In vitro development to blastocysts of early porcine embryos produced in vivo or in vitro

Maslinic Acid Supplementation during the In Vitro Culture Period Ameliorates Early Embryonic Development of Porcine Embryos by Regulating Oxidative Stress

As a pentacyclic triterpene, MA exhibits effective free radical scavenging capabilities. The purpose of this study was to explore the effects of MA on porcine early-stage embryonic development, oxidation resistance and mitochondrial function. Our results showed that 1 μM was the optimal concentration of MA, which resulted in dramatically increased blastocyst formation rates and improvement of blastocyst quality of in vitro-derived embryos from parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). Further analysis indicated that MA supplementation not only significantly decreased the abundance of intracellular reactive oxygen species (ROS) and dramatically increased the abundance of intracellular reductive glutathione (GSH) in porcine early-stage embryos, but also clearly attenuated mitochondrial dysfunction and inhibited apoptosis. Moreover, Western blotting showed that MA supplementation upregulated OCT4 (p < 0.01), SOD1 (p < 0.0001) and CAT (p < 0.05) protein expression in porcine early-stage embryos. Collectively, our data reveal that MA supplementation exerts helpful effects on porcine early embryo development competence via regulation of oxidative stress (OS) and amelioration of mitochondrial function and that MA may be useful for increasing the in vitro production (IVP) efficiency of porcine early-stage embryos.

Electroporation-Mediated Genome Editing of Livestock Zygotes

The introduction of genome editing reagents into mammalian zygotes has traditionally been accomplished by cytoplasmic or pronuclear microinjection. This time-consuming procedure requires expensive equipment and a high level of skill. Electroporation of zygotes offers a simplified and more streamlined approach to transfect mammalian zygotes. There are a number of studies examining the parameters used in electroporation of mouse and rat zygotes. Here, we review the electroporation conditions, timing, and success rates that have been reported for mice and rats, in addition to the few reports about livestock zygotes, specifically pigs and cattle. The introduction of editing reagents at, or soon after, fertilization can help reduce the rate of mosaicism, the presence of two of more genotypes in the cells of an individual; as can the introduction of nuclease proteins rather than mRNA encoding nucleases. Mosaicism is particularly problematic in large livestock species with long generation intervals as it can take years to obtain non-mosaic, homozygous offspring through breeding. Gene knockouts accomplished via the non-homologous end joining pathway have been more widely reported and successfully accomplished using electroporation than have gene knock-ins. Delivering large DNA plasmids into the zygote is hindered by the zona pellucida (ZP), and the majority of gene knock-ins accomplished by electroporation have been using short single stranded DNA (ssDNA) repair templates, typically less than 1 kb. The most promising approach to deliver larger donor repair templates of up to 4.9 kb along with genome editing reagents into zygotes, without using cytoplasmic injection, is to use recombinant adeno-associated viruses (rAAVs) in combination with electroporation. However, similar to other methods used to deliver clustered regularly interspaced palindromic repeat (CRISPR) genome-editing reagents, this approach is also associated with high levels of mosaicism. Recent developments complementing germline ablated individuals with edited germline-competent cells offer an approach to avoid mosaicism in the germline of genome edited founder lines. Even with electroporation-mediated delivery of genome editing reagents to mammalian zygotes, there remain additional chokepoints in the genome editing pipeline that currently hinder the scalable production of non-mosaic genome edited livestock.

Transcriptome dynamics in early in vivo developing and in vitro produced porcine embryos

BACKGROUND

The transcriptional changes around the time of embryonic genome activation in pre-implantation embryos indicate that this process is highly dynamic. In vitro produced porcine blastocysts are known to be less competent than in vivo developed blastocysts. To understand the conditions that compromise developmental competence of in vitro embryos, it is crucial to evaluate the transcriptional profile of porcine embryos during pre-implantation stages. In this study, we investigated the transcriptome dynamics in in vivo developed and in vitro produced 4-cell embryos, morulae and hatched blastocysts.

RESULTS

In vivo developed and in vitro produced embryos displayed largely similar transcriptome profiles during development. Enriched canonical pathways from the 4-cell to the morula transition that were shared between in vivo developed and in vitro produced embryos included oxidative phosphorylation and EIF2 signaling. The shared canonical pathways from the morula to the hatched blastocyst transition were 14-3-3-mediated signaling, xenobiotic metabolism general signaling pathway, and NRF2-mediated oxidative stress response. The in vivo developed and in vitro produced hatched blastocysts further were compared to identify molecular signaling pathways indicative of lower developmental competence of in vitro produced hatched blastocysts. A higher metabolic rate and expression of the arginine transporter SLC7A1 were found in in vitro produced hatched blastocysts.

CONCLUSIONS

Our findings suggest that embryos with compromised developmental potential are arrested at an early stage of development, while embryos developing to the hatched blastocyst stage display largely similar transcriptome profiles, irrespective of the embryo source. The hatched blastocysts derived from the in vitro fertilization-pipeline showed an enrichment in molecular signaling pathways associated with lower developmental competence, compared to the in vivo developed embryos.

Effect of Triclosan Exposure on Developmental Competence in Parthenogenetic Porcine Embryo during Preimplantation

Triclosan (TCS) is included in various healthcare products because of its antimicrobial activity; therefore, many humans are exposed to TCS daily. While detrimental effects of TCS exposure have been reported in various species and cell types, the effects of TCS exposure on early embryonic development are largely unknown. The aim of this study was to determine if TCS exerts toxic effects during early embryonic development using porcine parthenogenetic embryos in vitro. Porcine parthenogenetic embryos were cultured in in vitro culture medium with 50 or 100 µM TCS for 6 days. Developmental parameters including cleavage and blastocyst formation rates, developmental kinetics, and the number of blastomeres were assessed. To determine the toxic effects of TCS, apoptosis, oxidative stress, and mitochondrial dysfunction were assessed. TCS exposure resulted in a significant decrease in 2-cell rate and blastocyst formation rate, as well as number of blastomeres, but not in the cleavage rate. TCS also increased the number of apoptotic blastomeres and the production of reactive oxygen species. Finally, TCS treatment resulted in a diffuse distribution of mitochondria and decreased the mitochondrial membrane potential. Our results showed that TCS exposure impaired porcine early embryonic development by inducing DNA damage, oxidative stress, and mitochondrial dysfunction.

