Efficiency of Two Enucleation Methods Connected to Handmade Cloning to Produce Transgenic Porcine Embryos

Vitamin C Protects Porcine Oocytes From Microcystin-LR Toxicity During Maturation

Microcystin-leucine arginine (MC-LR) is the most toxic cyanotoxin found in water bodies. Microcystins are produced as secondary products of cyanobacteria metabolism. They have a stable structure, and can bioaccumulate in living organisms. Humans and livestock who drink fresh water containing MC-LR can be poisoned. However, few studies have reported the effects of MC-LR exposure on livestock or human reproduction. In this study, we used porcine oocytes as a model to explore the effects of MC-LR on oocyte maturation, and studied the impact of vitamin C (VC) administration on MC-LR-induced meiosis defects. Exposure to MC-LR significantly restricted cumulus cell expansion and decreased first polar body extrusion. Further studies showed that MC-LR exposure led to meiosis arrest by disturbing cytoskeleton dynamics with MC-LR exposed oocytes displaying aberrant spindle organization, low levels of acetylate α-tubulin, and disturbed actin polymerization. Additionally, MC-LR exposure impaired cytoplasmic maturation by inducing mitochondria dysfunction. Moreover, MC-LR also produced abnormal epigenetic modifications, and induced high levels of oxidative stress, caused DNA damage and early apoptosis. The administration of VC provided partial protection from all of the defects observed in oocytes exposed to MC-LR. These results demonstrate that MC-LR has a toxic effect on oocyte meiosis through mitochondrial dysfunction-induced ROS, DNA damage and early apoptosis. Supplementation of VC is able to protect against MC-LR-induced oocyte damage and represents a potential therapeutic strategy to improve the quality of MC-LR-exposed oocytes.

The Effect of L-Carnitine Additive During In Vitro Maturation on the Vitrification of Pig Oocytes

Cryopreservation of oocytes/embryos is an important technique for genetic resources; however, the success of vitrification in pig oocytes remained at a relatively lower level due to the high content of lipid droplets (LDs). Considering the positive effect of L-carnitine on the function of LDs, the present study was designed to investigate the effect of the addition of L-carnitine on the vitrification of porcine cumulus cells of complexes (cumulus/oocyte complexes [COCs]). First, COCs were randomly divided into two groups: one group of COCs were commonly in vitro maturation (IVM) for 42-46 hours (nonvitrification [NV]), while another group of COCs were IVM with 10 mM L-carnitine (NVL [nonvitrification with L-carnitine addition in IVM]). In addition, random parts of COCs with L-carnitine addition were vitrified (VL [vitrification with L-carnitine addition in IVM]), while vitrification was performed on COCs without L-carnitine used as control group (V). Results showed that the maturation rate of pig oocytes reduced significantly when the vitrification was performed at 16 hours during IVM (VL vs. NVL, 40.09 ± 2.85 vs. 90.76 ± 1.16; V vs. NV, 34.41 ± 2.55 vs. 89.71 ± 1.33, p < 0.01). With the addition of L-carnitine, intracellular LDs were decreased significantly (p < 0.01). However, no difference was observed on the efficiency of vitrification in pig oocytes (VL vs. V, 40.09 ± 2.85 vs. 34.41 ± 2.55, p > 0.05). In addition, not only the reactive oxygen species (ROS) level in pig oocytes with the L-carnitine addition group reduced significantly (p < 0.01), but also the expression of SOD1 gene was improved (p < 0.05). In conclusion, results demonstrated that although no difference could be observed on pig COC vitrification, the LDs and ROS level in pig oocytes could be modified by the addition of L-carnitine, which might be helpful for further development.

