oocyte stage such as maturation status (germinal vesicle stage, metaphase II stage), presence/absence of cumulus cells before vitrification, and the effect of follicle size, as well as different culture systems and media for in vitro production of embryos, the types and concentrations of cryoprotectants, and cooling and warming rates at vitrification are considered. Special attention is paid to various cryocarriers used for low-volume vitrification, which ensures safe storage of oocytes/embryos in liquid nitrogen and their successful post-thaw recovery. At the end, we focussed on how age of oocyte donors (heifers, cows) influences post-thaw development. This review summarizes results of recently published studies describing different methodologies of cryopreservation and post-thaw oocyte development with the main focus on vitrification of bovine oocytes.

Consequences of assisted reproductive techniques on the embryonic epigenome in cattle

Procedures used in assisted reproduction have been under constant scrutiny since their inception with the goal of improving the number and quality of embryos produced. However, invitro production of embryos is not without complications because many fertilised oocytes fail to become blastocysts, and even those that do often differ in the genetic output compared with their invivo counterparts. Thus only a portion of those transferred complete normal fetal development. An unwanted consequence of bovine assisted reproductive technology (ART) is the induction of a syndrome characterised by fetal overgrowth and placental abnormalities, namely large offspring syndrome; a condition associated with inappropriate control of the epigenome. Epigenetics is the study of chromatin and its effects on genetic output. Establishment and maintenance of epigenetic marks during gametogenesis and embryogenesis is imperative for the maintenance of cell identity and function. ARTs are implemented during times of vast epigenetic reprogramming; as a result, many studies have identified ART-induced deviations in epigenetic regulation in mammalian gametes and embryos. This review describes the various layers of epigenetic regulation and discusses findings pertaining to the effects of ART on the epigenome of bovine gametes and the preimplantation embryo.

Overgrowth Syndrome

Large offspring syndrome (LOS) is a fetal overgrowth condition in bovines most often observed in offspring conceived with the use of assisted reproductive technologies (ART). Phenotypes observed in LOS include, overgrowth, enlarged tongues, umbilical hernias, muscle and skeleton malformations, abnormal organ growth and placental development. Although LOS cases have only been reported to be associated with ART, fetal overgrowth can occur spontaneously in cattle (S-LOS). S-LOS refers to oversized calves that are born at normal gestation lengths. ART-induced LOS has been characterized as an epigenetic syndrome, more specifically, a loss-of-imprinting condition. We propose that S-LOS is also a loss-of-imprinting condition.

Detection of bovine herpesvirus 1 in genital organs of naturally infected cows

Bovine herpesvirus 1 (BoHV-1) is a causative agent of respiratory diseases in cattle, and infection with BoHV-1 can cause reproductive failure. There are few studies regarding infections in natural conditions in the reproductive organs of bovine animals. In this context, this study investigated the presence of BoHV-1 in the uterus, oviducts, and ovarian tissues of naturally infected cows. The three genital structures were evaluated for the presence or absence of BoHV-1 by immunofluorescence assay using confocal scanning laser microscopy. Blood and genital organ samples of 75 cows unvaccinated against BoHV-1 were used. Fragments of uterus, oviduct, and ovarian tissue were processed and analyzed by confocal scanning laser microscopy. Neutralization by antibodies was observed in 54.7% (41/75) of the serum samples tested. BoHV-1 were detected in the uterus of all the seropositive cows. The oviducts contained BoHV-1 in 73.2% of the samples and the ovaries contained BoHV-1 in 58.5% of the samples from seropositive animals. The presence of the virus was not observed in any of the genital organs of seronegative animals. There was no correlation between the antibody titer and the detection of BoHV-1 in positive tissue in the different genital organs or with the number of infected structures per animal. The detection of BoHV-1 in 100% of the uterus samples from seropositive cows suggests that this organ may be a source of infection for the fetus, resulting in abortion. Further studies on the mechanism by which BoHV-1 infects the fetus via the uterine route should be performed.

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.

Detection of bovine herpesvirus 1 in cumulus-oocyte complexes of cows

Bovine herpesvirus 1 (BoHV-1) is the causative agent of infectious bovine rhinotracheitis (IBR) and is also associated with reproductive failure. This study investigated the presence of BoHV-1 in cumulus-oocyte complexes (COCs) of naturally-infected cows without clinical signs of IBR. The presence of BoHV-1 in COCs was evaluated by immunofluorescence using confocal laser scanning microscopy. Blood samples and ovaries from 82 cows that had not been vaccinated against BoHV-1 were collected for serological analysis. COCs were divided into two pools: COCs derivate from seropositive cows and from seronegative cows. Then, the samples were processed for confocal microscopy analysis. The results indicated that 61% (50/82) of cows were seropositive for BoHV-1. A total of 719 COCs were obtained from the cows and processed. None of 276 COCs from the 32 seronegative cows presented BoHV-1. However, BoHV-1 was present in the cytoplasm of cumulus cells from 158 out of 443 COCs aspirated from the seropositive cows. The detection of BoHV-1 in the COCs of seropositive cows suggests that the COCs of naturally-infected, asymptomatic cows may be infected with BoHV-1.

