Effect of maturation media and oocytes derived from sows or gilts on the development of cloned pig embryos

Effect of Growth Factors and Hormones during In Vitro Growth Culture of Cumulus-Oocyte-Complexes Derived from Small Antral Follicles in Pigs

This study evaluated the effect of various growth factors and hormones in an in vitro growth (IVG) medium on the in vitro maturation (IVM) and developmental competence of oocytes derived from small antral follicles (SAFs) in pigs. Cumulus–oocyte complexes (COCs) derived from SAFs were either untreated or treated with epidermal growth factor (EGF), insulin-like factor-1 (IGF-1), insulin, or growth hormone (GH) for 2 days of IVG. Following IVG, COCs were cultured for maturation, and IVM oocytes were induced for parthenogenesis (PA). During IVG, the nuclear maturation of oocytes was significantly increased by the insulin treatment compared to other treatments. Moreover, the insulin treatment significantly increased blastocyst formation after PA relative to the No-IVG, control, EGF, and GH treatments. The cumulus expansion score after IVG-IVM was significantly higher in the insulin group than in the other groups. The glutathione (GSH) contents in IVM oocytes were increased through treatment with IGF, insulin, and GH compared to those of No-IVG oocytes. The level of reactive oxygen species (ROS) in IVM oocytes in all treatment groups was significantly lower after IVG culture than in the No-IVG group. The maturation-promoting factor (MPF) activity after IVM in the insulin-treated oocytes was significantly higher than that of the oocytes treated with EGF, IGF-1, and GH. In conclusion, this study demonstrates that insulin treatment during IVG culture improves the maturational and developmental competence of oocytes derived from SAFs in pigs through its effect on cumulus cell expansion and cytoplasmic microenvironments, such as GSH, ROS, and MPF activity.

Establishment and optimization of an in vitro guinea pig oocyte maturation system

Guinea pigs are a valuable animal model for studying various diseases, including reproductive diseases. However, techniques for generating embryos via embryo engineering in guinea pigs are limited; for instance, in vitro maturation (IVM) technique is preliminary for guinea pig oocytes. In this study, we aimed to establish and optimize an IVM method for guinea pig oocytes by investigating various factors, such as superovulation induced by different hormones, culture supplementation (e.g., amino acids, hormone, and inhibitors), culture conditions (e.g., oocyte type, culture medium type, and treatment time), and in vivo hCG stimulation. We found that oocytes collected from guinea pigs with superovulation induced by hMG have a higher IVM rate compared to those collected from natural cycling individuals. Moreover, we found that addition of L-cysteine, cystine, and ROS in the culture medium can increase the IVM rate. In addition, we demonstrated that in vivo stimulation with hCG for 3-8 h can further increase the IVM rate. As a result, the overall IVM rate of guinea pig oocytes under our optimized conditions can reach ~69%, and the mature oocytes have high GSH levels and normal morphology. In summary, we established an effective IVM method for guinea pig oocytes by optimizing various factors and conditions, which provides a basis for embryo engineering using guinea pigs as a model.

Copper deficiency affects the developmental competence of porcine oocytes matured in vitro

The trace element Cu is required for the activity of various enzymes essential for physiological processes. In this study, we elucidated the copper transport system in porcine follicular cells and investigated the effect of Cu chelation during in vitro maturation (IVM) of porcine oocytes and subsequent embryonic development after parthenogenetic activation (PA). Cu chelation was induced by adding tetraethylenepentamine (TEPA) to the maturation media (TCM199-PVA). First, we identified the localization and relative levels of the copper transporter CTR1 in follicular cells. The level of CTR1 protein was the highest in mature cumulus cells; moreover, CTR1 was mainly localized in the cytoplasmic vesicular compartment in oocytes, whereas it was evenly distributed in the cytoplasm in cumulus cells. A total of 42 h after IVM, the TEPA-treated group showed reduced maturation rates compared to those of the control (p < 0.05). This negative effect of TEPA disappeared when it was added to the media with Cu (Cu + TEPA group). The TEPA treatment during IVM significantly increased the mRNA levels of the Has2 gene, which is related to cumulus expansion (p < 0.05). Both Cu supplementation and chelation significantly increased the reactive oxygen species (ROS) levels in porcine oocytes (p < 0.05). When we analyzed the transcript levels of folliculogenesis-related genes in Cu chelation conditions, only the expression of MAPK3 in cumulus cells significantly increased compared to that of the control. We also evaluated the subsequent embryonic development of PA embryos. TEPA-treated oocytes showed significantly decreased blastocyst formation rates compared to those of the control. The TEPA-induced toxic effect was alleviated when Cu was added with TEPA. Our findings suggest that the Cu transport system plays an important role in the porcine follicular development process and that the Cu deficiency negatively affects porcine oocyte maturation, as well as their subsequent developmental competence.

In vitro maturation using αMEM containing reduced NaCl enhances maturation and developmental competence of pig oocytes after somatic cell nuclear transfer

Background

Compared to medium containing 108 mM sodium chloride (NaCl), in vitro maturation (IVM) using a simple medium with reduced (61.6 mM) NaCl increases the cytoplasmic maturation and embryonic development of pig oocytes.

Objectives

This study determines the effect of a complex medium containing reduced NaCl on the IVM and embryonic development of pig oocytes.

Methods

Pig oocytes were matured in Minimum Essential Medium Eagle-alpha modification (αMEM) supplemented with 61.6 (61αMEM) or 108 (108αMEM) mM NaCl, and containing polyvinyl alcohol (PVA) (αMEMP) or pig follicular fluid (PFF) (αMEMF). Medium-199 (M199) served as the control for conventional IVM. Cumulus cell expansion, nuclear maturation, intra-oocyte glutathione (GSH) contents, size of perivitelline space (PVS), and embryonic development after parthenogenesis (PA) and somatic cell nuclear transfer (SCNT) were evaluated after IVM.

Results

Regardless of PVA or PFF supplementation, oocytes matured in 61αMEM showed increased intra-oocyte GSH contents and width of PVS (p < 0.05), as well as increased blastocyst formation (p < 0.05) after PA and SCNT, as compared to oocytes matured in 108αMEMP and M199. Under conditions of PFF-enriched αMEM, SCNT oocytes matured in 61αMEMF showed higher blastocyst formation (p < 0.05), compared to maturation in 108αMEMF and M199, whereas PA cultured oocytes showed no significant difference.

Conclusions

IVM in αMEM supplemented with reduced NaCl (61.6 mM) enhances the embryonic developmental competence subsequent to PA and SCNT, which attributes toward improved oocyte maturation.

Challenges and Considerations during In Vitro Production of Porcine Embryos

Genetically modified pigs have become valuable tools for generating advances in animal agriculture and human medicine. Importantly, in vitro production and manipulation of embryos is an essential step in the process of creating porcine models. As the in vitro environment is still suboptimal, it is imperative to examine the porcine embryo culture system from several angles to identify methods for improvement. Understanding metabolic characteristics of porcine embryos and considering comparisons with other mammalian species is useful for optimizing culture media formulations. Furthermore, stressors arising from the environment and maternal or paternal factors must be taken into consideration to produce healthy embryos in vitro. In this review, we progress stepwise through in vitro oocyte maturation, fertilization, and embryo culture in pigs to assess the status of current culture systems and address points where improvements can be made.

