Chemical activation of buffalo (Bubalus bubalis) oocytes by different methods: effects of aging on post-parthenogenetic development

Oocyte competence and gene expression in parthenogenetic produced embryos from repeat breeder and normally fertile buffaloes (Bubalus bubalis) raised in sub-humid tropical climate

The reproductive management of the buffalo species still faces several unresolved problems, which directly affect the productivity of the herd, one of them being the presence of repeat breeder females. Given this scenario, this study aimed to verify the developmental competence of oocytes obtained from repeat breeder females and submitted to parthenogenetic activation. In addition, embryo gene expression was compared to normally fertile females. Murrah buffaloes were divided into two groups: repeat breeder (RB, n = 8) and normally fertile or control (CR, n = 7). Cumulus-oocyte complexes (COCs) were aspirated by transvaginal ovum pick-up from estrus synchronized females. The COCs were submitted to IVM for 24 h, and subsequently, the oocytes were activated using ionomycin, followed by 6-DMAP. Afterwards, the presumptive parthenotes were cultured for six or seven days in a microenvironment of 5 % CO2, 5 % O2, and 90 % N2 at 38.5 °C. The expression of OCT4, GLUT1, BCL2 and TFAM genes from blastocysts was evaluated. The overall COCs recovery rate was 70.9 % (190/268). The maturation (57.8 vs 71.1), cleavage (45.2 vs 62.2) and blastocyst (30.1 vs 45.9) rates did not differ (P > 0.05) between RB and CR females, respectively. Similarly, no significant difference (P > 0.05) was observed for the expression of studied genes in both RB and CR females. In conclusion, oocytes obtained from RB were as developmentally competent as those collected from CR females, with similar energy metabolism and in vitro development capacity. Thus, the low fertility rate of repeat breeder buffaloes, when compared to normal cyclic females, must be due to subsequent events to the blastocyst stage.

Low oxygen concentration improves yak oocyte maturation and inhibits apoptosis through HIF-1 and VEGF

The gas-phase environment of in vitro culture system plays an important role in the development of oocytes, and oxygen concentration is one of the important factors. In the present study, we aimed to explore the effect of different oxygen concentrations (20%, 10%, 5% or 1% O₂ ) in yak oocyte maturation and to detect the expression of HIF-1α, VEGF and cell apoptosis in yak COCs. First, the maturation rate of oocytes, cleavage rate and blastocysts rate following parthenogenetic activation in the group with 5% oxygen concentration were significantly higher (p < 0.05) than the other groups. Then, TUNEL analysis showed that the 5% oxygen concentration group significantly inhibited apoptosis of cumulus-oocyte complexes (COCs) compared to the other group, and the transcription and protein levels of pro-apoptotic factor Bax, HIF-1α and VEGF in yak COCs significantly reduced, while anti-apoptotic factor Bcl-2 significantly increased. Furthermore, immunohistochemical staining results indicated that HIF-1α protein was mainly located in theca follicle interna, mural follicular stratum granulosum, corona radiata and ovarian stroma in the follicular ovarian tissue; while VEGF protein was mainly located in the granulosa and theca cell layers. In summary, our findings demonstrate that 5% oxygen concentration may promote maturation and inhibit apoptosis of oocytes through HIF-1α-mediated VEGF expression.

FSH Stimulation with Short Withdrawal Improves Oocyte Competence in Italian Mediterranean Buffalo (Bubalus bubalis)

The aim of this work was to evaluate the efficiency of different FSH doses and FSH coasting times before ovum pick-up (OPU) on follicular growth and oocyte competence in buffalo. Experiment 1 involved two different FSH treatments: 40 mg FSH given three (FSH3) or six (FSH6) times, 2 days after dominant follicle removal were tested, with OPU carried out after 40-44 h of coasting. In experiment 2, OPU was carried out after FSH6 protocol followed by 28-32 h (C1), 40-44 h (C2), or 64-68 h (C3) of coasting time. Cumulus oocyte complexes (COCs) were classified, in vitro matured, fertilized, and cultured. The results demonstrated that FSH6 increased the total number of follicles, the number and percentages of medium and large follicles, the number and the proportion of good quality oocytes, and the number of grade 1,2 and fast-developing blastocysts compared to the control. C3 decreased the percentage of good quality oocyte and blastocyst rates compared to C1 and C2. A higher percentage of fast blastocysts and average number of grade 1,2 blastocysts was observed in C1 compared to C3, with intermediate values found in C2. The improved efficiency in terms of blastocyst yields suggests the use of FSH6 + C1 protocol for ovarian superstimulation in buffalo.