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

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

Embryotropic effects of vascular endothelial growth factor on porcine embryos produced by in vitro fertilization

Current research suggests that supplementing in vitro culture (IVC) media with vascular endothelial growth factor (VEGF) may have beneficial effects on the development of porcine embryos in vitro. However, the molecular signaling mechanisms underlying this effect are unclear. Therefore, we aimed to investigate the effects of VEGF on molecular signaling events during in vitro embryonic development of porcine embryos. Porcine oocytes matured in vitro were fertilized, and the resultant zygotes were cultured with 5 ng/mL of VEGF supplemented with or without fetal bovine serum from day 4 till day 7. Without VEGF and/or FBS served as the control group. Real-time quantitative PCR was used to detect expression patterns of apoptosis- and oxidative stress-related genes in day 7 blastocysts (BLs). Early-stage apoptosis was detected by annexin-V assays in day 2 and day 7 embryos. We found that the addition of VEGF throughout the culture period with or without FBS supplementation significantly improved embryo survival and development. Supplementation with VEGF in the IVC medium significantly increased early BL formation (p < 0.05), although addition of FBS on day 4 significantly increased hatched BL formation (p < 0.05) regardless of VEGF supplementation. However, supplementation of media with both VEGF and FBS increased the formation of expanded BLs synergistically. The average total cell numbers per BL were significantly (p < 0.05) higher in embryos supplemented with VEGF and FBS than in those supplemented with either VEGF or FBS alone. We also found that accumulation of reactive oxygen species in VEGF-treated embryos was significantly lower (p < 0.05) than that in untreated embryos. The mRNA levels of caspase-3 were significantly lower (p < 0.05), and those of Bcl-2 and Nrf-2 were significantly higher (p < 0.05) in embryos grown in VEGF-supplemented media than in embryos grown in non-supplemented media. Furthermore, on day 2, the numbers of viable embryos (44.06 ± 3.94%) and blastomeres (67.18 ± 3.60%) were significantly higher (p < 0.05), and the numbers of early apoptotic embryos (55.94 ± 3.94) and blastomeres (23.23 ± 4.22) were significantly lower (p < 0.05) in VEGF-treated BLs than in controls. Furthermore, the numbers of early apoptotic cells in BLs on day 7 were also significantly lower (p < 0.05) in VEGF-treated BLs than in controls. Overall, our results indicate that supplementing IVC media with VEGF during in vitro culture of porcine embryos increases their developmental potential.

Supplementation of culture medium with L-carnitine improves the development and cryotolerance of in vitro-produced porcine embryos

Porcine oocytes and embryos contain substantial amounts of lipid, with little known regarding its metabolic role during development. This study investigated the role of lipid metabolism and the interaction between carbohydrate and lipid substrates in porcine embryos. Following in vitro fertilisation, presumptive zygotes were transferred to culture medium supplemented with L-carnitine, a co-factor required for the metabolism of fatty acids. In porcine zygote medium-3 (PZM-3), which contains pyruvate and lactate, 3mM L-carnitine was the only dose that improved cleavage rates compared with the control. In the absence of carbohydrates, all doses of L-carnitine from 1.5 to 12mM increased cleavage rates compared with the control. Culture in a PZM-3-based sequential media system (Days 0-3: pyruvate and lactate; Days 4-7: glucose) significantly increased blastocyst cell numbers compared with culture in standard PZM-3. Supplementing PZM-3 with 3mM L-carnitine produced blastocysts with cell numbers equivalent to those obtained in the sequential media system. After vitrification, the post-warming survival rates of blastocysts obtained in media supplemented with 3mM L-carnitine were significantly greater than those of blastocysts obtained in standard PZM-3. In conclusion, L-carnitine supplementation improved embryo development when the medium contained pyruvate and lactate or was lacking carbohydrates completely, indicating a role for fatty-acid metabolism when the embryo's requirements for carbohydrates are not adequately met.

Improved quality of porcine embryos cultured with hyaluronan due to the modification of the mitochondrial membrane potential and reactive oxygen species level

Although considerable progress has been made in pig embryo culture systems, the developmental competence and quality of the produced embryos are still lower than their in vivo-derived counterparts. Because hyaluronan (HA) regulates various cellular processes and possesses antioxidant properties, this glycosaminoglycan seems to be a promising supplement in culture media. However, until now, its beneficial influence on in vitro pig embryo development has been debatable. Hence, we aimed to investigate the effect of 0.25 mg/mL, 0.5 mg/mL and 1 mg/mL concentrations of HA on the developmental potential and quality of cultured porcine embryos. We found that 1 mg/mL HA supplementation significantly increased the obtained percentages of cleaved embryos to ∼95%, morulae to ∼87% and blastocysts to ∼77%. At 0.5 mg/mL and 1 mg/mL HA concentrations, we observed a significantly improved blastocyst quality, expressed as the total number of cells per blastocyst, number of cells in the inner cell mass, number of TUNEL-positive nuclei per blastocyst, the TUNEL index and the blastocyst diameter. Because the inner mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) level are important for proper embryo development, for the first time, we measured these two parameters in cultured embryos at various HA concentrations and during their development up to the expanded blastocyst stage. For blastocysts cultured with 1 mg/mL HA, the ΔΨm and ROS level were ∼1.6 and 2.7 times lower, respectively, than those of the control blastocysts. Both ΔΨm and the ROS level were increased in parallel during in vitro embryo development with and without HA, but this increase was less pronounced in the presence of HA. Hence, our quantitative data unequivocally show that supplementation of NCSU-23 culture medium with 1 mg/mL HA improves the developmental potential and quality of pig embryos. This effect results from a significant decrease in the ROS level induced by the HA-dependent ΔΨm reduction.