Immature Follicular Origins and Disrupted Oocyte Growth Pathways Contribute to Decreased Gamete Quality During Reproductive Juvenescence in Mice

Egg quality dictates fertility outcomes, and although there is a well-documented decline with advanced reproductive age, how it changes during puberty is less understood. Such knowledge is critical, since advances in Assisted Reproductive Technologies are enabling pre- and peri-pubertal patients to preserve fertility in the medical setting. Therefore, we investigated egg quality parameters in a mouse model of the pubertal transition or juvenescence (postnatal day; PND 11-40). Animal weight, vaginal opening, serum inhibin B levels, oocyte yield, oocyte diameter, and zona pellucida thickness increased with age. After PND 15, there was an age-associated ability of oocytes to resume meiosis and reach metaphase of meiosis II (MII) following in vitro maturation (IVM). However, eggs from the younger cohort (PND 16-20) had significantly more chromosome configuration abnormalities relative to the older cohorts and many were at telophase I instead of MII, indicative of a cell cycle delay. Oocytes from the youngest mouse cohorts originated from the smallest antral follicles with the fewest cumulus layers per oocyte, suggesting a more developmentally immature state. RNA Seq analysis of oocytes from mice at distinct ages revealed that the genes involved in cellular growth signaling pathways (PI3K, mTOR, and Hippo) were consistently repressed with meiotic competence, whereas genes involved in cellular communication were upregulated in oocytes with age. Taken together, these data demonstrate that gametes harvested during the pubertal transition have low meiotic maturation potential and derive from immature follicular origins.

Pig Cloning Using Somatic Cell Nuclear Transfer

Porcine cloning technology can be used to produce progenies genetically identical to the donor cells from high-quality breeding pigs. In addition, genetically modified pigs have been produced by somatic cell nuclear transfer using genetically modified porcine fetal fibroblasts. The method of preparing genetically modified pigs is critical for establishing pig models for human diseases, and for generating donor animals for future xenotransplantation. This chapter describes detailed procedures for generating cloned pigs using fetal fibroblasts as nuclear donors.

Optimization of donor cell cycle synchrony, maturation media and embryo culture system for somatic cell nuclear transfer in the critically endangered Vietnamese Ỉ pig

Our aim was to establish an efficient culture system to produce embryos by SCNT of the endangered Vietnamese Ỉ pig. Reducing the serum concentration from 10.0% to 0.2% during culture efficiently synchronized Ỉ pig fibroblasts used as donor cells at the G0/G1 stage. Oocyte maturation in a defined porcine oocyte medium (POM) supplemented with EGF and gonadotrophins resulted in higher cleavage and blastocyst rates compared with a non-defined POM containing pig follicular fluid (but without EGF) and both the defined and non-defined variants of NCSU-37. For embryo culture PZM3 and PZM5 media were superior to NCSU-37, in terms of the percentage of cleaved embryos. Addition of serum to PZM3 medium on Day 5 of culture (Day 0 = SCNT) improved blastocyst development. When SCNT embryos were transferred at the blastocyst stage, 7 of 11 recipients became pregnant. However, live offspring were not obtained. In conclusion, we established a system for the production of Ỉ pig embryos by SCNT and achieved blastocyst production rate at 26.4% by improving culture systems for donor cells, oocytes and embryos culture. Transfer of embryos resulted in pregnancies; however, live offspring were not obtained.

In vitro Production of Porcine Embryos: Current Status and Possibilities – A Review

This paper presents the current possibilities, state of knowledge and prospects of in vitro production (IVP) of pig embryos, which consists of in vitro oocyte maturation, in vitro fertilization and in vitro embryo culture. In pigs, oocyte maturation is one of the most important stages in the embryo IVP process. It determines the oocyte’s fertilization ability as well as its embryonic development. Through many research studies of the proper selection of oocytes and appropriate maturation medium composition (especially the addition of various supplements), the in vitro maturation of pig oocytes has been significantly improved. Recent studies have demonstrated that modifications of the diluents and in vitro fertilization media can reduce polyspermy. Furthermore, several adjustments of the porcine culture media with the addition of some supplements have enhanced the embryo quality and developmental competence. These updates show the progress of IVP in pigs that has been achieved; however, many problems remain unsolved.

Efficient production of GGTA1 knockout porcine embryos using a modified handmade cloning (HMC) method

Handmade cloning is a zona-free nuclear transfer approach and an economical, efficient, and simple micromanipulation-free alternative to dolly based traditional cloning (TC). In this study, based on handmade cloning with minor modifications, an optimized bi-oocyte fusion (BOF) cloning method was established to produce GGTA1 KO porcine embryos using the CRISPR/Cas9 gene editing system. The GGTA1 gene is responsible for the generation of Gal epitopes on the surface of porcine cells, triggering hyperacute immune rejection in preclinical porcine-to-human xenotransplantation. The purpose of the present study is to establish an efficient protocol for activation of porcine oocyte cytoplast-fibroblast fused constructs developed to GGTA1 KO blastocysts by the zona-free bi-oocyte fusion cloning method. High percentages of cleavage (90 ± 2.6%) and blastocyst rates (39 ± 4.0%) were achieved upon treatment with demecolcine-assisted oocyte enucleation followed by 6 V alternating current for proper alignment and single-step fusion technique using a single direct current pulse of 1.0 kV/cm for 9 μs duration, compared to the double-step fusion method with combined chemical activation using thimerosal and dithiothreitol. Overall blastocyst rate was higher for oocyte enucleation by demecolcine (0.4 μg/ml) and 45 min incubation (42 ± 1.5%) compared to without demecolcine incubation followed by complete chemical thimerosal/dithiothreitol activation (33 ± 1.1%). The blastocyst rate (39 ± 1.0%) was found to be significantly higher 1 h post-electrofusion, compared to at 0 and 4 h (28 ± 1.5 and 6 ± 1.5%, respectively). Blastocyst development rates for GGTA1 knockout embryos (38 ± 1.76%) were comparable to those obtained with wild-type embryos (41.1 ± 0.67%). In conclusion, we achieved high overall efficiency in production of GGTA1 KO blastocysts by modified HMC protocol.

Choosing a culture medium for SCNT and iSCNT reconstructed embryos: from domestic to wildlife species

Over the past decades, in vitro culture media have been developed to successfully support IVF embryo growth in a variety of species. Advanced reproductive technologies, such as somatic cell nuclear transfer (SCNT), challenge us with a new type of embryo, with special nutritional requirements and altered physiology under in vitro conditions. Numerous studies have successfully reconstructed cloned embryos of domestic animals for biomedical research and livestock production. However, studies evaluating suitable culture conditions for SCNT embryos in wildlife species are scarce (for both intra- and interspecies SCNT). Most of the existing studies derive from previous IVF work done in conventional domestic species. Extrapolation to non-domestic species presents significant challenges since we lack information on reproductive processes and embryo development in most wildlife species. Given the challenges in adapting culture media and conditions from IVF to SCNT embryos, developmental competence of SCNT embryos remains low. This review summarizes research efforts to tailor culture media to SCNT embryos and explore the different outcomes in diverse species. It will also consider how these culture media protocols have been extrapolated to wildlife species, most particularly using SCNT as a cutting-edge technical resource to assist in the preservation of endangered species.

The transgenic cloned pig population with integrated and controllable GH expression that has higher feed efficiency and meat production

Sustained expression of the GH gene has been shown to have detrimental effects on the health of animals. In the current study, transgenic founder pigs, with controllable pig growth hormone (pGH) expression, were cloned via the handmade cloning method (HMC), and pGH expression levels were examined at the cellular and organismal levels. The serum pGH levels in 3 founder male pigs were found to be significantly higher after induction with intramuscular injection of doxycycline (DOX) compared to baseline. A daily dose of DOX was administered via feed to these animals for a period of 65 to 155 days. The growth rate, feed efficiency and pGH serum concentration increased in the DOX-induced transgenic group compared with the other groups. 8 numbers of animals were euthanized and the dressing percentage, loin muscle and lean meat percentage were significantly higher in the DOX-induced F1 transgenic group compared with the other groups. In this study a large population of transgenic pigs, with integrated controllable expression of a transgene, was obtained. The transgenic pigs were healthy and normal in terms of reproductive capability. At the same time, feed efficiency was improved, production processes were accelerated and meat yield was increased.