Profiling bovine blastocyst microRNAs using deep sequencing

MicroRNAs (miRNAs) are known to control several reproductive functions, including oocyte maturation, implantation and early embryonic development. Recent advances in deep sequencing have allowed the analysis of all miRNAs of a sample. However, when working with embryos, due to the low RNA content, miRNA profiling is challenging because of the relatively large amount of total RNA required for library preparation protocols. In the present study we compared three different procedures for RNA extraction and prepared libraries using pools of 30 bovine blastocysts. In total, 14 of the 15 most abundantly expressed miRNAs were common to all three procedures. Furthermore, using miRDeep discovery and annotation software (Max Delbrück Center), we identified 1363 miRNA sequences, of which bta-miR-10b and bta-miR-378 were the most abundant. Most of the 179 genes identified as experimentally validated (86.6%) or predicted targets (13.4%) were associated with cancer canonical pathways. We conclude that reliable analysis of bovine blastocyst miRNAs can be achieved using the procedures described herein. The repeatability of the results across different procedures and independent replicates, as well as their consistency with results obtained in other species, support the biological relevance of these miRNAs and of the gene pathways they modulate in early embryogenesis.

Lysophosphatidic acid accelerates development of porcine embryos by activating formation of the blastocoel

Culture media modifications, including the addition of various factors, are important for the in vitro production of oocytes and embryos. In this study, we investigated the effects of lysophosphatidic acid (LPA) on porcine embryo development. Porcine parthenogenetic embryos were cultured with 0, 0.1, 1, and 10 μM LPA for 7 days, or cultured in basic medium until Day 4 and then treated with LPA from Days 4 to 7. No difference in the in vitro development of embryos cultured with LPA for 7 days was observed. Conversely, rates of blastocyst and over-expanded blastocyst formation were higher in the 0.1 and 1 µM LPA-treated versus the other groups of embryos treated from Days 4 to 7. Moreover, formation of early blastocysts occurred earlier and embryo size was larger in LPA-treated compared to control embryos. Expression of Connexin 43 and gap junction and cell adhesion-related genes (GJC1 and CDH1, respectively) was also higher in LPA-treated compared to control embryos. Despite no difference in the blastocyst total cell number between groups, the apoptotic index was lower in the LPA-treated group than in the control group; indeed, BCL2L1 (B-cell lymphoma 2-like protein 1) expression increased while BAK (Bcl-2 homologous antagonist killer) decreased in the LPA-treated group. Thus, addition of LPA to the medium from Days 4 to 7 of culture improves blastocyst formation and aids the development of preimplantation embryos.

In vitro production of bovine embryos derived from individual donors in the Corral® dish

Background

Since the identity of the embryo is of outmost importance during commercial in vitro embryo production, bovine oocytes and embryos have to be cultured strictly per donor. Due to the rather low yield of oocytes collected after ovum pick-up (OPU) per individual cow, oocyte maturation and embryo culture take place in small groups, which is often associated with inferior embryo development. The objective of this study was to improve embryonic development in small donor groups by using the Corral^® dish. This commercial dish is designed for human embryo production. It contains two central wells that are divided into quadrants by a semi-permeable wall. In human embryo culture, one embryo is placed per quadrant, allowing individual follow-up while embryos are exposed to a common medium. In our study, small groups of oocytes and subsequently embryos of different bovine donors were placed in the Corral^® dish, each donor group in a separate quadrant.

Results

In two experiments, the Corral^® dish was evaluated during in vitro maturation (IVM) and/or in vitro culture (IVC) by grouping oocytes and embryos of individual bovine donors per quadrant. At day 7, a significantly higher blastocyst rate was noted in the Corral^® dish used during IVM and IVC than when only used during IVM (12.9% ± 2.10 versus 22.8% ± 2.67) (P < 0.05). However, no significant differences in blastocyst yield were observed anymore between treatment groups at day 8 post insemination.

Conclusions

In the present study, the Corral^® dish was used for in vitro embryo production (IVP) in cattle; allowing to allocate oocytes and/or embryos per donor. As fresh embryo transfers on day 7 have higher pregnancy outcomes, the Corral^® dish offers an added value for commercial OPU/IVP, since a higher blastocyst development at day 7 is obtained when the Corral^® dish is used during IVM and IVC.

Proteome profiling of bovine follicular fluid-specific proteins and their effect on in vitro embryo development

The objective of this study was to determine the effect of bovine follicular fluid proteins (bFF) and their differently charged groups as maturation media supplements for in vitro embryo development. bFF was obtained by aspiration from large healthy follicles (4–10 mm in diameter) and was precipitated by 30–50% (NH₄)₂SO₄. The precipitated protein was fractionated into basic and acidic fractions by ion-exchanger columns. In experiment 1, the oocytes were matured in TCM-199 with 1) FBS+hormones (control) and 2) 10% bFF. The oocyte maturation rate, the development to the blastocyst stage rate and blastocyst cell number were not significantly different between the groups. However, the INFα and IGF-2r expression levels in the 10% bFF were higher than in the control (P<0.05). In experiment 2, the specific charge proteins of bFF (basic and acidic) were also used as media supplements in the maturation medium. The basic fraction had higher oocyte maturation rate and blastocyst cell number when compared with addition of acidic fraction (P<0.05). The expression levels for almost all developmentally important genes in the basic fraction were greater than those in the acidic fraction, particularly INFα (P<0.05). Most of the protein in the basic fraction was associated with the immune response and mRNA processing. In conclusion, supplementation of 10% bFF alone in maturation medium can support oocyte maturation and embryo development. The basic fraction in bFF seemed to have effect on oocyte maturation rate and blastocyst cell number.