Inhibition of cathepsin B activity reduces apoptosis by preventing cytochrome c release from mitochondria in porcine parthenotes

Cathepsin B, a lysosomal cysteine protease of the papain family, has recently been implicated in the quality and developmental competence of bovine preimplantation embryos. In this study, to determine whether inhibition of cathepsin B activity can improve porcine oocyte maturation and early embryo developmental competence, we supplemented in vitro maturation or embryo culture media with E-64, a cathepsin B inhibitor. Cathepsin B activity was high in poor quality germinal vesicle stage oocytes, but no differences in mRNA expression or protein localization were observed between good and poor quality oocytes, which were categorized based on morphology. Following treatment with 1 μM E-64, cathepsin B activity sharply decreased in 4-cell and blastocyst stage embryos. E-64 had no effect on cell number but significantly (P < 0.05) increased blastocyst formation and decreased the number of apoptotic cells in blastocysts. It also significantly (P < 0.05) enhanced mitochondrial membrane potential in blastocysts, reducing the release of cytochrome c and resulting in decreased expression of Caspase-3 and Caspase-9. In conclusion, inhibition of cathepsin B activity in porcine parthenotes using 1 μM E-64 resulted in attenuation of apoptosis via a reduction in the release of cytochrome c from mitochondria.

Usefulness of bovine and porcine IVM/IVF models for reproductive toxicology

Women presenting fertility problems are often helped by Assisted Reproductive Techniques (ART), such as in vitro fertilization (IVF) programs. However, in many cases the etiology of the in/subfertility remains unknown even after treatment. Although several aspects should be considered when assisting a woman with problems to conceive, a survey on the patients' exposure to contaminants would help to understand the cause of the fertility problem, as well as to follow the patient properly during IVF. Daily exposure to toxic compounds, mainly environmental and dietary ones, may result in reproductive impairment. For instance, because affects oocyte developmental competence. Many of these compounds, natural or synthetic, are endocrine disruptors or endocrine active substances that may impair reproduction. To understand the risks and the mechanism of action of such chemicals in human cells, the use of proper in vitro models is essential. The present review proposes the bovine and porcine models to evaluate toxic compounds on oocyte maturation, fertilization and embryo production in vitro. Moreover, we discuss here the species-specific differences when mice, bovine and porcine are used as models for human.

Selection of in vitro-matured porcine oocytes based on localization patterns of lipid droplets to evaluate developmental competence

Localization patterns of lipid droplets in the cytoplasm of porcine oocytes were evaluated as a novel marker for in vitro maturation (IVM) of oocytes with high developmental competence. Porcine oocytes were cultured in TCM-199, which is a complete synthetic medium, for 44 h at 38.5 C. Localization patterns were divided into 2 classes: lipid droplets localized uniformly in the whole cytoplasm (class I) and those that were centrally located (class II). After IVM in TCM-199, 60% of matured oocytes exhibited the class II pattern. To investigate the relation between the distribution of lipid droplets and the developmental rate of the oocyte, the developmental rates of class I and class II oocytes were compared after in vitro fertilization (IVF). Class II oocytes showed a significantly higher rate of blastocyst development than class I oocytes. These results suggest that porcine oocytes with high developmental competence can be selected based on the localization patterns of lipid droplets.

Piglets produced from cloned blastocysts cultured in vitro with GM-CSF

In general, pig embryos established by somatic cell nuclear transfer (SCNT) are transferred at the one-cell stage because of suboptimal embryo culture conditions. Improvements in embryo culture can increase the practical application of late embryo transfer. The goal of this study was to evaluate embryos cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro, and to track the in vivo developmental competency of SCNT-derived blastocysts from these GM-CSF embryos. The receptor for GM-CSF was up-regulated in in vitro-produced embryos when compared to in vivo-produced cohorts, but the level decreased when GM-CSF was present. In vitro fertilized (IVF) embryos, supplemented with GM-CSF (2 or 10 ng/ml), showed a higher frequency of development to the blastocyst stage compared to controls. The total cell numbers of the blastocysts also increased with supplementation of GM-CSF. Molecular analysis demonstrates that IVF-derived blastocysts cultured with GM-CSF exhibit less apoptotic activity. Similarly, an increase in development to the blastocyst stage and an increase in the average total-cell number in the blastocysts were observed when SCNT-derived embryos were cultured with either concentration of GM-CSF (2 or 10 ng/ml). When SCNT-derived embryos, cultured with 10 ng/ml GM-CSF, were transferred into six surrogates at Day 6, five of the surrogates became pregnant and delivered healthy piglets. Our findings suggest that supplementation of GM-CSF can provide better culture conditions for IVF- and SCNT-derived embryos, and pig SCNT-derived embryos cultured with GM-CSF in vitro can successfully produce piglets when transferred into surrogates at the blastocyst stage. Thus, it may be practical to begin performing SCNT-derived embryo transfer at the blastocyst stage.

Cryotolerance of in vitro-produced porcine blastocysts is improved when using glucose instead of pyruvate and lactate during the first 2 days of embryo culture

The objective of the present study was to determine the effects of replacing glucose with pyruvate and lactate during the first 48 h of in vitro culture (IVC) in NCSU-23 medium on embryo development, embryo quality and survival of porcine blastocysts after vitrification. To this end, in vitro-produced (IVP) porcine oocytes were cultured with either glucose for 6 days (IVC-Glu) or pyruvate–lactate from Day 0 to Day 2 and then with glucose until Day 6 (IVC-PyrLac). Blastocysts were vitrified on Day 6 using the Cryotop device and, after warming, survival rate and the apoptosis index were evaluated after 24 h incubation in NCSU-23 medium. No significant differences were observed between IVC-Glu and IVC-PyrLac in terms of cleavage rate, blastocyst yield, total number of cells per blastocyst or the apoptosis index (1.82 ± 0.75% vs 3.18 ± 0.88%, respectively) of non-vitrified embryos. However, a significant increase was seen in hatching/hatched blastocysts in the IVC-PyrLac compared with IVC-Glu treatment group (12.71 ± 1.20% vs 3.54 ± 0.47%, respectively). Regardless of treatment, vitrification impaired the survival rate and the apoptosis index. When comparing both treatments after warming, the percentage of apoptotic cells was significantly higher for blastocysts in the IVC-PyrLac compared with IVC-Glu group (18.55 ± 3.49% vs 9.12 ± 2.17%, respectively). In conclusion, under the conditions of the present study, replacement of glucose with pyruvate–lactate during the first 48 h of culture resulted in a lower cryotolerance of IVP porcine embryos.

