Preimplantation development of cloned canine embryos recovered by hysterectomy or surgical uterine flushing and subsequent pregnancy outcomes

Prolonged glucocorticoid administration affects oocyte morphology in cats (Felis catus) undergoing an ovarian stimulation protocol

While captivity-related stress and the associated rise in baseline glucocorticoid (GC) concentrations have been linked to ovarian quiescence in some felid species, no study has examined the effects of elevated GC on oocyte quality. This study examined the effects of exogenous GC administration on the ovarian response and oocyte quality of domestic cats after an ovarian stimulation protocol. Entire mature female cats were divided into treatment (n = 6) and control (n = 6) groups. Cats in the GC treatment (GCT) group were given 1 mg kg-1 oral prednisolone daily from Day 0-45. All cats (n = 12) were given 0.088 mg kg-1 day-1 progesterone orally from Day 0-37, before treatment with 75 IU eCG im to induce follicular growth on Day 40, followed by 50 IU hCG im 80 h later to induce ovulation. Cats were ovariohysterectomised 30 h after the hCG treatment. Blood samples were collected on Days 0, 10, 30 and 40 (prior to eCG treatment), 80 h after eCG treatment, and on Day 45 for cortisol, glucose, prednisolone, oestradiol, and progesterone analysis. Cortisol concentrations did not differ between treatment groups throughout the study. Mean glucose concentrations were higher in the GCT cats (P = 0.004). Prednisolone was undetectable in all samples. Oestradiol and progesterone concentrations confirmed that the eCG treatment stimulated follicular activity and ovulation in all cats. Following ovariohysterectomy, the ovarian responses were graded (1 = excellent, 4 = poor) and oocytes retrieved from the oviducts. Each oocyte was given a total oocyte score (TOS: using an 9-point scale, 8 = best) based on four parameters: oocyte morphology, size, ooplasm uniformity and granularity, and zona pellucida (ZP) thickness and variation. Ovulation was confirmed in all cats, with a mean of 10.5 ± 1.1 ovulations per cat. Ovarian mass, ovarian response, number of ovulations, and oocyte recovery did not differ between groups. Oocyte diameter did not differ between the groups, but the ZP was thinner in the GCT group (3.1 ± 0.3 μm vs. 4.1 ± 0.3 μm, P = 0.03). The TOS was similar between treatment and control cats, but the ooplasm grade was lower (1.5 ± 0.1 vs. 1.9 ± 0.1, P = 0.01) and there was a tendency for ZP grade to be poorer (0.8 ± 0.1 vs. 1.2 ± 0.2; P = 0.08) in the treatment group. In conclusion, the GC treatment resulted in morphological changes to oocytes collected following ovarian stimulation. Whether these changes would affect fertility warrants further investigation.

Impact of co-transfer of embryos produced by somatic cell nuclear transfer using two types of donor cells on pregnancy outcomes in dogs

Objective

The present study analyzed the influence of co-transferring embryos with high and low cloning efficiencies produced via somatic cell nuclear transfer (SCNT) on pregnancy outcomes in dogs.

Methods

Cloned dogs were produced by SCNT using donor cells derived from a Tibetan Mastiff (TM) and Toy Poodle (TP). The in vivo developmental capacity of cloned embryos was evaluated. The pregnancy and parturition rates were determined following single transfer of 284 fused oocytes into 21 surrogates and co-transfer of 47 fused oocytes into four surrogates.

Results

When cloned embryos produced using a single type of donor cell were transferred into surrogates, the pregnancy and live birth rates were significantly higher following transfer of embryos produced using TP donor cells than following transfer of embryos produced using TM donor cells. Next, pregnancy and live birth rates were compared following single and co-transfer of these cloned embryos. The pregnancy and live birth rates were similar upon co-transfer of embryos and single transfer of embryos produced using TP donor cells but were significantly lower upon single transfer of embryos produced using TM donor cells. Furthermore, the parturition rate for TM dogs and the percentage of these dogs that remained alive until weaning was significantly higher upon co-transfer than upon single transfer of embryos. However, there was no difference between the two embryo transfer methods for TP dogs. The mean birth weight of cloned TM dogs was significantly higher upon single transfer than upon co-transfer of embryos. However, the body weight of TM dogs did not significantly differ between the two embryo transfer methods after day 5.