Parthenogenetic activation of buffalo (Bubalus bubalis) oocytes: comparison of different activation reagents and different media on their developmental competence and quantitative expression of developmentally regulated genes

This study was carried out to compare the efficacy of different methods to activate buffalo A + B and C + D quality oocytes parthenogenetically and to study the in vitro developmental competence of oocytes and expression of some important genes at the different developmental stages of parthenotes. The percentage of A + B oocytes (62.16 ± 5.06%, range 53.8-71.3%) was significantly higher (P < 0.001) compared with that of C + D oocytes (37.8 ± 5.00%, range 28.6-46.1%) retrieved from slaughterhouse buffalo ovaries. Among all combinations, ethanol activation followed by culture in research vitro cleave medium gave the highest cleavage and blastocyst yields for both A + B and C + D grade oocytes. Total cell numbers, inner cell mass/trophectoderm ratio and apoptotic index of A + B group blastocysts were significantly different (P < 0.05) from their C + D counterpart. To determine the status of expression patterns of developmentally regulated genes, the expression of cumulus-oocyte complexes, fertilization, developmental competence and apoptotic-related genes were also studied in parthenogenetically produced buffalo embryos at different stages, and indicated that the differential expression patterns of the above genes had a role in early embryonic development.

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.

Maternal transcription profiles at different stages for the development of early embryo in buffalo

Maternal mRNAs deposited in the egg during oogenesis are critical during the development of early embryo, before the activation of the embryonic genome. However, there is little known about the dynamic expression of maternally expressed genes in mammals. In this study, we made buffalo parthenogenesis as our research model to analyse maternal transcription profiles of pre-implantation embryo in buffalo using RNA sequencing. In total, 3,567 unique genes were detected to be differentially expressed among all constant stages during early embryo development (FPKM > 0). Interestingly, a total of 10,442 new genes were discovered in this study, and gene ontology analysis of the new differentially expressed genes indicated that the new genes have a wide cellular localization and are involved in many molecular functions and biological processes. Moreover, we identified eight clusters that were only highly expressed in a particular developmental stage and enriched a number of GO terms and KEGG pathways that were related to specific stage. Furthermore, we identified 1,530 hub genes (or key members) from the maternally expressed gene networks, and these hub genes were involved in 11 stage-specific modules. After visualization using Cytoscape 3.2.1 software, we obtained complex interaction network of hub genes, indicating the highly efficient cooperation between genes during the development in buffalo embryos. Further research of these genes will greatly deepen our understanding of embryo development in buffalo. Collectively, this research lays the foundation for future studies on the maternal genome function, buffalo nuclear transfer and parthenogenetic embryonic stem cells.

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.

Expression pattern of pluripotent markers in different embryonic developmental stages of buffalo (Bubalus bubalis) embryos and putative embryonic stem cells generated by parthenogenetic activation

In this study, we describe the production of buffalo parthenogenetic blastocysts and subsequent isolation of parthenogenetic embryonic stem cell (PGESC)-like cells. PGESC colonies exhibited dome-shaped morphology and were clearly distinguishable from the feeder layer cells. Different stages of development of parthenogenetic embryos and derived embryonic stem cell (ESC)-like cells expressed key ESC-specific markers, including OCT-4, NANOG, SOX-2, FOXD3, REX-1, STAT-3, TELOMERASE, NUCLEOSTEMIN, and cMYC. Immunofluorescence-based studies revealed that the PGESCs were positive for surface-based pluripotent markers, viz., SSEA-3, SSEA-4, TRA 1-80, TRA 1-60, CD-9, and CD-90 and exhibited high alkaline phosphatase (ALP) activity. PGEC cell-like cells formed embryoid body (EB)-like structures in hanging drop cultures and when cultured for extended period of time spontaneously differentiated into derivatives of three embryonic germ layers as confirmed by RT-PCR for ectodermal (CYTOKERATIN8, NF-68), mesodermal (MSX1, BMP-4, ASA), and endodermal markers (AFP, HNF-4, GATA-4). Differentiation of PGESCs toward the neuronal lineage was successfully directed by supplementation of serum-containing media with retinoic acid. Our results indicate that the isolated ESC-like cells from parthenogenetic blastocyst hold properties of ESCs and express markers of pluripotency. The pluripotency markers were also expressed by early cleavage-stage of buffalo embryos.

