Prepubertal propagation of transgenic cloned goats by laparoscopic ovum pick-up and in vitro embryo production

Laparoscopic ovum-pick up and in vitro embryo production in gonadotropin-stimulated gilts: Preliminary results and envisioned applications

The present study was conducted to establish if laparoscopic ovum pick-up (LOPU) could be adapted to the swine species, and if the developmental competence of LOPU-sourced oocytes from peripubertal gilts could be improved by gonadotropin stimulation, by comparing with oocytes sourced from slaughtered gilts lacking hormonal stimulation. Estrus was synchronized in 34 gilts of ∼6-8 months of age by daily oral administration of 17.6 mg altrenogest for 13 days and 10 mg dinoprost IM on the last day of altrenogest. Follicular development was stimulated in all gilts with a single injection of 1250 IU eCG given 3 days before LOPU (together with the 12th dose of altrenogest). In about half of the gilts (Group eCG-hCG), 500 IU hCG were injected IM ∼72 h after eCG injection, or ∼16-18 h prior to LOPU, to initiate oocyte maturation in vivo, while the remaining animals only received eCG (Group eCG). Most gilts underwent LOPU twice alternating the gonadotropin protocol, thereby decreasing the impact of individual variation on results. Abattoir-sourced oocytes from prepubertal gilts served as Control. Following LOPU, oocytes were in vitro matured, fertilized, and cultured to the blastocyst stage following standard procedures, while oocytes collected from Group eCG-hCG gilts were considered partly matured in vivo and were matured for ∼24 h instead of ∼44 h. Embryos reaching the blastocyst stage were fixed and stained to assess quality through cell numbers. There were no significant differences in the number of follicles aspirated and cumulus-oocyte complexes (COCs) recovered between Groups eCG-hCG and eCG (22.4 and 16.9 vs. 22.6 and 17.6, P > 0.05), as well as the recovery rate (76.6 vs. 78.1, P > 0.05). Cleavage rate was not different between Group eCG-hCG, Group eCG and Control (61.1 vs. 64.4 vs. 53.4 %, P > 0.05). However, the blastocyst rate over total oocytes (32.2 vs. 36.9 vs. 11.1 %, P < 0.05), blastocyst rate over cleaved oocytes (51.8 vs. 55.1 vs. 21.2 %, P < 0.01) and the average number of cells/blastocyst (89.6 vs. 87.5 vs. 62.2, P < 0.01) were unaffected by hCG treatment in LOPU-sourced oocytes, but both LOPU groups were significantly higher than abattoir-sourced oocytes, respectively. Our results suggest LOPU may become a powerful tool for sourcing swine oocytes with higher developmental competence than abattoir-sourced oocytes and known disease status for creating swine models for human biomedical applications, as well as for accelerated genetic gain in swine breeding programs.

Factors Affecting the Efficiency of In Vitro Embryo Production in Prepubertal Mediterranean Water Buffalo

Embryos from prepubertal water buffalo can be produced using laparoscopic ovum pickup (LOPU) and in vitro embryo production (IVEP). However, to date, it is unclear what factors and environmental conditions can affect LOPU-IVEP efficiency in prepubertal animals, especially buffalo. In this study, we explored the impact of season, age and individual variation among female donor animals, as well as the effect of the sire used for in vitro fertilization. Donor animals between 2 and 6 months of age were stimulated using gonadotropins prior to LOPU, which was performed at two-week intervals. Following in vitro maturation and fertilization, the resulting embryos were then cultured to the blastocyst stage until they were either vitrified or transferred into recipient animals. The number of follicles available for aspiration and embryo development rates was stable throughout the year. As animals became older, there was a slight trend for fewer COCs recovered from LOPU and better embryo development. There was a large individual variation in both ovarian response and the developmental competence of oocytes among donors. The bull used for fertilization also had a significant impact on embryo development. Upon embryo transfer, pregnancy rates were not affected by the number of embryos transferred per recipient. The best pregnancy rates were achieved when transferring blastocysts, compared to compact morula or hatched blastocysts. Finally, vitrification had no effect on pregnancy rate compared to fresh embryos.