Transporting bovine oocytes in a medium supplemented with different macromolecules and antioxidants: Effects on nuclear and cytoplasmic maturation and embryonic development in vitro

We investigated whether supplementing the medium used to transport bovine oocytes with different macromolecules [foetal calf serum (FCS) or bovine serum albumin (BSA)] or a mixture of antioxidants (cysteine, cysteamine and catalase) affects their nuclear and cytoplasmic maturation and thereby affects their subsequent embryonic development and cryotolerance. Oocytes were transported for 6 hr in a portable incubator and then subjected to standard in vitro maturation (IVM) for 18 hr. The oocytes in the control groups were cultured (standard IVM) for 24 hr in medium containing 10% FCS (Control FCS) or 10% FCS and the antioxidant mixture (Control FCS+Antiox). The intracellular concentrations of reactive oxygen species (ROS) at the end of IVM period were lower in the oocytes subjected to simulated transport in the presence of a macromolecular supplement or the antioxidant mixture than that of the control group (FCS: 0.62 and BSA: 0.66 vs. Control FCS: 1.00, p < .05; and Transp: 0.58 and Transp Antiox: 0.70 vs. Control FCS: 1.00, p < .05). After IVM, the mitochondrial membrane potentials of the transported oocytes were lower than those of the non-transported oocytes (FCS: 0.41 and BSA: 0.57 vs. Control FCS: 1.00, p < .05; and Transp: 0.48 and Transp Antiox: 0.51 vs. Control FCS: 1.00 and Control Antiox: 0.84, p < .05). The blastocyst formation rates (36.9% average) and the re-expansion rates of vitrified-warmed blastocysts (53%, average) were unaffected (p > .05) by the treatments. In conclusion, supplementing the medium in which bovine oocytes are transported with antioxidants or different macromolecules did not affect their in vitro production of embryos or their cryotolerance.

Effect of human adipose tissue-derived mesenchymal-stem-cell bioactive materials on porcine embryo development

Human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) secrete bioactive materials that are beneficial for tissue repair and regeneration. In this study, we characterized human hAT-MSC bioactive material (hAT-MSC-BM), and examined the effect of hAT-MSC-BM on porcine embryo development. hAT-MSC-BM was enriched with several growth factors and cytokines, including fibroblast growth factor 2 (FGF2), vascular endothelial growth factor A (VEGFA), and interleukin 6 (IL6). Among the various concentrations and days of treatment tested, 10% hAT-MSC-BM treatment beginning on culture Day 4 provided the best environment for the in vitro growth of parthenogenetic porcine embryos. While the addition of 10% fetal bovine serum (FBS) increased the hatching rate and the total cell number of parthenogenetic porcine embryos compared with the control and hAT-MSC culture medium group, the best results were from the group cultured with 10% hAT-MSC-BM. Mitochondrial activity was also higher in the 10% hAT-MSC-BM-treated group. Moreover, the relative mRNA expression levels of development and anti-apoptosis genes were significantly higher in the 10% hAT-MSC-BM-treated group than in control, hAT-MSC culture medium, or 10% FBS groups, whereas the transcript abundance of an apoptosis gene was slightly lower. Treatment with 10% hAT-MSC-BM starting on Day 4 also improved the development rate and the total cell number of in vitro-fertilized embryos. This is the first report on the benefits of hAT-MSC-BM in a porcine embryo in vitro culture system. We conclude that hAT-MSC-BM is a new, alternative supplement that can improve the development of porcine embryos during both parthenogenesis and fertilization in vitro.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of gaseous atmosphere and antioxidants on the development and cryotolerance of bovine embryos at different periods of in vitro culture

This study examined the effects of antioxidant supplementation and O2 tension on embryo development, cryotolerance and intracellular reactive oxygen species (ROS) levels. The antioxidant supplementation consisted of 0.6 mM cysteine (CYST); 0.6 mM cysteine + 100 μM cysteamine (C+C); 100 IU catalase (CAT) or 100 μM β-mercaptoethanol (β-ME) for 3 or 7 days of in vitro culture (IVC). Two O2 tensions (20% O2 [5% CO2 in air] or 7% O2, 5% CO2 and 88% N2 [gaseous mixture]) were examined. After 7 days of antioxidant supplementation, the blastocyst frequencies were adversely affected (P < 0.05) by CYST (11.2%) and C+C (1.44%), as well as by low O2 tension (17.2% and 11.11% for 20% and 7% O2, respectively) compared with the control (26.6%). The blastocyst re-expansion rates were not affected (P > 0.05) by the treatments (range, 66-100%). After 3 days of antioxidant supplementation, the blastocyst frequencies were not affected (P > 0.05) by any of the antioxidants (range, 43.6-48.5%), but they were reduced by low O2 tension (P < 0.05) (52.1% and 38.4% for 20% and 7% O2, respectively). The intracellular ROS levels, demonstrated as arbitrary fluorescence units, were not affected (P > 0.05) by antioxidant treatment (range, 0.78 to 0.95) or by O2 tension (0.86 and 0.88 for 20% and 7% O2, respectively). The re-expansion rates were not affected (P > 0.05) by any of the treatments (range, 63.6-93.3%). In conclusion, intracellular antioxidant supplementation and low O2 tension throughout the entire IVC period were deleterious to embryo development. However, antioxidant supplementation up to day 3 of IVC did not affect the blastocyst frequencies or intracellular ROS levels.

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

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

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.