Porcine androgenetic embryos develop to fetal stage in recipient mothers

In livestock, parthenogenic embryos are simple to produce, but androgenetic embryos have been successfully produced only in sheep and cows. In the present study, matured porcine oocytes were enucleated by micromanipulation and then fertilized with sperm in vitro, thereby producing porcine androgenetic embryos. Porcine androgenetic embryos, which had only sperm genomes, were assessed for cleavage and for blastocyst formation 2 and 6 d after IVF, respectively. There was no difference in cleavage rate between androgenetic embryos and biparental IVF embryos (mean ± SD androgenetic: 65.5 ± 5.4%; biparental IVF: 63.2 ± 3.6%), but there was a difference in the rate of blastocyst formation (androgenetic: 4.5 ± 0.7%; biparental IVF: 30.2 ± 2.6%, P < 0.05). The average number of cells in Day 6 androgenetic blastocysts (34.3 ± 18.2) was lower (P < 0.05) than that in biparental IVF blastocysts (44.1 ± 19.5), but did not differ from that in parthenogenetic embryos (35.7 ± 16.7). The androgenetic embryos were transferred into recipient mothers to examine the competence of post-implantation development. Androgenetic fetuses were present on Days 21 and 25, but not on Days 28, 31, or 35. Of the six androgenetic fetuses recovered on Day 21, five had normal, translucent bodies, and two of these five had beating hearts. The four fetuses recovered on Day 25 were all non-viable. In conclusion, porcine androgenetic embryos initiated embryogenesis and had reached a viable fetal stage 21 days after IVF.

Comparative transcriptome analysis of in vivo- and in vitro-produced porcine blastocysts by small amplified RNA-serial analysis of gene expression (SAR-SAGE)

Production of embryos in vitro has enormous potential for research and commercial applications. Unfortunately, in vitro production of porcine embryos is extremely inefficient. Despite the characterization of distinct phenotypes, little is known about the molecular mechanisms and altered physiological processes of in vitro-produced embryos. The objective of this study was to compare global gene expression patterns from in vivo- (IVO) and in vitro-produced (IVP) porcine embryos using small amplified RNA-serial analysis of gene expression (SAR-SAGE). Whole-cell RNA from pools of Day 6 IVO and IVP blastocysts was used to construct SAR-SAGE libraries. Sequence analysis of the IVO and IVP libraries yielded 98,771 and 98,408 tags, respectively. A total of 20,029 and 23,453 putative transcripts were detected in the IVO and IVP libraries, respectively. Statistical analyses of SAGE tag frequencies between the IVO and IVP libraries indicated that 938 and 193 tags were differentially expressed at a P < 0.05 and P < 0.001 level of significance, respectively, suggesting significant deviations in transcriptome profiles from IVO and IVP embryos. Categorization of differentially expressed transcripts into functional groupings indicated a significant deviation in gene expression from IVP blastocysts compared with IVO blastocysts for a number of biological processes including cellular metabolism, organization, and response to stress. Real-time PCR confirmed differential expression for several transcripts from independent IVO and IVP blastocysts. These results demonstrate compromised gene expression in IVP blastocysts compared with IVO blastocysts for a number of biological processes, particularly processes involved in mitochondrial function; thereby providing potential target pathways for improvement of IVP methods.

Isolation and characterization of porcine visceral endoderm cell lines derived from in vivo 11-day blastocysts

Two porcine cell lines of yolk-sac visceral endoderm, designated as PE-1 and PE-2, were derived from in vivo 11-d porcine blastocysts that were either ovoid (PE-1) or at the early tubular stage of elongation (PE-2). Primary and secondary culture of the cell lines was done on STO feeder cells. The PE-1 and PE-2 cells morphologically resembled visceral endoderm previously cultured from in vivo-derived ovine and equine blastocysts and from in vitro-derived bovine blastocysts. Analysis of the PE-1- and PE-2-conditioned medium by 2D-gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry demonstrated that they produced serum proteins. Reverse transcriptase polymerase chain reaction analysis showed that the cells expressed several genes typical for yolk-sac endoderm differentiation and function including GATA-6, DAB-2, REX-1, HNF-1, transthyretin, alpha-fetoprotein, and albumin. Unlike a porcine liver cell line, the PE-1 and PE-2 cell lines had relatively low inducible P-450 content and EROD activity, and, while they cleared ammonia from the cell culture medium, they did not produce urea. Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complex junctions resembling tight junctions and by lateral desmosomes. Rough endoplasmic reticulum was prominent within the cells. Immunocytochemistry indicated that the PE-1 cells expressed cytokeratin 18 and had robust microtubule networks similar to those observed in in vivo porcine yolk-sac endoderm. Metaphase spreads prepared at passage 26 of the PE-1 cell line indicated a diploid porcine karyotype of 38 chromosomes. The cells have been grown for over 1 yr for multiple passages at 1:10 or 1:20 split ratios on STO feeder cells. The cell lines will be of interest as an in vitro model of the porcine preimplantation yolk-sac tissue.

