Parthenogenetic development of bovine oocytes treated with ethanol and cytochalasin B after in vitro maturation

Proteomic analysis demonstrates that parthenogenetically activated swamp buffalo embryos have dysregulated energy metabolism

The comprehensive understanding of early embryo development is essential to optimize in vitro culture conditions. Protein expression landscape of parthenogenetically produced embryo remains unexplored. This study aimed to investigate the protein expression dynamics with a particular focus on energy metabolism throughout the early developmental stages of parthenogenetic buffalo embryos. For this purpose, we performed iTRAQ-based quantitative mass spectrometry and identified 280 proteins common in all stages. A total of 933 proteins were identified during the proteomics analysis. The data depicted that morula and blastocyst had distinct protein expression dynamics as compared to 2- to 16-cell-stage embryo. KEGG pathway analysis showed 23 proteins belonging to energy metabolism appeared in the data. Study of energy metabolism-related protein's expression pattern demonstrated that there was asynchrony in proteins related to glycolysis throughout the examined developmental stages. The expression pattern of pyruvate kinase mutase (PKM), an essential protein of glycolysis, indicated a slightly decreasing trend from 2-cell-stage embryo to blastocyst, and it was supported by expression of proteins involved in lactate production (LDHA and LDHB) suggesting the decreasing rate of aerobic glycolysis (Warburg Effect) at morula and blastocyst stage. The increased Warburg Effect is considered as the hallmark of proliferating cells or embryo at the blastocyst stage. Furthermore, the proteins involved in the citric acid cycle also showed down-regulation at the blastocyst stage, indicating a lesser role of oxidative phosphorylation at this stage. Therefore, it could be divulged from the study that there may be an irregular pattern of energy metabolism in early parthenogenetic embryos. Further studies are recommended to understand this phenomenon.

Sire contribution to pregnancy loss in different periods of embryonic and fetal development of beef cows

The objective was to evaluate the effect of service sire on pregnancy results during different periods of embryonic and fetal development. Angus cows (n = 658) were timed artificially inseminated (TAI) on day 0 after synchronization of estrus using one of eight Angus sires. Estrus expression prior to TAI was evaluated using estrus breeding indicators. Blood samples were collected on days 0, 24 and 31 for quantification of circulating pregnancy-associated glycoprotein (PAG). Pregnancy was diagnosed at day 24 based on blood-based test, and on days 31 and 60 by transrectal ultrasonography to determine early embryonic mortality (EEM; between days 24 and 31) and late embryonic/early fetal mortality (LEM; between days 31 and 60). Sires were retrospectively classified according to the amount of pregnancy loss in each evaluated interval. Overall EEM was 5.54%, with values ranging from 1.8 to 11.7% among sires, whereas LEM was 6.7% with values ranging from 2.3 to 12.6% among sires. Individual sires had different phenotypes in regard to pregnancy loss during different developmental periods, indicating the importance of evaluating multiple milestones of embryonic development when classifying sire fertility. No difference (P ≥ 0.05) was observed in serum concentrations of PAG in cows bred with sires of different phenotypes. Pregnancy rate by sire was also influenced by estrus expression. Sires with a greater number of cows pregnant without estrus expression, had similar incidence of early (P = 0.71) but greater incidence of late embryonic mortality (P = 0.05). These results are significant to characterize sire contribution to pregnancy maintenance and establishment in beef cows and to serve as basis of studies to identify markers to improve sire fertility evaluation.

The transfer of parthenogenetic embryos following artificial insemination in cows can enhance pregnancy recognition via the secretion of interferon tau

Repeat breeding is a reproductive disorder in cattle. Embryo transfer following artificial insemination (AI) improves pregnancy rate by replenishing interferon tau (IFNT), but it results in a notably higher rate of twin occurrence. This study hypothesized that parthenogenetic (PA) embryo transfer following AI (AI + PA) could improve the conception rate because that PA embryo become as a supplemental source of IFNT without twins. PA embryos showed higher IFNT mRNA expression than in vitro fertilization (IVF) embryos. An examination of the effect of the cultured conditioned media (CM) of PA or IVF embryos on Madin-Darby bovine kidney cells with stably introduced promoter-reporter constructs of interferon-stimulated gene 15 (ISG15, marker of IFN response) showed higher stimulation levels of ISG15 promoter activity with PA than with IVF embryo. We investigated in vivo the effect of AI + PA on healthy Japanese Black cattle. Cattle transferred with PA embryo alone were non-fertile, but those that underwent AI + PA showed a pregnancy rate of 53.3%, the similar as that with AI alone (60%). In pregnant cattle in AI + PA group, adding the PA embryo upregulated the expression of ISGs and plasma progesterone concentration. No twin were generated in AI only and AI + PA groups. Using repeat breeding Holstein cows that did not become pregnant with 4-9 times of AI, transfer of PA embryo following AI resulted in a higher pregnancy rate than that of control (AI only). We suggest that AI + PA may be beneficial for improving maternal pregnancy recognition in repeat breeder cattle while avoiding twin generation.

The cyclin-dependent kinase inhibitor, JNJ-7706621, improves in vitro developmental competence of porcine parthenogenetic activation and somatic cell nuclear transfer embryos

In this study we examined the effects of JNJ-7706621, a cyclin-dependent kinase inhibitor, on the in vitro growth of pig embryos that had been produced either by parthenogenetic activation (PA) or somatic cell nuclear transfer (SCNT). A significantly higher percentage of PA embryos reached the blastocyst stage by Day 7 after exposure to 10 µM JNJ-7706621 for 4 h compared with embryos exposed to 5 µg mL−1 cytochalasin B for 4 h (P < 0.05). Similarly, the rate of Tyr15 phosphorylation of the complex of cyclin and p34cdc2 (CDK1) was significantly elevated in the JNJ-7706621-treated embryos compared with embryos exposed to cytochalasin B or non-treated controls (P < 0.05). In contrast, Thr161 phosphorylation of CDK1 was significantly lower in the JNJ-7706621-treated group compared with the cytochalasin B-treated as well as the non-treated group (P < 0.05). Similarly, the level of M-phase-promoting factor (MPF) in embryos was significantly lower in the JNJ-7706621-treated group compared with the cytochalasin B-treated and non-treated groups (P < 0.05). In addition, more SCNT embryos reached the blastocyst stage after treatment with JNJ-7706621 than following exposure to cytochalasin B (P < 0.05). In conclusion, these results reveal that exposure to 10 µM JNJ-7706621 for 4 h improves early development of PA and SCNT porcine embryos by suppressing the activity of CDK1 and a concomitant reduction in the level of MPF.