An in vitro comparison study: the effects of fetal bovine serum concentration on retinal progenitor cell multipotentiality

Retinal progenitor cells (RPCs) are an excellent resource for retinal replacement therapy, because they show enormous potential to differentiate into retinal-specific cell types. While the differentiating influence of serum has long been appreciated, the effects of serum concentration on RPC differentiation into specified retinal neural cells have not been investigated. Using cultured murine RPCs, this study compared the effects of different levels of fetal bovine serum (FBS) (1%, 5%, 10% and 20%) on RPC differentiation in vitro. RPC multipotentiality was assessed by using quantitative polymerase chain reaction (qPCR) to determine the relative expression levels of 10 genes involved in retinal development. In addition, analyses of cell morphology and retinal development-related protein expression were performed using microscopy and immunocytochemistry. The data revealed that 1% FBS-induced cultures preferentially generated rhodopsin- and PKC-α-positive cells. Calbindin and AP2α expression levels were greater in 5% FBS-induced cultures. Brn3a was expressed at similar levels in 1%, 5% and 10% FBS treatment conditions but diminished in 20% FBS conditions. Twenty percent FBS induced more glial fibrillary acid protein (GFAP)-immunoreactive cells corresponding to glia populations. These findings suggest that the concentration of FBS plays an important role in RPC differentiation in vitro. Treatment with low levels of FBS favors differentiation of rhodopsin-positive photoreceptors, interneurons and retinal ganglion cells (RGCs), while high FBS concentrations preferentially induce differentiation of glia cells. These results are expected to facilitate research in the treatment of neurodegenerative retinal diseases.

Forskolin effect on the cryosurvival of in vitro-produced bovine embryos in the presence or absence of fetal calf serum

The objective of this study was to assess the viability and cryotolerance of zebu embryos produced in vitro with or without the addition of fetal calf serum (FCS) and forskolin (F). Embryos produced in vivo were used as a control. Presumptive zygotes were cultured in modified synthetic oviductal fluid supplemented with amino acids (SOFaa), bovine serum albumin (BSA) and with (2.5%) or without (0%) FCS. On day 6 of growth, the embryos from each group were divided into treatments with or without 10 μM F to induce embryonic lipolysis, comprising a total of four experimental groups: 2.5% FCS, 0% FCS, 2.5% + F and 0% + F. For vitrification, embryos were exposed to vitrification solution 1 (5 M EG (ethylene glycol)) for 3 min and then transferred to vitrification solution 2 (7 M EG, 0.5 M galactose solution and 18% (w/v) Ficoll 70) before being introduced to liquid nitrogen. The presence of FCS in the culture medium resulted in the production of embryos with a similar rate of damaged cells compared with in vivo-produced embryos. After vitrification, the 2.5% FCS group had a significantly higher rate of damaged cells when compared with the other groups (P < 0.05). The results of this experiment indicated that the omission of FCS and the addition of forskolin do not have deleterious effect on embryo production rates. In addition, embryos produced in the presence of FCS had greater sensitivity to cryopreservation, but this effect was reversed when forskolin was added to the medium, which improved embryo survival without affecting embryo development and quality after vitrification.

The effect of horse serum on in vitro development of porcine parthenogenetic embryos

The objective of this study was to examine the effect of different sera and serum-like substances on the preimplantation development of porcine parthenogenetic embryos. Chemically activated (calcium ionophore A23187+cytochalasin B) pig oocytes were pre-cultured for five days. On day 5, the parthenogenetic embryos were treated with porcine follicular fluid (PFF), fetal bovine serum (FBS), horse serum (HS) or porcine serum albumin (PSA), and were cultured two more days. Horse serum was found to be the most effective protein source in enhancing parthenote development judging by blastocyst formation and hatching. Next, three different concentrations of HS (10, 20 and 30%) were used to determine the optima HS concentration needed to improve the development of porcine parthenogenetic embryos. All HS concentrations increased the blastocyst cell number and decreased the incidence of blastocyst apoptotic cells with 20% being the most effective. In conclusion, horse serum enhanced parthenogenetic embryo development and the quality of porcine parthenogenetic embryos.

In vitro maturation of ovine oocytes using different maturation media: effect of human menopausal serum

OBJECTIVE

To compare the effect of human menopausal serum with estrous sheep serum, estrous goat serum, ovine follicular fluid and bovine follicular fluid on in vitro maturation, in vitro fertilization and embryo development of sheep oocytes METHOD (S): Oocytes were treated in culture with different sera and follicular fluids supplemented media to examine effects on embryo development.

RESULTS

Basic culture medium supplemented with human menopausal serum, estrous sheep serum and estrous goat serum supported better rates of in vitro maturation, in vitro fertilization and embryo development. Ovine follicular fluid and bovine follicular fluid supplementations supported similar rates of In vitro maturation, In vitro fertilization and embryo development which were lower than those supported by human menopausal serum, estrous sheep serum, estrous goat serum and control medium.

CONCLUSION

Human menopausal serum, estrous sheep serum, and estrous goat serum resulted in higher maturation, fertilization and embryo development than ovine follicular fluid, bovine follicular fluid and control media.

The effects of macromolecular and serum supplements and oxygen tension during bovine in vitro procedures on kinetics of oocyte maturation and embryo development

Aiming to standardize in vitro production of bovine embryos and to obtain supplements to replace serum in culture media, this study evaluated the nuclear maturation kinetics and embryonic development in bovine after in vitro maturation (IVM) and culture (IVC) with several macromolecules (animal origin: bovine serum albumin (BSA), fetal calf serum (FCS); synthetic: polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), Ficoll, and Knockout) at two oxygen tensions (20% and 5% O(2)). Regarding nuclear kinetics, neither the presence of the expected stage (metaphase I, transition anaphase to telophase, and metaphase II) at each evaluation moment (6, 18, and 24 h after IVM, respectively) nor the accelerated polar body emission (at 18 h after IVM) related developmental competence to blastocyst stage when different supplements were compared. Independently of supplement, cleavage rates at 20% O(2) (61.6-79.2%) were higher than at 5% O(2) (38.9-58.7%). At 20% O(2), higher blastocyst and hatching rates, respectively, were obtained in treatments BSA, FCS, Knockout, and control group (IVM with FCS and IVC with BSA + FCS, 14.0-23.5% and 6.8-15.4%) in comparison to PVA, PVP, and Ficoll (0%). The same was observed at 5% O(2) for blastocyst rates with BSA, FCS, Knockout, and control (5.4-16.8%) and for hatching rates with BSA, FCS, and control (2.0-11.1%). We can conclude that producing bovine embryos at 20% O(2) during the entire IVP process resulted in higher developmental rates than at 5% O(2). In addition, while defined macromolecules PVA, PVP, and Ficoll were not suitable for embryonic development, the synthetic serum Knockout was able to replace serum and albumin for IVP in bovine at 20% O(2).

