Effects of duration, concentration, and timing of ionomycin and 6-dimethylaminopurine (6-DMAP) treatment on activation of goat oocytes

Alpha-linolenic acid alleviates the detrimental effects of lipopolysaccharide during in vitro ovine oocyte development

During the transition period and early lactation of ruminants with higher production, the reproductive organs are exposed to various stressors, like inflammation stimulators such as lipopolysaccharides (LPS), as a consequence of high concentrate consumption. In this study, we aimed to determine the probable potential of α-linolenic acid (ALA) in alleviating LPS-induced effects in ovine oocytes in vitro as well as the underlying controlling mechanisms. Different concentrations of LPS (0, 0.01, 0.1, 1, and 10 μg/mL) were added to the oocyte maturation medium to evaluate its effect on oocyte developmental competence. Likewise, different concentrations of ALA (0, 10, 50, 100, and 200 μM/mL) were added to the maturation medium to define its effects on oocyte developmental competence. Accordingly, a combination of ALA and LPS in a dose-dependent manner was added to the maturation medium to elucidate their effect on oocyte developmental competence and uncover any possible potential of ALA to alleviate the detrimental effect induced by the presence of LPS. The expressions of candidate genes were measured in mature oocytes treated either with ALA, LPS, or ALA plus LPS. Adding LPS to the maturation medium decreased the cleavage rate of the treated oocytes, and those oocytes reached the blastocyst stage at a lower rate. Adding ALA to the maturation medium in the presence of LPS alleviated the detrimental effects of LPS in a dose-dependent manner, which ultimately led to higher cleavage and blastocyst formation. A higher expression of Trim26, GRHPR, NDUFA, PGC-1α, SOD, CS, SDH, p53, and CAT was observed in LPS-treated oocytes compared with the ALA and control groups. Additionally, CS and CAT transcripts were down-regulated in oocytes in LPS plus ALA-treated group compared to that of the LPS-treated group. These findings revealed that ALA has the potential to alleviate the detrimental effects induced by LPS on in ovine oocytes during maturation in vitro. Thus, LPS-detrimental effect and ALA-preventing mechanisms seem to be regulated through the expression of genes involved in mitochondrial biogenesis and function, oxidative stress, and antioxidant systems.

The anti-infective crotalicidin peptide analog RhoB-Ctn[1-9] is harmless to bovine oocytes and able to induce parthenogenesis in vitro

Crotalicidin is a cathelicidin-related anti-infective (antimicrobial) peptide expressed in the venom glands of the South American rattlesnake Crotalus durissus terrificus. Congener peptides of crotalicidin, named vipericidins, are found in other pit vipers inhabiting South America. Crotalicidin is active against bacteria and pathogenic yeasts and has anti-proliferative activity for some cancer cells. The structural dissection of crotalicidin produced fragments (e.g., Ctn [15-34]) with multiple biological functionalities that mimic the native peptide. Another structural characteristic of crotalidicin and congeners is a unique repetitive stretch of amino acid sequences in tandem embedded in their primary structures. One of the encrypted vipericidn peptides (Ctn [1-9]) was synthesized, and the analog covalently conjugated with rhodamine B (RhoB-Ctn [1-9]) displayed considerable antimicrobial activity and selective cytotoxicity. Methods to evaluate antimicrobial peptides' toxicity include lysis of red blood cells (hemolysis) in vitro and cytotoxicity of healthy cultured cells (e.g., fibroblasts). Here, as a non-conventional model of toxicity, the bovine oocytes were exposed to two standardized concentrations of RhoB-Ctn [1-9], and embryo viability and development at its first stage of cleavage (division of cells) and blastocyst formation were evaluated. Oocytes treated with peptide at 10 and 40 μM induced cleavage rates of 44.94% and 51.53%, resulting in the formation of blastocysts of 7.07% and 11.73%, respectively. Light sheet microscopy and in silico prediction analysis indicated that RhoB-Ctn [1-9] peptide interacts with zona pellucida and internalizes into bovine oocytes and developing embryos. The ADMET prediction estimated good bioavailability of RhoB-Ctn [1-9]. In conclusion, the peptide appeared harmless to bovine oocytes and, remarkably, activated the parthenogenesis in vitro.