Homocysteine impairs porcine oocyte quality via deregulation of one-carbon metabolism and hypermethylation of mitochondrial DNA†

Homocysteine (Hcy) is an intermediate in the one-carbon metabolism that donates methyl groups for methylation processes involved in epigenetic gene regulation. Although poor oocyte quality in polycystic ovarian syndrome (PCOS) patients is associated with elevated Hcy concentration in serum and follicular fluid, whether Hcy directly affects oocyte quality and its mechanisms are poorly understood. Here we show that Hcy treatment impaired oocyte quality and developmental competence, indicated by significantly reduced survival rate, polar body extrusion rate, and cleavage rate. Hcy treatment resulted in mitochondrial dysfunction, with increased production of mitochondrial ROS, reduced mtDNA copy number, and the expression of 7 out of 13 mtDNA-encoded genes and 2 ribosome RNA genes, 12S rRNA and 16S rRNA. Upon Hcy treatment, the expression of one-carbon metabolic enzymes and DNMT1 was enhanced. Interestingly, DNA methyltransferase inhibitor 5'AZA rescued Hcy-induced mitochondrial dysfunction, impaired oocyte quality and developmental competence. Concurrently, expression of one-carbon metabolic enzymes and methylation status of mtDNA coding sequences were also normalized, at least partially, by 5'AZA treatment. Our findings not only extend the understanding about how Hcy induces poor oocyte quality, but also contribute to a novel angle of identifying targets for enhancing the quality of oocyte from PCOS patients.

Improved functional oocyte enucleation by actinomycin D for bovine somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) allows animal cloning but remains technically challenging. This study investigated limitations to functional oocyte enucleation by actinomycin D (AD) as a means of making SCNT easier to perform. Denuding oocytes or inhibiting transcription before AD treatment revealed that the toxicity of this compound during bovine oocyte maturation is mediated by cumulus cells. Exposure of denuded oocytes to higher concentrations of AD (5-20μgmL-1 ) and stepwise reductions of the incubation period (from 14.0 to 0.25h) led to complete inhibition of parthenogenetic development. Bovine SCNT using this improved AD enucleation protocol (NT(AD)) restored cleavage rates compared with rates in the parthenogenetic and SCNT controls (P(CTL) and NT(CTL) respectively). However, NT(AD) was associated with increased caspase-3 activity in cleavage stage embryos and did not recover blastocyst rates. The removal of AD-treated oocyte spindle before reconstruction (NT(AD+SR)) improved embryo development and reduced caspase-3 activity to levels similar to those in the P(CTL) and NT(CTL) groups. Furthermore, mid-term pregnancies were achieved using NT(AD+SR) blastocysts. In conclusion, improvements in AD functional enucleation for bovine SCNT circumvents most cellular roadblocks to early embryonic development and future investigations must focus on restoring blastocyst formation.

Heat stress induces distinct responses in porcine cumulus cells and oocytes associated with disrupted gap junction and trans-zonal projection colocalization

Cumulus cells (CCs), the granulosa cells surrounding the oocytes, play critical roles in oocytes maturation through intercellular communication by extending trans-zonal projections (TZPs) to contact oocytes via gap junctions (GJs). The adverse effect of heat stress (HS) on oocyte maturation has been well documented, whereas the HS responses of CCs and the oocytes in association with GJ/TZP colocalization remain unclear. In this study, porcine cumulus-oocyte complexes (COCs) were subjected to HS at 41.5°C for 24 hr during in vitro maturation. Cumulus expansion was impaired and oocyte quality was reduced with lower survival rate, polar body extrusion rate, and early embryo developmental potentials. CCs and oocytes isolated from COCs demonstrated distinct responses to HS. The messenger RNA abundance of heat shock protein-related genes and mitochondrial DNA-encoded genes, together with ATP content, were significantly increased in CCs, yet decreased in oocytes, despite activation of caspase 3 detected in both CCs and oocytes. Similar changes were observed when denuded oocytes and isolated CCs subjected to HS separately, except mitochondria reactive oxygen species (mROS). In heat-stressed COCs, mROS was significantly increased only in oocytes. However, when isolated CCs and denuded oocytes were heat-stressed separately, mROS was significantly increased only in CCs. Moreover, F-actin, a TZP marker, and its colocalization with a GJ protein connexin-45, were significantly reduced in heat-exposed COCs. These results indicate that HS induces distinct responses in porcine CCs and oocytes in association with disrupted GJ and TZP colocalization.