Parthenogenetic activation and somatic cell nuclear transfer of porcine oocytes activated by an electric pulse and AZD5438 treatment

We examined the in vitro developmental competence of parthenogenetic activation (PA) oocytes activated by an electric pulse (EP) and treated with various concentrations of AZD5438 for 4 h. Treatment with 10 µM AZD5438 for 4 h significantly improved the blastocyst formation rate of PA oocytes in comparison with 0, 20, or 50 µM AZD5438 treatment (46.4% vs. 34.5%, 32.3%, and 24.0%, respectively; P 0.05). Furthermore, 66.67% of blastocysts derived from these AZD5438-treated PA oocytes had a diploid karyotype. The blastocyst formation rate of PA and somatic cell nuclear transfer (SCNT) embryos was similar between oocytes activated by an EP and treated with 2 mM 6-dimethylaminopurine for 4 h and those activated by an EP and treated with 10 µM AZD5438 for 4 h (11.11% vs. 13.40%, P > 0.05). In addition, the level of maturation-promoting factor (MPF) was significantly decreased in oocytes activated by an EP and treated with 10 µM AZD5438 for 4 h. Finally, the mRNA expression levels of apoptosis-related genes (Bax and Bcl-2) and pluripotency-related genes (Oct4, Nanog, and Sox2) were checked by RT-PCR; however, there were no differences between the AZD5438-treated and non-treated control groups. Our results demonstrate that porcine oocyte activation via an EP in combination with AZD5438 treatment can lead to a high blastocyst formation rate in PA and SCNT experiments.

Self-diploidization of human haploid parthenogenetic embryos through the Rho pathway regulates endomitosis and failed cytokinesis

A diploid genome is necessary for normal mammalian development, thus haploid parthenogenetic embryos undergo frequent self-diploidization during preimplantation development; however, the underlying mechanism is unclear. In this study, time-lapse recording revealed that human haploid parthenotes (HPs) undergo self-diploidization via failed cytokinesis (FC) and endomitosis (EM). The frequencies of FC/EM were significantly higher in HPs than in normal fertilized embryos (26.3% vs. 1.6%, P < 0.01; 19.7% vs. 0, P < 0.01), and above 90% of FC/EM occurred at the first cell cycle in HPs. Fluorescent in situ hybridization of chromosome 16,18 and X in HPs identified diploid recovery after the appearance of FC/EM, and FC/EM HPs showed improved blastocyst formation compared with non-FC/EM HPs (18.8% and 40.0% vs. 15.4%, P > 0.05). In 66.7% of the 1-cell stage HPs, furrow ingression was not observed during the time for normal cleavage, and both immunostaining and gene expression analysis of 1-cell stage HPs revealed the absence or down-regulation of several key genes of the Rho pathway, which regulates cytomitosis. Our results suggested that the major mechanism for self-diploidization is Rho pathway inhibition leading to FC/EM in the first cell cycle, and fine-tuning of this signalling pathway may help to generate stable haploid embryos for stem cell biology studies.

Epigenetic analysis of bovine parthenogenetic embryonic fibroblasts

Although more than 100 imprinted genes have already been identified in the mouse and human genomes, little is known about genomic imprinting in cattle. For a better understanding of these genes in cattle, parthenogenetically activated bovine blastocysts were transferred to recipient cows to obtain parthenotes, and fibroblasts derived from a Day 40 (Day 0 being the day of parthenogenetic activation) parthenogenetic embryo (BpEFs) were successfully obtained. Bovine embryonic fibroblasts (BEFs) were also isolated from a normal fertilized embryo obtained from an artificially inseminated cow. The expression of imprinted genes was analyzed by RT-PCR. Paternally expressed genes (PEGs) in mouse (viz., IGF2, PEG3, ZAC1, NDN, DLK1, SGCE, and PEG10) were expressed in BEFs, but not in BpEFs, suggesting that these genes are also imprinted in cattle. However, other PEGs in mouse (viz., IMPACT, MAGEL2, SNRPN, and PEG1/MEST) were expressed in both BEFs and BpEFs. These genes may not be imprinted in BEFs. The expression of seven maternally expressed genes in mouse was also analyzed, and only CDKN1C was not expressed in BpEFs. The DNA methylation patterns of repetitive elements (Satellite I, Satellite II, alpha-satellite, and Art2) were not different between the BEFs and BpEFs; however, the differentially methylated region (DMR) of paternally methylated H19 was hypomethylated, whereas those of maternally methylated PEG3 and PEG10 were hypermethylated in BpEFs, as expected. The methylation of the SNRPN DMR was not different between the BEFs and BpEFs, in accordance with the SNRPN expression levels in both cell types. The XIST gene, which is essential for X chromosome inactivation in females, was expressed in BpEFs, whereas its DMR was half-methylated, suggesting that X chromosome inactivation is normal in these cells. Microarray analysis was also applied to identify novel PEGs that should be expressed only in BEFs but not in BpEFs. More than 300 PEG candidate genes, including IGF2, PEG3, and PEG10, were obtained. These results illustrate the epigenetic characteristic of bovine parthenogenetic embryos and contribute to the identification of novel imprinted genes in cattle.

Effects of cytochalasin B on DNA methylation and histone modification in parthenogenetically activated porcine embryos

DNA methylation and histone modification play important roles in the development of mammalian embryos. Cytochalasin B (CB) is an actin polymerization inhibitor that can significantly affect cell activity and is often used in studies concerning cytology. In recent years, CB is also commonly being used in in vitro experiments on mammalian embryos, but few studies have addressed the effect of CB on the epigenetic modification of embryonic development, and the mechanism underlying this process is also unknown. This study was conducted to investigate the effects of CB on DNA methylation and histone modification in the development of parthenogenetically activated porcine embryos. Treatment with 5 μg/mL CB for 4 h significantly increased the cleavage rate, blastocyst rate and total cell number of blastocysts. However, the percentage of apoptotic cells and the expression levels of the apoptosis-related genes BCL-XL, BAX and CASP3 were significantly decreased. Treatment with CB significantly decreased the expression levels of DNMT1, DNMT3a, DNMT3b, HAT1 and HDAC1 at the pronuclear stage and promoted the conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). After CB treatment, the level of AcH3K9 was upregulated and the level of H3K9me3 was downregulated. When combined with Scriptaid and 5-Aza-Cdr, CB further improved the embryonic development competence and decreased the expression of BCL-XL, BAX and CASP3 In conclusion, these results suggest that CB could improve embryonic development and the quality of the blastocyst by improving the epigenetic modification during the development of parthenogenetically activated embryos.

Effect of in vitro and in vivo conditions on development of parthenogenetic rabbit embryos after vitrification

Parthenote embryos offer multiple opportunities in biotechnological research, so it is important to analyse the possibilities for their cryopreservation in order to establish a biobank. The aim of this experiment was to determine the effect of culture conditions and vitrification on rabbit parthenogenetic embryos. Parthenotes were cultured under in vivo and in vitro conditions until day 3 (late morula/early blastocyst), when they were vitrified. Immediately after warming, they were newly cultured under in vivo and in vitro conditions till day 6 (blastocyst stage). Both culture conditions showed similar late morula/early blastocyst (0.39±0.056 vs. 0.46±0.043, for in vivo and in vitro, respectively) and blastocyst rates (0.12±0.068 vs. 0.13±0.070, for in vivo and in vitro, respectively). However, no parthenote was recovered when a combination of culture conditions was performed. To our best knowledge, this is the first demonstration of the ability of rabbit parthenogenetic embryos to develop after vitrification, with similar embryo development after in vivo or in vitro culture. Nevertheless, our results highlight the importance of culture conditions on the morphology of parthenote embryos. Therefore, we have described that special attention should be paid on culture conditions to generate parthenote embryos, with a view to their subsequent use, for example in embryonic stem cell production.