The evolution of porcine embryo in vitro production

The in vitro production of porcine embryos has presented numerous challenges to researchers over the past four decades. Some of the problems encountered were specific to porcine gametes and embryos and needed the concerted efforts of many to overcome. Gradually, porcine embryo in vitro production systems became more reliable and acceptable rates of blastocyst formation were achieved. Despite the significant improvements, the problem of polyspermic fertilization has still not been adequately resolved and the embryo in vitro culture conditions are still considered to be suboptimal. Whereas early studies focused on increasing our understanding of the reproductive processes involved, the technology evolved to the point where in vitro-matured oocytes and in vitro-produced embryos could be used as research material for developing associated reproductive technologies, such as SCNT and embryo cryopreservation. Today, the in vitro procedures used to mature oocytes and culture embryos are integral to the production of transgenic pigs by SCNT. This review discusses the major achievements, advances, and knowledge gained from porcine embryo in vitro production studies and highlights the future research perspectives of this important technology.

The effects of artificial activation timing on the development of SCNT-derived embryos and newborn piglets

This study investigated the effects of two different activation regimens on the developmental potential of somatic cell nuclear transfer (SCNT) embryos and postnatal survivability of the cloned piglets. In vitro matured oocytes were enucleated and reconstructed with porcine fetal fibroblasts. On the basis of the activation regimen used, the reconstructed porcine embryos were allocated into two groups: Group 1-simultaneous electrical pulses and activation group (SFA group); and Group 2-electrical fusion without calcium followed by electrical pulses with calcium after colcemid and cytochalasin B treatment for 5h (DA group). Embryonic development in both SFA and DA groups was determined at day 6 of culture in NSCU-23 medium. To investigate the post-implantation development after the two activation methods, embryos were cultured for 1 day and then transferred into the oviducts of estrus-synchronized recipients. DA group had significantly (p<0.05) higher cleavage rates than SFA group. However, the developmental rate to the blastocyst stage and the mean cell number of blastocysts did not differ (p>0.05) between SFA and DA groups. Moreover, the pregnancy rate of SFA group was not significantly different compared to DA group. A total of 20 cloned piglets (SFA group-8 live piglets, DA group-11 live piglets and one stillborn) were obtained in the present study. The birth weight of the cloned piglets (live births) did not differ (p>0.05) between the two groups. Furthermore, no difference was observed in the postnatal survival rates of the cloned piglets obtained using two different activation regimens. These results suggest that the timing of artificial activation and additional chemical treatments do not affect the developmental rate of porcine SCNT embryos. Remarkably, the pregnancy rate and postnatal survivability of the cloned piglets did not vary between SFA and DA groups.

Developmental potential of pig embryos reconstructed by use of sow versus pre-pubertal gilt oocytes after somatic cell nuclear transfer

In this study, the developmental ability of cloned embryos using gilt versus sow oocytes was evaluated under the hypothesis that the efficiency of nuclear transfer using gilt oocytes was lower than that of sow oocytes, but that it could be optimized. Five experiments were performed with routine production of cloned embryos with sow oocytes serving as the control. Results showed that: Experiment 1: Blastocyst rates of cloned embryos with gilt oocytes was about half compared with control. Experiment 2: An extended maturation time of 48 h used for gilt oocytes resulted in lower blastocyst rates after cloning. Experiment 3: Development of cloned embryos with gilt oocytes was improved by co-culture with sow oocytes. Experiment 4: After maturation of gilt oocytes using follicular fluid from gilt instead of sow, the oocytes were sorted into large and small oocytes, and after cloning, blastocyst rates were higher using large gilt oocytes compared with small oocytes; however, the rate remained lower compared with control. Experiment 5: Six sow recipients received a total of 503 morulae and blastocysts cloned from gilt oocytes (four recipients) and 190 cloned from sow oocytes (two recipients). All recipients became pregnant and went to term, resulting in 26 (gilt oocytes) and six (sow oocytes) piglets. In conclusion, results confirmed that nuclear transfer efficiency was higher using sow versus gilt oocytes, but the use of gilt oocytes can be optimized by sorting after ooplasm size following maturation and by maturing gilt and sow oocytes together.

What is the optimal condition for fertilization of IVM oocytes?

Application of in vitro maturation (IVM) is recently increasing for human infertility, especially to rescue patients of polycystic ovarian syndrome and ovarian hyperstimulation syndrome. To increase the application of IVM oocytes for embryo production and the efficiency of successful production of babies using IVM oocytes, quality control of oocytes and achievement of fertilization in the most suitable condition may be very important. In this paper, suitable conditions for fertilization of IVM oocytes will be discussed with recent knowledge about IVM and in vitro fertilization of oocytes in domestic animals. Currently, human oocytes are collected mainly from patients' ovaries 36 h following mild gonadotropin stimulation and used for IVM for 24-26 h. However, asynchronous progression of those oocytes to reach the metaphase-II stage may have occurred during the IVM culture. In the oocytes that have already progressed to the metaphase-II stage, sudden aging such as reduction in maturation promoting factor and MAP kinases will start to occur. Application of specific inhibitors of phosphodiesterase to control intracellular cAMP (cyclic adenosine monophosphate) level may be effective to synchronize timings of the germinal vesicle breakdown and consequently the meiotic progression of oocytes, and to improve the developmental competence. Furthermore, treatment of aging oocytes with caffeine appears to rescue them from reductions in maturation promoting factor and MAP kinases and to improve the developmental competence. Assessment methods to select oocytes with good quality may also be important to improve the successful rates.

Efficiency of in vitro fertilization is influenced by the meiotic competence of porcine oocytes and time of their maturation

The effect of meiotic competence of oocytes and time of their maturation on the efficiency of fertilization was studied in pigs. Cycling gilts with synchronized estrous cycles were used as oocyte donors. To obtain oocytes with different meiotic competence, oocytes were recovered separately from small and medium follicles in the early, middle and late luteal or early follicular phase. They were matured for 40 h, 43 h or 47 h and fertilized by spermatozoa of a proven boar. The penetration and monospermy rates, and total efficiency of fertilization were assessed. The same data were related to the follicle size, with or without regard to the phase, and to the maturation time. Regardless of the phase and the time of maturation, the monospermy rate and total efficiency of fertilization were significantly lower for the small follicle-derived oocytes than for the medium follicle-derived oocytes (38.5±10.4% vs 63.1±7.0% and 24.7±6.3% vs 42.5±3.8%). With regard to the phase, in the small follicle-derived oocytes, the monospermy rate increased significantly (P<0.05) from the early luteal to the late luteal phase (from 25.4±2.4% to 46.4±3.9%) and remained unchanged in the early follicular phase. A similar tendency was observed in the total efficiency of fertilization. No differences were found in either of these parameters in medium follicle-derived oocytes in the late luteal and early follicular phase. With regard to the time of maturation, the total efficiency of fertilization was significantly higher (P<0.05) in the small follicle-derived oocytes matured for 47 h than in those matured for 40 h (27.7±7.4% vs. 20.5±6.1%) and in the medium follicle-derived oocytes matured for 40 h as compared with those matured for 47 h (47.1±1.9% vs. 32.7±1.1%). With regard to the phase and the time of maturation, the differences were significant only in the late luteal and early follicular phases. It can be concluded that greater meiotic competence of porcine oocytes positively influences monospermy rate and total efficiency of fertilization process. However adequate time of maturation is an important factor for oocytes with different meiotic competence to improve the IVF procedure.