Embryotrophic effects of ethylenediaminetetraacetic acid and hemoglobin on in vitro porcine embryos development

This study investigated the embryotrophic effects of ethylenediaminetetraacetic acid (EDTA) and hemoglobin (Hb) on porcine preimplantation embryo development. Porcine embryos produced by in vitro maturation/fertilization were cultured for 6 days in modified North Carolina State University-23 medium (mNCSU-23) supplemented with EDTA and/or Hb. In Exp. 1, culturing porcine zygotes with 100 microM EDTA significantly increased cleavage frequencies (85.3%) at 48 h post insemination and the number of inner cell mass (ICM) (9.6+/-5.5) compared to the control (7.0+/-2.8). However, 100 microM EDTA did not improve blastocyst formation compared to 0, 1 or 10 microM EDTA. In Exp. 2, in vitro fertilized oocytes were cultured with 0, 1 or 10 microg/ml Hb. Culturing with Hb did not promote porcine embryo development, but significantly increased the cell numbers of blastocysts in 1 microg/ml Hb compared to 0 or 10 microg/ml Hb. In Exp. 3, culturing embryos with 100 microM EDTA+1 microg/ml Hb significantly improved frequencies of cleavage, blastocyst formation, and total cell numbers in blastocysts compared to the control. Moreover, 100 microM EDTA, 1 microg/ml Hb and their combination reduced reactive oxygen species (ROS) accumulation and decreased the incidence of apoptosis. In conclusion, the present study clearly demonstrated that the combining treatment of EDTA and Hb improved IVF porcine embryo development.

Effects of type and state of co-culture cells on in-vitro development of porcine oocytes matured and fertilized in vitro

PURPOSE

The present study was to investigate the impact of type and state of co-culture cells on developmental competence of porcine oocytes matured and fertilized in vitro.

METHODS

Porcine zygotes were co-cultured with granulosa cells (GCs) (Group 1) or porcine oviductal epithelial cells (pOECs) at follicular stage (Group 2), ovulation stage (Group 3) or corpus luteum (CL) stage (Group 4) or cultured in a medium without co-culture cells (control group).

RESULTS

The proportion of oocytes developed to 2-cell stage embryos in Group 2 was similar to that in control group, but significantly (p < 0.05) lower than that in Groups 1, 3 and 4. The proportions of oocytes developed to > or = 4-cell stage embryos in Groups 3 and 4 were significantly (p < 0.05) higher than that in Groups 1 and 2. At 144 h after insemination, 12.0, 14.8 and 20.0% of oocytes developed to blastocysts in Groups 1, 3 and 4, respectively. However, no embryos in control group developed beyond 4-cell stage and no embryos in Group 2 developed to blastocyst stage.

CONCLUSION

As compared with GCs and pOECs at follicular stage, the pOECs at ovulation and CL stages had a better competence to support porcine embryo development under in vitro conditions.

Susceptibility of in vivo- and in vitro-produced porcine embryos to classical swine fever virus

The objective of this study was to investigate the susceptibility of in vivo- and in vitro-produced (IVP) porcine embryos to classical swine fever virus (CSFV). IVP zona pellucida (ZP)-intact porcine embryos (n = 721) were co-cultured with CSFV for 120 h. After washing according to the International Embryo Transfer Society guidelines (without trypsin) and transferring embryos to CSFV-susceptible porcine kidney cells (PK15 cell line), no virus was isolated. However, when 88 IVP ZP-intact porcine embryos were co-cultured with CSFV for only 48 h before being transferred to PK15 cells, virus was isolated in three of six replicates. Similarly, 603 in vivo-produced porcine embryos were co-cultured with CSFV for 120 h. Subsequently, CSFV was isolated in eight of 50 groups (16%) and the ability of these to form a blastocyst was significantly reduced when compared with the control group (68.2 +/- 19.9% vs 81.9 +/- 9.7%; p < or = 0.001). In contrast, the development of CSFV-exposed IVP porcine embryos was not affected when compared with control embryos (19.1 +/- 10.8% vs 18.9 +/- 10.6%; p > or = 0.05). After removal of the ZP of IVP embryos and subsequent co-culture with CSFV, the virus was isolated from all groups of embryos. These data suggest that virus replication had occurred in the embryonic cells. In conclusion, data indicate that in vivo- and in vitro-produced ZP-intact porcine embryos differ in their susceptibility to CSFV. Hatched or micro-manipulated embryos may increase the risk of transmission of CSFV by embryo transfer, which has to be confirmed by in vivo tests under isolation conditions.

Ovarian activity and oocyte development during follicular development in pigs at different reproductive phases estimated by the repeated endoscopic method

The aim of the present study was to assess follicular and oocyte development in the same gilts during three phases of their reproductive life [prepuberal gilts (PP; 6.0 months of age), puberal gilts (P; 9.5 months of age) and primiparous sows (S)]. Follicular development was stimulated by the injection of 1,000 IU of equine chorionic gonadotropin (eCG) followed by 500 IU of human chorionic gonadotropin (hCG) 72 h later. Cumulus-oocyte-complexes (COCs) were recovered by endoscopic ovum pick up/aspiration from preovulatory follicles of the left ovary, and the follicular fluid (FF) from the right ovary was collected 34 h after the hCG treatment by endoscopy. Altogether, 19 pigs were used in the PP and P trials and 12 in the S trial. From the left ovaries, 168, 190 and 82 follicles were aspirated and 106, 125 and 42 COCs, respectively, were recovered (recovery rate 61 +/- 27, 63 +/- 21 and 53 +/- 22%, respectively). The mean number of follicles was greater in the P phase than in the PP phase (19.7 +/- 6.8 vs. 15.7 +/- 6.8; p=0.06) and S phases (14.2 +/- 4.0; p<0.05). More uniform oocytes with an expanded cumulus were aspirated in the P and PP phases than in the S phase (90 and 78 vs. 46%; p<0.05). Furthermore, the meiotic configuration in oocytes (T I/M II stage) differed between the three phases (56 and 62 vs. 0%; p<0.05). Progesterone (P4) levels in FF decreased from 590.0 +/- 333.6 (PP) to 249.1 +/- 72.6 (P) and 161.4 +/- 75.2 ng/ml (S) (p<0.05). Estradiol-17beta (E2) levels differed between PP and P gilts and S sows (9.3 +/- 2.9, 21.9 +/- 10.6 and 94.0 +/- 15.9 pg/ml, respectively; p<0.05), and the P4/E2 ratio was 72, 15 and 5, respectively. These results indicate differences in follicular and oocyte development between the reproductive phases investigated. Puberal gilts should preferably be used in IVF and breeding programs. The lower reproductive potential of primiparous sows must be taken into consideration in breeding. Any prediction of lifetime performance based on individual ovarian reactions of prepuberal gilts is unreliable.

