Exogenous Melatonin in the Culture Medium Does Not Affect the Development of In Vivo-Derived Pig Embryos but Substantially Improves the Quality of In Vitro-Produced Embryos

Cloned and transgenic pigs are relevant human disease models and serve as potential donors for regenerative medicine and xenotransplantation. These technologies demand oocytes and embryos of good quality. However, the current protocols for in vitro production (IVP) of pig embryos give reduced blastocyst efficiency and embryo quality compared to in vivo controls. This is likely due to culture conditions jeopardizing embryonic homeostasis including the effect of reactive oxygen species (ROS) influence. In this study, the antioxidant melatonin (1 nM) in the maturation medium, fertilization medium, or both media was ineffective in enhancing fertilization or embryonic development parameters of in vitro fertilized oocytes. Supplementation of melatonin in the fertilization medium also had no effect on sperm function. In contrast, the addition of melatonin to the embryo culture medium accelerated the timing of embryonic development and increased the percentages of cleaved embryos and presumed zygotes that developed to the blastocyst stage. Furthermore, it increased the number of inner mass cells and the inner mass cell/total cell number ratio per blastocyst while increasing intracellular glutathione and reducing ROS and DNA damage levels in embryos. Contrarily, the addition of melatonin to the embryo culture medium had no evident effect on in vivo-derived embryos, including the developmental capacity and the quality of in vivo-derived 4-cell embryos or the percentage of genome-edited in vivo-derived zygotes achieving the blastocyst stage. In conclusion, exogenous melatonin in the embryo culture medium enhances the development and quality of in vitro-derived embryos but not in in vivo-derived embryos. Exogenous melatonin is thus recommended during embryo culture of oocytes matured and fertilized in vitro for improving porcine IVP efficiency.

Biotechnological bases of the development of cloned pig embryos

The term ‘clone’ in animal biotechnology refers to an organism derived from non-sexual reproduction, which is both a direct offspring and a genetic copy of the parent organism. To date, the pig appears to be the most interesting object in cloning research. Somatic cell nuclear transfer in pigs has a wide range of potential applications in various fields of human scientific and economic activities. However, the efficiency of producing cloned embryos in swine is still lower than that of other livestock species, in particular horses and cattle. Somatic cell nuclear transfer is a technically complex multi-stage technology, at each stage of which the pig oocytes, which are more susceptible to changes of surrounding conditions, are affected by various factors (mechanical, physical, chemical). At the stage of oocyte maturation, changes in the cell ultrastructures of the ooplasm occur, which play an important role in the subsequent nuclear reprogramming of the transferred donor cell. Before transfer to the oocyte donor somatic cells are synchronized in the G0/G1 stage of the cell cycle to ensure the normal ploidy of the cloned embryo. When removing the nucleus of pig oocytes maturated in vitro, it is necessary to pay attention to the problem of preserving the viability of cells, which were devoid of their own nuclear material. To perform the reconstruction, a somatic cell is placed, using micro-tools, in the perivitelline space, where the first polar body was previously located, or in the cytoplasm of an enucleated oocyte. The method of manual cloning involves the removal of the oocyte nucleus with subsequent fusion with the donor cell without the use of micromanipulation techniques. The increased sensitivity of oocytes to the environmental conditions causes special requirements for the choice of the system for in vitro culture of cloned pig embryos. In this work, we have reviewed the modern methods used for the production of cloned embryos and identified the technological issues that prevent improving the efficiency of somatic cloning of pigs.

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.

Developmental competence of porcine genome-edited zygotes

Genome editing in pigs has tremendous practical applications for biomedicine. The advent of genome editing technology, with its use of site-specific nucleases-including ZFNs, TALENs, and the CRISPR/Cas9 system-has popularized targeted zygote genome editing via one-step microinjection in several mammalian species. Here, we review methods to optimize the developmental competence of genome-edited porcine embryos and strategies to improve the zygote genome-editing efficiency in pigs.