LC3-Dependent Autophagy in Pig 2-Cell Cloned Embryos Could Influence the Degradation of Maternal mRNA and the Regulation of Epigenetic Modification

In this study, the distribution as well as the effect of autophagy on reprogramming in pig cloned embryos were observed immediately after somatic cell nuclear transfer. Results showed that the LC3 was at the highest level in cloned embryos at 2-cell stage, and it decreased with the development from 2-cell stage to blastocyst. Different to cloned embryos, the intensity of LC3 in parthenogenetic activation (PA) embryos was at the highest level at 4-cell stage. A markedly higher level of Bmp15, H1foo, and Dppa3 was shown in cloned embryos at 2-cell stage (p < 0.05 or p < 0.01), but a significantly lower level of LC3, Sox2, and eIF1A was observed at 4-cell stage (p < 0.05), compared with PA embryos. When the efficient interfering by the LC3 siRNA was performed on the cloned embryos (p < 0.01), not only the mRNA level of maternal Cyclin B, Bmp15, Gdf9, c-mos, H1foo, and Dppa3 was increased significantly (p < 0.05), but also the expression of Dnmt1 and Dnmt3b was obviously upregulated (p < 0.05). Although the expression of Sox2 and Oct4 is not changed, the expression of Stat3 decreased significantly (p < 0.05). Furthermore with the treatment of 200 nM rapamycin, the expression of eIF1A and Stat3 was significantly increased at 4-cell stage. In conclusion, the LC3-dependent autophagy mainly occurred in cloned embryos at 2-cell stage, but at 4-cell stage in PA embryos. In addition, the modulation of autophagy could affect genome activation by influencing the degradation of maternal mRNA and regulating the expression of DNA methyltransferase.

Dynamic Reorganization of Nucleosome Positioning in Somatic Cells after Transfer into Porcine Enucleated Oocytes

The nucleosome, the fundamental structural unit of chromatin, is a critical regulator of gene expression. The mechanisms governing changes to nucleosome occupancy and positioning during somatic cell reprogramming remain poorly understood. We established a method for generating genome-wide nucleosome maps of porcine embryonic fibroblasts (PEF), reconstructed 1-cell embryos generated by somatic cell nuclear transfer (SCNT), and fertilized zygotes (FZ) using MNase sequencing with only 1,000 cells. We found that donor PEF chromatin, especially X chromosome, became more open after transfer into porcine oocytes and nucleosome occupancy decreased in promoters but increased in the genic regions. Nucleosome arrangements around transcriptional start sites of genes with different expression levels in somatic cells tended to become transcriptionally silent in SCNT; however, some pluripotency genes adopted transcriptionally active nucleosome arrangements. FZ and SCNT had similar characteristics, unlike PEF. This study reveals the dynamics and importance of nucleosome positioning and chromatin organization early after reprogramming.

The influence of delipidation on triglyceride and LIPIN1 of porcine embryos derived from parthenogenetic activation

Proteins in the LIPIN family play key roles in lipid synthesis mainly on triacylglycerol (TAG) biosynthesis, and they also act as transcriptional coactivators to regulate the expression of genes involved in lipid metabolism with other nuclear factors. Hence, this study was designed to investigate LIPIN1 in pig oocytes and embryos by the delipidation. After delipidation, the content of lipids (LDs) and TAG in MII oocyte was significantly reduced; however, a similar increasing tendency of TAG was shown during embryos development. Subsequently, the expression of genes related to TAG biosynthesis including GPAT1, AGPAT1, AGPAT2, LIPIN1, DGAT and the nuclear factors interacted with LIPIN1 including PPARα and PPARγ was investigated. It is obvious that DGAT and GPAT1, and LIPIN1 increased significantly after delipidation at 1-cell and 4-cell stage, and the expression of PPARα and PPARγ also increased at 4-cell stage. By immunofluorescence staining and Western blots, LIPIN1 was found to exhibit a dynamic localization pattern and gradually increase with the development of delipated embryo. In the early developmental stages (1-, 2- and 4-cell stages), it was distributed over the cortical layer. But at the blastocyst stage, a homogeneous distribution of LIPIN1 was observed in cytoplasm. At 2-cell stage, the expression of PPARα decreased when LIPIN1 was interfered by small interfering RNA, but PPARγ has no significant difference. Therefore, in this study, we find after delipidation, the content of TAG and LIPIN1 will gradually increase during embryo development and nuclear factor PPARα and PPARγ can also be affected by delipidation. The interaction of LIPIN1 and PPARα exists in porcine embryo.