Effects of delipidation and oxygen concentration on in vitro development of porcine embryos

The effects of delipidation and the oxygen (O(2)) concentration in the atmosphere during culture on in vitro development and H(2)O(2) content were investigated in porcine in vivo fertilized embryos and embryos after in vitro maturation and in vitro fertilization (IVM/IVF embryos). There was no significant difference in the developmental rates to the blastocyst stage between the intact and delipidated IVM/IVF embryos. However, the mean number of cells in blastocysts derived from delipidated IVM/IVF embryos (19.8 +/- 0.8 cells) was significantly smaller than that from intact embryos (24.2 +/- 1.2 cells). Although there were no significant differences in the developmental rates to the blastocyst stage of intact and delipidated IVM/IVF embryos between the cultures under 5% O(2) and 20% O(2), the developmental rate of intact IVM/IVF embryos cultured under 5% O(2) (27.1%) was significantly higher than that of the delipidated embryos cultured under 20% O(2) (19.3%). On the other hand, there was no difference in the developmental rate to the blastocyst stage between in vivo fertilized embryos cultured under 5% O(2) and 20% O(2). Hydrogen peroxide (H(2)O(2)), one of the reactive oxygen species (ROS), is thought to cause damage to embryos. The H(2)O(2) content per embryo derived from oocytes cultured under 5% O(2) (in vivo fertilized, 58.0 +/- 2.5 pixels; IVM/IVF, 79.6 +/- 3.2 pixels) was significantly lower than that (in vivo fertilized, 100.2 +/- 3.8 pixels; IVM/IVF, 103.9 +/- 3.2 pixels) under 20% O(2). Furthermore, the level of H(2)O(2) in delipidated IVM/IVF embryos (94.7 +/- 3.9 pixels) was significantly lower than that in intact embryos (103.9 +/- 3.2 pixels) cultured under 20% O(2). The present results indicate that the delipidation of porcine IVM/IVF embryos and reduction of the O(2) concentration decreased the H(2)O(2) level rather than the in vitro developmental rate to the blastocyst stage.

Cumulus cells steroidogenesis is influenced by the degree of oocyte maturation

BACKGROUND

The possibility to predict the ability of a germ cell to properly sustain embryo development in vitro or in vivo as early as possible is undoubtedly the main problem of reproductive technologies. To date, only the achievement of nuclear maturation and cumulus expansion is feasible, as all the studies on cytoplasmic maturation are too invasive and have been complicated by the death of the cells analyzed. The authors studied the possibility to test the cytoplasmic quality of pig oocytes by evaluating their ability to produce steroidogenesis enabling factor(s). To this aim, oocytes matured under different culture conditions that allowed to obtain gradable level of cytoplasmic maturation, were used to produce conditioned media (OCM). The secretion of the factor(s) in conditioned media was then recorded by evaluating the ability of the spent media to direct granulosa cells (GC) steroidogenesis.

METHODS

In order to obtain germ cells characterized by a different degree of developmental competence, selected pig oocytes from prepubertal gilts ovaries were cultured under different IVM protocols; part of the matured oocytes were used to produce OCM, while those remaining were submitted to in vitro fertilization trials to confirm their ability to sustain male pronuclear decondensation. The OCM collected were finally used on cumulus cells grown as monolayers for 5 days. The demonstration that oocytes secreted factor(s) can influence GC steroidogenesis in the pig was confirmed in our lab by studying E2 and P4 production by cumulus cells monolayers using a radioimmunoassay technique.

RESULTS

Monolayers obtained by growing GC surrounding the oocytes for five days represent a tool, which is practical, stable and available in most laboratories; by using this bioassay, we detected the antiluteal effect of immature oocytes, and for the first time, demonstrated that properly matured germ cells are able to direct cumulus cells steroidogenesis by inhibiting E2 production (P < 0.01). Nevertheless, only fully competent oocytes were able to suppress estrogens production, while those cultured under unfavourable conditions were unable to exert any inhibitory effect on the functions of cumulus cells (P < 0.01).

CONCLUSION

These results demonstrated that good quality oocytes can be easily selected on the basis of their ability to affect granulosa cell steroidogenesis thus reducing failures in reproductive technologies due to the transfer of fertilized oocytes with a scarce ability to sustain embryo development.

In vitro fertilisation of in vivo matured porcine oocytes obtained from prepuberal gilts at different time intervals after hCG injection

The goal of the present study was to find out the best interval after hCG injection in PMSG primed prepuberal gilts for retrieval of in vivo matured oocytes for in vitro fertilisation (IVF). Altogether 66 gilts were superovulated with 1500 IU PMSG and 500 IU hCG 72 h later. Ovum pick up was performed endoscopically 24, 28, 32 or 36 h after hCG and a total of 869 cumulus-oocyte-complexes (COCs) were aspirated from 1400 follicles. COCs were tested for quality, and an aliquot was immediately fixed and stained to determine meiotic configuration. The remaining COCs were fertilised in vitro using frozen-thawed epididymal semen. Quality and developmental stage of embryos were tested after IVF, and the number of nuclei was counted. At 24 to 32 h after hCG only few oocytes have entered the second meiotic cycle (18 to 25% vs. 58% at 36 h, p < 0.05). The overall cleavage rate was significantly influenced by insufficient maturation rate at the early collection times (14% at 24 h vs. 49% at 36 h). Additionally, when oocytes were collected 24 to 32 h vs. 36 h the cleavage rate based on mature oocytes was lower (26 vs. 62%, p < 0.05). Once embryonic development has been initiated, the further in vitro development to blastocyst stages did not differ between groups. However, the number of cells was lower at collection times 24 to 32 h as compared to 36 h after hCG (12 to 15 cells vs. 22 cells, p < 0.05). The results indicate that the time of COC collection affects the in vitro developmental competence up to the blastocyst stage and should not be performed earlier than 36 h after hCG treatment.