Analysis of Cyclin E1 Functions in Porcine Preimplantation Embryonic Development by Fluorescence Microscopy

Cyclin E1 (CCNE1) is a core component of cell cycle regulation that drives the transition into the S phase. CCNE1 plays critical roles in cell cycle, cell proliferation, and cellular functions. However, the function of CCNE1 in early embryonic development is limited. In the present study, the function and expression of Ccne1 in porcine early parthenotes were examined. Immunostaining experiments showed that CCNE1 localized in the nucleus, starting at the four-cell stage. Knockdown of Ccne1 by double-stranded RNA resulted in the failure of blastocyst formation and induced blastocyst apoptosis. Ccne1 depletion increased expression of the pro-apoptotic gene Bax, and decreased the expression of Oct4 and the rate of inner cell mass (ICM)/trophectoderm formation. The results indicated that CCNE1 affects blastocyst formation by inducing cell apoptosis and ICM formation during porcine embryonic development.

Maternal effect gene expression in porcine metaphase II oocytes and embryos in vitro: effect of epidermal growth factor, interleukin-1β and leukemia inhibitory factor

Maternal effect genes (MEG) play a crucial role in early embryogenesis. In vitro culture conditions may affect MEG expression in porcine oocytes and embryos. We investigated whether in vitro culture medium supplementation with epidermal growth factor (EGF), IL-1β or LIF (leukemia inhibitory factor) affects the mRNA level of ZAR-1 (zygote arrest 1), NPM2 (nucleoplasmin 2) and DPPA3 (developmental associated protein 3) in porcine MII oocytes and embryos. Cumulus-oocyte complexes (COCs) were matured in NCSU-37 medium (control) or in NCSU-37 with EGF 10 ng/ml, IL-1β 10 ng/ml or LIF 50 ng/ml. After maturation for 44-46 h, MII oocytes were preserved for the analysis of MEG mRNA levels (experiment 1). In experiment 2, COCs were fertilized, and the presumptive zygotes were cultured in the same groups. Then, 2-, 4-, 8-cell embryos, morulae and blastocysts were collected for the analysis of MEG mRNA levels. LIF addition to the maturation medium increased MII oocyte numbers (P < 0.05), while EGF and IL-1β did not affect oocyte maturation. Medium supplementation with EGF resulted in lower DPPA3 mRNA levels in MII oocytes and in 2- and 4-cell embryos versus control embryos (P < 0.05). LIF treatment increased DPPA3 mRNA levels in morulae and blastocysts (P < 0.05). Culture with EGF and IL-1β decreased ZAR-1 and NPM2 mRNA levels in 2-cell embryos (P < 0.05). The inclusion of EGF or IL-1β in the porcine in vitro production system influences ZAR-1, NPM2 and DPPA3 mRNA in MII oocytes and embryos but not beyond the 4-cell stage. LIF stimulates oocyte maturation and affects DPPA3 mRNA in porcine morulae and blastocysts in vitro.

Combination effects of epidermal growth factor and glial cell line-derived neurotrophic factor on the in vitro developmental potential of porcine oocytes

The developmental potential of in vitro matured porcine oocytes is still lower than that of oocytes matured and fertilized in vivo. Major problems that account for the lower efficiency of in vitro production include the improper nuclear and cytoplasmic maturation of oocytes. With the aim of improving this issue, the single and combined effects of epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) on oocyte developmental competence were investigated. Porcine cumulus-oocyte cell complexes (COCs) were matured in serum-free medium supplemented with EGF (0, 10 or 50 ng/ml) and/or GDNF (0, 10 or 50 ng/ml) for 44 h, and subsequently subjected to fertilization and cultured for 7 days in vitro. The in vitro-formed blastocysts derived from selected growth factor groups (i.e. EGF = 50 ng/ml; GDNF = 50 ng/ml; EGF = 50 ng/ml + GDNF = 50 ng/ml) were also used for mRNA expression analysis, or were subjected to Hoechst staining. The results showed that the addition of EGF and/or GDNF during oocyte maturation dose dependently enhanced oocyte developmental competence. Compared with the embryos obtained from control or single growth factor-treated oocytes, treatment with the combination of EGF and GDNF was shown to significantly improve oocyte competence in terms of blastocyst formation, blastocyst cell number and blastocyst hatching rate (P < 0.05), and also simultaneously induced the expression of BCL-xL and TERT and suppressed the expression of caspase-3 in resulting blastocysts (P < 0.05). These results suggest that both GDNF and EGF may play an important role in the regulation of porcine in vitro oocyte maturation and the combination of these growth factors could promote oocyte competency and blastocyst quality.