Abnormally activated one-carbon metabolic pathway is associated with mtDNA hypermethylation and mitochondrial malfunction in the oocytes of polycystic gilt ovaries

Polycystic ovarian syndrome (PCOS) is associated with hyperhomocysteinemia and polycystic ovaries (PCO) usually produce oocytes of poor quality. However, the intracellular mechanism linking hyperhomocysteinemia and oocyte quality remains elusive. In this study, the quality of the oocytes isolated from healthy and polycystic gilt ovaries was evaluated in vitro in association with one-carbon metabolism, mitochondrial DNA (mtDNA) methylation, and mitochondrial function. PCO oocytes demonstrated impaired polar body extrusion, and significantly decreased cleavage and blastocyst rates. The mitochondrial distribution was disrupted in PCO oocytes, together with decreased mitochondrial membrane potential and deformed mitochondrial structure. The mtDNA copy number and the expression of mtDNA-encoded genes were significantly lower in PCO oocytes. Homocysteine concentration in follicular fluid was significantly higher in PCO group, which was associated with significantly up-regulated one-carbon metabolic enzymes betaine homocysteine methyltransferase (BHMT), glycine N-methyltransferase (GNMT) and the DNA methyltransferase DNMT1. Moreover, mtDNA sequences coding for 12S, 16S rRNA and ND4, as well as the D-loop region were significantly hypermethylated in PCO oocytes. These results indicate that an abnormal activation of one-carbon metabolism and hypermethylation of mtDNA may contribute, largely, to the mitochondrial malfunction and decreased quality of PCO-derived oocytes in gilts.

Handmade cloning: recent advances, potential and pitfalls

Handmade cloning (HMC) is the most awaited, simple and micromanipulator-free version of somatic cell nuclear transfer (SCNT). The requirement of expensive micromanipulators and skilled expertise is eliminated in this technique, proving it as a major revolution in the field of embryology. During the past years, many modifications have been incorporated in this technique to boost its efficiency. This alternative approach to micromanipulator based traditional cloning (TC) works wonder in generating comparable or even higher birth rates in addition to declining costs drastically and enabling cryopreservation. This technique is not only applicable to intraspecies nuclear transfer but also to interspecies nuclear transfer (iSCNT) thus permitting conservation of endangered species. It also offers unique possibilities for automation of SCNT which aims at production of transgenic animals that can cure certain human diseases by producing therapeutics hence, providing a healthier future for the wellbeing of humans. The present review aims at highlighting certain aspects of HMC including recent advancements in procedure and factors involved in elevating its efficiency besides covering the potentials and pitfalls of this technique.

Influence of Delipation on the Energy Metabolism in Pig Parthenogenetically Activated Embryos

This study was designed not only to measure the effect of delipation on the developmental viability of pig parthenogenetically activated (PA) embryos, but also to evaluate the changes of mitochondria DNA (mtDNA), reactive oxygen species (ROS) level, adenosine triphosphate (ATP) content and gene (Acsl3, Acadsb, Acaa2, Glut1) expression level at different stages after delipation. Results showed that no effect was observed on the cleavage ability, but significant lower blastocyst rate was obtained in delipated embryos. Copy number of mtDNA decreased gradually from MII to four-cell stages and subsequently kept consistent with blastocyst stage both in delipated and control embryos, but the copy number of mtDNA in delipated embryos was similar to that in the control groups no matter at which developmental stage was observed. Both in delipated and control embryos, ATP content progressive decreased from one-cell to blastocyst stages, while just at one-cell stage, a significant decrease of ATP level was observed in delipated embryos compared with that of control. The level of ROS increased obviously after delipation at cleavage stage, but no difference was seen at blastocyst stage. Finally, the expression level of genes related to fatty acids beta-oxidation (Acadsb and Acaa2) was decreased, while the expression level of genes related to glucose metabolism (Glut 1) was upregulated after delipation. In conclusion, the reduction of lipids in pig oocytes will affect the developmental competence of pig PA embryos by disturbed energy metabolism and ROS stress.

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.