Conclusion

For cloned embryos with a lower developmental competence, the parturition rate and percentage of dogs that remain alive until weaning are increased when they are co-transferred with cloned embryos with a greater developmental competence.

Transcriptional activities of human elongation factor-1α and cytomegalovirus promoter in transgenic dogs generated by somatic cell nuclear transfer

Recent advances in somatic cell nuclear transfer (SCNT) in canines facilitate the production of canine transgenic models. Owing to the importance of stable and strong promoter activity in transgenic animals, we tested human elongation factor 1α (hEF1α) and cytomegalovirus (CMV) promoter sequences in SCNT transgenic dogs. After transfection, transgenic donor fibroblasts with the hEF1α-enhanced green fluorescence protein (EGFP) transgene were successfully isolated using fluorescence-activated cell sorting (FACS). We obtained four puppies, after SCNT, and identified three puppies as being transgenic using PCR analysis. Unexpectedly, EGFP regulated by hEF1α promoter was not observed at the organismal and cellular levels in these transgenic dogs. EGFP expression was rescued by the inhibition of DNA methyltransferases, implying that the hEF1α promoter is silenced by DNA methylation. Next, donor cells with CMV-EGFP transgene were successfully established and SCNT was performed. Three puppies of six born puppies were confirmed to be transgenic. Unlike hEF1α-regulated EGFP, CMV-regulated EGFP was strongly detectable at both the organismal and cellular levels in all transgenic dogs, even after 19 months. In conclusion, our study suggests that the CMV promoter is more suitable, than the hEF1α promoter, for stable transgene expression in SCNT-derived transgenic canine model.

Ethics in animal breeding

Ethical breeding involves the use of healthy animals true to their species in behaviour and physical appearance, and when applicable, showing a sustainable performance. The concerns for the species/breed are essential parts of the breeding goals, including preservation of genetic resources within the species/breed, and the health and welfare of the individual animal. Ethical and welfare considerations were often not prioritized in developing new breeds of production or companion animals. As a result, animal breeding practices are increasingly becoming part of the debate on animal welfare. In companion animals, breeding for curiosity or "cuteness" may be a goal in itself, although dogs are also bred for utility. In production animals, breeding focus is on performance, i.e., quantitative entities and financial income, rather than physical appearance. For instance, dairy cows are bred to be larger and to have higher milk yields, sows and ewes to produce more offspring, and horses are designed for riding, racing, and companionship. Overbreeding in relation to current demand of horses, cats, and dogs raises welfare issues due to abandonment or killing of horses and millions of cats and dogs every year. There is variable regulation of health requirements for breeding animals in different countries of the world. In many countries, consumers are becoming increasingly aware of animal welfare issues such as negative effects of certain production traits in farm animals, leading to decreased demand for their meat at a time where increased food production is becoming crucial. Amidst these dilemmas are the veterinarians. This paper deals with issues connected to traditional breeding as well as some of the breeding technologies, and includes food safety, ethics, and animal welfare.

Establishment of TP53-knockout canine cells using optimized CRIPSR/Cas9 vector system for canine cancer research

Background

Genetic engineering technology such as clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system provides a powerful tool for developing disease models and determining gene functions. Recent interests in canine cancer models have highlighted the necessity of developing genetic engineering tools for dogs. In this study, we attempted to generate optimized CRISPR/Cas9 system to target canine tumor protein 53 (TP53), one of the most crucial tumor suppressor genes, to establish TP53 knockout canine cells for canine cancer research.

Results

We constructed CRISPR/Cas9 vectors using each of three TP53 gene-targeting guide RNAs (gRNAs) with minimal off-target potential. After transfection, we obtained several clones of TP53 knockout cells containing “indel” mutations in the targeted locus which had infinite cellular life span, resistance to genotoxicity, and unstable genomic status in contrast to normal cells. Of the established TP53 knockout cells, TP53KO#30 cells targeted by TP53 gRNA #30 showed non-cancerous phenotypes without oncogenic activation both in vitro and in vivo. More importantly, no off-target alteration was detected in TP53KO#30 cells. We also tested the developmental capacity of TP53 knockout cells after application of the somatic cell nuclear transfer technique.