Comparative effects of adding β-mercaptoethanol or L-ascorbic acid to culture or vitrification-warming media on IVF porcine embryos

The aims of the present study were to; (1) determine the effects of supplementation with two antioxidants during in vitro culture (IVC) on embryo development and quality; and (2) test the effects of adding the antioxidants to vitrification-warming media on the cryotolerance of in vitro-produced (IVP) porcine blastocysts. In Experiment 1, presumptive zygotes were cultured without antioxidants, with 50 µM β-mercaptoethanol (β-ME) or with 100 µM L-ascorbic acid (AC). After culture, blastocyst yield, quality and cryotolerance were evaluated in each treatment group. In Experiment 2, survival rates (3 and 24 h), total cell number, apoptosis index and the formation of reactive oxygen species (ROS) in blastocysts vitrified-warmed with 100 µM AC or 50 µM β-ME or without antioxidants added to the vitrification medium were compared. Antioxidant addition during IVC had no effect on embryo development, total cell number or the apoptosis index, and culturing embryos in the presence of β-ME had no effects on cryotolerance. In contrast, ROS levels and survival rates after vitrification-warming were significantly improved in embryos cultured with AC. Furthermore, addition of AC into vitrification-warming media enhanced embryo survival and embryo quality after warming. In conclusion, our results suggest that supplementing culture or vitrification media with 100 µM AC improves the quality and cryosurvival of IVP porcine blastocysts.

Oocyte induction of EGF responsiveness in somatic cells is associated with the acquisition of porcine oocyte developmental competence

Oocytes progressively acquire the competence to support embryo development as oogenesis proceeds with ovarian folliculogenesis. The objectives of this study were to investigate oocyte-secreted factor (OSF) participation in the development of somatic cell epidermal growth factor (EGF) responsiveness associated with oocyte developmental competence. A well-established porcine model was employed using oocytes from small (<4 mm) vs medium sized (>4 mm) antral follicles, representing low vs moderate developmental competence, respectively. Cumulus-oocyte complexes (COCs) were treated in vitro with inducers of oocyte maturation, and cumulus cell functions and oocyte developmental competence were assessed. COCs from small follicles responded to FSH but, unlike COCs from larger follicles, were incapable of responding to EGF family growth factors known to mediate oocyte maturation in vivo, exhibiting perturbed cumulus expansion and expression of associated transcripts (HAS2 and TNFAIP6). Low and moderate competence COCs expressed equivalent levels of EGF receptor (EGFR) mRNA; however, the former had less total EGFR protein leading to failed activation of phospho-EGFR and phospho-ERK1/2, despite equivalent total ERK1/2 protein levels. Native OSFs from moderate, but not from low, competence oocytes established EGF responsiveness in low competence COCs. Four candidate recombinant OSFs failed to mimic the actions of native OSFs in regulating cumulus expansion. Treatment with OSFs and EGF enhanced oocyte competence but only of the low competence COCs. These data suggest that developmental acquisition by the oocyte of capacity to regulate EGF responsiveness in the oocyte's somatic cells is a major milestone in the oocyte's developmental program and contributes to coordinated oocyte and somatic cell development.

Generation of large pig and bovine blastocysts by culturing in human induced pluripotent stem cell medium

We investigated the effect of human induced pluripotent stem cell (hiPS) medium on porcine somatic cell nuclear transfer and bovine in vitro fertilized early blastocysts, in comparison with North Carolina State University (NCSU)-37 medium and in vitro culture (IVC)-II medium. After 2 days of culture, the diameter of the portion of the blastocyst that was extruded from the zona pellucid dramatically differed between porcine blastocysts cultured in hiPS medium and those cultured in NCSU-37 medium (221.47 ± 38.94 μm versus 481.87 ± 40.61 μm, P < 0.01). Moreover, the diameter of the portion of the blastocyst significantly differed between bovine blastocysts cultured in hiPS medium and those cultured in IVC-II medium (150.30 ± 29.49 μm versus 195.58 ± 41.59 μm, P < 0.01). Furthermore, the total number of cells per porcine and bovine blastocyst was more than two-fold higher in blastocysts cultured in hiPS medium than in those cultured in NCSU-37 medium (44.33 ± 5.28 and 143.33 ± 16.05, P < 0.01) or IVC-II medium (172.12 ± 45.08 and 604.83 ± 242.64, P < 0.01), respectively. These results indicate that hiPS medium markedly improves the quality of porcine and bovine blastocysts.