Genomic imprinting effects on complex traits in domesticated animal species

Monoallelically expressed genes that exert their phenotypic effect in a parent-of-origin specific manner are considered to be subject to genomic imprinting, the most well understood form of epigenetic regulation of gene expression in mammals. The observed differences in allele specific gene expression for imprinted genes are not attributable to differences in DNA sequence information, but to specific chemical modifications of DNA and chromatin proteins. Since the discovery of genomic imprinting some three decades ago, over 100 imprinted mammalian genes have been identified and considerable advances have been made in uncovering the molecular mechanisms regulating imprinted gene expression. While most genomic imprinting studies have focused on mouse models and human biomedical disorders, recent work has highlighted the contributions of imprinted genes to complex trait variation in domestic livestock species. Consequently, greater understanding of genomic imprinting and its effect on agriculturally important traits is predicted to have major implications for the future of animal breeding and husbandry. In this review, we discuss genomic imprinting in mammals with particular emphasis on domestic livestock species and consider how this information can be used in animal breeding research and genetic improvement programs.

Effects of high hydrostatic pressure on genomic expression profiling of porcine parthenogenetic activated and cloned embryos

Handmade cloning (HMC) has been used to generate transgenic pigs for biomedical research. Recently, we found that parthenogenetic activation (PA) of porcine oocytes and improved HMC efficiency could be achieved by treatment with sublethal high hydrostatic pressure (HHP). However, the molecular mechanism underlying the effects of HHP treatment on embryonic development is poorly understood and so was investigated in the present study. Thus, in the present study, we undertook genome-wide gene expression analysis in HHP-treated and untreated oocytes, as well as in 4-cell and blastocyst stage embryos derived by PA or HMC. Hierarchical clustering depicted stage-specific genomic expression profiling. At the 4-cell and blastocyst stages, 103 and 163 transcripts were differentially expressed between the HMC and PA embryos, respectively (P<0.05). These transcripts are predominantly involved in regulating cellular differentiation, gene expression and cell-to-cell signalling. We found that 44 transcripts were altered by HHP treatment, with most exhibiting lower expression in HHP-treated oocytes. Genes involved in embryonic development were prominent among the transcripts affected by HHP. Two of these genes (INHBB and ME3) were further validated by quantitative reverse transcription-polymerase chain reaction. We also observed that HHP treatment activated expression of the imprinting gene DLX5 in 4-cell PA embryos. In conclusion, our genomic expression profiling data suggest that HHP alters the RNA constitution in porcine oocytes and affects the expression of imprinting genes during embryonic development.

Comparison of chemical, electrical, and combined activation methods for in vitro matured porcine oocytes

Factors influencing porcine oocyte activation were systematically studied. This study included (1) the effect of ionomycin plus various chemical agents on activation, (2) comparison of different electrical activation parameters, (3) optimization of combined activation, and (4) evaluation of the optimized protocols. The results showed that (1) blastocyst rates of ionomycin (Ion) + 6-dimethylaminopurine (6-DMAP) (29.7 ± 1.1%), Ion + cytochalasin B (CB) + cycloheximide (CHX) (29.8 ± 1.2%), Ion + CB + 6-DMAP (30.4 ± 1.6%), and Ion + CB + CHX + 6-DMAP (30.2 ± 2.7%) were significantly higher than Ion + CHX (15.8 ± 1.5%, p < 0.05); (2) the parthenogenetic blastocyst formation of electrical activation was optimal when oocytes were activated by three direct current (DC) pulses of 1.00 kV cm(-1) for 80 μs (39.5 ± 1.1%); (3) blastocyst rates of DC + CB + CHX (55.4 ± 1.2%) and DC + CB + 6-DMAP (50.4 ± 2.9%) were significantly higher than DC + 6-DMAP, DC + CB + CHX + 6-DMAP, electrical activation, and chemical activation alone (p < 0.05); and (4) approximately 84% of parthenogenetic blastocysts yielded by the optimized protocol were diploid, which was significantly higher than that of electrical activation blastocysts (40%). Using the optimized electrical and combined activation protocol, high blastocyst rates were generated by intracytoplasmic sperm injection (ICSI) (34.6 ± 1.1%), cytoplasmic microinjection (CI) (52.3 ± 2.2%), and handmade cloning (HMC) (31.2 ± 1.0%), respectively. This study concludes that the optimal activation protocol of in vitro matured porcine oocytes was combined activation with parameter as three DC pulses of 1.00 kV cm(-1) for 80 μs plus CB and CHX treatment.

Development of parthenote following in vivo transfer of embryos in Capra hircus

The aim of this study is to generate parthenogenetic embryos from chemically activated in vitro matured caprine oocytes and to study the in vivo developmental potency of such embryos. The parthenogenetic embryos (2-8 and 16 cells to morula stage) were surgically transferred in 26 recipients. Pregnancy in recipients following embryo transfer was monitored by ultrasonography. The recipient aborted a foetus on day 34 post transfer. Sexing of parthenogenetic foetus showed a single band of amelogenin gene indicating female cell DNA. Microsatellite analysis revealed that the recipient has not contributed genetically to the parthenogenetic foetus confirming the identity of aborted foetus of parthenogenetic origin. The authors believe that this is the first authentic report on in vivo development of parthenogenetic foetus in Capra hircus.

Toxicity evaluation of ethanol treatment during in vitro maturation of porcine oocytes and subsequent embryonic development following parthenogenetic activation and in vitro fertilization

Ethanol is frequently used as a solvent in several techniques for in vitro production (IVP). It is also used for the parthenogenetic activation (PA) of oocytes. Although a number of studies have suggested that ethanol has detrimental effects on fibroblasts and neuronal cells, little attention has been paid to the effects of ethanol on porcine oocytes. Thus, the aim of this study was to evaluate the effects of the addition of ethanol to in vitro maturation (IVM) medium. We investigated the effects of ethanol (0, 1 and 3%) on the following parameters: nuclear maturation, intracellular glutathione (GSH) and reactive oxygen species (ROS) levels, and subsequent embryonic development following PA and in vitro fertilization (IVF). After 44 h of IVM, the 3% group showed a significant (P<0.05) decrease in nuclear maturation (34.0%) compared with the control group (70.3%). The 1 and 3% groups exhibited a significant (P<0.05) decrease in GSH levels and an increase in ROS levels compared with the control group. Compared with the control group, the 3% group had significantly (P<0.05) lower cleavage rates following PA (51.6 vs. 86.9%) and IVF (53.2 vs. 70.6%), as well as lower blastocyst formation rates and decreased total cell numbers following PA (11.3% and 31.8 vs. 53.6% and 65.4, respectively) and IVF (4.1% and 22.0 vs. 36.1% and 70.3, respectively). We evaluated the mRNA expression levels of DNA repair‑related and apoptosis‑related genes in the cumulus oocyte complexes (COCs). The 1% ethanol group showed significantly (P<0.05) higher mRNA expression levels of poly(ADP‑ribose) polymerase‑1 (PARP‑1), Bax, Bak and caspase‑3, and the 3% ethanol group had significantly (P<0.05) increased PARP‑1, Bax and caspase‑3 mRNA expression levels compared with the control group. Our results suggest that treatment with >1% ethanol during IVM exerts a toxic effect on the developmental potential of PA and IVF porcine embryos by decreasing the intracellular GSH level, thereby increasing the intracellular ROS level and upregulating the expression of apoptosis‑related genes.