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.

Development of bovine embryos cultured in CR1aa and IVD101 media using different oxygen tensions and culture systems

The aim of the present study was to optimise the culture conditions for the in vitro production of bovine embryos. The development of in vitro fertilised bovine oocytes in CR1aa supplemented with 5% calf serum and IVD101 culture media were compared using traditional microdrops and Well of the Well (WOW) culture systems either under 5% or 20% oxygen tension. After 7 days of culture, a significantly higher blastocyst formation rate was obtained for embryos cultured in CR1aa medium compared to those cultured in IVD101, irrespective of O2 tensions and culture systems. The blastocyst formation in IVD101 was suppressed under 20% O2 compared to 5% O2 . Despite their similar total cell numbers, higher rates of inner cell mass (ICM) cells were observed in blastocysts developed in IVD101 medium than in those developed in CR1aa, irrespective of O2 tensions. There was no significant difference in blastocyst formation, total, ICM and trophectoderm (TE) cell numbers between embryos obtained by microdrop and WOW culture systems irrespective of the culture media and O2 tensions used. In conclusion, CR1aa resulted in higher blastocyst formation rates irrespective of O2 tension, whereas IVD101 supported blastocyst formation only under low O2 levels but enhanced the proliferation of ICM cells.

Fetal calf serum enhances in vitro production of Bos taurus indicus embryos

The objective of this study was to determine the effect of fetal calf serum (FCS) on the quality of in vitro produced bovine embryos. Cumulus oocyte-complexes (COCs, n = 2 449) recovered by ovum pick-up from Bos taurus indicus donors were randomly assigned to experimental groups. Sperm selected by Percoll gradient was used for in vitro fertilization (insemination = Day 0). In Experiment 1 (n = 1 745 COCs), zygotes were cultured in vitro in Synthetic Oviduct Fluid + 4 mg/mL of bovine serum albumin (BSA), or BSA + 2% FCS (BSA+FCS). In Experiment 2 (n = 704 COCs), the COCs were cultured in SOF + BSA, BSA + 2% FCS, or BSA + 2% FCS on D4 (BSA + FCSD4). In Experiment 1, blastocyst yield (51%) and Quality I blastocysts (41%) at Day 7 were higher (P < 0.05) in the BSA + FCS treatment than in BSA (42 and 30%, respectively). In Experiment 2, blastocyst yield was higher (P < 0.05) in the BSA+FCS (47%) treatment. Quality I blastocyst yield was higher (P < 0.05) for BSA + FCS (34%) and BSA+FCSD4 (32%) compared to the BSA treatment (20%). A total of 820 embryos were transferred, with no significant differences among groups in pregnancy rates. In conclusion, in vitro culture in SOFaaci + BSA + FCS enhanced blastocyst yield and Quality I blastocysts; adding FCS to the culture medium increased the efficiency of IVP of bovine embryos.

[Follicular fluid in mammals]

Follicular fluid is a complex extracellular fluid, semi-viscous and yellow in colour, which accumulates in the antrum of ovarian follicles during their growing phase. Follicular fluid provides the microenvironment within which the cumulus-oocyte complex matures and granulosa cells differentiate. Scientists agree that follicular fluid derives mainly from plasma via the vascular compartment in the follicle wall. However, it also contains factors produced locally by the follicle cells, the production of which varies during different reproductive states. The aim of this paper is to review current knowledge on the formation, composition and roles of follicular fluid.

Production of cloned sei whale (Balaenoptera borealis) embryos by interspecies somatic cell nuclear transfer using enucleated pig oocytes

In this study, we examined the feasibility of using subzonal cell injection with electrofusion for interspecies somatic cell nuclear transfer (iSCNT) to produce sei whale embryos and to improve their developmental capacity by investigating the effect of osmolarity and macromolecules in the culture medium on the in vitro developmental capacity. Hybrid embryos produced by the electrofusion of fetal whale fibroblasts with enucleated porcine oocytes were cultured in modified porcine zygote medium-3 to examine the effects of osmolarity and fetal serum on their in vitro developmental capacity. More than 66% of the whale somatic cells successfully fused with the porcine oocytes following electrofusion. A portion (60~81%) of the iSCNT whale embryos developed to the two- to four-cell stages, but no embryos were able to reach the blastocyst stage. This developmental arrest was not overcome by increasing the osmolarity of the medium to 360 mOsm or by the addition of fetal bovine or fetal whale serum. Our results demonstrate that sei whale-porcine hybrid embryos may be produced by SCNT using subzonal injection and electrofusion. The pig oocytes partly supported the remodeling and reprogramming of the sei whale somatic cell nuclei, but they were unable to support the development of iSCNT whale embryos to the blastocyst stage.