Effects of ovary storage temperature and embryo vitrification on somatic cell nuclear transfer outcomes in goats

Improving the genetic potential of farm animals is one of the primary aims in the field of assisted reproduction. In this regard, somatic cell nuclear transfer (SCNT) can be used to produce a large number of embryos from genetically elite animals. The aims of the present study were to assess the effects of: (1) ovary storage conditions on preimplantation development of recovered oocytes and the freezability of the derived blastocysts; and (2) vitrification of goat SCNT-derived blastocysts on postimplantation development. Goat oocytes were recovered from ovaries and stored under warm (25°C-27°C) or cold (11°C-12°C) conditions before being used to produce SCNT embryos. There were no differences in oocytes recovered from ovaries kept under cold versus warm storage conditions in terms of cleavage (mean (±s.d.) 95.68±1.67% vs 95.91±2.93% respectively) and blastocyst formation (10.69±1.17% vs 10.94±0.9% respectively) rates. The re-expansion rate of vitrified blastocysts was significantly lower for cold- than warm-stored ovaries (66.3±8.7% vs 90±11% respectively). To assess the effects of vitrification on postimplantation development, blastocysts from cold-stored ovaries only were transferred from fresh and vitrified-warmed groups. The pregnancy rate was comparable between the fresh and vitrified-warmed groups (41.65% and 45.45% respectively). In addition, established pregnancy in Day 28-38 and full-term pregnancy rates were similar between the two groups. In conclusion, this study shows similar invitro preimplantation developmental potential of warm- and cold-stored ovaries. This study introduces the vitrification technique as an appropriate approach to preserve embryos produced by SCNT for transfer to recipient goats at a suitable time.

Development of prepubertal goat oocytes after their in vitro maturation and chemical activation

Experiments were conducted to study in vitro maturation of prepubertal goat oocytes and their developmental potential after chemical activation. In Experiment 1, cumulus-oocytes complexes collected from the ovaries of prepubertal goats slaughtered at a local abattoir were matured in vitro in TCM-199-based medium supplemented with 10 µg/ml luteinizing hormone (LH) (treatment 1) or 10 µg/ml LH + 0.1 mM l-cysteine (treatment 2). In Experiment 2, mature oocytes were activated with either 5 µM ionomycin or 7% ethanol. After 18 h, some oocytes were randomly fixed and stained to evaluate their chromatin status, while others were cultured in embryo culture medium to study their further development. In Experiment 3, oocytes activated with 5 µM ionomycin were cultured for 7 days in one of the four different culture media [Charles Rosenkrans medium (CR-1), TCM-199, potassium simplex optimization medium (KSOM) and synthetic oviductal fluid (SOF)] to study their developmental potential. The maturation rate in control, treatment 1, and treatment 2 media did not differ from each other (P > 0.05). However, the lowest degeneration of oocytes was observed in treatment 3 (P < 0.05) when compared with the other two groups. The proportion of activated oocytes was higher, while non-activated oocytes were lower in ionomycin group when compared with the group activated with ethanol (P < 0.05). The proportions of oocytes cleaved were 65.7, 56.8, 61.0 and 54.4% in CR-1, TCM-199, KSOM and SOF medium, respectively, with no significant difference. However, further development of cleaved oocytes was better in KSOM followed by SOF.

Linolenic acid improves oocyte developmental competence and decreases apoptosis ofin vitro-produced blastocysts in goat

The effects of α-linolenic acid (ALA) on developmental competence of oocytes in goats were evaluated in this study. Initially, the level of ALA in small and large antral follicles was determined to be in a range of 0.018–0.028 mg/ml (64.6–100.6 μM, respectively).In vitromaturation was performed in the presence of various concentrations (10, 50, 100, or 200 μM) of ALA. Cumulus expansion, meiotic maturation, levels of intracellular glutathione (GSH), embryonic cleavage, blastocyst formation following parthenogenetic activation (PA) andin vitrofertilization (IVF), number of total and apoptotic cells in blastocyst, and expression ofBax, Bcl-2, and p53 genes in blastocyst cells were determined. Compared with the control, no improvement was observed in cumulus expansion in ALA-treated groups. At 50 μM concentration, ALA increased meiotic maturation rate but had no effect on GSH level. When oocytes treated with 50 μM ALA were subsequently used for PA or IVF, a higher rate of blastocyst formation was observed, and these embryos had a higher total cell number and a lower apoptotic cell number. Expression analyses of genes in blastocysts revealed lesser transcript abundances forBaxgene, and higher transcript abundances forBcl-2gene in 50 μM ALA group. Expression ofp53gene was also less observed in ALA-treated blastocysts. Our results show that ALA treatment at 50 μM duringin vitromaturation (IVM) had a beneficial effect on maturation of goat oocytes and this, in turn, stimulated embryonic development and regulated apoptotic gene expression.