The effects of extracellular ATP and its receptor antagonists on pig oocytes during in vitro maturation

We measured the ATP concentrations in the porcine follicular fluid derived from three sizes of follicles (small: 6 mm in diameter). Then, the effects of pre-treatment (100 μM each for 30 min before maturation) with antagonists for extracellular ATP receptor P2X or P2Y on the nuclear maturation rate of cumulus-cell-enclosed (COs) or -denuded oocytes (DOs) up to the preovulatory stage in the presence or absence of 20 nM ATP (a similar concentration to that of medium-sized follicle fluid) were investigated. The antagonists used were pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) or reactive blue 2 (RB2), for extracellular ATP receptor P2X and P2Y, respectively. In addition, the embryonic development rates of COs pre-treated with RB2 were also evaluated. It was found that when the follicular sizes increased, the ATP concentrations significantly decreased (P < 0.05). No differences were observed in the nuclear maturation rates among all COs, regardless of pre-treatment with (+) or without (-) PPADS and in the presence (+) or absence (-) of ATP during maturation. In contrast, the nuclear maturation rate of the COs, but not DOs, in the ATP(-) RB2(+) group was significantly lower (P < 0.05) than that of the ATP(-) RB2(-) and ATP(+)RB2(-) groups. The pronuclear formation and blastocyst formation rates by parthenogenetic activation in the ATP(-) RB2(+) and ATP(+) RB2(+) groups were significantly lower (P < 0.05) than those in the ATP(-) RB2(-) group. In conclusion, it is suggested that the nuclear maturation of porcine oocytes may be influenced by the ATP receptor P2Y present in the cumulus cells.

Increasing efficiency in production of cloned piglets

The low efficiency in obtaining piglets after production of cloned embryos was challenged in two steps-first by performing in vitro culture for 5-6 days after cloning to obtain later-stage embryos for more precise selection for transfer, and second by reducing the number of embryos transferred per recipient sow. The data set consisted of combined results from a 4-year period where cloning was performed to produce piglets that were transgenic for important human diseases. For this, different transgenes and cell types were used, and the cloning work was performed by several persons using oocytes from different pig breeds, but following a standardized and optimized protocol. Results showed that in vitro culture is possible with a relatively stable rate of transferable embryos around 41% and a pregnancy rate around 90%. Furthermore, a reduction from around 80 embryos to 40 embryos transferred per recipient was possible without changing the efficiency of around 14% (piglets born out of embryos transferred). It was concluded that this approach can increase the efficiency in obtaining piglets by means of in vitro culture and selection of high-quality embryos with subsequent transfer into more recipients. Such changes can also reduce the need for personnel, time, and material when working with this technology.

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.

Improvement of cloned embryos development by co-culturing with parthenotes: a possible role of exosomes/microvesicles for embryos paracrine communication

It is well known that embryos cultured in a group can create a microenvironment through secretion of autocrine and paracrine factors that can support and improve the embryos' development when compared to the embryos cultured individually. In this study, we used a co-culture system for paracrine communication between different kinds of embryos. The results showed that co-culture of porcine parthenogenetic (PA) embryos significantly improved the in vitro development of cloned (nuclear transfer, NT) embryos. To reveal the possible mechanism of communication between the two groups, we isolated exosomes/microvesicles (EXs/MVs) from the PA embryos conditioned medium (PA-CM) through differential centrifugation and identified them through transmission electron microscope and immunoflourescence against exosomal/membrane marker CD9. Furthermore, these EXs/MVs were found to contain mRNA of pluripotency genes (Oct4, Sox2, Klf4, c-Myc, and Nanog), and the PKH67-labeled EXs/MVs could be internalized by the NT embryos. The current study demonstrates that cloned embryos' developmental competence can be improved through co-culturing with PA embryos and revealed, for the first time, that in vitro-produced embryos can secrete EXs/MVs as a possible communication tool within their microenvironment. Moreover, it provides a new paradigm for embryo-to-embryo communication in vitro.