The effect of interaction between macromolecule supplement and oxygen tension on bovine oocytes and embryos culturedin vitro

Aiming to improvein vitroproduction of bovine embryos and to obtain supplements to replace serum forin vitromaturation (IVM), this study evaluated the effects of macromolecular supplementation of IMV medium (bovine serum albumin – BSA, polyvinyl alcohol – PVA, polyvinyl pyrrolidone – PVP, Ficoll, KnockoutSR, or fetal calf serum – FCS) and oxygen tension [5% CO2in air (20% O2) or 5% CO2, 5% O2and 90% N2(5% O2)] on oocyte maturation and embryo development. Nuclear progression to germinal vesicle breakdown, metaphase I and metaphase II stages were evaluated and overall results revealed that undefined (FCS) and semi-defined (BSA) media gave better results at 20% O2and defined media (PVA, PVP and Ficoll) at 5% O2. Independent of macromolecule supplement, IVM at 20% O2was considered optimal for nuclear maturation. To evaluate embryo development, oocytes matured in the previously described conditions were fertilized and cultured at the same oxygen tension used for IVM and assessed for cleavage (43.0 to 74.8%) and development to morulae (16.4 to 33.8%), blastocyst (7.7 to 52.9%) and hatched blastocyst (9.6 to 48.1%). Apart from oxygen tension, all treatments, except Knockout (22.7%), gave similar results for blastocyst development (26.5 to 38.7%). Independently of macromolecule supplement, higher development rates were obtained in an oxygen tension of 20% O2(67.4% cleavage, 29.2% morulae, 40.8% blastocyst and 34.0% hatched blastocyst) when compared with 5% O2(52.5, 21.8, 18.2 and 15.6%, respectively). This study indicates that BSA, PVA, PVP and Ficoll can replace serum during IVM and that the optimal atmospheric condition forin vitroproduction of bovine embryos is 5% CO2and 20% O2.

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.

Profile and regulation of annexin II expression during early embryogenesis in cattle

The presence of annexin II (Ann-II) during the initial stages of bovine embryo development and the regulation of Ann-II expression by retinol and insulin-like growth factor I (IGF-I) were studied. Bovine embryos at different stages of development were produced in vitro on Synthetic Oviductal Fluid (SOF) medium (control group), SOF supplemented with retinol (retinol group; 0.1ng/ml), or IGF-I (IGF-I group; 10ng/ml). The embryos were processed for mRNA extraction, cDNA production and polymerase chain reaction (PCR) using Ann-II-specific oligonucleotides. Ann-II was detected in all stages of early embryo development, except for the 16-cell stage. The blastocyst rates were significantly higher (P<0.05) in the group supplemented with retinol (37.8%, 45/119) during in vitro embryo culture (IVC) than in those cultured in SOF (20.5%, 24/117) or SOF with IGF-I (25.8%, 24/93). Semiquantitative analysis of Ann-II expression in embryos produced in medium supplemented with IGF-I or retinol revealed a lower expression of this gene when compared with embryos cultured in SOF (P<0.05). The Ann-II expression was not different in embryos cultured in the presence of retinol and IGF-I. The presence of retinol increased the production of embryos in vitro by decreasing the expression of Ann-II in early-stage of bovine embryo.

Effects of co-culture and embryo number on the in vitro development of bovine embryos

It is generally accepted that culturing embryos in groups or with somatic cells improves both the yield and quality of the blastocysts obtained. The aims of this study were 1) to compare the yield and quality of the embryos obtained after culture in several number conditions and in several culture systems and 2) to assess the effect of co-culture started at various stages of embryo development. Under cell-free culture conditions (modified synthetic oviduct fluid [mSOF] supplemented with 10% fetal calf serum [FCS] 48 h post insemination, the rate of Day 10 blastocysts was lower when embryos were cultured in small groups (1 to 6 per drop) than in large groups (4 versus 23% ; P < 0.01). There was no group effect when embryos were co-cultured either with Buffalo rat liver (BRL) cells in TCM 199, or in a culture system allowing the progressive development of cumulus cells in mSOF, even if co-culture started at 66 or 114 h post insemination. However, embryos cultured singly had lower cell numbers than embryos cultured in large groups when co-culture started at 114 h post insemination. This suggests that 1) somatic cells improve the development of singly cultured bovine embryos up to the blastocyst stage after the 9-16 cell stage; 2) co-culture affects blastocyst cell number of singly cultured embryos by acting roughly between the 5-8 and the 9-16 cell stage; and 3) cooperation between embryos could replace the effect of co-culture either on the yield of blastocysts or on blastocyst cell number. Blastocysts appeared significantly earlier in co-culture with cumulus cells in mSOF than in co-culture with BRL cells in TCM 199 (detection of the blastocysts: 7.3 +/- 0.1 d post insemination with cumulus cells versus 8.1 +/- 0.1 d with BRL cells; P < 0.001) and had a significant higher number of cells (143 +/- 9 versus 85 +/- 11; P < 0.001). This system thus seems suitable for the culture of small numbers of embryos resulting from in vitro maturation and fertilization of oocytes from individual donor cows.

Postnatal exposure to octylphenol decreases semen quality in the adult ram

The aim of this experiment was to determine if maternal exposure to octylphenol pre- and/or postnatally influenced FSH concentrations and semen quantity and quality in postpubertal rams. Rams were born to ewes that received twice-weekly s.c. injections of octylphenol equivalent to 1000microg/kg/day for one of the following periods: (1) day 70 of gestation (D70) to weaning (at 20 weeks postnatally; n=4); (2) D70 to birth (n=6); (3) birth to weaning (n=7), controls received corn oil from D70 to weaning (n=5). Rams were blood-sampled weekly and semen characteristics were evaluated at 1 year of age. Maternal exposure to octylphenol, pre- and/or postnatally did not affect FSH concentrations, semen volume, concentration, percentage live, motility or IVM/IVF characteristics. However, exposure to octylphenol from birth to weaning increased the number of morphologically abnormal sperm cells in the ejaculates of these rams.