Chemically assisted somatic cell nuclear transfer without micromanipulator in the goat: effects of demecolcine, cytochalasin-B, and MG-132 on the efficiency of a manual method of oocyte enucleation using a pulled Pasteur pipette

The present study aimed to facilitate widespread application of a previously described manual method of somatic cell nuclear transfer (SCNT) by investigating the effects of demecolcine (a microtubule-depolymerizing chemical), cytochalasin-B (a microfilament-depolymerizing chemical: 2.5μg/ml for 15min) and MG-132 (a proteasome inhibitor chemical) on the (i) incidence of cytoplasmic protrusion of MII chromosomes, (ii) improvement of manual oocyte enucleation, and (iii) in vitro and in vivo developmental competence of SCNT embryos in the goat. Following in vitro maturation, around 65% of goat oocytes contained a characteristic cytoplasmic protrusion of MII-chromosomes. Treatment with demecolcine (0.4μg/ml for 30min) significantly increased this rate to 92.2±4.5%. Treatment with MG-132 (2μM for 30min) could not improve this rate when used alone (61.4±11.5%), but when combined with demecolcine (86.4±8.1%). Treatment with cytochalasin-B completely suppressed this rate whenever used, either alone (7.7±5.1%) or in combination with demecolcine (3.9±1.3%). In a direct comparison, there was no significant difference in quantity and quality of embryos propagated by the manual vs. micromanipulation-based methods of SCNT (cleavage: 85.3±4.5 vs. 89.5±8.9%, blastocyst: 19.5±4.3 vs. 24.3±4.4%, grade 1 and 2 blastocyst: 33.8±7.1 vs. 29.5±6.3%, total cell count: 125±11.1 vs. 122±10.5, respectively). Furthermore, development to live kids at term was not significant between the two SCNT methods. From both technical and economical points of view, the overall in vitro and in vivo efficiency of this manual method of SCNT proved it a simple, fast and efficient alternative for large scale production of cloned goats.

Effect of Linolenic acid during in vitro maturation of ovine oocytes: embryonic developmental potential and mRNA abundances of genes involved in apoptosis

PURPOSE

To study the effect of α-linolenic acid (ALA) on meiotic maturation, mRNA abundance of apoptosis-related (Bax and Bcl-2) molecules, and blastocyst formation in ovine oocytes.

METHODS

A preliminary experiment was conducted to analyze the concentration of ALA in "small" (≤2 mm) and "large" (≥6 mm) follicles using gas chromatography/mass spectrometry analysis. The concentration of ALA in small and large follicles was determined to be in a range of 75.4 to 125.7 μM, respectively. In vitro maturation (IVM) of oocyte was then performed in presence of 0 (control), 10 (ALA-10), 50 (ALA-50), 100 (ALA-100), and 200 (ALA-200) μM of ALA. Meiotic maturation and mRNA abundance of Bax, and Bcl-2 genes was evaluated after 24 h of IVM. The embryonic cleavage and blastocyst formation following parthenogenetic activation were also determined for each group.

RESULTS

The highest concentration of ALA (ALA-200) decreased the oocyte maturation rate compared with the control group. Analysis of apoptosis-related genes in oocytes after IVM revealed lesser transcript abundances for Bax gene, and higher transcript abundances for Bcl-2 gene in ALA-treated oocytes as compared with the control oocytes. In term of cleavage rate (considered as 2-cell progression), we did not observe any differences among the groups. However, ALA-100 group promoted more blastocyst formation as compared with the control group.

CONCLUSION

Our results suggested that ALA treatment during IVM had a beneficial effect on developmental competence of ovine oocytes by increasing the blastocyst formation and this might be due to the altered abundance of apoptosis-regulatory genes.

Specific activation requirements of zona-free sheep oocytes before and after somatic cell nuclear transfer