Effects of chemical combinations on the parthenogenetic activation of mouse oocytes

The aim of this study was to identify an optimal method for the parthenogenetic activation of mouse oocytes. Ethanol (EH), strontium chloride (SrCl₂) and ionomycin calcium salt were each combined with cytochalasin B to induce the parthenogenetic activation of CD-1^® mouse oocytes. Among the EH combination groups, the blastocyst formation and hatching rates of the group that was activated with EH and CB for 5 min were significantly higher compared with those of the groups that were activated for 7 and 10 min (P<0.05). Among the SrCl₂ combination groups, the blastocyst formation and hatching rates of the group that was activated with SrCl₂ and CB for 30 min were significantly higher compared with those of the groups that were activated for 1 and 2 h (P<0.05). Among the ionomycin calcium salt combination groups, the blastocyst formation and hatching rates of the group that was activated with ionomycin and CB for 3 min were higher compared with those of the groups that were activated for 5 and 7 min (P<0.05). Compared with the other two combinations, the experimental indicators of the EH combination groups were notably superior (P<0.05). For combined activation, simultaneous activation with two substances was significantly more effective than successive activation (P<0.05). For combined activation with EH and cytochalasin B in mouse oocytes, 5 min of parthenogenetic activation had significant advantages with regard to cleavage, blastocyst formation and blastocyst hatching rates. In addition, the activation rate of combined activation was higher than that of single activators. For combined activation, the simultaneous application of two activators has a superior effect.

Influence of the duration of in vitro maturation and gamete co-incubation on the efficiency of in vitro embryo development in Italian Mediterranean buffalo (Bubalus bubalis)

The aim of this study was to investigate the effect of the duration of oocyte in vitro maturation (IVM) and gamete co-incubation on the in vitro embryo (IVEP) production efficiency in River buffalo. In Experiment 1, abattoir-derived cumulus oocyte complexes were fixed at 0, 3, 6, 9, 12, 15, 18, 21 and 24 h after the start of in vitro maturation to study the kinetics of nuclear maturation. In Experiment 2, cumulus oocyte complexes were fertilized in vitro following in vitro maturation for 18, 21, 24, 27 or 30 h. After 20 h of gamete co-incubation, presumptive zygotes were denuded and cultured in vitro in synthetic oviduct fluid (SOF) medium. In Experiment 3, following in vitro maturation and fertilization, presumptive zygotes were removed from fertilization drops at 8, 12, 16 and 20 h post-insemination (pi) and placed in culture as described above. Representative samples of oocytes were fixed at 4, 8, 12, 16 and 20 h to evaluate the sperm penetration rate and the incidence of polyspermy at different co-incubation times. The main conclusions of the study are that: (1) the majority of buffalo oocytes accomplish nuclear maturation between 21 and 24 h after the start of in vitro maturation; (2) both cleavage and blastocyst rates linearly decrease with increasing duration of in vitro maturation (from 18 to 30 h); (3) sperm-oocyte incubation for at least 16 h is required for maximum blastocyst yields.