Intrafollicular oocyte transfer (IFOT): Potential feasibility in the ovine species

Intra-follicular oocyte transfer (IFOT) is a promising and innovative technique for in vivo embryo production previously described for equines and bovines. The aim of this study was to assess the feasibility of IFOT in the ovine species. Two preliminary in vivo and in vitro trials were performed to test the optimal procedures and timing for IFOT. In the in vivo trial, follicular growth was monitored with transrectal ultrasonography in ten adult ewes to preliminarily determine the ovulation and ideal timing for IFOT. The in vitro trial assessed i) the optimal inner diameter of the injection needle and ii) the recovery rate and integrity of injected cumulus-oocyte complexes (COCs) after follicle aspiration. For IFOT and embryo collection, five ewes were synchronized by CIDR insertion. Forty hours after CIDR removal, in ewes under sedation and general anesthesia, the ovaries were exposed by laparotomy, and the preovulatory follicle was injected with COCs previously collected from ovaries obtained from an abattoir. At 4 h after surgery, fully recovered ewes were housed in a paddock with a ram of proven fertility. Crayon marking on ram's chest was used to detect mating. Ovulation was assessed 40 h after the transfer of oocytes by transrectal ultrasonography. On day 6 after IFOT, embryo collection was performed by uterine flushing. In the in vitro testing, injection of >5 mm follicles with a 28 G needle loaded with 30 COCs in a 5 μL volume resulted in higher recovery rates and better preservation of COCs integrity. In the in vivo trial, ultrasound scanning revealed that ovulation occurred between 60 and 72 h after CIDR removal in all animals. In one ewe subjected to IFOT, 22/24 oocytes were effectively injected into the preovulatory follicle, but no embryos were collected after flushing. In the remaining four animals, 85/102 oocytes were injected, and six cleaved embryos, 12 morulae and 1 blastocyst were collected, including native embryos. This preliminary investigation indicated that IFOT in ovine species resulted in ovulation, fimbrial capture, tubal transport of heterologous oocytes and in vivo embryo production. Further studies are needed to optimize the embryo recovery rate and develop less invasive techniques for oocyte injection and uterine flushing, such as through a laparoscopic or transcervical approach.

Generating Cloned Goats by Somatic Cell Nuclear Transfer-Molecular Determinants and Application to Transgenics and Biomedicine

The domestic goat (Capra aegagrus hircus), a mammalian species with high genetic merit for production of milk and meat, can be a tremendously valuable tool for transgenic research. This research is focused on the production and multiplication of genetically engineered or genome-edited cloned specimens by applying somatic cell nuclear transfer (SCNT), which is a dynamically developing assisted reproductive technology (ART). The efficiency of generating the SCNT-derived embryos, conceptuses, and progeny in goats was found to be determined by a variety of factors controlling the biological, molecular, and epigenetic events. On the one hand, the pivotal objective of our paper was to demonstrate the progress and the state-of-the-art achievements related to the innovative and highly efficient solutions used for the creation of transgenic cloned does and bucks. On the other hand, this review seeks to highlight not only current goals and obstacles but also future challenges to be faced by the approaches applied to propagate genetically modified SCNT-derived goats for the purposes of pharmacology, biomedicine, nutritional biotechnology, the agri-food industry, and modern livestock breeding.

Laparoscopic Ovum Pick-Up Followed by In Vitro Embryo Production and Transfer in Assisted Breeding Programs for Ruminants

The potential of laparoscopic ovum pick-up (LOPU) followed by in vitro embryo production (IVEP) as a tool for accelerated genetic programs in ruminants is reviewed in this article. In sheep and goats, the LOPU-IVEP platform offers the possibility of producing more offspring from elite females, as the procedure is minimally invasive and can be repeated more times and more frequently in the same animals compared with conventional surgical embryo recovery. On average, ~10 and ~14 viable oocytes are recovered by LOPU from sheep and goats, respectively, which results in 3-5 transferable embryos and >50% pregnancy rate after transfer. LOPU-IVEP has also been applied to prepubertal ruminants of 2-6 months of age, including bovine and buffalo calves. In dairy cattle, the technology has gained momentum in the past few years stemming from the development of genetic marker selection that has allowed predicting the production phenotype of dairy females from shortly after birth. In Holstein calves, we obtained an average of ~22 viable oocytes and ~20% transferable blastocyst rate, followed by >50% pregnancy rate after transfer, declaring the platform ready for commercial application. The present and future of this technology are discussed with a focus on improvements and research needed.

Expression profile of genes as indicators of developmental competence and quality of in vitro fertilization and somatic cell nuclear transfer bovine embryos