Distribution and content of lipid droplets and mitochondria in pig parthenogenetically activated embryos after delipation

The present study examines the effect of delipation on developmental competence and the distribution pattern of lipid droplets (LDs) and mitochondria in parthenogenetically activated (PA) pig embryos. Mature oocytes were delipated by centrifugation after partial digestion of the zonae pellucidae, subjected to parthenogenetic activation after total removal of zonae pellucidae by pronase, and then cultured in vitro up to the blastocyst stage. The contents and distributions of LDs and mitochondria in the oocytes and/or embryos were observed by staining with Oil Red O and MitoTracker Red CMXRos, respectively. The LD and mitochondrial contents were significantly reduced by the delipation process, and only smaller LDs remained in the delipated oocytes and/or embryos. Their content remained constant from the metaphase II oocyte to the blastocyst stage, but they became gradually smaller as the oocytes and/or embryos developed. The distribution pattern of the LDs in the delipated embryos changed over time and in a manner different to that seen in the controls. In the early developmental stages (1- to 4-cell stages), they were distributed peripherally and formed a ring around the nucleus. However, by the blastocyst stage, a homogeneous distribution of LDs was observed in both the inner cell mass and trophectoderm. The distribution pattern of mitochondria also changed with the development of the delipated PA embryos and again, in ways different to those seen in the controls. In the early 1- to 4-cell stages, a peripheral distribution of mitochondrial foci was observed in each blastomere. However, in blastocysts, the mitochondria were homogeneously distributed throughout the inner cell mass and trophectoderm. Although the cleavage rate at the 2- and 4-cell stages of the PA embryos was not affected by delipation (95.83 ± 2.25% vs. 97.44 ± 0.67%; 79.17 ± 4.47% vs. 84.62 ± 1.19%), it was reduced significantly in the blastocyst compared with the controls (21.67 ± 3.78% vs. 49.36 ± 1.77%). The distribution pattern of the LDs in oocytes and/or embryos at different developmental stages, and that of the mitochondria in metaphase II oocytes, was affected by delipation. The developmental competence of porcine PA embryos would appear to be affected by delipation.

Developmental potential and kinetics of pig embryos with different cytoplasmic volume

The effects of cytoplasmic volumes on development and developmental kinetics of in vitro produced porcine embryos were investigated. During hand-made cloning (HMC), selected cytoplasts were separated into two groups according to their size in relation to the initial oocyte: ~75% or ~50%. Following two fusion steps and activation (day 0), reconstructed embryos were cultured in vitro for 6 days. Cleavage rates on day 2 as well as blastocyst rates and cell numbers on day 6 were recorded. Results showed that embryo development was no different for ~50% versus ~75% cytoplasm at first fusion. This result was used in the following experiments, where the effect of varying cytoplasm volume in second fusion to obtain a final cytoplasm volume of ~75% to ~200% was tested. The results showed that the lowest quality was obtained when the final cytoplasm volume was ~75% and the highest quality at ~200% of the original oocyte. Similar results were observed in parthenogenetic (PA) embryos activated with different cytoplasmic volumes. A common pattern for the developmental kinetics of HMC and PA embryos was observed: the smaller group tended to have a longer time for the first two cell cycles, but subsequently a shorter time to form morula and blastocyst. In conclusion, the developmental kinetics of in vitro produced embryos was affected by the cytoplasm volume of the initial oocyte, and this further accounted for the developmental ability of the reconstructed embryos.

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.

Developmental kinetics of pig embryos by parthenogenetic activation or by handmade cloning