In this study, the effect of the steps involved in zona-free somatic cell nuclear transfer (SCNT) on oocyte transcripts was investigated in sheep. To establish the reliable combined electrical-chemical activation for zona-free oocytes, oocytes were first exposed to an electrical pulse and then treated with 18 chemical activation regimens designed through modifying duration and concentration of ionomycin and 6-dimethyl aminopurine (6-DMAP), which is routinely used for SCNT. Electrofusion-mediated nuclear transfer significantly reduced transcript abundances of CCNB1, POU5F1, NPM2, GMMN, and CX43 compared to intact oocytes. Maximum parthenogenetic blastocyst development was obtained when oocytes were submitted to electric pulse and then to (1) 5 μM ionomycin for 5 or 2.5 min, both followed by 2 h of incubation with 6-DMAP (41.7±1.1, and 42.4±1.4%, respectively), (2) 5 μM ionomycin for 1 min+6-DMAP for 4 h (43.1±1.4%), and (3) 2.5 μM ionomycin for 1 min+6-DMAP for 2 h (42.4±1.4%), with significant differences compared to all the other groups. Statistical assessment of interactions between duration and concentration of ionomycin and duration of 6-DMAP exposure revealed that (1) concentration of ionomycin may be a more important factor than its duration, (2) both a long exposure period and a low concentration of ionomycin had marked decreasing effects on parthenogenetic development of zona-free oocytes, and (3) high duration of exposure to 6-DMAP can reduce parthenogenetic development. Despite an activation preference of parthenogenetic oocytes, a significantly higher rate of cloned blastocyst development was observed when reconstructed oocytes were activated with 5 μM ionomycin for 5 min rather than 2.5 μM ionomycin for 1 min (8.8±2.5 vs. 1.25±2.2%). These results suggested that SCNT steps have determining effects on oocyte transcripts and activation preferences of the reconstituted oocytes compared to intact counterparts. In this sense, reconstituted oocytes may need a higher concentration of ionomycin for a longer period than intact oocytes.

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.

Effects of activation on functional aster formation, microtubule assembly, and blastocyst development of goat oocytes injected with round spermatids

A systematic study was conducted on round spermatids (ROS) injection (ROSI) using the goat model. After ROSI, the oocytes were treated or not with ionomycin (ROSI+I and ROSI-I, respectively) and compared with intracytoplasmic sperm injection (ICSI). After ROSI-I, most oocytes were arrested with premature chromatin condensation and few oocytes formed pronuclei. In contrast, most oocytes formed pronuclei after ROSI+I. Some ROS were observed to form asters that organized a dense microtubule network after ROSI+I, but after ROSI-I, no ROS asters were observed. Whereas most of the oocytes showed Ca(2+) rises and a significant decline in maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK) activities after ROSI+I, no such changes were observed after ROSI-I. Due to the lack of Ca(2+) oscillations after ROSI-I, oocytes were injected with more ROS. Interestingly, different from the results observed in a single ROS injection, injection with four ROS effectively activated oocytes by inducing typical Ca(2+) oscillations. Whereas ROSI+I oocytes and ICSI oocytes both showed extensive microtubule networks, no such a network was observed in parthenogenetic oocytes. Together, the results suggest that goat ROS is not able to trigger intracellular Ca(2+) rises and thus to inhibit MPF and MAPK activities, but artificial activation improved fertilization and development of ROSI goat oocytes. Goat ROS can organize functional microtubular asters in activated oocytes. A ROS-derived factor(s) may be essential for organization of a functional microtubule network to unite pronuclei. Goat centrosome is of paternal origin because both ROS and sperm asters organized an extensive microtubule network after intra-oocyte injection.

Successful reprogramming of differentiated cells by somatic cell nuclear transfer, using in vitro-matured oocytes with a modified activation method

Therapeutic cloning has tremendous potential for cell therapy and tissue repair in some diseases. However, the efficiency of development of cloned human embryos by somatic cell nuclear transfer is still low. In the present study, the activation of cloned human embryos was investigated while using in vitro-matured oocytes. Pseudo-pronuclear formation and the subsequent development was compared with different activation parameters, including different durations of ionomycin and 6-dimethylaminopurine treatment. The results showed that somatic cells were successfully reprogrammed by modification of activation treatments while using in vitro-matured oocytes. The activation efficiency of cloned human embryos was significantly increased at durations of ionomycin at both 5 and 7 min, despite different durations of 6-DMAP treatment. The results of blastocyst development showed that 20% of activated embryos developed to the blastocyst stage when the embryos were activated with 5 µm ionomycin for 5 min and 2 mm 6-DMAP for 5 h, which was significantly higher than those activated with other parameters. Moreover, we found that an increasing duration of 6-DMAP induced the formation of a single, large, pseudo-pronucleus in cloned human embryos and impaired subsequent development competence. In conclusion, successful reprogramming of human somatic cells was achieved using in vitro-matured oocytes by somatic cell nuclear transfer and improved with a modified activation method.

Analysis of cat oocyte activation methods for the generation of feline disease models by nuclear transfer

BACKGROUND

Somatic cell nuclear transfer in cats offers a useful tool for the generation of valuable research models. However, low birth rates after nuclear transfer hamper exploitation of the full potential of the technology. Poor embryo development after activation of the reconstructed oocytes seems to be responsible, at least in part, for the low efficiency. The objective of this study was to characterize the response of cat oocytes to various stimuli in order to fine-tune existing and possibly develop new activation methods for the generation of cat disease models by somatic cell nuclear transfer.