Enhancement of maternal recognition of pregnancy with parthenogenetic embryos in bovine embryo transfer

This study was performed to elucidate the changes in IFNT messenger RNA (mRNA) levels in in vivo-fertilized and parthenogenetic bovine embryos and their interferon-τ (IFNT) secretion amounts during the elongation phase. We assessed the induction capability of maternal recognition of pregnancy by parthenogenetic embryos and attempted cotransfer of in vivo-fertilized and parthenogenetic embryos. The expression level of IFNT mRNA in in vivo-fertilized embryos peaked on Day 18 after estrus, and the highest amount of uterine IFNT was observed on Day 20. Transfer of 10 parthenogenetic embryos produced a detectable amount of uterine IFNT. Transfer of one or three parthenogenetic embryos inhibited luteolysis. An increase in ISG15 mRNA levels in peripheral granulocytes was induced by the transfer of three parthenogenetic embryos. Cotransfer of three parthenogenetic embryos significantly improved the pregnancy rate on Day 40 in code 3 in vivo-fertilized embryos compared with single transfer without parthenogenetic embryos (65% vs. 35%). However, the pregnancy rate on Day 90 (35%) in cotransfer of code 3 in vivo-fertilized embryos did not differ from that upon single transfer (29%), because the cotransfer group had a higher incidence of pregnancy loss than with single transfer (47% vs. 17%) after Day 40. Cotransfer did not affect the pregnancy rate of code 2 in vivo-fertilized embryos. The incidence of pregnancy loss was higher in cotransfer of code 2 in vivo-fertilized embryos than in single transfer (30% vs. 7%). In conclusion, parthenogenetic embryos in the elongation phase secreted IFNT, enabling induction of maternal recognition of pregnancy. The present study revealed that enhancement of the maternal recognition of pregnancy using parthenogenetic embryos promoted the viability of poor-quality embryos until Day 40 of gestation. However, the incidence of pregnancy loss increased after Day 40 in the cotransfer of parthenogenetic embryos. A technique for promoting the full-term survival of poor-quality embryos is needed.

Microarray analysis of gene expression in parthenotes and in vitro-derived goat embryos

The present work was carried out to investigate the global gene expression profile to search differentially expressed candidate transcripts between parthenogenetic and in vitro-fertilized (IVF) caprine morula. For this study, total RNA was isolated from diploid parthenogenetic and IVF embryos, and complementary DNA was synthesized. Microarray and relative real-time polymerase chain reaction analysis were performed to check global gene expression profile and validation, respectively. According to the microarray analysis, the total number of upregulated (UR) and downregulated (DR) genes was 613 and 220, respectively in diploid parthenogenetic morula as compared with IVF morula. The number of genes showing about two-, two- to five-, five- to 10-, 10- to 20-, and above 20-fold UR and DR genes was 147, 229, 122, 59, and 56 and 94, 73, 18, 13, and 22, respectively. Five UR genes validated (PTEN, PHF3, CTNNB1, SELK, and NPDC1) and all of them were significantly higher in parthenotes, which was in accordance with microarray results, whereas the expression of DR (AURKC and KLF15) genes were downregulated in parthenotes as observed in microarray results but the difference was not significant (P < 0.05). In conclusion, our findings demonstrate differential expression of a large number of genes in parthenotes compared with IVF embryos, which may be the reason for aberrant parthenogenetic embryo development in caprine species.

Comparative expression analysis of embryonic development-related genes at different stages of parthenogenetic and in vitro fertilized embryos in caprine

Aberrant gene expression occurs in parthenogenetic embryos due to abnormal epigenetic modifications in the genome that probably diminish viability and enhance developmental abnormalities in these embryos. In the present study, five developmentally important genes (HPRT1, Cx43, Sox2, Mest and IGF2R) were analysed at different stages in parthenotes (haploid and diploid) and compared with similar stages in in vitro fertilized (IVF) embryos. The results indicated that in haploid parthenotes expression of HPRT1 was upregulated (P < 0.05) only at the 2-4-cell stage whereas Cx43 expression was significantly (P < 0.05) downregulated in all stages as compared with the control. However, expression of this gene was upregulated (P < 0.05) in 2-4-cell and morula stages of diploid parthenotes. Expression of Sox2 was significantly (P < 0.05) downregulated in morula stage haploid parthenotes, whereas it was upregulated (P < 0.05) in 8-16-cell stage diploid embryos. The expression of Mest was upregulated (P < 0.05) at the 2-4-cell stage of both haploid and diploid parthenotes, whereas it was downregulated in 8-16-cell stage diploid embryos as compared with control. IGF2R expression was upregulated (P < 0.05) only in morula stage haploid and diploid parthenote as compared with control. These results indicate that parthenogenetic embryos showed aberrant gene expression of developmentally important genes such as HPRT1, Cx43, Sox2, Mest and IGF2R in comparison with IVF embryos, this finding may be one of the major reasons for the poor developmental competence of parthenogenetic embryos.

Effect of actin polymerization inhibitor during oocyte maturation on parthenogenetic embryo development and ploidy in Capra hircus

This study was designed to observe the effect of cytochalasin B (CCB) concentrations on ploidy and early development of parthenogenetic embryos in a caprine species. Caprine oocytes were matured in the presence of different concentrations of CCB (5, 10, 15, and 20 μg/ml) and activated by 7% ethanol followed by incubation with 2 mM DMAP. For embryos fertilized in vitro, oocytes were matured in maturation medium without CCB. The cleavage rate and further embryo development were significantly higher (P < 0.05) when oocytes were treated in this way. The percentage of embryos showed higher diploid values in 15 μg/ml CCB (83.66 ± 1.13), followed by 20 (72.22 ± 1.22), 10 (68.57 ± 1.17), and 5 μg/ml (62.00 ± 2.48). These results indicate that CCB with a concentration of 15 μg/ml in maturation medium can be used for the production of diploid parthenogenetic embryos in the caprine species.

In vivo and in vitro differentiation of uniparental embryonic stem cells into hematopoietic and neural cell types

The biological role of genomic imprinting in adult tissue is central to the consideration of transplanting uniparental embryonic stem (ES) cell-derived tissues. We have recently shown that both maternal (parthenogenetic/gynogenetic) and paternal (androgenetic) uniparental ES cells can differentiate, both in vivo in chimeras and in vitro, into adult-repopulating hematopoietic stem and progenitor cells. This suggests that, at least in some tissues, the presence of two maternal or two paternal genomes does not interfere with stem cell function and tissue homeostasis in the adult. Here, we consider implications of the contribution of uniparental cells to hematopoiesis and to development of other organ systems, notably neural tissue for which consequences of genomic imprinting are associated with a known bias in development and behavioral disorders. Our findings so far indicate that there is little or no limit to the differentiation potential of uniparental ES cells outside the normal developmental paradigm. As a potentially donor MHC-matching source of tissue, uniparental transplants may provide not only a clinical resource but also a unique tool to investigate aspects of genomic imprinting in adults.