Conclusions

Our results indicated that TP53 in canine cells was effectively and specifically targeted by our CRISPR/Cas9 system. Thus, we suggest our CRISPR/Cas9-derived canine TP53 knockout cells as a useful platform to reveal novel oncogenic functions and effects of developing anti-cancer therapeutics.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0491-5) contains supplementary material, which is available to authorized users.

SV40 Large T Antigen Disrupts Embryogenesis of Canine and Porcine Somatic Cell Nuclear Transfer Embryo

Background

Somatic cell nuclear transfer (SCNT) is a useful biotechnological tool for transgenic animal production using genetically modified somatic cells (GMSCs). However, there are several limitations preventing successful transgenic animal generation by SCNT, such as obtaining proper somatic donor cells with a sufficiently long life span and proliferative capacity for generating GMSCs. Here, we established simian virus 40 large T antigen (SV40LT)-mediated lifespan-extended canine fibroblast cells (SV40LT-K9 cells) and evaluated their potential as nuclei donors for SCNT, based on cellular integrity and SCNT embryo development.

Results

SV40LT did not cause canine cell transformation, based on cell morphology and proliferation rate. No anchorage-independent growth in vitro and tumorigenicity in vivo were observed. After SCNT with SV40LT-K9 cells, embryos were transferred into surrogate dogs. All dogs failed to become pregnant. Most embryos did not proceed past the 8-cell stage and only one surrogate showed an implantation trace in its oviduct, indicating that the cells rarely developed into blastocysts. Because of the absence of an in vitro maturation method for canine embryos, we performed identical experiments using porcine fibroblast cells. Similarly, SV40LT did not transform porcine fibroblast cells (SV40LT-Pig cells). During in vitro development of SV40LT-Pig cell-driven SCNT embryos, their blastocyst formation rate was clearly lower than those of normal cells. Karyotyping analysis revealed that both SV40LT-K9 and SV40LT-Pig cells had aberrant chromosomal statuses.

Conclusions

Although lifespan-extended canine and porcine cells via SV40LT exhibit no apparent transforming changes, they are inappropriate for use as nuclei donors for SCNT because of their aneuploidy.

Relationship between time post-ovulation and progesterone on oocyte maturation and pregnancy in canine cloning

Canine oocytes ovulated at prophase complete meiosis and continue to develop in presence of a high progesterone concentration in the oviduct. Considering that meiotic competence of canine oocyte is accomplished in the oviductal environment, we postulate that hormonal milieu resulting from the circulating progesterone concentration may affect oocyte maturation and early development of embryos. From 237 oocyte donors, 2620 oocytes were collected and their meiotic status and morphology were determined. To determine optimal characteristics of the mature oocytes subjected to nuclear transfer, a proportion of the meiotic status of the oocytes were classified in reference to time post-ovulation as well as progesterone (P4) level. A high proportion of matured oocytes were collected from >126h (55.5%) post-ovulation or 40-50ngmL^-1 (46.4%) group compared to the other groups. Of the oocyte donors that provided mature oocytes in vivo, there was no correlation between serum progesterone of donors and time post ovulation, however, time post-ovulation were significantly shorter for <30ng/mL group (P<0.05). Using mature oocytes, 1161 cloned embryos were reconstructed and transferred into 77 surrogates. In order to determine the relationship between pregnancy performance and serum progesterone level, embryos were transferred into surrogates showing various P4 serum levels. The highest pregnancy (31.8%) and live birth cloning efficacy (2.2%) rates were observed when the embryos were transferred into surrogates with circulating P4 levels were from 40 to 50ngmL^-1. In conclusion, measurement of circulating progesterone of female dog could be a suitable an indicator of the optimal time to collect quality oocyte and to select surrogates for cloning.