Birth of piglets derived from porcine zygotes cultured in a chemically defined medium

We evaluated the in vitro development of porcine zygotes that were cultured in a novel culture medium, porcine zygote medium (PZM), under different conditions and compared to in vivo development. The viability of these zygotes to full term after culture was also evaluated by embryo transfer to recipients. Porcine single-cell zygotes were collected from gilts on Day 2 after hCG injection. Culture of zygotes in PZM containing 3 mg/ml of BSA (PZM-3) produced better results in terms of proportion of Day 6 blastocysts, Day 8 hatching rate, and numbers of inner cell mass (ICM) cells and total cells in Day 8 embryos than that in North Carolina State University (NCSU)-23 medium. In culture with PZM-3, embryo development was optimized in an atmosphere of 5% CO2:5% O2:90% N2 compared to 5% CO2 in air. The ICM and total cell numbers in Day 6 embryos cultured in PZM-3 or in PZM-3 in which BSA was replaced with 3 mg/ml of polyvinyl alcohol (PZM-4) were also greater than those of NCSU-23 but less than those developed in vivo. However, no difference was found in the ratio of ICM to total cells among embryos developed in PZM-3, PZM-4, or in vivo. When the Day 6 embryos that developed in PZM-4 (99 embryos) or in vivo (100 embryos) were each transferred into six recipients, no difference was found in the farrowing rate (83.3% for both treatments) and in the number of piglets born (33 and 42 piglets, respectively). Our results indicate that porcine zygotes can develop into blastocysts in a chemically defined medium and to full term by transfer to recipients after culture.

Progress in reproductive biotechnology in swine

This article summarizes recent progress in reproductive biotechnology in swine with special reference to in vitro production of embryos, generation of identical multiples, and transgenic pigs useful for xenotransplantation. In vitro production (in vitro maturation, in vitro fertilization, and in vitro culture) of viable porcine embryos is possible, although with much lower success rates than in cattle. The main problems are insufficient cytoplasmic maturation of porcine oocytes, a high proportion of polyspermic fertilization and a low proportion of blastocysts that, in addition, are characterized by a low number of cells, hampering their development in vivo upon transfer to recipients. Microsurgical bisection of morula and blastocyst stage embryos leads to a 2 to 3% monozygotic twinning rate of the transferred demiembryos, which is similar to that in rabbits and mice but considerably lower than in ruminants. It was found that with decreasing quality an increasing proportion of demi-embryos did not possess an inner cell mass. Porcine individual blastomeres derived from 4- and 8-cell embryos can be cultured in defined medium to the blastocyst stage. Leukemia inhibitory factor has been shown to be effective at defined embryonic stages and supports the formation of the inner cell mass in cultured isolated blastomeres in a concentration-dependent manner. For maintaining pregnancies with micromanipulated porcine embryos, it is not necessary to transfer extraordinarily high numbers of embryos. Porcine nuclear transfer is still struggling from the inefficiency of producing normally functioning blastocysts. Blastomeres, blastocyst-derived cells, fibroblasts and granulosa cells have been employed as donor cells in porcine nuclear transfer and have yielded blastocysts. Recently, the generation of the first piglets from somatic cell nuclear transfer has been achieved. DNA-microinjection into pronuclei of porcine zygotes has reliably resulted in the generation of transgenic pigs, which have special importance for the production of valuable pharmaceutical proteins in milk and xenotransplantation. It has been demonstrated that by expression of human complement regulatory proteins in transgenic pigs the hyperacute rejection response occurring after xenotransplantation can be overcome in a clinically relevant manner. Although biotechnological procedures in swine have recently undergone tremendous progress, the development is still lagging behind that in cattle and sheep. With regard to genetic engineering, considerable progress will originate from the possibility of employing homologous recombination in somatic cell lines and their subsequent use in nuclear transfer. In combination with the increasing knowledge in gene sequences this will allow in the foreseeable future widespread use in the pig industry either for agricultural or biomedical purposes.

Ovulation and follicular growth in gonadotropin-treated gilts followed by in vitro fertilization and development of their oocytes

We investigated whether porcine ovaries derived from FSH-pituitary (FSH-P) or hCG-treated animals can produce oocytes with better in vitro cytoplasmic maturation and in vitro embryonic development relative to those derived from saline-treated animals. The size of the follicle producing the oocyte was also studied. Each of 25 prepubertal gilts received 1 of 6 treatments by intramuscular injection: 1) saline (3 mL, once, n = 5); 2) FSH-P8-3 (8 mg, 3 times, with a 24-h interval, n = 4); 3) FSH-P16-3 (16 mg, 3 times, with a 24-h interval, n = 4); 4) FSH-P16-1-P4-2 (16 mg, once, 4 mg, twice, with a 24-h interval, n = 4); 5) FSH-P16-1 (16 mg, once, n = 4); or 6) hCG (100 IU, 3 times, with a 24-h interval, n = 4). The ovaries were removed by mid-ventral laparotomy 72 h after the first injection. The numbers of corpora hemorrhagica (CH) with each FSH-P treatment were similar (P > 0.05). However, compared with gilts treated with saline or hCG, those treated with FSH-P8-3 had a greater (P < 0.05) number of CH. Treatment with FSH-P8-3 or FSH-P16-3 induced significant growth of medium/large follicles (4 to 8 mm in diameter) compared with saline or FSH-P16-1. The same results were observed when FSH-P8-3 was compared with FSH-P16-P4-2 or hCG. After in vitro fertilization, the rates of male and female pronuclei in oocytes derived from medium/large follicles did not differ (P > 0.05) between treatments, but in oocytes derived from small follicles they were lower (P < 0.05) in saline-treated than in FSH-P16-1-P4-2-treated gilts. After 120 h in culture, the percentages of the inseminated oocytes from 1 to 3 mm or 4 to 8 mm follicles developing to > or = 2-cell did not differ (P > 0.05) between saline- and gonadotropin-treated gilts. However, a higher (P < 0.05) percentage of the inseminated oocytes from 4 to 8 mm follicles had developed to the morula stage or beyond, than those from the 1 to 3 mm follicles. In conclusion, administration of single or multiple doses of FSH-P induced ovulation, but only 8 or 16 mg FSH-P injected 3 times with 24-h intervals for 72 h induced growth of 4 to 8 mm follicles. The size of follicle from which the oocyte derived also had a significant effect on its development in vitro.