The developmental kinetics of pig embryos produced by parthenogenetic activation without (PAZF) or with (PAZI) zona pellucida or by handmade cloning (HMC) was compared by time-lapse videography. After cumulus cell removal, the matured oocytes were either left zona intact (PAZI) or were made zona free by pronase digestion (PAZF) before they were activated (PA). Other matured oocytes were used for HMC based on foetal fibroblast cells. On Day 0 (day of PA or reconstruction), the embryos were cultured for 7 days in vitro in our time-lapse system. Pictures were taken every 30 min, and afterwards, each cell cycle was identified for each embryo to be analysed. Results showed that the PA embryos (both PAZF and PAZI) had shorter first cell cycle compared with HMC (17.4. 17.8 vs 23.6 h), but had a longer time length from four cell to morula stages (57.9, 53.8 vs 44.9 h). However, at the second cell cycle, PAZF embryos needed shorter time, while PAZI embryos had similar time length as HMC embryos, and both were longer than PAZF (23.4, 24.8 vs 14.6 h). Both PAZF and PAZI embryos used similar time to reach the blastocyst stage, and this was later than HMC embryos. In addition, when all of these embryos were grouped into viable (developed to blastocysts) and non-viable (not developed to blastocysts), the only difference in the time length was observed on the first cell cycle (18.6 vs 24.5 h), but not on the later cell cycles. In conclusion, our results not only give detailed information regarding the time schedule of in vitro-handled pig embryos, but also indicate that the first cell cycle could be used as a selecting marker for embryo viability. However, to evaluate the effect of the produced techniques, the whole time schedule of the pre-implantation developmental kinetics should be observed.

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

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

Generation of SV40-transformed rabbit tracheal-epithelial-cell-derived blastocyst by somatic cell nuclear transfer

The prospect of developing large animal models for the study of inherited diseases, such as cystic fibrosis (CF), through somatic cell nuclear transfer (SCNT) has opened up new opportunities for enhancing our understanding of disease pathology and for identifying new therapies. Thus, the development of species-specific in vitro cell systems that will provide broader insight into organ- and cell-type-specific functions relevant to the pathology of the disease is crucial. Studies have been undertaken to establish transformed rabbit airway epithelial cell lines that display differentiated features characteristic of the primary airway epithelium. This study describes the successful establishment and characterization of two SV40-transformed rabbit tracheal epithelial cell lines. These cell lines, 5RTEo- and 9RTEo-, express the CF transmembrane conductance regulator (CFTR) gene, retain epithelial-specific differentiated morphology and show CFTR-based cAMP-dependent Cl(-) ion transport across the apical membrane of a confluent monolayer. Immunocytochemical analysis indicates the presence of airway cytokeratins and tight-junction proteins in the 9RTEo- cell line after multiple generations. However, the tight junctions appear to diminish in their efficacy in both cell lines after at  least 100 generations. Initial SCNT studies with the 9RTEo- cells have revealed that SV40-transformed rabbit airway epithelial donor cells can be used to generate blastocysts. These cell systems provide valuable models for studying the developmental and metabolic modulation of CFTR gene expression and rabbit airway epithelial cell biology.

Short-term treatment with 6-DMAP and demecolcine improves developmental competence of electrically or Thi/DTT-activated porcine parthenogenetic embryos

Treatment with 6-dimethylaminopurine (6-DMAP) or demecolcine (DE) for several (at least 2) hours after artificial activation is known to improvein vitrodevelopment of porcine embryos. However, several reports have also shown that treatments with these chemicals induce apoptosis. The aim of this study was to find out whether short-term treatment with 6-DMAP and DE combined with electrical or thimerosal/dithiothreitol (Thi/DTT) activation had a beneficial effect on development of parthenogenetically activated porcine oocytes. We additionally treated embryos with 6-DMAP (2 mM) and/or DE (0.4 μg/ml) for a short time (40 min) after an electrical pulse (EP) or Thi/DTT. As a result, short-term treatment with 6-DMAP and DE successfully induced development of electrically or Thi/DTT-activated porcine parthenogenetic embryos with no significant difference in cleavage rate, blastocyst formation rate and total cell number compared with long-term treatment. To find optimal activation protocol, cleavage rate, blastocyst formation rate and total cell number were compared between EP and Thi/DTT treatments. Thi/DTT + 6-DMAP + DE showed significantly higher blastocyst formation rate (36.1 ± 3.5%) and total cell number (46.9 ± 1.0) than other groups (EP + 6-DMAP + DE, EP + Thi/DTT + 6-DMAP + DE: 23.3 ± 3.0%, 42.2 ± 1.1 and 17.2 ± 2.7%, 36.7 ± 1.5, respectively). In conclusion, this study demonstrates that short-term treatment with 6-DMAP and DE is as effective as the standard long-term treatment and Thi/DTT + 6-DMAP + DE exerts a synergistic effect.