Nutritional restriction of pre-pubertal liveweight gain impairs ovarian follicle growth and oocyte developmental competence of replacement gilts

The objective was to investigate the effects of moderate restriction of pre- and peri-pubertal liveweight gain on ovarian development and oocyte meiotic competence. At 70 d of age, and 27.7 ± 0.4 kg liveweight (LW), 64 Large White/Landrace crossbred gilts were allocated to two treatment groups (n = 32 gilts/treatment); one group was fed to attain a LW of 70 kg at 161 d of age (LIGHT), while the other group was fed to reach 100 kg LW (HEAVY). At 161 d of age, half of the gilts in each group (n = 16) were fed to gain LW at 0.5 kg/d (LOW), while the remaining half (n = 16) were fed to gain LW at 1.0 kg/d (HIGH) between 161 and 175 d of age, at which point they were killed and ovaries collected. For each gilt, surface antral follicles were counted and aspirated according to three size categories: 1-2.9 mm (small); 3-6 mm (medium); and > 6 mm (large). Follicles were pooled for each size class and treatment. Cumulus-oocyte-complexes (COC) recovered from small and medium follicles were matured in vitro (IVM) for 44 to 46 h, and meiotic maturation assessed. There was an effect of treatment (LIGHT versus HEAVY) on the number of medium sized follicles: 25.1 ± 2.59 versus 34.3 ± 2.60 (P < 0.05). The ovaries of LOW gilts had more small follicles and fewer medium follicles compared to those of HIGH gilts: 92.8 ± 8.35 versus 59.8 ± 5.24, and 25.1 ± 2.59 versus 32.5 ± 2.86 (P < 0.05). Target LW at 161 d did not affect meiotic progression of oocytes. However, LOW compared to HIGH LW gain between 161 and 175 d resulted in fewer oocytes reaching MII (0.40 versus 0.54; P < 0.05). In conclusion, moderately restricting feed intake impaired follicle growth beyond 3 mm and reduced oocyte meiotic competence. Further, although a carry-over effect of long-term feed restriction on follicle growth was evident, acute changes in feed intake during the 14 d prior to ovary collection had the greatest effect on oocyte nuclear maturation in vitro.

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

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

In vitro maturation and development of porcine oocytes cultured in a straw or dish using a portable incubator with a CO2 chamber

We investigated the effects of a portable incubator with a CO(2) chamber on the viability and development of porcine oocytes/embryos for their transportation and examined the operational suitability of a straw or dish as a container for culturing the oocytes or embryos in the portable incubator. In the first experiment, the cumulus-oocyte complexes (COCs) were placed either in a dish or straw; and they were then cultured for 44 h in a standard CO(2) incubator, in the CO(2) chamber in an incubator, or in the CO(2) chamber in a portable incubator. The matured oocytes were fertilized with frozen-thawed spermatozoa and then cultured in a dish in the standard CO(2) incubator for 8 days. There were no differences in the proportions of oocytes reaching metaphase II stage among the groups. However, the proportions of cleavage and development to blastocysts derived from oocytes matured in a straw were lower than those from oocytes matured in a dish, irrespective of the type of incubator used. In the second experiment, the COCs were matured in a dish in the standard CO(2) incubator, and the matured oocytes were fertilized and then placed either in a dish or straw. These were then cultured for 8 days in the standard CO(2) incubator or portable incubator. Some zygotes cultured in the portable incubator developed to the blastocyst stage. The proportions of cleavage and development to blastocysts were significantly lower for putative zygotes cultured in straw than for those cultured in dish, irrespective of the type of incubator used. Our results indicate that a portable incubator with a CO(2) chamber can maintain the viability and development of oocytes/embryos, but the straw is not a suitable system for in vitro culture of the oocytes/embryos during transportation.

Oocyte activation procedures and influence of serum on porcine oocyte maturation and subsequent parthenogenetic and nuclear transfer embryo development

The viability of SCNT embryos is poor, with an extremely low cloned piglet production rate. In the present work, we studied the effect of three activation protocols based on ionomycin treatment (5 μM ionomycin for 5 min and incubated in 2 mM 6-DMAP for 3.5 h) or electric stimuli (two square wave electrical DC pulses of 1.2 kV/cm for 30 μs) combined or not with 6-DMAP on parthenogenetic embryo development. Oocytes activated by ionomycin plus 6-DMAP showed lower cleavage (47.2 vs. 78.5–81.5; p < 0.05) and blastocyst rates (11.3 vs. 29.2–32.1; p < 0.05) than those activated by electrical and electrical plus 6-DMAP treatments. Also, we studied the effect of addition of serum to maturation medium (0% vs. 10%) on nuclear maturation and further parthenogenetic and SCNT embryo development. We observed in the parthenogenetic embryos that cleavage rates in the serum-free group were significantly higher than in the serum-supplemented group (81.8 vs. 69.6% respectively; p < 0.05), although these differences were not detected in blastocyst rates or blastocyst nuclei numbers. Regarding SCNT embryos, no significant differences were observed in cleavage or blastocyst rates between different experimental groups of SCNT embryos. In conclusion, electrical pulse followed or not by 6-DMAP was found to be an efficient procedure to artificially activate MII porcine oocytes. Moreover, the addition of serum to oocyte maturation media did not seem to improve parthenogenetic or SCNT porcine embryo development.

Sexual maturity and reproductive phase of oocyte donor influence the developmental ability and apoptosis of cloned and parthenogenetic porcine embryos

This study investigated the influence of the sexual maturity and reproductive phase of oocyte donor on the developmental ability and quality of porcine embryos produced by somatic cell nuclear transfer (SCNT) or parthenogenesis (PA). Blastocyst quality was evaluated in terms of hatching ability, total nuclei number and types of apoptosis. Results revealed that maturation rate was not influenced by the reproductive status of the oocyte donor. However, when subjected to PA or SCNT, embryos derived from sexually mature sow oocytes developed to blastocysts at higher rates and had higher cell number than those derived from immature gilt oocytes (p<0.05). Significant effect of reproductive phase, luteal versus follicular, was also noted with luteal stage oocytes yielding higher (p<0.05) rate of blastocyst formation (PA: 54.3+/-1.3% versus 44.8+/-0.3%; SCNT: 29.4+/-0.2% versus 22.7+/-0.1%). Blastocysts derived from luteal phase oocytes also had higher (p<0.05) hatching ability (PA: 44.2+/-1.1%; SCNT: 39.6+/-4.7%) and cell number (PA: 77.4+/-4.9; SCNT: 54.9+/-2.4) than those derived from follicular phase oocytes (PA: 34.9+/-0.9%, 67.2+/-3.9; SCNT: 34.6+/-2.7%, 47.5+/-2.9). TUNEL assay and Hoechst 33342 staining revealed that percentage of blastocysts showing total apoptosis did not differ among the groups. However, luteal phase oocyte-derived blastocysts had the highest incidence of nuclear fragmentation. Among cloned blastocysts that showed the signs of apoptosis, the highest index of total apoptosis was observed in prepubertal oocyte-derived blastocysts (5.2+/-0.7). Blastocysts derived from luteal phase oocytes showed the lowest TUNEL index (2.0+/-0.5). The present study therefore, indicates that the sexual maturity and reproductive phase of cytoplast donor significantly influences the developmental ability, apoptosis and quality of blastocysts produced by SCNT or PA. Oocytes from sexually mature sows in luteal phase of their reproductive cycle may be better cytoplast recipients for SCNT.