Up-regulation of insulin-like growth factor I and uteroglobin in in vivo-developed parthenogenetic embryos

Parthenote embryos are being considered as an alternative source of embryonic stem cells. However, as there is still a dearth of knowledge of this kind of embryos, a better understanding of their biology is needed for their application. In this work, we studied the differences and similarities between parthenotes and normal embryos at the blastocyst stage in vivo developed. We analysed the expression of factor OCT-4, vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-I) and uteroglobin (UG) by real-time PCR. To do so, oocytes were recovered and after activation procedure were transferred by ventral middle laparoscopy to receptive does to undergo completely in vivo development. Does were slaughtered 6 days post-ovulation induction, and parthenote and normal embryos were recovered for mRNA expression analysis. Our results reported that parthenotes and normal embryos showed similar mRNA expression for OCT-4 and VEGF. However, IGF-I and UG showed to be over-expressed in parthenote embryos. Thus, our study highlights that despite the in vivo development of parthenotes, they still seem to have an altered expression and, therefore, to be different to normal embryos. The altered expression pattern of parthenote embryos suggests that these embryos should be studied carefully before future application.

cDNA microarray analysis of gene expression in parthenotes and in vitro produced buffalo embryos

The retarded development of parthenote embryo could be due to aberrant epigenetic imprinting, which may disrupt many aspects and lead to conceptus demise. The present work was conducted to: 1) compare the development of in vitro produced (IVP) and parthenogenetically developed (P) buffalo embryos from the 2-cell to blastocyst stage; 2) investigate the global gene expression profile and search for new candidate transcripts differing between IVP and P buffalo blastocyst using cDNA microarray analysis (validated by Real Time PCR); 3) follow the particular expression patterns of PLAC8 and OCT4 genes at five different stages of preimplantation development by Real Time PCR; and 4) study the expression of CDX2 at the blastcocyst stage. Cleavage rate was higher (P < 0.05) in P than IVP buffalo embryos, while, progression to blastocyst and number of cells per blastocyst were lower (P < 0.05) in P than IVP blastocysts. Microarray analysis indicate that 56 differentially expressed genes between the two groups, of which 51 genes (91.07%) were up-regulated, and five genes were downregulated in IVP blastocyst, using 1.4 fold-changes as a cutoff. Differentially expressed genes are related to translation, nucleic acid synthesis, cell adhesion and placentation. Validation of candidate genes revealed that the transcript abundance of PTGS2, RPS27A, TM2D3, PPA1, AlOX15, RPLO and PLAC8 were downregulated (7/8) in parthenote blastocyst compared to the IVP blastocyst. PLAC8 gene expression was higher (P < 0.05) at 2-cell, morula and blastocyst stages in IVP embryos compared with parthenote embryos. The OCT4 gene expression was higher (P < 0.05) in 2-cell, 4-cell, 8-cell and blastocysts produced in vitro. In conclusion, the retarded development of parthenogenetic buffalo embryos could be due to downregulation of genes related to translation, nucleic acid synthesis, cell adhesion, and placental development. The low expression of PLAC8 and OCT4 during the different stages of development may be responsible, in part, to the failure of development of parthenote buffalo embryos.

Parthenogenic blastocysts cultured under in vivo conditions exhibit proliferation and differentiation expression genes similar to those of normal embryos

Parthenote embryos offer multiple possibilities in biotechnological investigation, such as stem cell research. However, there is still a dearth of knowledge of this kind of embryo. In this study, development and ploidy were analysed in parthenotes under in vitro and in vivo culture conditions. Subsequently, using real-time PCR, the expressions of factor OCT-4, Vascular Endothelial Growth Factor, Epidermal Growth Factor Receptor 3 and Transforming Growth Factor β2 genes were analysed to compare the embryo types at the blastocyst stage. Development and implantation of parthenote embryos were described after transfer at day 10 of pregnancy. Parthenotes showed similar blastocyst development for both culture conditions and most of the parthenotes produced were diploid. However, parthenotes developed under in vivo conditions showed similar mRNA expression of OCT-4, VEGF and TGF-β2 to 5 and 6 day old blastocysts. In contrast, parthenotes developed under in vitro conditions had altered the expression pattern of these genes, except for erbB3 mRNA. Finally, transferred parthenotes had the ability to implant but showed severe growth retardation and lesser size. This is the first demonstration of the influence of culture conditions on parthenote mRNA expression. Our study highlights the importance of culture conditions in subsequent uses of parthenotes, such as the production of stem cell lines.

Gene expression analysis of bovine blastocysts produced by parthenogenic activation or fertilisation

The processes underlying the very first moments of embryonic development are still not well characterised in mammals. To better define the kinetics of events taking place following fertilisation, it would be best to have perfect synchronisation of sperm entry. With fertilisation occurring during a time interval of 6 to 12 h in the same group of fertilised oocytes, this causes a major variation in the time of activation of embryonic development. Bovine parthenogenesis could potentially result in better synchronisation and, if so, would offer a better model for studying developmental competence. In the present study, bovine oocytes were either parthenogenetically activated or fertilised and cultured in vitro for 7 days. Gene expression analysis for those two groups of embryos at early and expanded stages was performed with BlueChip, a customised 2000-cDNA array developed in our laboratory and enriched in clones from various stages of bovine embryo development. The microarray data analysis revealed that only a few genes were differentially expressed, showing the relative similarity between those two kinds of embryos. Nevertheless, the fact that we obtained a similar diversity of developmental stages with parthenotes suggests that synchronisation is more oocyte-specific than sperm entry-time related. We then analysed our data with Ingenuity pathway analysis. Networks of genes involved in blastocyst implantation but also previous stages of embryo development, like maternal-to-embryonic transition, were identified. This new information allows us to better understand the regulatory mechanisms of embryonic development associated with embryo status.

DNA methylation status of bovine blastocyst embryos obtained from various procedures

DNA methylation is an important factor for the regulation of gene expression in early embryos. It is well known that the satellite I sequence is more heavily methylated in bovine somatic cell nuclear transfer (NT-SC) embryos than in embryos derived from in vitro fertilization (IVF). However, the methylation status of bovine embryos obtained by other procedures is not well known. To clarify DNA methylation levels of bovine embryos obtained from various procedures, we examined satellite I sequences in bovine blastocyst (BC) embryos derived from NT-SC, NT using embryonic blastomeres (NT-EM), in vivo (Vivo), IVF and parthenogenetic treatment (PA). Furthermore, in order to evaluate the efficacy of DNA demethylation by the NT procedure, we determined the DNA methylation levels in bovine embryos in which NT was recapitulated (Re-NT). Although the DNA methylation levels in the NT-SC embryos were higher than those in the other embryos, the NT-EM embryos exhibited lower DNA methylation levels. The satellite I sequence in the NT-SC embryos was more demethylated than that in the donor cells. Although the DNA methylation level in the individual NT-SC embryos showed variation, the full-term developmental efficacy of these embryos were not different. These findings suggest that the methylation level of the satellite I sequence at the BC stage is not related to the abnormalities of bovine embryos produced by NT-SC. There was no difference in methylation levels between Re-NT and NT-SC embryos. Our results indicated that the DNA methylation status differed among embryos produced by various methods and that at least some of the demethylation of the donor cell genome occurred in the recipient cytoplast after NT-SC, but the demethylation ability of the NT procedure was noted in the first NT but not in the second NT.