Reproductive biotechnologies such as in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) enable improved reproductive efficiency of animals. However, the birth rate of in vitro-derived embryos still lags behind that of their in vivo counterparts. Thus, it is critical to develop an accurate evaluation and prediction system of embryo competence, both for commercial purposes and for scientific research. Previous works have demonstrated that in vitro culture systems induce alterations in the relative abundance (RA) of diverse transcripts and thus compromise embryo quality. The aim of this work was to analyze the RA of a set of genes involved in cellular stress (heat shock protein 70-kDa, HSP70), endoplasmic reticulum (ER) stress (immunoglobulin heavy chain binding protein, Bip; proteasome subunit β5, PSMB5) and apoptosis (BCL-2 associated X protein, Bax; cysteine aspartate protease-3, Caspase-3) in bovine blastocysts produced by IVF or SCNT and compare it with that of their in vivo counterparts. Poly (A) ⁺ mRNA was isolated from three pools of 10 blastocysts per treatment and analyzed by real-time RT-PCR. The RA of three of the stress indicators analyzed (Bax, PSMB5 and Bip) was significantly increased in SCNT embryos as compared with that of in vivo-derived blastocysts. No significant differences were found in the RA of HSP70 and Caspase-3 gene transcripts. This study could potentially complement morphological analyses in the development of an effective and accurate technique for the diagnosis of embryo quality, ultimately aiding to improve the efficiency of assisted reproductive techniques (ART).

Influence of heparin or the presence of cumulus cells during fertilization on the in vitro production of goat embryos

Considerable research has been focused on in vitro production (IVP) of goat embryos to improve its efficiency. In Experiment 1, the effect of the cumulus cells by comparing slaughterhouse-oocytes denuded on purpose (DOP) prior to IVF to intact COC, and the effect of heparin during IVF were assessed. In Experiment 2, oocytes that were already denuded at collection (DOC), DOP and intact COC were studied. Three treatments used oocytes denuded at collection: DOC oocytes were cultured alone for both IVM and IVF; DOC and COC were cultured together for both IVM and IVF or DOC were IVM alone and then mixed with COC for IVF. In other treatments, COC were allocated to four IVF treatments: Intact COC; COC were denuded prior to IVF; COC were denuded and IVF with added cumulus cells; COC were denuded and IVF mixed with intact COC giving two sub-treatments: Denuded oocytes that were IVF with COC; and COC that were IVF with denuded oocytes. After fertilization, all presumptive zygotes were cultured for 8 days. In Experiment 1, the yield of blastocysts as a proportion of total oocytes was greater (P<0.05) for COC that were IVF in the presence of heparin (54%) than without heparin (42%) or oocytes already denuded at collection that were IVF with or without heparin (41%; 38%; respectively). In Experiment 2, the developmental potential of oocytes denuded at collection was reduced (cleavage and blastocyst rates calculated from total oocytes: 34%; 11%, respectively) as compared to COC (77%; 59%, P<0.05). However, when equal numbers of both were mixed at the start of IVM, the rates were not significantly different to COC alone (68%; 45%), but when both were mixed equally only for IVF, the rates were reduced (57%; 40%, P<0.05). Denuded oocytes co-cultured with cumulus cells were not significantly different to intact COC (76%; 55%). The effect of adding COC during IVF to oocytes denuded after IVM was similar to adding cumulus cells to the same type of oocytes. In conclusion, both the use of heparin and the association of oocytes with cumulus cells, either detached or in intimate contact, during IVM and/or IVF significantly improve IVP of goat embryos. Furthermore, some oocytes that are already denuded at collection will develop satisfactorily to blastocysts when matured and fertilized with intact COC.

Recombinant human butyrylcholinesterase from milk of transgenic animals to protect against organophosphate poisoning

Dangerous organophosphorus (OP) compounds have been used as insecticides in agriculture and in chemical warfare. Because exposure to OP could create a danger for humans in the future, butyrylcholinesterase (BChE) has been developed for prophylaxis to these chemicals. Because it is impractical to obtain sufficient quantities of plasma BChE to treat humans exposed to OP agents, the production of recombinant BChE (rBChE) in milk of transgenic animals was investigated. Transgenic mice and goats were generated with human BChE cDNA under control of the goat beta-casein promoter. Milk from transgenic animals contained 0.1-5 g/liter of active rBChE. The plasma half-life of PEGylated, goat-derived, purified rBChE in guinea pigs was 7-fold longer than non-PEGylated dimers. The rBChE from transgenic mice was inhibited by nerve agents at a 1:1 molar ratio. Transgenic goats produced active rBChE in milk sufficient for prophylaxis of humans at risk for exposure to OP agents.