Gene expression profiling of the uterus with embryos cloned by somatic cell nuclear transfer on day 30 of pregnancy

Cloning by somatic cell nuclear transfer (SCNT) in pigs has great value for research and biomedical applications. However, cloning pigs is inefficient, and cloning procedures often lead to the birth of abnormal offspring because of the inadequate nuclear remodeling of donor cells as well as inadequate subsequent development. To understand the problems of the cloning process, it is necessary to understand how the uterus interacts with cloned embryo during pregnancy and supports placentation and fetal development. In this study, we compared gene expression profiles of the uterus with SCNT embryos to those of the uterus with normal embryos by natural mating. We obtained the uterine endometrial tissues on day 30 of pregnancy and conducted gene expression profiling using the Platinum Pig 13K oligonucleotide microarrays. Of the 13,610 genes analyzed, expression of 351 genes significantly increased or decreased in the uterine tissues with SCNT embryos compared to those with normal embryos. The differentially regulated genes included enzymes involved in steroidogenesis and extracellular matrix remodeling and uterine secretory proteins. Analyses of real-time reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization of selected genes confirmed the validity of the gene expression patterns observed in the microarray analysis. Results of this study showed that the transcriptional profile of the genes in the uterus with SCNT embryos was regulated differently indicating that the maternal responsiveness to the SCNT embryos was impaired, resulting in the altered gene expression in the uterus and, in turn, abnormal placental and fetal development and increased embryonic loss.

A comparative study on the efficiency of two enucleation methods in pig somatic cell nuclear transfer: effects of the squeezing and the aspiration methods

In this study, two enucleation methods, the squeezing and the aspiration methods, were compared. The efficiency of these two methods to enucleate pig oocytes and the in vitro and in vivo viability of somatic cell nuclear transfer (SCNT) pig embryos, were evaluated. In the squeezing method, the zona pellucida was partially dissected and a small amount of cytoplasm containing metaphase II (MII) chromosomes and the first polar body (PB) were pushed out. In the aspiration method, the PB and MII chromosomes were aspirated using a beveled micropipette. After injection of fetal fibroblasts into the perivitelline space, reconstructed oocytes were fused and activated electrically, and then cultured in vitro for 6 days or transferred to surrogates. The squeezing method resulted in a higher proportion of degenerated oocytes than the aspiration method (14% vs. 5%). The squeezing method took longer to enucleate 100 oocytes (306 minutes) than the aspirating method (113 minutes). Fusion rate (72-78%) and cleavage rate (67%) were not influenced by the enucleation method but blastocyst formation was improved (P < 0.05) in oocytes enucleated by the aspiration method (5 vs. 9%). When SCNT embryos were transferred to recipients, pregnancy rates to term were similar (27%, 3/11 and 27%, 3/11) in both methods with the birth of 10 piglets/3 litters and 16 piglets/3 litters in the squeezing and the aspiration methods, respectively. Our results indicate that the aspiration method for oocyte enucleation is more efficient than the squeezing method in producing a large number of pig SCNT embryos with normal in vivo viability.

An epigenetic modifier results in improved in vitro blastocyst production after somatic cell nuclear transfer

The present study was designed to examine the effect of trichostatin A (TSA), an inhibitor of histone deacetylase, on development of porcine cloned embryos. Our results showed that treatment of cloned embryos derived from sow oocytes with 50 nM TSA for up to 24 h after the onset of activation could significantly improve blastocyst yield compared to the control (46.4+/-4.6% vs 17.7+/-4.9% for treated and untreated embryos, respectively; p<0.05), whereas similar cleavage rate and total cell number per blastocyst were observed. In order to assess if the improvement is cell line specific, three cell lines were tested, and for all cell lines an enhancement in blastocyst development compared to their corresponding control was observed. Our data demonstrate that TSA treatment after somatic cell nuclear transfer in the pig can significantly improve the in vitro blastocyst production.

Effect of different parthenogenetic activation methods on the developmental competence of in vitro matured porcine oocytes

The aim of this study was to investigate the effect of electrical pulse, ethanol, and ionomycin combined with cycloheximide (CHX), cytochalasin B (CB), and 6-dimethylaminopurine (6-DMAP) on parthenogenetic developmental competence of in vitro matured porcine oocytes. In experiment 1, oocytes were treated with direct current electrical pulse (DC pulse) and then incubated in the NCSU-23 medium supplemented with CHX, 6-DMAP, CB + CHX, and CB + 6-DMAP for 6 h, respectively. The rate of blastocyst development in DC pulse + CB + 6-DMAP group was significantly higher than those in other groups (42.4% vs 23.9% approximately 35.8%; P < 0.05); however, there were no differences in both of the cleavage rate and the cell number of blastocysts among four groups. In experiment 2, oocytes were treated with NCSU-23 medium containing 20 muM ionomycin for 40 min and then incubated in the NCSU-23 medium supplemented with CHX, 6-DMAP, CB + CHX and CB + 6-DMAP for 6 h, respectively. The rates of cleavage and blastocyst development in ionomycin + 6-DMAP group were higher than those obtained in other groups (66.2% vs 46.3% approximately 57.3%; 22.3% vs 7.4% approximately 16.1%; P < 0.05). In experiment 3, the activation effects of ethanol combined with 6-DMAP, CHX, CB + 6-DMAP and CB + CHX were investigated. The rates of cleavage and blastocyst development in ethanol + CB + 6-DMAP group were significantly higher than those in other groups (55.5% vs 42% approximately 46.2%; 18.0% vs 7.1% approximately 11.9%; P < 0.05). In experiment 4, the optimal activation protocols in each group plus DC pulse + ionomycin + 6-DMAP were compared. The results showed the rates of cleavage in DC pulse + CB + 6-DMAP group and ionomycin + 6-DMAP were higher than those in ethanol + CB + 6-DMAP and DC pulse + ionomycin + 6-DMAP (73.8-74.4% vs 56.5-57.5%; P < 0.05), but the blastocyst development only in DC pulse + CB + 6-DMAP group was significantly higher than that in other groups (34.1% vs 13.4% approximately 22.3%; P < 0.05). Total cell number of blastocysts in the group of DC pulse + ionomycin + 6-DMAP was higher than that in other groups (34.1 vs 25.3-27.2; P < 0.05). In conclusion, DC pulse, ethanol, CB, and 6-DMAP all affected the parthenogenesis of porcine oocytes matured in vitro, but their combination of DC pulse + CB + 6-DMAP showed the best result in both of cleavage and blastocyst development.

Effects of fusion/activation methods on development of embryos produced by nuclear transfer of porcine fetal fibroblast

The present studies were carried out to investigate the effects of intensity of dc pulse, number of dc pulse and equilibration before fusion/activation on developmental ability of porcine embryos derived from nuclear transfer. In experiment 1, different fusion/activation intensity (two dc pulses of 0.4, 0.8, 1.2, 1.6 and 2.0 kV/cm for 30 micros, respectively) was carried out to investigate development of embryos. In experiment 2, the reconstructed oocytes were fused and activated with one, two or three dc pulses of 1.2 kV/cm for 30 micros. In experiment 3, reconstructed oocytes were equilibrated in TCM-199 medium for 0-6 h, respectively, and fused/activated with one dc pulse of 1.2 kV/cm for 30 micros. The reconstructed embryos were cultured in PZM-3 medium containing 0.3% BSA. When oocytes were fused with donor cell by two dc pulses of 0.4 kV/cm for 30 micros, the rates of cleavage and blastocyst formation were significantly lower (32.9% and 2.5%) than those of fused by 0.8 kV/cm (59.0% and 17.4%) or 1.2 kV/cm (63.3% and 18.4%), respectively. One dc pulse of 1.2 kV/cm for 30 micros was enough to fuse and activate embryos to develop to blastocyst (24.8%). Equilibration for 2-3 h in TCM-199 before fusion/activation was beneficial for improving the developmental ability of embryos produced by nuclear transfer (25.6-23.3% at blastocysts).