Comparison of early development in utero of cloned fetuses derived from bovine fetal fibroblasts at the G1 and G0/G1 phases

In bovine somatic cell nuclear transfer (NT), embryos are more likely to develop to full term when they are derived from fibroblasts at the G1 phase instead of cells at the G0/G1 phase. To better understand the reason for this difference, we examined morphological development in the early pregnancy of NT embryos using G1 phase cells (G1-NT embryos) and G0/G1 phase cells (G0/G1-NT embryos). Blastocysts derived from G1 and G0/G1-NT embryos were transferred to recipient heifers, and the conceptuses at day 50 of gestation were retrieved non-surgically using prostaglandin F(2alpha) and oxytocin. In vitro-fertilized (IVF), parthenogenetic and artificially inseminated (AI) embryos were used as controls. The percentages of embryos that developed to the blastocyst stage did not differ between G1 and G0/G1-NT embryos. Pregnancy rates at day 30 of recipient heifers carrying G1-NT, G0/G1-NT, IVF, parthenogenetic and AI embryos were similar (57-100%). Two recipient heifers carrying parthenogenetic embryos returned to estrus between days 30 and 50 of gestation, whereas all other pregnancies remained viable. Most fetuses at day 50 of gestation of all experimental groups (83%) were recovered non-surgically by several PGF(2alpha) and oxytocin treatments. Recovery rates of normal fetuses derived from G1-NT embryos (83%), IVF embryos (80%) and AI embryos (88%) were greater than those of G0/G1-NT embryos (33%) and parthenogenetic embryos (0%). Our results suggest that NT embryos reconstructed with cells at the G1 phase have a high developmental competence from the time of embryo transfer to day 50 of gestation.

Gene expression in early expanded parthenogenetic and in vitro fertilized bovine blastocysts

Mammalian oocytes can undergo artificial parthenogenesis in vitro and develop to the blastocyst stage. In this study, using real-time PCR, we analyzed the expression of genes representative of essential events in development. In vitro matured oocytes were either fertilized or activated with ionomycin + 6-DMAP and cultured in simple medium. The pluripotency-related gene Oct3/4 was downregulated in parthenotes, while the de novo methylation DNMT3A gene was unchanged. Among the pregnancy recognition genes, IFN-t was upregulated, PGRMC1 was downregulated and PLAC8 was unchanged in parthenotes. Among the metabolism genes, SLC2A1 was downregulated, while AKR1B1, COX2, H6PD and TXN were upregulated in parthenotes; there was no difference in SLC2A5. Among the genes involved in compaction/blastulation, GJA1 expression increased in parthenotes, but no differences were detected within ATP1A1 and CDH1. Expression of p66(shc) and the Bax/Bcl2 ratio were higher in parthenotes, and there was no difference in p53. Parthenotes and embryos may differ in the way they stimulate apoptosis, with a preponderant role for p66(shc) within parthenotes. Differentially affected functions may also include pluripotency, de novo methylation and early embryonic signalling.

In vitrodevelopment of goat parthenogenetic and somatic cell nuclear transfer embryos derived from different activation protocols

Oocyte activation is an essential step in animal cloning to allow subsequent development of the reconstructed embryos. A special activation protocol is required for different animal species. The present study investigated low temperature, electrical pulses, ethanol, ionomycin and strontium for goat oocyte activation in order to optimize the protocols. We found, as a result, effective activation and parthenogenetic development of goat oocytes that had been derived from ionomycin, strontium and electrical pulse groups. Within each group 79.3–81.6%, 2.2–78.8% and 65.5% of the oocytes cleaved and 16.2–24.8%, 0–15.6% and 11.1% of the cleaved embryos developed into blastocysts when the oocytes were activated by ionomycin combined with 6-dimethylaminopurine, strontium plus cytochalasin B and electrical pulses combined with cytochalasin B, respectively. However, low temperature and ethanol were both unable to activate goat oocytes under our experimental conditions. When ionomycin combined with 6-dimethylaminopurine and strontium plus cytochalasin B was applied to activate somatic cell nuclear transfer embryos derived from cultured cumulus, 51.0% and 72.5% of the embryos cleaved, respectively. After transfer of 4-cell embryos into recipients, one (1/19 and 1/7) of the recipients from each group was found to be pregnant as detected by ultrasound, but both of these recipients lost the embryos between 45 and 60 days of pregnancy.

Effects of gonadotropins on in vitro maturation and of electrical stimulation on parthenogenesis of canine oocytes

The objective of this study was to determine the effects of gonadotropins on in vitro maturation (IVM) and electrical stimulation on the parthenogenesis of canine oocytes. In experiment I, cumulus oocyte complexes were collected from ovaries at a random phase of the oestrus cycle and cultured on maturation medium treated with hCG or eCG for 48 or 72 h. There were no significant differences in the effects on the metaphase II (MII) rate between the hCG and eCG treatment groups over 48 h (5.4% vs 5.5%). The MII rate in the co-treatment group of hCG and eCG for 48 h was higher than in each hormone treated group (15.5%, p < 0.05). In experiment 2, the parthenogenetic effect on oocyte development, at various electrical field strengths (1.0, 1.5, 2.0 kV/cm DC) for 60 or 80 mus with a single DC pulse after IVM on the co-treatment of hCG and eCG, was examined. The rate of pronuclear formation (37.1%) in electrical activation at 1.5 kV/60 mus without cytochalasin B (CB) was higher than that of oocytes activated in the other groups (p < 0.05). However, we did not observe the cleavage stages. Also, CB did not influence parthenogenesis of canine oocytes. The results showed that the pronucleus formation rate, indicative of the parthenogenesis start point, could be increased by electrical stimulation. Therefore, these results can provide important data for the parthenogenesis of canine oocytes and suggest the probability of parthenogenesis in canines.

Biological differences between in vitro produced bovine embryos and parthenotes

Parthenotes may represent an alternate ethical source of stem cells, once biological differences between parthenotes and embryos can be understood. In this study, we analyzed development, trophectoderm (TE) differentiation, apoptosis/necrosis, and ploidy in parthenotes and in vitro produced bovine embryos. Subsequently, using real-time PCR, we analyzed the expression of genes expected to underlie the observed differences at the blastocyst stage. In vitro matured oocytes were either fertilized or activated with ionomycin +6-DMAP and cultured in simple medium. Parthenotes showed enhanced blastocyst development and diploidy and reduced TE cell counts. Apoptotic and necrotic indexes did not vary, but parthenotes evidenced a higher relative proportion of apoptotic cells between inner cell mass and TE. The pluripotence-related POU5F1 and the methylation DNMT3A genes were downregulated in parthenotes. Among pregnancy recognition genes, TP-1 was upregulated in parthenotes, while PGRMC1 and PLAC8 did not change. Expression of p66(shc) and BAX/BCL2 ratio were higher, and p53 lower, in parthenotes. Among metabolism genes, SLC2A1 was downregulated, while AKR1B1, PTGS2, H6PD, and TXN were upregulated in parthenotes, and SLC2A5 did not differ. Among genes involved in compaction/blastulation, GJA1 was downregulated in parthenotes, but no differences were detected within ATP1A1 and CDH1. Within parthenotes, the expression levels of SLC2A1, TP-1, and H6PD, and possibly AKR1B1, resemble patterns described in female embryos. The pro-apoptotic profile is more pronounced in parthenotes than in embryos, which may differ in their way to channel apoptotic stimuli, through p66(shc) and p53 respectively, and in their mechanisms to control pluripotency and de novo methylation.