Laparoscopic ovum pick-up followed by in vitro embryo production for the reproductive rescue of aged goats of high genetic value

The efficiency of laparoscopic ovum pick-up (LOPU) followed by in vitro embryo production (IVEP) in the propagation of aged goats with poor reproductive performance was evaluated in the present study. Follicular development was stimulated in donor goats with 80 mg follicle-stimulating hormone and 300 IU equine chorionic gonadotrophin administered 36 h before LOPU. In addition, goats were heat synchronised with intravaginal sponges containing 60 mg medroxyprogesterone acetate for 10 days and a luteolytic injection of 125 µg cloprostenol 36 h before sponge removal and LOPU. Following in vitro maturation (IVM), oocytes were fertilised in vitro with frozen–thawed semen produced using the egg yolk-free Bioxcell extender (IVM, L’Aigle, France). The average number of follicles aspirated (17.9 ± 8.0 per goat), oocytes recovered (15.7 ± 8.4 per goat) and cleavage after IVM/in vitro fertilisation followed by a short 24-h in vitro culture in modified synthetic oviduct fluid medium (72 ± 7%) were similar to results reported previously by our group and others in younger goats. A total of 296 embryos was transferred into 50 heat-synchronised recipients, of which 40 became pregnant (80%) and 38 progressed all the way to term, delivering 86 live kids. The present study indicates that LOPU-IVEP can be used successfully to extend the reproductive life of valuable goats that have acquired difficulties becoming pregnant by artificial insemination after multiple kiddings.

Improved vitrification method allowing direct transfer of goat embryos

The aim of this study was to design a vitrification method suited to field embryo transfer experiments in goat. In a first experiment, a standard vitrification protocol, previously designed for sheep embryos was compared to slow freezing of goat embryos. No significant difference was observed on kidding rate (48% versus 69%, respectively), nor on embryo survival rate (35% versus 45%). Second experiment: all embryos were vitrified. After warming, embryos were either transferred directly (direct transfer), or after in vitro dilution of the cryoprotectants (conventional transfer). The kidding rate was not affected by the transfer method (38% versus 23%, respectively). However, embryo survival rate tended to be higher after direct transfer (26% versus 14%). Third experiment: OPS vitrification was compared to standard vitrification. The kidding rate was not affected (22% versus 39%, respectively), but the embryo survival rate was lower after OPS (14% versus 28%). Fourth experiment: 0.4M sucrose was added with cryoprotectants in vitrification. The kidding rate after direct transfer was significantly enhanced after addition of sucrose (56% versus 27%, respectively), whereas embryo survival rate was not significantly affected (32% versus 18%). Fifth experiment: vitrification with sucrose supplementation was compared to slow freezing. No significant difference was observed after direct transfer on kidding rate (52% versus 31%, respectively), but embryo survival rate tended to be higher after vitrification (34% versus 21%). In conclusion, our results indicate that addition of 0.4M sucrose in association with direct transfer improves significantly the viability of goat vitrified embryos.

Developmental expression of pluripotency determining factors in caprine embryos: Novel pattern of NANOG protein localization in the nucleolus

Transcription factors, POU5F1/OCT4 and NANOG, whose expression is restricted to the inner cell mass (ICM) in mouse and human blastocysts, are used to characterize undifferentiated embryonic stem cells (ESC) in vitro. However, POU5F1 may not be a useful marker in domestic animals due to its expression in both ICM and trophectoderm (TE), while NANOG mRNA and protein expression have only been described fully in mice. In an effort to identify ESC markers for domestic animals, expression patterns of NANOG, POU5F1, and the cell surface markers (SSEA1, SSEA4, TRA-1-60, TRA-1-81) were examined in preimplantation goat embryos, a species that has proven to be a superior choice for the production of transgenic proteins in milk (biopharming). Our results indicate that while goat embryos express POU5F1, SSEA1, and SSEA4 proteins, their expression is not strictly restricted to the ICM. In a unique staining pattern, NANOG protein was localized to the nucleoplasm and nucleoli in ICM cells, but was localized strictly to nucleoli in TE. This pattern may reflect down-regulation of protein by sequestration/degradation utilizing a nucleolar mechanism known to operate in stem cells. Furthermore, NANOG mRNA in TE was also significantly down-regulated as compared with that in ICM. Taken together, this novel expression pattern of NANOG in goat preimplantation embryos suggests that NANOG could serve as marker of pluripotency in goats and may be useful in derivation and characterization of caprine ESC. This study is the first to characterize both NANOG mRNA and protein expression in any species other than the mouse.

Advanced assisted reproduction technologies (ART) in goats

Assisted reproduction technologies (ART) are reviewed with special emphasis on goat genetic improvement programs. Estrous synchronization and artificial insemination are the most commonly used ART worldwide because of their simplicity and excellent cost/benefit, especially when proven sires are used. Multiple ovulation and embryo transfer (MOET) has not become widely used due to its unpredictability. In vitro embryo production using oocytes collected by laparoscopy from valuable donors has the potential to improve the results obtained from MOET and expand its applications (for example, using prepubertal donors). However, the costs and inefficiencies of the system might restrict its use to special situations. Finally, transgenesis and cloning are expected to have a significant impact on the future genetic improvement of livestock. However, because of low efficiencies and high costs, their present use is restricted to applications with high returns such as the production of recombinant proteins of pharmaceutical and biomedical interest.