The new system of shorter porcine oocyte in vitro maturation (18 hours) using ≥8 mm follicles derived from cumulus-oocyte complexes

Despite recent efforts to improve in vitro maturation (IVM) systems for porcine oocytes, developmental competence of in vitro-matured oocytes is still suboptimal compared with those matured in vivo. In this study, we compared oocytes obtained from large (≥8 mm; LF) and medium (3-7 mm; MF) sized follicles in terms of nuclear maturation, intracellular glutathione and reactive oxygen species levels, gene expression, and embryo developmental competence after IVM. In the control group, cumulus-oocyte complexes (COCs) were aspirated from MF and matured for 22 hours with hormones and subsequently matured for 18 to 20 hours without hormones at 39 °C, 5% CO2 in vitro. In the LF group, COCs were obtained from follicles larger than 8 mm and were subjected to IVM for only 18 hours. The ovaries have LF were averagely obtained with 1.7% per day during 2012 and it was significantly higher in the winter season. The results of the nuclear stage assessment of the COCs from the LFs are as follows: before IVM (0 hours); germinal vesicle stage (15.2%), metaphase I (MI) stage (55.4%), anaphase and telophase I stages (15.8%), and metaphase II (MII) stage (13.6%). After 6 hours IVM; germinal vesicle (4.2%), MI (43.6%), anaphase and telophase I (9.4%), and MII (42.8%). After 18-hour IVM; MI (9.7%) and MII (90.3%). Oocytes from LF showed a significant (P < 0.001) increase in intracellular glutathione (1.41 vs. 1.00) and decrease in reactive oxygen species (0.8 vs. 1.0) levels compared with the control. The cumulus cells derived from LFs showed lower (P < 0.1) mRNA expression of COX-2 and TNFAIP6, and higher (P < 0.1) mRNA expression of PCNA and Nrf2 compared with the control group-derived cumulus cells. After parthenogenetic activation, in vitro fertilization and somatic cell nuclear transfer (SCNT) using matured oocytes from LFs, the embryo development was significantly improved (greater blastocyst formation rates and total cell numbers in blastocysts) compared with the control group. In conclusion, oocytes from LFs require only 18 hours to complete oocyte maturation in vitro and their developmental competence is significantly greater than those obtained from MFs. Although their numbers are limited, oocytes from LFs might offer an alternative source for the efficient production of transgenic pigs using SCNT.

A simplified one-step nuclear transfer procedure alters the gene expression patterns and developmental potential of cloned porcine embryos

Various somatic cell nuclear transfer (SCNT) techniques for mammalian species have been developed to adjust species-specific procedures to oocyte-associated differences among species. Species-specific SCNT protocols may result in different expression levels of developmentally important genes that may affect embryonic development and pregnancy. In the present study, porcine oocytes were treated with demecolcine that facilitated enucleation with protruding genetic material. Enucleation and donor cell injection were performed either simultaneously with a single pipette (simplified one-step SCNT; SONT) or separately with different pipettes (conventional two-step SCNT; CTNT) as the control procedure. After blastocysts from both groups were cultured in vitro, the expression levels of developmentally important genes (OCT4, NANOG, EOMES, CDX2, GLUT-1, PolyA, and HSP70) were analyzed by real-time quantitative polymerase chain reaction. Both the developmental rate according to blastocyst stage as well as the expression levels CDX2, EOMES, and HSP70 were elevated with SONT compared to CTNT. The genes with elevated expression are known to influence trophectoderm formation and heat stress-induced arrest. These results showed that our SONT technique improved the development of SCNT porcine embryos, and increased the expression of genes that are important for placental formation and stress-induced arrest.