Parthenogenesis-derived multipotent stem cells adapted for tissue engineering applications

Embryonic stem cells are envisioned as a viable source of pluripotent cells for use in regenerative medicine applications when donor tissue is not available. However, most current harvest techniques for embryonic stem cells require the destruction of embryos, which has led to significant political and ethical limitations on their usage. Parthenogenesis, the process by which an egg can develop into an embryo in the absence of sperm, may be a potential source of embryonic stem cells that may avoid some of the political and ethical concerns surrounding embryonic stem cells. Here we provide the technical aspects of embryonic stem cell isolation and expansion from the parthenogenetic activation of oocytes. These cells were characterized for their stem-cell properties. In addition, these cells were induced to differentiate to the myogenic, osteogenic, adipogenic, and endothelial lineages, and were able to form muscle-like and bony-like tissue in vivo. Furthermore, parthenogenetic stem cells were able to integrate into injured muscle tissue. Together, these results demonstrate that parthenogenetic stem cells can be successfully isolated and utilized for various tissue engineering applications.

Parthenogenesis as an approach to pluripotency: advantages and limitations involved

Embryonic stem cells (ESCs) are invaluable cells derived from the inner cell mass of the mammalian blastocyst. They have nearly indefinite self-renewal, retain their developmental potential after prolonged periods in culture and display great plasticity that allow them to differentiate into all cell types of the body. They provide exciting opportunities to develop unique models for developmental research and hold great potential for cell and tissue replacement therapy. However, these unique cells cannot be obtained without destroying an embryo and, despite the potential therapeutic usefulness, their derivation in the human raises substantial ethical as well as legal and political concerns because it unavoidably involves the destruction of viable embryos. In the recent years a number of scientific proposals that do not require the generation and subsequent destruction of human embryos have been put forward in an attempt to fill the gap between ethical questions and potential scientific and medical benefits. In this review we briefly summarize data obtained from the literature related to these different alternative approaches and focus in more details on our experience in the derivation of parthenothes, as a possible alternative source for pluripotent cells, discussing the advantages as well as the limits of these cell lines.

Parthenotes as a source of embryonic stem cells

The derivation and study of human embryonic stem cell lines, despite their potential therapeutic usefulness, raise considerable ethical, religious, legal and political concerns because it inevitably leads to the destruction of viable embryos. In an attempt to bridge the division between ethical questions and potential scientific and medical benefits, considerable efforts have been devoted to the search for alternative sources of pluripotent cell lines. In this review we discuss the use of artificial parthenogenesis as a way to create entities, called parthenotes, that may represent an alternative ethical source for pluripotent cell lines. We describe the biological differences between parthenotes and embryos, in order to provide a rationale for the discussion on whether their use can be acceptable as a source of stem cells. We present data derived from animal models on the extent parthenogenetic stem cells are similar to biparental cell lines and discuss these aspects in the context of their extension to the human species. Finally, we present experiments recently carried out in our laboratory that allowed us to generate human parthenotes through artificial activation of human oocytes and to use them as a source for the derivation of parthenogenetic pluripotent cell lines.

Effects of activation methods and culture conditions on development of parthenogenetic porcine embryos

The effects of different activation methods and culture conditions on early development of porcine parthenotes were examined. Three different activation methods were tested: (1) electroporation; (2) electroporation followed by incubation in the presence of butyrolactone I, an inhibitor of cdc2 and cdk2 kinases; and (3) electroporation followed by a treatment with cycloheximide, a blocker of protein synthesis. The activated oocytes were cultured in two different media, NCSU-23 and PZM-3 under 5% CO2 in air. In a separate experiment, the effects of high (approximately 20%) or low (5%) O2 tension on early embryo development were also evaluated. The average pronuclear formation was less (p<0.05) in the electroporated oocytes (83.9+/-1.7%) compared with those activated by electroporation and butyrolactone I or electroporation plus cycloheximide (92.8+/-0.8 and 93.0+/-1.0%). In PZM-3 medium, the average frequencies of blastocyst formation (59.7+/-3.6%) and hatching (10.6+/-1.3%) were greater than those in NCSU-23 medium (39.9+/-3.1% blastocyst formation, p<0.05; and 0.2+/-0.2% hatching; p<0.001). Furthermore, the average nuclear number was also greater (p<0.001) in blastocysts developed in PZM-3 (50.2+/-1.3) than in those developed in NCSU-23 (35.3+/-1.1). Blastocyst formation was similar (p>0.10) among the three activation procedures when parthenotes were cultured in NCSU-23, while in PZM-3 more (p<0.05) parthenotes produced by electroporation plus butyrolactone or electroporation plus cycloheximide developed into blastocysts compared to electroporation alone (64.9+/-5.2 and 68.6+/-3.5% compared with 45.6+/-4.7%). Incidences of apoptotic nuclei were similar (p>0.10) among all treatments. No difference in development was found between parthenotes that developed under high versus low O2 tension (p>0.10). These results demonstrate that activation methods targeting the calcium signaling pathway at several points trigger embryonic development more efficiently than electroporation alone. The data also imply that the PZM-3 medium provides for enhanced culture conditions for the early development of parthenogenetic porcine embryos than NCSU-23.

Diploid porcine parthenotes produced by inhibition of first polar body extrusion during in vitro maturation of follicular oocytes

We investigated nuclear progression andin vitroembryonic development after parthenogenetic activation of porcine oocytes exposed to cytochalasin B (CB) duringin vitromaturation (IVM). Nuclear progression was similar in control oocytes and oocytes matured in the presence of 1 μg/ml CB (IVM-CB group) by 37 h IVM; at this time the proportion of oocytes that had reached or passed through the anaphase-I stage did not differ significantly between the IVM-CB and the control groups (61.3 and 69.9% respectively;P< 0.05). After IVM for 37 h, no polar body extrusion was observed in the IVM-CB group. In these oocytes, the two lumps of homologous chromosomes remained in the ooplasm after their segregation and turned into two irregular sets of condensed chromosomes. By 41 h IVM, the double sets of chromosomes had reunited in 89.5% IVM-CB oocytes and formed a single large metaphase plate, whereas 68.8% of the control oocytes had reached the metaphase-II stage by this time. When IVM-CB oocytes cultured for 46 h were stimulated with an electrical pulse and subsequently cultured for 8 h without CB, 39.0% of them extruded a polar body and 82.9% of them had a female pronucleus. Chromosome analysis revealed that the majority of oocytes that extruded a polar body were diploid in both the control and the IVM-CB groups. However, the incidence of polyploidy in the IVM-CB group was higher than that in the control group (P< 0.05).In vitrodevelopment of diploid parthenotes in the control and the IVM-CB groups was similar in terms of blastocyst formation rates (45.8 and 42.8% respectively), number of blastomeres (39.9 and 44.4 respectively), the percentage of dead cells (4.3 and 2.9% respectively), and the frequency of apoptotic cells (7.3 and 6.3% respectively). Tetraploid embryos had a lower blastocyst formation rate (25.5%) and number of cells (26.2); however, the proportion of apoptotic nuclei (7.0%) was similar to that in diploid parthenotes. These results suggest that the proportion of homozygous and heterozygous genes does not affectin vitroembryo development to the blastocyst stage.