Selection of oocytes for in vitro maturation by brilliant cresyl blue staining: a study using the mouse model

Selecting oocytes that are most likely to develop is crucial for in vitro fertilization and animal cloning. Brilliant cresyl blue (BCB) staining has been used for oocyte selection in large animals, but its wider utility needs further evaluation. Mouse oocytes were divided into those stained (BCB+) and those unstained (BCB-) according to their ooplasm BCB coloration. Chromatin configurations, cumulus cell apoptosis, cytoplasmic maturity and developmental competence were compared between the BCB+ and BCB- oocytes. The effects of oocyte diameter, sexual maturity and gonadotropin stimulation on the competence of BCB+ oocytes were also analyzed. In the large- and medium-size groups, BCB+ oocytes were larger and showed more surrounded nucleoli (SN) chromatin configurations and higher frequencies of early atresia, and they also gained better cytoplasmic maturity (determined as the intracellular GSH level and pattern of mitochondrial distribution) and higher developmental potential after in vitro maturation (IVM) than the BCB- oocytes. Adult mice produced more BCB+ oocytes with higher competence than the prepubertal mice when not primed with PMSG. PMSG priming increased both proportion and developmental potency of BCB+ oocytes. The BCB+ oocytes in the large-size group showed more SN chromatin configurations, better cytoplasmic maturity and higher developmental potential than their counterparts in the medium-size group. It is concluded that BCB staining can be used as an efficient method for oocyte selection, but that the competence of the BCB+ oocytes may vary with oocyte diameter, animal sexual maturity and gonadotropin stimulation. Taken together, the series of criteria described here would allow for better choices in selecting oocytes for better development.

Improvement of canine somatic cell nuclear transfer procedure

The purpose of the present study on canine somatic cell nuclear transfer (SCNT) was to evaluate the effects of fusion strength, type of activation, culture media and site of transfer on developmental potential of SCNT embryos. We also examined the potential of enucleated bovine oocytes to serve as cytoplast recipients of canine somatic cells. Firstly, we evaluated the morphological characteristics of in vivo-matured canine oocytes collected by retrograde flushing of the oviducts 72 h after ovulation. Secondly, the effectiveness of three electrical strengths (1.8, 2.3 and 3.3 kV/cm), used twice for 20 micros, on fusion of canine cytoplasts with somatic cells were compared. Then, we compared: (1) chemical versus electrical activation (a) after parthenogenetic activation or (b) after reconstruction of canine oocytes with somatic cells; (2) culture of resulting intergeneric (IG) embryos in either (a) mSOF or (b) TCM-199. The exposure time to 6-DMAP was standardized by using bovine oocytes reconstructed with canine somatic cells. Bovine oocytes were used for SCNT after a 22 h in vitro maturation interval. The fusion rate was significantly higher in the 3.3 kV/cm group than in the 1.8 and 2.3 kV/cm treatment groups. After parthenogenesis or SCNT with chemical activation, 3.4 and 5.8%, respectively, of the embryos developed to the morula stage, as compared to none of the embryos produced using electrical activation. Later developmental stages (8-16 cells) were transferred to the uterine horn of eight recipients, but no pregnancy was detected. However, IG cloned embryos (bovine cytoplast/canine somatic cell) were capable of in vitro blastocyst development. In vitro developmental competence of IG cloned embryos was improved after exposure to 6-DMAP for 4 h as compared to 0, 2 or 6h exposure, although the increase was not significantly different among culture media. In summary, for production of canine SCNT embryos, we recommend fusion at 3.3 kV/cm, chemical activation, culture in mSOF medium and transfer of presumptive zygotes to the oviduct of recipient animals. The feasibility of IG production of cloned canine embryos using bovine cytoplasts as recipient of canine somatic cells was demonstrated.

Somatic cell nuclear transfer: Past, present and future perspectives

It is now over a decade since the birth, in 1996, of Dolly the first animal to be produced by nuclear transfer using an adult derived somatic cell as nuclear donor. Since this time similar techniques have been successfully applied to a range of species producing live offspring and allowing the development of transgenic technologies for agricultural, biotechnological and medical uses. However, though applicable to a range of species, overall, the efficiencies of development of healthy offspring remain low. The low frequency of successful development has been attributed to incomplete or inappropriate reprogramming of the transferred nuclear genome. Many studies have demonstrated that such reprogramming occurs by epigenetic mechanisms not involving alterations in DNA sequence, however, at present the molecular mechanisms underlying reprogramming are poorly defined. Since the birth of Dolly many studies have attempted to improve the frequency of development, this review will discuss the process of animal production by nuclear transfer and in particular changes in the methodology which have increased development and survival, simplified or increased robustness of the technique. Although much of the discussion is applicable across species, for simplicity we will concentrate primarily on published data for cattle, sheep, pigs and mice.

Gilts and sows produce similar rate of diploid oocytes in vitro whereas the incidence of aneuploidy differs significantly

Oocytes derived from prepubertal gilts show reduced developmental competence when compared to oocytes collected from adult sows. Therefore, the aim of the study was to investigate whether gilts (4-5 months old) and adult sows (average age 3.5 years) of the same breed (Polish Landrace x Polish Large White crossbred) differ with regard to the rate of chromosomally unbalanced oocytes after IVM. COCs derived from individual pairs of slaughterhouse ovaries were matured in vitro and analyzed cytogenetically by conventional staining (Giemsa) and FISH methods (probes corresponding to centromeric regions of pig chromosomes 1 and 10). Altogether, 72 females (31 sows, 41 gilts) and 430 secondary oocytes (194 and 236 oocytes of sows and gilts, respectively) were investigated. Cytogenetic analysis revealed diploid (Giemsa, FISH) and aneuploid (FISH) spreads. The incidence of diploid oocytes was similar for sows (26.0%) and gilts (24.5%) whereas the rate of aneuploid oocytes (nullisomic/disomic) was eight times higher in gilts (10.8%) than in sows (1.3%). Diploid and aneuploid oocytes were observed in 64% of investigated females. Pig chromosome 10 was more frequently disomic/nullisomic compared to chromosome 1 suggesting, that like in human, small porcine chromosomes are often involved in the nondisjunction process. In conclusion, chromosomal imbalance significantly contributes to in vitro embryo production in the pig, since over 60% of females produced diploid or aneuploid gametes. The significantly higher rate of aneuploidy among oocytes derived from gilt ovaries may contribute to the reduced developmental competence of gametes collected from nonmature female pigs.

Production of Viable Pigs from Fetal Somatic Stem Cells

Fetal somatic stem cells (FSSCs) are a novel type of somatic stem cells that have recently been discovered in primary fibroblast cultures from pigs and other species. The goal of the present study was to produce viable piglets from FSSCs. NT complexes were prepared from both FSSCs and porcine fetal fibroblasts (pFF) to permit comparison of these two donor cell types. FSSCs from isolated attached colonies were compared with pFF in their ability to form blastocysts upon use in NT. Fusion and cleavage rates were similar between the two groups, while blastocyst rates were significantly higher when using pFF as donor cells. FSSCs of three different size categories derived from dissociation of spheroids yielded similar results. The use of FSSCs of 15-20 microm in size yielded similar cleavage and blastocyst rates as fetal fibroblasts. In the final experiment NT complexes produced from FSSCs were transferred to foster mothers. After transfer to prepubertal gilts, three of seven recipients established pregnancies and delivered seven piglets, of which three piglets were viable and showed normal development. Results for the first time demonstrate that FSSCs are able to produce cloned embryos, and that pregnancies can be established and viable piglets can be produced.