Treatment of porcine donor cells and reconstructed embryos with the antioxidant melatonin enhances cloning efficiency

This study was conducted to investigate the effect of melatonin during the culture of donor cells and cloned embryos on the in vitro developmental competence and quality of cloned porcine embryos. At concentrations of 10(-6 )M or 10(-8) M, melatonin significantly enhanced the proliferation of porcine fetal fibroblasts (PFFs), and the blastocyst rate was significantly increased in the 10(-10) M melatonin-treated donor cell group. Cloned embryo development was also improved in embryo culture medium that was supplemented with 10(-9) M or 10(-12) M melatonin. When both donor cells and cloned embryos were treated with melatonin, the cleavage rate and total cell number of blastocysts were not significantly affected; however, the blastocyst rate was increased significantly (20.0% versus 11.7%). TUNEL assays showed that combined melatonin treatment reduced the rate of apoptotic nuclei (3.6% versus 6.1%). Gene expression analysis of the apoptosis-related genes BAX, BCL2L1, and p53 showed that the expression of BCL2L1 was significantly elevated 2.7-fold relative to the control group, while the expression of BAX and p53 was significantly decreased by 3.7-fold and 23.2-fold, respectively. In addition, we detected the expression of two melatonin receptors (MT1 and MT2) in PFFs but not in porcine cloned embryos. We conclude that exogenous melatonin enhances the development of porcine cloned embryos and improves embryo quality by inhibiting p53-mediated apoptotic pathway. The proliferation of PFFs may be mediated by receptor binding, but the beneficial effects of melatonin on embryonic development may be receptor-independent, possibly through melatonin's ability to directly scavenge free radicals.

Transcriptome profile of bovine elongated conceptus obtained from SCNT and IVP pregnancies

In the present study we analyzed the gene expression changes induced by somatic cell nuclear transfer (SCNT) and in vitro production (IVP) in bovine elongated embryos using Affymetrix bovine genome array. For this, Day-16 bovine embryos from SCNT, IVP, and artificial insemination (AI) were recovered from recipients and used for transcriptome analysis. Despite comparable in vivo development rates, considerable reduction in elongation size was observed in SCNT compared to non-cloned embryos (93.3 mm for SCNT vs. 186.6 mm and 196.3 mm for IVP and AI embryos, respectively). Gene expression analysis revealed that the transcript levels of 477 genes, which are involved in various pathways including arginine and proline or glycerolipid and fatty acid metabolism, were significantly altered in SCNT compared to AI embryos. Similarly, 365 genes were differentially expressed in IVP embryos compared to AI. Thus, several pathways including TNRF-1 signaling and tight junction pathways were affected. To predict whether the altered transcripts were associated with culture condition or errors in transcriptional reprogramming, unique or common differentially expressed genes were analyzed in SCNT and IVP embryos compared to AI or fibroblast donor cells. Accordingly, 71 transcripts were found to be not transcriptionally reprogrammed, as their expression resembled the donor cells more than AI embryos; the remaining transcripts were either partially or incompletely reprogrammed. In conclusion, the present study identified deviations in elongation size, gene expression, and the corresponding molecular pathways in Day-16 SCNT and IVP conceptuses compared to their AI counterparts, which may subsequently be associated with the outcome of fetal development.

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.

Blastocysts cloned from the Putian Black pig ear tissues frozen without cryoprotectant at -80 and -196 degrees Celsius for 3 yrs

The Putian Black pig, as one of elite cultivars of endemic species in China, has been on the verge of extinction and urgently needs protection. Somatic cell nuclear transfer (SCNT) and noncryoprotected frozen tissue technology have successfully resurrected several mammalian species. Therefore, this study explored the primary feasibility of conserving this breed using a combination of both technologies. Skin tissues obtained from the ears of adult Putian Black boars were frozen without cryoprotectant at -20, -80, or -196 °C and stored for 3 yrs. Primary cell culture, passage and subculture were performed on frozen samples after being rapidly thawed at 39 °C and on fresh pig ear tissues (control). Cloned embryos were reconstructed using fibroblasts (from frozen and fresh tissues) with enucleated oocytes. Live cell lines were obtained from tissues frozen at -80 and at -196 °C and appeared to have normal proliferative activity after passage; furthermore, they directed cloned embryos to develop to the blastocyst stage after nuclear transfer. We concluded that the population of Putian Black pig might be increased in the future by transferring cloned blastocysts into synchronized recipient pigs.