Fertilization and in vitro development of porcine oocytes following intracytoplasmic injection of round spermatid or round spermatid nuclei

The objective of this study was to determine fertilization rates and developmental ability of porcine oocytes following injection of round spermatid and round spermatid nucleus with artificial activation either 2 h before or immediately after injection. Electrical stimulation at 2 h before spermatid injection significantly increased the incidence of normal fertilization compared with that following injection without stimulation or with stimulation immediately after injection. Incidences of formation of 2 pronuclei and of apposition were not different in oocytes following intracytoplasmic spermatid and spermatid nucleus injection. Chromosome analysis revealed that most oocytes were diploid either following round spermatid or round spermatid nucleus injection. There was no diploid set of chromatin in oocytes at 20 h following sham injection. At 6 d following injection blastocoele formation was seen in the oocytes following round spermatid (25%) and round spermatid nucleus injection (27%). However, none of the oocytes developed to the blastocyst stage 6 d following sham injection. The average cell numbers of blastocysts 8 d after injection of spermatid and spermatid nucleus were 99 and 87, respectively. These results suggest that electrical stimulation before injection enhances the incidence of fertilization following round spermatid injection in the pig. Our study also indicates that either the round spermatid or it's nucleus can be used to produce viable embryos by injection into unfertilized porcine oocytes.

Practical considerations for the in vitro production of pig embryos

The routine maturation, fertilization, and development of pig embryos in vitro has only recently been achieved. Many of the conditions for in vitro production of embryos have been undefined and thus difficult to replicate. The major problems of in vitro production of pig embryos have included maturation of oocytes, both nuclear and cytoplasmic, and development from one-cell to blastocyst. While these barriers have been at least partially overcome there is still a significant problem with polyspermy. Nevertheless, numerous offspring have been produced from in vitro maturation, in vitro fertilization, followed by a brief culture prior to embryo transfer. Here is provided a review of the literature encompassing the current status of the in vitro production of pig embryos.

Effects of fetal calf serum, amino acids, vitamins and insulin on blastocoel formation and hatching of in vivo and IVM/IVF-derived porcine embryos developing in vitro

The objective of this study was to determine the effects of fetal calf serum (FCS), non-essential MEM amino acids, MEM vitamins and insulin on blastocoel formation, expansion and hatching in porcine embryos developing in vitro. Addition of 20% FCS to the NCSU 23 medium significantly (P < 0.05) decreased by the compaction and blastocoel formation of 1- to 2-cell embryos developing in vitro. In contrast, more 1- to 2-cell embryos commenced hatching in the media containing amino acids than in control medium (25.7 vs 2.6%, P < 0.01). Amino acids and insulin synergistically enhanced the incidence of blastocoel formation and hatching of porcine embryos developing in vitro (P < 0.05). When early compacted embryos which developed in vitro in NCSU 23 medium were cultured in BSA-free NCSU 23 medium supplemented with 20% FCS, the incidence of hatching was significantly increased compared with that of the control groups (35.7 vs 4.1%, P < 0.01). However, addition of amino acids, vitamins or insulin to the NCSU 23 medium did not enhance the development of early morulae to the hatched embryos (P > 0.1). When either in vivo or IVM/IVF-derived 1- to 2-cell stage embryos were cultured 4 d in the modified NCSU 23 and an additional 4 days in the modified NCSU 23 supplemented in the FCS, the percentages (61.8 and 17.8%, in vivo- and IVM/TVF-derived, respectively) of hatched blastocysts were significantly higher (P < 0.01) than in the control groups (2.9 and 0%, in vivo and IVM/IVF-derived, respectively). These results suggested that dual culture conditions are required to optimize an in vitro culture system for the development of the porcine embryo in vitro.

In vitro maturation of porcine oocytes in follicular fluid with subsequent effects on fertilization and embyo yield in vitro

The objective of the present study was to test the ability of porcine follicular fluid (pFF) to improve maturation of porcine cumulus-oocyte-complexes (COC) in vitro and to observe subsequent effects on fertilization and development to late morula/blastocyst stages under in vitro conditions. The COC were incubated in Tissue Culture Medium (TCM) 199, supplemented with 1% fetal calf serum (FCS), 10% pFF collected from immature follicles (2 to 5 mm), with or without addition of 1microg/ml FSH. Control groups were matured in TCM 199 with or without FSH. Follicular aspirates were centrifuged (1700 x g, 5min.) and the supematants were stored at -20 degrees in 1.5-ml Eppendorff cups until used. On 7 experimental days a total of 3849 immature COC was aspirated from follicles ranging from 2 to 5 mm in diameter. A total of 1117 COC was selected for the experiments, and 239 COC were fixed and stained with 1.5% aceto-orcein after 48 h of in vitro maturation at 39 degrees C with 5% CO(2) in humidified air. Germinal vesicle breakdown (GVBD; 91.7%) and development to metaphase II (60.4%) were superior (P <or= 0.05) when 10% pFF and 1microg/ml FSH were present in the maturation medium. Another 878 COC were mechanically denuded and used for in vitro fertilization (IVF). Eighteen hours after IVF, 561 oocytes were fixed and stained with aceto orcein. No diffeences were found among groups at this time point. Another 317 embryos were continuously cultured to morula and blastocyst stages in medium NCSU 23. Cleavage rates differed significantly (P <or= 0.05) 48 h after IVF, and were superior (52.5% vs 32.5% vs 30.7%) when oocytes were matured in maturation medium supplemented with pFF and FSH as compared with maturation rates in TCM 199 without pFF and/or FSH. Once the embryos had cleaved, no further differences were observed in the development to morula and blastocyst stages. These data indicate that GVBD and nuclear matuation to metaphase II are enhanced by a combination of pFF and FSH and that cytoplasmatic maturation is more complete and better synchronized as indicated by the increased cleavage rates.