Somatic cell nuclear transfer in pigs: recent achievements and future possibilities

During the past 6 years, considerable advancement has been achieved in experimental embryology of pigs. This process was mainly generated by the rapidly increasing need for transgenic pigs for biomedical research purposes, both for future xenotransplantation to replace damaged human organs or tissues, and for creating authentic animal models for human diseases to study aetiology, pathogenesis and possible therapy. Theoretically, among various possibilities, an established somatic cell nuclear transfer system with genetically engineered donor cells seems to be an efficient and reliable approach to achieve this goal. However, as the result of unfortunate coincidence of known and unknown factors, porcine embryology had been a handicapped branch of reproductive research in domestic animals and a very intensive and focused research was required to eliminate or minimise this handicap. This review summarises recent achievements both in the background technologies (maturation, activation, embryo culture) and the actual performance of the nuclear replacement. Recent simplified methods for in vivo development after embryo transfer are also discussed. Finally, several fields of potential application for human medical purposes are discussed. The authors conclude that although in this early phase of research no direct evidence can be provided about the practical use of transgenic pigs produced by somatic cell nuclear transfer as organ donors or disease models, the future chances even in medium term are good, and at least proportional with the efforts and sums that are invested into this research area worldwide.

Somatic cell nuclear transfer using transported in vitro-matured oocytes in cynomolgus monkey

Somatic cell nuclear transfer (SCNT) is not successful so far in non-human primates. The objective of this study was to investigate the effects of stimulation cycles (first and repeat) on oocyte retrieval and in vitro maturation (IVM) and to evaluate the effects of stimulation cycles and donor cell type (cumulus and fetal skin fibroblasts) on efficiency of SCNT with transported IVM oocytes. In this study, 369 immature oocytes were collected laparoscopically at 24 h following human chorionic gonadotrophin (hCG) treatment from 12 cynomolgus macaque (Macaca fascicularis) in 24 stimulation cycles, and shipped in pre-equilibrated IVM medium for a 5 h journey, placed in a dry portable incubator (37 °C) without CO2 supplement. A total of 70.6% (247/350) of immature oocytes reached metaphase II (MII) stage at 36 h after hCG administration, MII spindle could be seen clearly in 80.6% (104/129) of matured IVM oocytes under polarized microscopy. A total of 50.0% (37/74) of reconstructive SCNT embryos cleaved after activation; after cleavage, 37.8% (14/37) developed to the 8-cell stage and 8.1% (3/37) developed to morula, but unfortunately none developed to the blastocyst stage. Many more oocytes could be retrieved per cycle from monkeys in the first cycle than in repeated cycles (19.1 vs. 11.7, p < 0.05). There were no significant differences in the maturation rate (70.0 vs. 71.4%, p > 0.05) and MII spindle rate under polarized microscopy (76.4 vs. 86.0%, p > 0.05) between the first and repeat cycles. There were also no significant differences in the cleavage rate, and the 4-cell, 8-cell and morula development rate of SCNT embryos between the first and repeat cycles. When fibroblast cells and cumulus cells were used as the donor cells for SCNT, first cleavage rate was not significantly different, but 4-cell (50.0 vs. 88.9%, p < 0.05) and 8-cell (0 vs. 51.9%, p < 0.01) development rate were significantly lower for the former. In conclusion, the number of stimulation cycles has a significant effect on oocyte retrieval, but has no effect on maturation and SCNT embryo development; however, different donor cell types (cumulus and fibroblast) resulted in different developmental potentials of SCNT embryos.

Development and apoptosis of pre-implantation porcine nuclear transfer embryos activated with different combination of chemicals

Artificial activation of oocytes is a pre-requisite for successful cloning by nuclear transfer (NT). This study investigated effect of different combination of activation chemicals such as electric pulse (E), thimerosal (Thi) + dithiothreitol (DTT), 6-dimethylaminopurine (6-DMAP), or cycloheximide (CH) on the developmental ability and the frequency of apoptosis of porcine NT embryos during the culture in vitro. NT embryos activated with chemicals showed significantly higher developmental rate to blastocyst stage compared to embryos activated with E alone (21.5%-26.6% vs. 15.7%, respectively). Of chemicals, Thi + DTT supported higher development to blastocyst stage as compared to 6-DMAP or CH (26.6% vs. 21.5%-23.4%, respectively). Apoptosis of NT embryos were analyzed by using a terminal deoxynucleatidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling (TUNEL) assay. The onset of apoptosis of embryos activated E alone was on Day 4, whereas embryos activated with chemicals showed apoptosis on Day 3 post-activation NT embryos exposed to chemicals for activation had higher frequency of apoptosis compared to that of embryos exposed to E alone from Day 3 to Day 7 during the culture. In conclusion, this study shows that chemical activation after fusion could increase not only the developmental ability of porcine NT embryos but also the mean cell number with an increased ratio of inner cell mass (ICM) to trophectoderm (TE) cells. However, the chemical activation also could increase the frequency of apoptosis and induced apoptosis earlier in porcine NT embryos.

High Overall In Vitro Efficiency of Porcine Handmade Cloning (HMC) Combining Partial Zona Digestion and Oocyte Trisection with Sequential Culture

We investigated the in vitro developmental competence of porcine embryos produced from in vitro matured (IVM) oocytes by improved HMC and parthenogenetic activation (PA). Embryos were cultured in a modified North Carolina State University (NCSU37) medium. Firstly, we compared the developmental competence between oocytes from sows and gilts by zona-intact (ZI) and zona-free (ZF) PA. Significantly higher (p < 0.05) blastocyst rates were obtained from sow oocytes (42 +/- 4% for ZF and 55 +/- 6% for ZI) than gilt oocytes (20 +/- 2% for ZF and 26 +/- 5% for ZI). Secondly, sow oocytes were used to establish the modified HMC that was based on a modified enucleation with partial zona digestion and trisection of porcine oocytes and the use of three cytoplasts and one somatic cell for embryo reconstruction. In vitro fertilization (IVF) and in parallel ZF PA were used as the control systems. After oocyte trisection, >90% of oocyte fragments were recovered, resulting in an average of 37 reconstructed embryos from 100 oocytes. Blastocyst rates of HMC, IVF, and ZF PA embryos were 17 +/- 4%, 30 +/- 6%, and 47 +/- 4%, respectively. Our results prove that HMC in pigs may result in high in vitro efficiency up until the blastocyst stage. In vivo developmental competence will be confirmed in embryo transfer experiments.

IVM media, oocyte diameter and donor genotype at RYR1 locus in relation to the incidence of porcine diploid oocytes after maturation in vitro

In the present study three factors were investigated that may affect the process of the first polar body extrusion in pig oocytes matured in vitro: IVM medium, oocyte diameter and donor genotype at the ryanodine receptor (RYR1) locus. In the first experiment, COCs were collected by the aspiration of slaughterhouse ovaries. Oocytes were matured in vitro at 39 degrees C, in humidified 5% CO(2) atmosphere for 44 h using the following media: (1) TCM199+hCG+eCG+follicular fluid (FF), (2) TCM199+hCG+17beta-estradiol and (3) NCSU23+hCG+eCG+FF. According to cytogenetic analysis, 98.1% of cells reached the second metaphase stage (MII). No significant differences were observed among IVM groups in terms of diploidy level. In the second experiment, oocytes collected by the aspiration or slicing of individual ovaries were matured in vitro in groups reflecting their origin. One ovary was considered a donor. IVM was carried out under conditions described in experiment I, with the use of TCM199+hCG+17beta-estradiol. A total of 68 ovaries/donors were included in this study. Granulosa cells collected from each ovary were used as DNA source in molecular (RFLP) analysis. Genotype frequencies at the RYR1 locus were as follows: CC, 0.46; CT, 0.48 and TT, 0.06. After maturation the diameter of each denuded oocyte was determined with the use of a computer aided system. Five size categories were distinguished: <90, 90-100, 100.1-110, 110.1-120 and >120 microm. The average diameter of haploid oocytes at MII stage was 111.7 microm, whereas that of diploid cells was 110.4 microm. According to statistical analysis, diploidy was not related to the oocyte diameter. That trait, however, was influenced by the donor genotype at the RYR1 locus. The TT genotype was associated with a higher rate of diploidy.