Effect of estrous cow serum during bovine embryo culture on blastocyst development and cryotolerance after slow freezing or vitrification

The present study investigated the effect of estrous cow serum (ECS) during culture of bovine embryos on blastocyst development and survival after cryopreservation by slow freezing or vitrification. Embryos were derived from in vitro maturation (IVM) and in vitro fertilization (IVF) of abbatoir-derived oocytes. At Day 3, embryos were cultured in three different media: Charles Ronsenkrans medium + amino acids (CR1aa; without bovine serum albumin (BSA)) + 5% estrous cow serum (CR1-ECS), CR1aa + 3 mg/mL BSA (CR1-BSA) or CR1aa + 5% ECS + 3 mg/mL BSA (CR1-ECS-BSA). At 7.5 d post-insemination (PI), blastocyst yield and quality were evaluated; blastocysts and expanded blastocysts from each media were cryopreserved by Open Pulled Straw (OPS) vitrification method or slow freezing (1.5 M ethylene glycol, EM). Total blastocyst yield did not differ among CR1-ECS, CR1-BSA and CR1-ECS-BSA (30.9, 33.1 and 32.9%, respectively, P < 0.05). Embryo survival (hatching rate) was higher in vitrified versus slow-frozen embryos (43% versus 12%, respectively, P < 0.01), and in embryos cultured in CR1-BSA (40.3%) compared with those cultured in serum-containing media (CR1-ECS, 21.5% and CR1-ECS-BSA, 19.8%; P < 0.01).

IN CONCLUSION

(a) it was possible to produce in vitro bovine embryos in serum-free culture medium without affecting blastocyst yield and quality; (b) serum-free medium produced the best quality embryos (in terms of post-cryopreservation survival); and (c) vitrification yielded the highest post-cryopreservation survival rates, regardless of the presence of serum in the culture medium.

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.

Gene expression and developmental competence of bovine embryos produced in vitro under varying embryo density conditions

The objective of this study was to determine the effects of oocyte/embryo density (embryo number:medium volume ratio) on developmental competence and relative transcription of developmentally important genes in in vitro-produced bovine embryos. Using standard procedures, bovine oocytes were matured, fertilized and cultured in vitro in groups of 5, 10, 20 or 30 oocytes/embryos per 100 microL medium drop (embryo number/medium volume ratios of 1:20, 1:10, 1:5 and 1:3.3, respectively). A semi-quantitative RT-PCR assay was used to determine the relative abundance of Hsp 70.1 and Glut-1 transcripts in Day-6 morulae, and in Day-7 and Day-8 blastocysts and expanded blastocysts. Cleavage rates (55.9, 49.1, 47.1 and 34.6%, respectively) and blastocyst developmental rates (24.1, 18.9, 20.4 and 12.6%, respectively) were higher in groups containing 5, 10 and 20 embryos versus 30 embryos per drop, but there were no significant differences among groups in hatching rates. The relative abundance of Hsp 70.1 transcripts in Day-7 blastocysts was higher in embryos produced in the 20-embryo than in the 5-embryo groups. There were no differences among embryos from all groups in the amount of Glut-1 mRNA (regardless of embryonic stage). However, there were differences in the pattern of Hsp 70.1 gene expression between distinct stages of embryo development and embryo density; these dissimilarities appeared to be associated with compromised development at higher embryo densities. In conclusion, the increase in embryo density during IVM, IVF, and IVC phases of in vitro embryo production might negatively affect embryo development and the pattern of gene expression of in vitro-produced bovine embryos.

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.

Impact of pro-oxidant agents on the morula-blastocyst transition in bovine embryos

Exposing day 5 bovine morulae to reactive oxygen species induces a delayed degeneration of some blastocysts on day 8 post-insemination (pi) but without affecting the blastocyst rates. The aim of this study was to characterize the resisting and the degenerating population of blastocysts. The kinetics of degeneration of the embryos exposed to the two pro-oxidant agents: 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and buthionine sulfoximine (BSO) was evaluated using time-lapse cinematography. With both agents the first signs of degeneration appeared at day 7.5 pi but the duration of the degeneration process was shorter in presence of AAPH than BSO (4.2 vs. 12.5 hr, ANOVA, P < 0.05). The resisting blastocysts derived from morulae with a larger diameter (mean diameter: 161 vs. 154 microm, ANOVA, P < 0.05) and showed an earlier cavitation (135 vs. 142 hpi, P < 0.05) than the degenerating ones. The profile of protein neosynthesis at day 7 was not affected by the treatment. The proportion of male embryos was more important in the resisting than in the degenerating population (70 vs. 55%, chi2, P < 0.05) especially when the stress was induced by AAPH. The quality of the resisting embryos, measured by the total cell number and the rate of apoptosis, did not seem to be affected when compared to control embryos. In conclusion, resistance to oxidative stress seems related to the kinetics of development and/or the sex of the embryos. Resisting embryos apparently display a quality similar to untreated embryos.