METHODS

First, changes in the intracellular free calcium concentration [Ca2+]i in the oocytes induced by a number of artificial stimuli were characterized. The stimuli included electroporation, ethanol, ionomycin, thimerosal, strontium-chloride and sodium (Na+)-free medium. The potential of the most promising treatments (with or without subsequent incubation in the presence of cycloheximide and cytochalasin B) to stimulate oocyte activation and support development of the resultant parthenogenetic embryos was then evaluated. Finally, the most effective methods were selected to activate oocytes reconstructed during nuclear transfer with fibroblasts from mucopolysaccharidosis I- and alpha-mannosidosis-affected cats.

RESULTS

All treatments were able to elicit a [Ca2+]i elevation in the ooplasm with various characteristics. Pronuclear formation and development up to the blastocyst stage was most efficiently triggered by electroporation (60.5 +/- 2.9 and 11.5 +/- 1.7%) and the combined thimerosal/DTT treatment (67.7 +/- 1.8 and 10.6 +/- 1.9%); incubation of the stimulated oocytes with cycloheximide and cytochalasin B had a positive effect on embryo development. When these two methods were used to activate oocytes reconstructed during nuclear transfer, up to 84.9% of the reconstructed oocytes cleaved. When the 2 to 4-cell embryos (a total of 220) were transferred into 19 recipient females, 4 animals became pregnant. All of the fetuses developed from oocytes activated by electroporation followed by cycloheximide and cytochalasin B incubation; no fetal development was detected as a result of thimerosal/DTT activation. Although heartbeats were detected in two of the cloned fetuses, no term development occurred.

CONCLUSION

Electroporation proved to be the most effective method for the activation of cat oocytes reconstructed by nuclear transfer. The combined thimerosal/DTT treatment followed by cycloheximide and cytochalasin B incubation triggered development effectively to the blastocyst stage; whether it is a viable option to stimulate term development of cloned cat embryos needs further investigations.

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.

Demecolcine-assisted enucleation of goat oocytes: protocol optimization, mechanism investigation, and application to improve the developmental potential of cloned embryos

Although demecolcine-assisted enucleation has been performed successfully in porcine and cattle, the mechanism and protocol optimization of chemically assisted enucleation need further investigation. The present study optimized the protocol for goat oocyte enucleation and demonstrated that a 30-min treatment with 0.8 ng/mL demecolcine-induced cytoplasmic protrusions in over 90% of the oocytes. Rates of enucleation, cell fusion, and blastocyst formation were significantly higher after demecolcine-assisted than after blind aspiration enucleation, although differences in rates of live births remain to be unequivocally determined between the two treatments. The ability to form protrusions decreased significantly as spindles became less organized in aged oocytes and the oocytes with a poor cumulus expansion. More than 93% of the demecolcine-induced protrusions persisted for 2 h in the absence of cytochalasin B (CB) but most disappeared within 30 min of CB treatment. The spindle disintegrated, an actin-rich ring formed around the chromosome mass and the MAP kinase activity increased significantly after demecolcine treatment. When oocytes with induced protrusions were treated with CB, however, the contractile ring disappeared, the spindle reintegrated, and both MPF and MAP kinase activities decreased significantly. It is concluded that (1) cytoplasmic protrusions can be induced in goat oocytes with a very low concentration of demecolcine; (2) oocyte selection and enucleation can be achieved simultaneously with demecolcine treatment; and (3) an interactive effect between the MAP kinase, MPF, microfilaments and microtubules might be implicated in the control of cytoplasmic protrusion formation after demecolcine treatment.

Interactive effects of low temperature and roscovitine (ROS) on meiotic resumption and developmental potential of goat oocytes