Comparative Studies on Lipid Analysis and Ultrastructure in Porcine and Southern Minke Whale (Balaenoptera Bonaerensis) Oocytes

The present study was conducted to clarify the difference in the color of the cytoplasm in immature follicular oocytes from prepubertal and adult minke whales. The four lipid contents (triglyceride, total cholesterol, phospholipids and non-esterified fatty acids) in vitrified immature oocytes from prepubertal and adult minke whales, and also in fresh and vitrified immature porcine oocytes, were measured. The lipid contents in vitrified-warmed minke whale oocytes were similarly high compared with those in vitrified-warmed porcine oocytes. In particular, the total cholesterol and phospholipid contents in the vitrified immature oocytes from prepubertal and adult minke whales were significantly (P<0.05) higher than those from prepubertal pigs. Furthermore, the distribution of lipid droplets in fresh and vitrified immature oocytes was observed in transmission electron microscopy. Lipid droplets in the prepubertal minke whale oocytes were distributed throughout the cytoplasm. In contrast, adult minke whales had larger lipid droplets which were distributed mainly in the central portion of the cytoplasm. The lipid droplets of immature oocytes from prepubertal pigs were larger than those in minke whale oocytes. These results indicated that the difference in the distribution of the cytoplasmic lipid droplets may result in the difference in the color tone of both prepubertal and adult whale oocyte cytoplasm.

Development of cloned pig embryos by nuclear transfer following different activation treatments

This study compared the effects of activation treatments on the development and ploidy of nuclear transferred (NT) pig embryos. After in vitro maturation of oocytes collected from the slaughterhouse, oocytes were enucleated and reconstructed by transfer of donor cells and fusion with three DC pulses (1.4 kV/cm, 20 musec). Oocytes were pulsed thrice electrically with 1.4 kV/cm for 20 musec and NT eggs were divided into three treatment groups: Group 1 (no further treatment), Group 2 (10 mug/mL cycloheximide [CHX], 3 hr), and Group 3 (1.9 mM 6-dimethylaminopurine [DMAP], 3 hr). All the eggs were cultured in sets of 30 in 60 muL drops of NCSU-23 supplemented with 4 mg/mL fatty acid free BSA, and compared for the rates of development and ploidy. The rates of cleavage, development, and total cell number of parthenotes in Group 3 were significantly (P < 0.05) higher than those in Groups 1 and 2. Cleavage rates of NT embryos in Group 1 were significantly (P < 0.05) lower than those in Groups 2 and 3 (73% vs. 81% and 82%, respectively). Development into blastocyst stage and total cell number of NT embryos in Group 3 were significantly (P < 0.05) higher than those in Groups 1 and 2. Although the embryos in Group 3 had higher development, approximately 58% of NT embryos evaluated were abnormal ploidy (6% haploidy, 9% polyploidy, and 42% mixoploid). The results suggested that although DMAP enhanced development and higher cell number, due attention should be paid to abnormal ploidy in pig NT embryos.

Improved developmental competence of cloned porcine embryos with different energy supplements and chemical activation

The present study investigated the effect of lactate/pyruvate supplement in culture medium and of chemical activation after electric stimulus on in vitro development of porcine somatic cell nuclear transfer (SCNT) embryos. In vitro matured gilt oocytes were enucleated, reconstructed with fetal fibroblasts, and simultaneously fused/activated using a single pulse of 2.0 kV/cm for 30 microsec. In Experiment 1, reconstructed embryos were cultured in North Carolina State University (NCSU)-23 medium supplemented with either 5.5 mM glucose (Group A) or lactate (5.0 mM)/pyruvate (0.5 mM) (Group B). Compared to Group A, cleavage rate (64% vs. 47%) was higher and more blastocysts developed in Group B (17% vs. 6% at Day 6, 21% vs.11% at Day 7). Experiment 2, embryos reconstructed by electric stimulus (2.0 kV/cm for 30 microsec) were subjected to three activation protocols: (1) no chemical activation (Group C), (2) 7.5 microg/ml cytochalasin B treatment at 2 hr after electric stimulus (Group D), and (3) 5 microg/ml 6-dimethylaminopurine (Group E) treatment at 2 hr after electric stimulus. The reconstructed embryos were cultured for 7 days in NCSU-23 medium supplemented with lactate (5.0 mM)/pyruvate (0.5 mM). The rates of blastocyst formation on Day 6 and Day 7 in Group C (17 and 20%, respectively) or Group D (15, 20%, respectively) were higher than in Group E (9 and 12%, respectively). The percentage of two pseudo-pronucleus (PPN) formations in Group D (88%) was significantly higher than in Group C (71%) and Group E (72%). Mean cell numbers of blastocysts in Group D (63.4 +/- 15.8) were higher than in Group C (43.9 +/- 16.5) and Group E (32.9 +/- 17.9), due to increased trophectoderm (TE) cell numbers. Our results indicate that supplementing NCSU-23 medium with lactate/pyruvate and exposure of cytochalasin B after electrical stimulus can improve in vitro developmental competence of porcine SCNT embryos.

Production of nuclear transfer-derived piglets using porcine fetal fibroblasts transfected with the enhanced green fluorescent protein

A system for somatic cell nuclear transfer (SCNT) was developed and led to the successful production of GFP-transfected piglets. In experiment 1, two groups of SCNT couplets reconstructed with porcine fetal fibroblasts (PFF) and enucleated sow (S) or gilt oocytes (G): 1). received a simultaneous electrical fusion/activation (S-EFA or G-EFA groups), or 2). were electrically fused followed by activation with ionomycin (S-EFIA or G-EFIA groups), or 3). were subjected to electrical fusion and subsequent activation by ionomycin, followed by 6-dimethylaminopurine treatment (S-EFIAD or G-EFIAD groups). The frequency of blastocyst formation was significantly higher in S-EFA (26%) compared with that observed in the other experimental groups (P < 0.05), but not with S-EFIA (23%). Sow oocytes yielded significantly higher cleavage frequencies (68%-69%) and total cell numbers of blastocysts when compared with gilt oocytes, regardless of fusion/activation methods (P < 0.05). However, the ratio of inner cell mass (ICM)/total cells in G-EFA and S-EFA was significantly lower than in the other groups (P < 0.05). In experiment 2, SCNT couplets reconstructed with PFF cultured in the presence or absence of serum and enucleated sow oocytes were subjected to EFA. There were no effects of serum starvation on cell-cycle synchronization, developmental competence, total cell numbers, and ratio of ICM/total cells. In experiment 3, SCNT couplets reconstructed with PFF transfected with an enhanced green fluorescence protein (EGFP) gene using FuGENE-6 and enucleated sow oocytes were subjected to EFA and cultured for 7 days. Expression frequencies of GFP gene during development were 100%, 78%, 72%, 71%, and 70% in fused, two-cell, four to eight cells, morulae, and blastocysts, respectively. In experiment 4, SCNT embryos derived from different recipient cytoplasts (sows or gilts) and donor karyoplasts (PFF or GFP-transfected) were subjected to EFA and transferred to the oviducts of surrogates. The pregnancy rates in SCNT embryos derived from sow oocytes (66%-69%) were higher than those with gilt oocytes (23%-27%) regardless of donor cell types. One live offspring from GFP-SCNT embryos and two from PFF-SCNT embryos were delivered. Microsatellite analysis confirmed that the clones were genetically identical to the donor cells and polymerase chain reaction (PCR) from genomic DNA of cloned piglets and subsequent southern blot analysis confirmed the integration of EGFP gene into chromosomes.