Isolation and characterization of a bovine visceral endoderm cell line derived from a parthenogenetic blastocyst

A cell line, BPE-1, was derived from a parthenogenetic 8-d in vitro-produced bovine blastocyst that produced a cell outgrowth on STO feeder cells. The BPE-1 cells resembled visceral endoderm previously cultured from blastocysts produced by in vitro fertilization (IVF). Analysis of the BPE-1 cells demonstrated that they produced serum proteins and were negative for interferon-tau production (a marker of trophectoderm). Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complex junctions resembling tight junctions in conjunction with desmosomes. Rough endoplasmic reticulum was prominent within the cells as were lipid vacuoles. Immunocytochemistry indicated the BPE-1 cells had robust microtubule networks. These cells have been grown for over 2 yr for multiple passages at 1:10 or 1:20 split ratios on STO feeder cells. The BPE-1 cell line presumably arose from embryonic cells that became diploid soon after parthenogenetic activation and development of the early embryo. However, metaphase spreads prepared at passage 41 indicated that the cell population had a hypodiploid (2n = 60) unimodal chromosome content with a mode of 53 and a median and mean of 52. The cell line will be of interest for functional comparisons with bovine endoderm cell lines derived from IVF and nuclear transfer embryos.

Isolation and characterization of a bovine trophectoderm cell line derived from a parthenogenetic blastocyst

A bovine trophectoderm cell line was established from a parthenogenetic in vitro-produced blastocyst. To initiate the cell line, 8-day parthenogenetic blastocysts were attached to a feeder layer of STO fibroblasts and primary outgrowths occurred that consisted of trophectoderm, endoderm, and very occasionally epiblast tissue. Any endoderm and epiblast outgrowths were removed from the primary cultures within the first 10 days of culture by dissection. One of the primary trophectoderm cell cultures was chosen for further propagation and was passaged by physical dissociation and replating on STO feeder cells. The cell culture, designated BPT-1, was maintained in T25 flasks and passaged at a 1:3 split ratio for the first 15 passages approximately once every 2 weeks. Thereafter, the cell culture was passaged at 1:10-1:40 split ratios. Transmission electron microscopic examination showed the cells to be a polarized epithelium with apical microvilli, a thin basal lamina, and lateral junctions consisting of tight junctions and desmosomes. Lipid vacuoles and digestive vacuoles were also prominent features of the BPT-1 cells. Metaphase spread analysis at passage 59 indicated a near diploid cell population (2n = 60) with a mode and median of 60 and a mean of 64. BPT-1 cells secreted interferon-tau into the medium as measured by anti-viral assay and Western blot analysis. The cell line provides an in vitro model of parthenogenote trophectoderm whose biological characteristics can be compared to trophectoderm cell lines derived from bovine embryos produced by normal fertilization or nuclear transfer.

Analysis of mRNA Transcripts for Insulin-Like Growth Factor Receptors and Binding Proteins in Bovine Embryos Derived from Somatic Cell Nuclear Transfer

The low efficiency of animal production using somatic cell nuclear transfer procedures is considered to be the result of an incomplete reprogramming of donor cell nucleus, which leads to abnormal expression of developmentally important genes. The objective of this study was to determine the abundance of gene transcripts of insulin-like growth factor (IGF)-related genes in cloned bovine embryos reconstructed with somatic cells. Single embryos derived from nuclear transfer reconstructed with somatic cells (NT-SC) or embryo blastomeres (NTEM), in vitro fertilization (IVF), in vivo production (Vivo), and parthenogenetic treatment (PA) were analyzed. The relative abundance of mRNA was examined by real-time PCR. Transcripts of the IGF-1 receptor (r) and IGF binding protein (BP)-2 were detected in all embryos, regardless of origin. IGF-IIr and IGFBP-3 transcripts signals in NT-SC embryos were detected with significantly lower frequencies of 25 and 50%, respectively. Although IGF-Ir and IGFIIr transcript levels were not significantly different in NT-SC, NT-EM, IVF, Vivo, and PA embryos, the relative abundance in individual embryos indicated large variation in NT-SC. IGFBP-2 and IGFBP-3 levels were high in the Vivo embryos compared with NT-SC, NT-EM, IVF, or PA embryos. These results suggest differences in levels of transcripts of IGF-related genes in the bovine embryos produced by NT compared with IVF, Vivo, and PA.

Parthenogenetic development of porcine oocytes treated by ethanol, cycloheximide, cytochalasin B and 6-dimethylaminopurine

This study was carried out to investigate the various concentrations and exposure times of ethanol, one of many intracellular calcium elevating agents, and a sequential combination of ethanol (8%), cycloheximide (CHX, 10 microg/ml), cytochalasin B (CCB, 7.5 microg/ml) and 6-dimethylaminopurine (6-DMAP, 2 mM) to improve parthenogenetic activation and development of in vitro matured porcine oocytes. Cumulus-oocyte complexes (COCs) were matured in tissue culture medium (TCM) 199 for 44 h at 38.5 degrees C, 5% CO2 in air. Cumulus-free oocytes showing first polar body were activated by concentrations of 0, 5, 6, 7, 8, 9 and 10% ethanol for 10 min and exposure times of 0, 5, 8, 10, 12 and 15 min with 8% ethanol in HEPES buffered (25 mM) NCSU-23 medium. Also, oocytes were activated with the NCSU-23 medium containing 8% ethanol for 10 min. After that, oocytes were incubated in the NCSU-23 medium supplemented with CHX, CCB, 6-DMAP, CHX + CCB, CHX + 6-DMAP, CCB + 6-DMAP and CHX + CCB + 6-DMAP for 3h, respectively. Following activation, oocytes were transferred into the NCSU-23 medium containing 0.4% BSA for further culture of 20 and 144 h at 38.5 degrees C, 5% CO2 in air. The activation rates of oocytes were higher in 6, 7 and 8% ethanol concentrations compared with 0, 5, 9 and 10% ethanol concentrations. Significantly, more oocytes (29.3-33.7%) were activated in the exposure for 8, 10, 12 and 15 min than those in the exposure for 0 and 5 min, but there was no difference due to exposure to 8% ethanol for 8-15 min. Oocytes treated by chemical agents (40.5-70.5%) after exposure to ethanol significantly improved the rate of oocyte activation compared with ethanol alone (31.2%). The percentage of cleaved oocytes was higher in the ethanol+CHX+CCB+6-DMAP treatment (66.4%) than in other treatments (24.9-57.6%). Also, the rate of blastocyst formation was higher in the ethanol+CHX+CCB+6-DMAP treatment (25.0%) than in other treatments (0.0-19.3%). In conclusion, the optimal activation treatment of ethanol exposure alone for the in vitro matured porcine oocytes was 8% ethanol for 8-15 min. Oocytes activated by 8% ethanol for 10 min and incubated in the NCSU-23 medium supplemented with CHX, CCB and 6-DMAP for 3 h were more efficient for parthenogenetic development of in vitro matured porcine oocytes.