Chemical activation of in vitro matured dromedary camel (Camelus dromedarius) oocytes: optimization of protocols

Experiments were conducted to study the efficiency of sequential treatments of ionomycine and ethanol combined with phosphorylation inhibitor (6-dimethylaminopurine) or the specific maturation promoting factor inhibitor (roscovitine) in inducing artificial activation in dromedary M-II oocytes. Cumulus oocyte complexes (COCs), collected from slaughterhouse ovaries were cultured at 38.5 degrees C in an atmosphere of 5% CO2 in air for 24-48 h. In experiment 1, the COCs were either fertilized in vitro or activated with 5 microM ionomycine for 5 min or 7% ethanol for 7 min, both followed by exposure to 6-diethylaminopurine or roscovitine for 4h. After 14-15 h of in vitro culture, the oocytes were fixed and stained with 1% aceto-orcein to evaluate their nuclear status. In experiment 2, the oocytes were activated in the same manner as in experiment 1 but were cultured for 7 days to evaluate their post-parthenogenetic development. In experiment 3, oocytes were exposed to the ionomycine for 2, 3, 4 or 5 min to evaluate the better exposure time while as in experiment 4, the oocytes matured for 28-48 h were activated to see the effect of aging on post-parthenogenetic development. Higher proportion (P<0.01) of oocytes was activated in ionomycine/6-DMAP and ionomycine/roscovitine groups when compared with ethanol/6-DMAP, ethanol/roscovitine and in vitro fertilized groups. However, there was no difference (P>0.05) in the proportion of oocytes activated with ethanol when compared with in vitro fertilized group. No significant difference was seen on the proportion of morula on day 7 of culture, however the development to blastocyst stage was higher (P<0.01) in ionomycine/6-DMAP and ionomycine/roscovitine when compared with ethanol/6-DMAP and ethanol/roscovitine treated oocytes. A higher proportion of oocytes reached blastocyst stage when they were exposed to ionomycine for 3 min but they were not significantly different from the others (P>0.05). The proportion of blastocysts obtained was higher (P<0.05) in oocytes activated after 28 h of maturation when compared with oocytes activated after 32, 36, 40, 44 and 48 h of maturation. In conclusion, a protocol for chemical activation of dromedary camel oocytes with ionomycine/6-DMAP is demonstrated and optimized in the present study for further use in the development of assisted reproductive techniques in this species.

Quality analysis of buffalo blastocysts derived from oocytes vitrified before or after enucleation and reconstructed with somatic cell nuclei

We investigated the potential of vitrified-warmed buffalo oocytes to develop to blastocysts after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). In vitro-matured oocytes before and after enucleation (M-II oocytes and enucleated oocytes, respectively) were put in 7.5% DMSO and 7.5% ethylene glycol (EG) for 4, 7 and 10 min, and then vitrified (Cryotop device) after 1-min equilibration in 15% DMSO, 15% EG and 0.5M sucrose. Following 4-, 7- and 10-min exposure, proportions of the post-warm oocytes with a normal vitelline membrane were similar (66-71% in M-II oocytes and 69-71% in enucleated oocytes). However, 18-20% of the normal M-II oocytes had no detectable first polar body in their perivitelline space (no potential for subsequent enucleation). When the post-warm M-II oocytes were treated for PA by 7% ethanol, 10 microg/mL cycloheximide and 1.25 microg/mL cytochalasin-D, parthenogenetic development into Day-7 blastocysts occurred in 10-13% of cultured oocytes, lower (P<0.05) than fresh (control) oocytes (24%). In the absence of the cooling and warming, blastocyst rates in the 4-min exposure group (22%), but not in the 7-min and 10-min exposure groups (14-15%), were similar to that in the fresh group (23%). The total cell number (group average 117-132 cells) and the ICM ratio (22-24%) of the PA blastocysts derived from vitrified M-II oocytes were comparable with fresh oocytes (127 cells and 25%). After SCNT (with fibroblast cells and vitrified-warmed oocytes), blastocyst rates were similar for the three exposure periods for M-II oocytes (8-10%) and enucleated oocytes (7-9%), but were lower (P<0.05) than in the fresh group (15%). The total cell number of the SCNT blastocysts derived from vitrified M-II and enucleated oocytes (80-90 and 82-101 cells) was smaller (P<0.05) than from fresh oocytes (135 cells); the ICM ratio of blastocysts derived from the M-II and enucleated oocytes after vitrification in 7- or 10-min exposure groups (20-22%) was not different (P>0.05) from fresh control oocytes (24%) or those in 4-min exposure group (M-II 23%, enucleated 24%). Thus, SCNT of swamp buffalo oocytes following vitrification before or after enucleation resulted in blastocysts with a slightly decreased cell number.