The objective of this article was to study the effects of low temperature and roscovitine (ROS) on meiotic resumption and developmental potential of goat oocytes. Goat oocytes were cultured at different temperatures in medium containing different concentrations of ROS, and at the end of culture, oocytes were either matured or processed for light/confocal microscopy. The matured oocytes were activated chemically or fertilized in vitro for embryo development. Meiotic arrest was successfully maintained for 24 hr with 0, 50, and 200 microM ROS at 5, 20, and 38.5 degrees C, respectively. Following chemical activation, morulae/blastocysts (M/B) rates similar to untreated oocytes were obtained in oocytes that had been inhibited for 24 hr at 5 degrees C without ROS (Protocol 5C) or at 20 degrees C with 50 microM ROS (Protocol 20C) or for 8 hr at 38.5 degrees C with 200 microM ROS (Protocol 8 hr), but no blastulation was observed after oocytes were inhibited at 38.5 degrees C with 200 microM ROS for 24 hr. Following fertilization, however, while M/B rates similar to controls were achieved in oocytes treated with protocols 5C and 20C, few oocytes inhibited with Protocol 8 hr developed into morulae, due to a high incidence of polyspermy. Changes in GV chromatin configuration were not observed after inhibition with Protocol 5C, but were apparent after inhibition with protocols 20C and 8 hr, leading to a precocious germinal vesicle breakdown (GVBD) during subsequent maturation. Cortical granule (CG) migration and the formation of microtubule organizing centers occurred during inhibition and were more obvious in the absence of ROS. Significantly more oocytes inhibited by protocols 5C and 20C than by Protocol 8 hr completed CG migration after maturation. In conclusion, goat oocytes were tolerant to chilling and culture at lower temperatures with less ROS was better than culture at higher temperatures with more ROS for oocyte GVBD inhibition.

Effects of different activation protocols on preimplantation development, apoptosis and ploidy of bovine parthenogenetic embryos

The objective of this study was to optimize the protocols for bovine oocytes activation through comparing the effectiveness of different treatments on the activation and subsequent development of oocytes and examining the effects of two combined activation treatments on the blastocyst apoptosis and ploidy. Cumulus-oocyte complexes (COCs) were recovered from abattoir-derived ovaries and matured in vitro. After maturation, cumulus-free oocytes were activated according to the experiment designs. Activated oocytes were cultured in vitro in modified synthetic oviductal fluid (mSOF) medium and assessed for pronuclear formation (15-16 h), cleavage (46-48 h) and development to the blastocyst stage. In Experiment 1, the matured oocytes were treated with single activation agents, including ionomycin (5 microM for 5 min), ethanol (7% for 7 min), calcium ionophore A23187 (5 microM for 5 min) or strontium (10mM for 5h). The pronuclear formation and cleavage rate were higher significantly in ionomycin (39.0 and 30.7%) and ethanol (41.5 and 28.1%) treatment alone compared to other treatments (9.7-25.2 and 11.3-23.7%, respectively, P<0.05). Very low blastocyst rates (3.9-5.3%) resulted which were not significantly different among treatments (P>0.05). For the combined activation treatment (Experiment 2), the same concentrations of ionomycin and ethanol as in Experiment 1 were used in combination with either 6-dimethylaminopurine (6-DMAP, 2.0 mM for 3 h) or cycloheximide (CHX)+cytochalasin B (CB, 10 microg/ml for 3 h). The pronuclear formation, cleavage rate, blastocyst rate and cell number of blastocyst were higher significantly (P<0.05) in ionomycin+6-DMAP treatment (67.1, 69.2, 28.0 and 91.3%, respectively) and ethanol+CHX+CB treatment (68.9, 70.2, 25.5 and 89.3%, respectively) compared to other treatments (11.7-58.1, 10.2-47.1, 1.5-24.2 and 34.2-62.7%, respectively). In Experiment 3, the parthenogenetic blastocysts produced by activation with ionomycin+6-DAMP and ethanol+CHX+CB and in vitro fertilized blastocysts (control group) were examined for apoptosis using a terminal deoxynucleotidyl transferase mediated deoxyuridine 5-triphosphate nick-end labeling (TUNEL) assay. The ethanol+CHX+CB treatment (7.0%) showed significantly lower blastocyst apoptosis index compared to ionomycin+6-DAMP treatment (9.1%, P<0.05). Furthermore, the chromosomal composition in the parthenotes embryos differed (P<0.05) among treatments. The percentage of haploid parthenotes was higher in ionomycin+6-DMAP treatment than ethanol+CHX+CB treatment. These results suggested that ethanol+CHX+CB treatment was more favorable protocol for parthenogenesis of bovine oocytes.