Promising system for selecting healthy in vitro-fertilized embryos in cattle

Conventionally, in vitro–fertilized (IVF) bovine embryos are morphologically evaluated at the time of embryo transfer to select those that are likely to establish a pregnancy. This method is, however, subjective and results in unreliable selection. Here we describe a novel selection system for IVF bovine blastocysts for transfer that traces the development of individual embryos with time-lapse cinematography in our developed microwell culture dish and analyzes embryonic metabolism. The system can noninvasively identify prognostic factors that reflect not only blastocyst qualities detected with histological, cytogenetic, and molecular analysis but also viability after transfer. By assessing a combination of identified prognostic factors—(i) timing of the first cleavage; (ii) number of blastomeres at the end of the first cleavage; (iii) presence or absence of multiple fragments at the end of the first cleavage; (iv) number of blastomeres at the onset of lag-phase, which results in temporary developmental arrest during the fourth or fifth cell cycle; and (v) oxygen consumption at the blastocyst stage—pregnancy success could be accurately predicted (78.9%). The conventional method or individual prognostic factors could not accurately predict pregnancy. No newborn calves showed neonatal overgrowth or death. Our results demonstrate that these five predictors and our system could provide objective and reliable selection of healthy IVF bovine embryos.

Effects of chemically defined medium on early development of porcine embryos derived from parthenogenetic activation and cloning

The present study was to investigate if a completely chemically defined medium (PZM-4) could support the early development of porcine embryos derived from parthenogenetic activation (PA) and cloning (somatic cell nuclear transfer, SCNT), and to lay the foundation for determining the physiological roles of certain supplements in this medium. Porcine embryos derived from PA and SCNT were cultured in media: PZM-3 (a chemically semi-defined medium), PZM-4 (a fully defined medium), and PZM-5 (an undefined medium). Early embryo development was observed. We found that the three medium groups (PZM-3, PZM-4 and PZM-5) exhibited no significant differences in cleavage rates of PA embryos (p > 0.05), while the blastocyst rate in PZM-3 was significantly higher than in PZM-4 and PZM-5 (78.9% vs. 36.0% and 52.3%) (p < 0.05). Moreover, total cell number per blastocyst in PZM-3 was clearly higher than in PZM-5 but similar to that in PZM-4. As for SCNT embryos, no significant differences were observed for the cleavage rates or the blastocyst rates among the three groups (p > 0.05). However, total cell number per blastocyst in PZM-3 was notably higher than in PZM-5, but was similar to that in PZM-4. In conclusion, our results suggested that the completely chemically defined medium PZM-4 can be used to efficiently support the early development of porcine PA and SCNT embryos.

Acetylation level of histone H3 in early embryonic stages affects subsequent development of miniature pig somatic cell nuclear transfer embryos

Successful cloning by somatic cell nuclear transfer (SCNT) requires a reprogramming process in which the epigenetic state of a differentiated donor nucleus must be converted into an embryonic totipotent state. However, this epigenetic reprogramming is incomplete in SCNT embryos, causing low production efficiency. Recently, it has been reported that trichostatin A (TSA), an inhibitor of histone deacetylase, potentially enhances cloning efficiency. The aim of the present study was to optimize the TSA treatment for miniature pig SCNT embryos and investigate the effect of the acetylation level of histone on developmental competence of SCNT embryos. In order to optimize the TSA treatment, we examined the developmental competence of SCNT embryos under various exposure times (0-50 h) and concentrations (0-500 nM). Treatment with 5 nM TSA for 15 and 20 h beginning at the start of activation significantly increased the blastocyst formation rate (34.6 and 32.4 vs. 18.2%, respectively) and mean cell number (57.0 +/- 2.7 and 56.6 +/- 2.7 vs. 43.5 +/- 2.1, respectively) as compared with the non-treated group (0 h). We then investigated the acetylation levels of histone H3 in SCNT embryos treated with or without TSA (TSA (+) or TSA (-)) as compared with in vitro- fertilized (IVF) embryos. The acetylation levels of the TSA (-) SCNT embryos at the pseudo-pronuclear and 2-cell stages were significantly lower than those of the IVF embryos at the same developmental stages. In contrast, the acetylation levels of the TSA (+) SCNT embryos were similar to those of the IVF embryos. There was no difference in the acetylation levels of all groups at the blastocyst stage. Our data therefore suggests that the acetylation level of histone H3 at the pseudo-pronuclear and 2-cell stages is positively correlated with subsequent development of SCNT embryos, which may be an important event for the vital development of SCNT embryos in miniature pigs.