Morphology of Dromedary Camel Oocytes and their Ability to Spontaneous and Chemical Parthenogenetic Activation

The present work was conducted to examine (1) the morphology of dromedary cumulus-oocytes complexes (COCs), (2) to study the incidence of spontaneous development of oocytes in vivo and (3) to assess the ability of in vitro matured dromedary oocytes to chemical parthenogenetic activation compared with in vitro fertilized (IVF) oocytes. COCs were recovered from dromedary ovaries classified according to their morphology into six categories. Oocyte diameter was measured using eye piece micrometer. For chemical activation, COCs with at least three layers of cumulus-cells were in vitro matured (IVM) in TCM 199 + 10 microg/ml FSH + 10 IU hCG/ml + 10% FCS + 50 microg/ml gentamycin. COCs were incubated for 40 h at 38.5 degrees C under 5% CO2 in humidified air. After IVM, matured oocytes with first polar body (first Pb) were divided into two groups. Group 1: activated in 7% ethanol (E) for 5 min followed by culture in 2 mM 6-dimethylaminopurin (6-DMAP, E D, subgroup 1) or 10 microg/ml cycloheximide (CHX, E CHX, subgroup 2) for 3.5 h at 38.5 degrees C under 5% CO2. In group 2, oocytes were activated using 50 microM Ca A23187 (Ca A) for 5 min followed by culture in 2 mM 6-DMAP (Ca D, subgroup 3) or 10 microg/ml CHX(Ca CHX, subgroup 4) for 3.5 h at 38.5 degrees C under 5% CO2. For control group, IVM oocytes were fertilized using frozen-thawed camel spermatozoa separated by swim-up method then suspended in Fert-TALP medium supplemented with 6 mg/ml BSA (FAF) + 10 microg/ml heparin. In all groups, oocytes were in vitro cultured in SOFaa medium + 5% FCS and 5 microg/ml insulin + 50 microg/ml gentamycin. Cleavage rate and embryo development were checked on Days 2, 5 and 8. An average of 11.3 +/- 0.3 COCs were recovered/dromedary ovary. Categories 1 and 2 represented 33.1% and 34.8%, respectively, and were significantly higher (p < 0.01) than the other categories (19.1, 9.2 and 2.6% for categories 3-5, respectively). Category 6 (embryo-like structures) represented 1.2% of the recovered oocytes, staining of these embryo-like structures with orcien dye indicated the presence of divided cells with condensed nuclei. Dromedary oocytes averaged 166.2 +/- 2.6 microm in diameter with black cytoplasm. Chemical activation of IVM dromedary oocyte with first Pb in 7% ethanol or 50 microM Ca A followed by culture in 2 mM 6-DMAP showed significantly higher (p < 0.01) cleavage and developmental rates to the morula stage than oocytes activated using 7% ethanol or 50 microM Ca A followed by 10 microg/ml CHX or in vitro fertilized control group. Higher (p < 0.01) proportion of oocytes sequentially cultured in 10 microg/ml CHX or that in vitro fertilized were arrested at the 2-4-cell stage compared with that cultured in 6-DMAP.

A comparative study of parthenogenic activation and in vitro fertilization of bubaline oocytes