The effects of delayed activation and MG132 treatment on nuclear remodeling and preimplantation development of embryos cloned by electrofusion are correlated with the age of recipient cytoplasts

The electrofusion method, used extensively in livestock cloning, cannot be used in mice, because it is believed that the mouse oocytes are more susceptible to detrimental effects of electrical stimulus than oocytes from other species. Reports on whether a delayed activation after electrofusion and a premature chromosome condensation (PCC) is essential for efficient cloning are inconclusive. To address these issues, effects of pulsing on activation and MPF activity of nonenucleated oocytes and effects of delayed activation and MG132 treatment on donor nuclear PCC and preimplantation development of embryos cloned by electrofusion or nuclear injection were compared between different cytoplast ages in mice and goats. The results indicated that the use of oocytes collected early after donor stimulation would make it possible to conduct somatic cell nuclear transfer in mice by electrofusion. Whether a delayed activation is essential was dependent upon the age, or rather, the level, of MPF activity of the cytoplasts at the time of electrofusion, as was the requirement for MG132 treatment. The competence for blastocyst formation of cloned embryos was highly correlated with the level of donor nuclear PCC in recipient cytoplasts. The nuclear injection technique was more adaptable to older cytoplast ages, and hence less dependent on drugs for inhibition of MPF inactivation, compared to electrofusion.

Brief exposure to cycloheximide prior to electrical activation improves in vitro blastocyst development of porcine parthenogenetic and reconstructed embryos

To investigate the effects of cycloheximide exposure before electrical activation of in vitro-matured porcine oocytes on the subsequent development of parthenogenetic embryos, cumulus-free mature oocytes were exposed to NCSU-23 medium containing cycloheximide (10 microg/mL) for 0, 5, 10, 20, 30 and 60 min, activated by electrical pulse treatment (1.5 kV/cm, 100 micros) and then cultured in PZM-3 for 7 days. To evaluate the effects of cycloheximide on the activation of nuclear transfer embryos, reconstructed embryos were electrically activated by two DC pulses (1.2 kV/cm, 30 micros) before or after exposure to cycloheximide. The reconstructed embryos were allocated into four groups: electrical pulse treatment alone (Ele); exposure to cycloheximide for 10 min followed by electrical activation (CHX+Ele); electrical activation followed by exposure to cycloheximide for 6h (Ele+CHX); exposure to cycloheximide for 10 min, followed by electrical activation and a further exposure to cycloheximide for 6h (CHX+Ele+CHX). The activated reconstructed embryos were cultured in PZM-3 for 6 days. Oocytes treated with 10 min exposure to cycloheximide followed by electrical activation had a significantly higher percentage of blastocyst formation compared to control oocytes and oocytes exposed for > or =30 min. In the reconstructed embryos, the blastocyst development rates of embryos exposed to cycloheximide (CHX+Ele, Ele+CHX and CHX+Ele+CHX) were significantly higher than those of the control group (Ele). Among the cycloheximide-treated groups, the CHX+Ele group had increased development rate and total blastocyst cell number, though these values were not significantly different from those observed in the other cycloheximide-treated groups. To evaluate the quality of NT embryos treated with cycloheximide, apoptosis in blastocysts was analyzed by TUNEL assay. The 10 min exposure to cycloheximide prior to electrical activation significantly reduced cell death compared with longer exposure to cycloheximide after electrical fusion. In conclusion, brief exposure to cycloheximide prior to electrical activation may increase the subsequent blastocyst development rates in porcine parthenogenetic and reconstructed embryos.

Effects of delayed excision of oviducts/ovaries on mouse oocytes and embryos

To achieve the best and reproducible results of experiments, effects of delayed excision of oviducts/ovaries on mouse ovarian/ovulated oocytes and embryos have been studied. Oviducts/ovaries were excised at different times after death of mice and effects of the postmortem interval on ovarian/ovulated oocytes and embryos were analyzed. When oviduct excision was delayed 10 min, many ovulated oocytes lysed or underwent in vitro spontaneous activation, and this postmortem effect aggravated with the extension of postmortem interval and oocyte aging. Oocytes from different mouse strains responded differently to delayed oviduct removal. Delayed oviduct excision did not cause lysis of zygotes or embryos but compromised their developmental potential. When ovaries were excised at 30 min after death, percentages of atretic follicles increased while blastocyst cell number declined significantly after oocyte maturation in vitro. Preservation of oviducts in vitro, in intact or opened abdomen at different temperatures and histological analysis of oviducts from different treatments suggested that toxic substance(s) were secreted from the dying oviducts which induced oocyte lysis and spontaneous activation and both this effect itself and the sensitivity of oocytes to this effect was temperature dependent. It is concluded that a short delay of oviduct/ovary removal had marked detrimental effects on oocytes and embryos. This must be taken into account in experiments using oocytes or embryos from slaughtered animals. The data may also be important for estimation of the time of death in forensic medicine and for rescue of oocytes from deceased valuable or endangered mammals.