Intracytoplasmic Glutathione Levels in Heifer Oocytes Cultured in different Maturation Media and its Effect on Embryo Development

The present study was carried out to study the effect of different maturation media on embryo development of heifer oocytes and on their glutathione (GSH) synthesis during in vitro maturation (IVM). Immature heifer oocytes were matured in parallel in one of four maturation media: (i) Tissue Culture Medium (TCM)-199 supplemented with 10 ng/ml of epidermal growth factor (EGF); (i) TCM-199 supplemented with 10 ng/ml of EGF plus 1 microg/ml of FSH; (iii) TCM-199 supplemented with 10% of foetal bovine serum (FBS) and (iv) TCM-199 supplemented with 10% of FBS plus 1 microg/ml of FSH. Cow oocytes were used as control and were matured in TCM-199 supplemented with 10 ng/ml of EGF. No differences were observed in blastocyst rate among the different heifer oocyte groups (8.8, 7.5. 8.4 and 6.8%, respectively) however, the percentage of blastocysts obtained from cow oocytes was significantly higher (30%; p < 0.01) than those obtained from heifer oocytes. De novo GSH synthesis during oocyte maturation of heifer and cow oocytes was detected. No significant differences in intracytoplasmic GSH levels were observed among the experimental heifer oocyte groups or between heifer and cow oocytes both before and after IVM. In conclusion, the blastocyst yield obtained from heifer oocytes was lower than that from cow oocytes and this fact could not be explained by significant differences in intracytoplasmic GSH contents of oocytes before or after IVM.

Effect of stage of follicular growth during superovulation on developmental competence of bovine oocytes

The final steps of oocyte capacitation and maturation are critical for embryonic development but detailed information is scarce on how the oocyte is affected during this period. In this study, 2033 oocytes were collected from 106 superovulated cattle at four different time points before ovulation. Follicular characteristics were measured and oocyte quality was assessed by morphology, mRNA expression of eight marker genes or developmental ability after in vitro/in vivo maturation and subsequent in vitro fertilization and culture. Approaching ovulation, expected increases in follicular size and cumulus expansion suggested progression of oocyte maturation. No differences were found in the expression patterns of analyzed genes, except for heat-shock-protein (Hsp) that was lower in in vivo matured oocytes collected shortly before ovulation. Oocytes collected at this time also had higher developmental ability measured as blastocyst rates (57.6%) after in vitro production while no differences were found between oocytes recovered earlier at the first three time points (39.3-41.5%). We conclude that oocytes recovered late in the preovulatory period are more developmentally competent than oocytes recovered at the pre-capacitation and the capacitation period, probably due to the former having matured in vivo. However, a precisely defined time for aspirating immature oocytes for subsequent in vitro development seems not to be crucial.

Effects of bovine oviduct epithelial cells, fetal calf serum and bovine serum albumin on gene expression in single bovine embryos produced in the synthetic oviduct fluid culture system

In this study the synthetic oviduct fluid (SOF) system with bovine oviduct epithelial cell (BOEC) co-culture is compared with an SOF system with common protein supplements. One thousand six hundred bovine embryos were cultured in SOF media supplemented with BOEC, fetal calf serum (FCS) and bovine serum albumin (BSA). Eight different culture groups were assigned according to the different supplementation factors. Developmental competence and the expression levels of five genes, namely glucose transporter-1 (Glut-1), heat shock protein 70 (HSP), connexin43 (Cx43), β-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), analysed as mRNA by using reverse transcription–polymerase chain reaction, were measured on bovine embryos cultured for 9 days. Gene expression of these in vitro-produced embryos was compared with the gene expression of in vivo-produced embryos. There was no significant difference found in embryo developmental competence between the Day 9 embryos in BOEC co-culture, FCS and BSA supplements in SOF media. However, differences in gene expression were observed. With respect to gene expression in in vivo and in vitro embryos, BOEC co-culture affected the same genes as did supplementation with FCS and BSA. HSP was the only gene that differed significantly between in vitro and in vivo embryos. When the different in vitro groups were compared, a significant difference between the BOEC co-culture and the FCS supplementation groups due to Glut-1 expression was observed.

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.

In vitro fertilization as a predictor of fertility from cervical insemination of sheep

The objective of this study was to determine if the quality of frozen-thawed ram semen could be effectively evaluated through in vitro fertilization (IVF) procedures prior to insemination as a means of improving pregnancy rate. In experiment 1, frozen semen from four Belclare rams was assessed using IVF and was used for cervical insemination of ewes (n = 181) in 13 pedigree Belclare flocks. There was a significant association between IVF score (proportion of oocytes cleaved at 48 h post insemination) and non-return rate (P < 0.001). For experiment 2, semen from nine Belclare rams was evaluated by IVF and semen from rams with the highest (n = 3) and lowest (n = 2) IVF scores was used for cervical insemination of ewes (n = 111) under experimental conditions. Differences in pregnancy rates between individual rams did not reach significance. Experiment 3 was designed to determine if differences detected between rams at field level could be accurately identified via IVF evaluation and involved frozen semen from eight Norwegian rams of known field fertility (non-return rates ranged from 45.7 to 73.8%). IVF score did not reflect the differences in field fertility. In the final experiment six of the eight Norwegian rams involved in experiment 3 were selected based on IVF score (three highest and three lowest) and their semen was used for cervical insemination (n = 90 ewes). While significant differences in pregnancy rate were found between individual rams (P < 0.02, range: 12.9-65.8%) they were not associated with IVF score. Ewe breed had a significant effect (P < 0.003) on pregnancy rate in both experiments 2 and 4. In conclusion, there was no evidence from this study that the evaluation of semen quality through IVF provided a useful predictor of pregnancy rate under field conditions. It may be that the IVF procedures as used routinely, which are essentially designed to maximize blastocyst yields rather than for detecting differences in fertilizing ability between batches of sperm, need to be modified.