The effect of chemical activation protocols on in vitro-matured oocytes were compared to results with IVF (natural activation). Buffalo ovaries were collected in normal saline and transported to the laboratory within 2 h of slaughter. Good quality oocytes, collected by aspiration from 3 to 10 mm follicles, were matured for 22-24 h. Matured oocytes were subjected to either IVF (control) or chemical activation (treatment). For IVF, in vitro-matured oocytes were co-incubated with in vitro-capacitated approximately 1x10(6) frozen/thawed sperm of a Murrah bull and fertilized in modified synthetic oviductal fluid (mSOF) medium. Chemicals for oocytes activation comprised (a) 7% ethanol (ET) for 7 min+2.5 mM 6-dimethyl amino purine (6-DMAP) for 4h, (b) 7% ET for 7 min+10 microg/ml cycloheximide (CHX) for 6h and (c) 7% ET for 7 min+2.5 mM 6-DMAP+10 microg/ml CHX for 6 h. To study embryo development, fertilized and chemically activated oocytes were cultured in mSOF medium for up to 8 days. In this study, a mean of 1.9+/-0.02 maturable oocytes/ovary were recovered and 90.4% matured. Cleavage rate was significantly higher following ET+DMAP, ET+CHX and ET+CHX+DMAP activation (52.5%, 52.5% and 44.4%, respectively) compared to IVF (36.5%, 23.4% and 26.8%, respectively). Blastocyst development (30.9% versus 15.2%) was also significantly higher following ET+CHX+DMAP activation than IVF. The results of parthenogenesis reveal that buffalo oocytes had better inherent developmental competence and that the poor cleavage and embryo development following IVF may be due partly to the poor quality of frozen/thawed sperm, improper sperm capacitation and/or fertilization.

Chemically Assisted Handmade Enucleation of Porcine Oocytes

The purpose of our work was to find an efficient and reliable chemically assisted procedure for enucleation of porcine oocytes connected to the handmade cloning (HMC) technique without the potentially harmful chromatin staining and ultraviolet (UV) irradiation for cytoplast selection. After 41-42 h in vitro maturation, porcine oocytes were incubated with 0.4 microg/mL demecolcine for 45 min. Subsequently, the cumulus cells were removed and zonae pellucidae were partially digested. Oocytes with extrusion cones or oocytes only with polar body (PB) were subjected to oriented bisection. Less than half of the cytoplasm with the extrusion cone or adjacent to the PB was removed with a microblade. The remaining putative cytoplasts, containing the major part of the cytoplasm, were used as recipients for reconstruction with porcine fetal fibroblasts as nuclear donors. The overall efficiency achieved with chemically assisted enucleation was higher compared to oriented bisection without demecolcine incubation (90 +/- 3% vs. 81 +/- 4%, respectively; mean +/- absolute deviation [AD]). Reconstructed and activated embryos were cultured in vitro for 7 days. Fusion, cleavage and blastocyst rates were 87 +/- 7%, 97 +/- 6%, and 28 +/- 9%, respectively. These rates are at least as good as those achieved with normal HMC (81 +/- 4%, 87 +/- 8%, and 21 +/- 9%, respectively). For traditional, micromanipulator-based cloning, fusion and blastocyst rates were similar (81 +/- 10% and 21 +/- 6%, respectively), but the cleavage rate was lower (69 +/- 9%). In conclusion, chemically assisted handmade enucleation seems to be a simpler and potentially superior alternative to more conventional methods used for somatic cell nuclear transfer in pigs.

Somatic cell nuclear transfer in buffalos: effect of the fusion and activation protocols and embryo culture system on preimplantation embryo development

The present study was conducted primarily to evaluate several factors that affect the nuclear transfer programme in water buffalos, in which relatively few studies have been performed. Embryos reconstructed with quiescent fetal fibroblasts and metaphase II cytoplasts were matured for 24 h, and activation was found to be comparatively better than in those matured for 30 h. A significantly higher proportion of embryos fused (52.0 ± 1.9) and cleaved (51.2 ± 1.7) when the couplets were fused 4–6 h before activation than when fused and activated simultaneously (46.5 ± 1.6 and 44.5 ± 2.0, respectively). Development of nuclear transfer embryos to the blastocyst stage (4.8 ± 2.2) was supported by a commercially available sequential medium, and cleavage (76.5 ± 2.8) was significantly higher in this medium compared with cleavage in TCM-199 with oviduct epithelial cell coculture (45.6 ± 1.5) and synthetic oviduct fluid (21.8 ± 6.6). Of the 16 cloned embryos transferred, none resulted in pregnancy. The present study demonstrates that optimal numbers of cloned buffalo blastocysts can be obtained from oocytes matured for 24 h, fused 3–4 h before activation and cultured in a commercially available sequential media (G1/G2), thus providing further information to enable successful nuclear transfer in buffalos.