Interactive effects of granulosa cell apoptosis, follicle size, cumulus–oocyte complex morphology, and cumulus expansion on the developmental competence of goat oocytes: a study using the well-in-drop culture system

Using a well-in-drop (WID) oocyte/embryo culture system that allows identification of follicular origin, we have investigated the effects of granulosa cells (GCs) apoptosis, follicle size, cumulus–oocyte complexes (COCs) morphology, and cumulus expansion on the developmental competence of goat oocytes matured and cultured individually following parthenogenetic activation. The WID system supported oocyte maturation and embryo development to a level similar to the conventional group system. The majority of goat oocytes acquired competence for development up to the 8–16 cell stage in follicles larger than 2 mm, but did not gain the ability to form morula/blastocyst (M/Bs) until follicles larger than 3 mm in diameter. The extent of atresia affected M/Bs formation. This effect varied according to the follicle size. Cumulus expansion increased with follicle size and decreased with increasing incidence of GCs apoptosis. Oocyte developmental potential was also correlated with cumulus expansion. Regardless of the degree of follicle atresia, 73–84% of the floating cells in the follicular fluid (FF) underwent apoptosis. Correlation between floating cell density in FF and oocyte developmental potency suggests the possibility to use the floating cell density as a simple and non-invasive marker for oocyte quality. It is concluded that the developmental potential of an oocyte is determined by multifactor interactions, and multiple factors must be considered together to accurately predict the quality of an oocyte.

Production of cloned goats by nuclear transfer of cumulus cells and long-term cultured fetal fibroblast cells into abattoir-derived oocytes

Dairy goats are ideal for the transgenic production of therapeutic recombinant proteins. The use of recombinant somatic cell lines for nuclear transfer (NT) allows the introduction of genes by transfection, increases the efficiency of transgenic animal production to 100%, and overcomes the problem of founder mosaicism. Although viable animals have been cloned via NT from somatic cells of 11 species, the efficiency has been extremely low. Both blastomere and somatic cell NT increased fetal loss and perinatal morbidity/mortality in cattle and sheep, but fetal loss and perinatal mortality appear to be relatively low in goats. In this study, we produced cloned goats by NT from cumulus cells and long-term cultured fetal fibroblast cells (FFCs) to abattoir-derived oocytes. NT embryos were constructed from electrofusion of cumulus cells (CCs), FFCs, or skin fibroblast cells (SFCs) with cytoplasts prepared from abattoir-derived ovaries. The NT embryos were activated with an optimized activating protocol (1 min exposure to 2.5 microM ionomycin followed by 2 hr incubation in 2mM 6-DMAP). Two viable cloned kids from CCs and one from long-term cultured FFCs (at passage 20-25) were born. Microsatellite analysis of 10 markers confirmed that all cloned offspring were derived from corresponding donor cells. To our knowledge, the production of cloned goat offspring using abattoir-derived oocytes receiving nuclei from CCs and long-term cultured FFCs has not been reported. The production of viable cloned animals after activation with reduced intensity of ionomycin and 6-DMAP treatment has also not been reported. Loss of cloned embryos was obvious after 45 and 90 days of pregnancy, and a lack of cotyledons, heart defects, and improperly closed abdominal wall were observed in the aborted fetuses and one cloned kid. The fusibility and in vitro developmental potential of embryos reconstructed from FFCs at passage 20-25 were significantly lower than those of embryos reconstructed from FFCs at passage 3-5, and the cloning efficiency of the long-term cultured cells was low (0.5%).

Embryonic Stem Cells from Parthenotes

While human embryonic stem cells (hESCs) hold tremendous therapeutic potential, they also create societal and ethical dilemmas. Adult and placental stem cells represent two alternatives to the hESC, but may have technical limitations. An additional alternative is the stem cell derived from parthenogenesis. Parthenogenesis is a reproductive mechanism that is common in lower organisms and produces a live birth from an oocyte activated in the absence of sperm. However, parthenogenetic embryos will develop to the blastocyst stage and so can serve as a source of embryonic stem cells. Parthenogenetic ESCs (pESCs) have been shown to have the properties of self-renewal and the capacity to generate cell derivatives from the three germ layers, confirmed by contributions to chimeric animals and/or teratoma formation when injected into SCID mice. Therefore, this mechanism for generating stem cells has the ethical advantage of not involving the destruction of viable embryos. Moreover, the cells do not involve the union of male and female and so genetic material will be derived exclusively from the female oocyte donor (with the attendant potential immunological advantages). This chapter describes the biology underlying parthenogenesis, as well as provides detailed technical considerations for the production of pESCs.