Effect of equine chorionic gonadotropin on the efficiency of superovulation induction for in vivo and in vitro embryo production in the cat

Vaginal stimulation enhances ovulation of queen ovaries treated using a combination of eCG and hCG

Follicular changes throughout the oestrous phase have been poorly documented in queens because of the location and the small size of ovaries. We investigated follicular development in queens treated with a combination of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) and evaluated the effects of vaginal stimulation by a tomcat on ovulation induction. A hormonal treatment was administered using a simple crossover design. Four queens were administered 150 IU of eCG (day 1) and 250 IU of hCG on day 5 and 6. Half of the queens were mated with a vasectomised tomcat for 3 days after hCG injection. Ultrasound imaging of the ovaries clamped at a subcutaneous site was performed once a day from day 1 to 7, and on day 13, and the serum concentrations of oestradiol and progesterone were examined on day 1, 5, 7 and 13. The mean number of follicles gradually increased with the eCG treatment and decreased after hCG injection. The ovulation rate of follicles was significantly higher in the vaginal stimulation group (70.0%) than in the control group (42.6%). During the hormonal treatments, the serum concentration of oestradiol and progesterone did not differ between the two groups. Ultrasound imaging of the ovaries clamped at a subcutaneous site showed that eCG and hCG treatment promoted the follicular growth and corpus luteum formation, respectively. The combination of hCG injection with vaginal stimulation by a vasectomised tomcat enhanced the ovulation rate of follicles.

Embryo aggregation allows the production of kodkod (Leopardus guigna) blastocysts after interspecific SCNT

The kodkod (Leopardus guigna) is a small felid endemic of Chile and is considered a vulnerable species. Domestic cat oocytes have been successfully used as recipient cytoplast to reprogram somatic cells from different felids by interspecific somatic cell nuclear transfer (iSCNT). The developmental competence of felid embryos generated by iSCNT can be improved by the aggregation method using a zona-free culture system. The objective of this research was to evaluate the developmental competence of kodkod embryos generated by iSCNT using domestic cat oocytes and the aggregation method. For this purpose, five experimental group were done: (1) cat embryos generated by IVF, (2) cat embryos generated by SCNT (Ca1x), (3) aggregated cat embryos generated by SCNT (Ca2x), (4) kodkod embryos generated by iSCNT (K1x) and (5) aggregated kodkod embryos generated by iSCNT (K2x). Cleavage, morulae and blastocyst rates were estimated. The blastocyst diameter was evaluated. The gene expression level of pluripotency (OCT4, SOX2 and NANOG) and differentiation markers (CDX2 and GATA6) was analyzed in blastocysts. Morulae rate was higher in the IVF group and when cloned embryos were cultured in aggregates (IVF: 68.2%, Ca2x: 58.0% and K2x: 62.4%) compared to individually cultured kodkod embryos (K1x: 37.0%) (P < 0.05). Embryo aggregation increased blastocysts formation in the Ca2x group (30.9%) to a similar rate compared to the IVF group (44.5%) (P > 0.05). No blastocysts were generated in the K1x group, whereas blastocysts formation was obtained in K2x group (5.9%). The diameter of blastocysts from the K2x group (172.8 μm) was significantly lower than blastocysts from the Ca2x group (P < 0.05). The relative expression of OCT4 was lower in blastocysts from Ca1x than in blastocysts from IVF (P < 0.05). Furthermore, CDX2 expression was lower in blastocysts from Ca2x than in blastocysts from Ca1x and IVF groups (P < 0.05). In kodkod embryos, only one blastocyst from the K2x group expressed OCT4. No expression of SOX2, NANOG, CDX2 and GATA6 was detected in kodkod blastocysts. In conclusion, after iSCNT, domestic cat oocytes support the development of kodkod embryos until the morula stage. The aggregation method increases the morulae rate of kodkod cloned embryos and allows blastocysts formation. However, kodkod blastocysts have a poor morphological quality and a lacking expression of pluripotency and differentiation markers, probably caused by an incomplete nuclear reprogramming.

In vitro and in vivo development of domestic cat embryos generated by in vitro fertilization after eCG priming and oocyte in vitro maturation

The objective of this study was to evaluate, in the domestic cat, the effect of ovarian stimulation with eCG prior to oocyte in vitro maturation (priming) on in vitro and in vivo development after in vitro fertilization (IVF). For this purpose, oocyte donors were either 1) treated with a single dose of 200 IU eCG four days before oocyte recovery (eCG group), or, 2) given no treatment before oocyte recovery (control group). Ovaries of both groups were collected by ovariohysterectomy (OVH) and cumulus-oocyte complexes (COCs) were recovered by slicing. Immature COCs from both groups were matured in vitro (IVM) for 26-28 h. IVF was done with refrigerated epididymal sperm. After 24 h co-incubation, presumptive zygotes were cultured in vitro for eight days. The rates of cleavage, morulae, blastocyst development and hatching were estimated. Some blastocysts were stained for total cell counting and others were used for gene expression analysis of pluripotency (OCT4, SOX2 and NANOG) and differentiation markers (CDX2 and GATA6). Additionally, to evaluate in vivo development, embryos from the eCG group were transferred at Day 5 and Days 7 or 8 of IVC to synchronized cat recipients. The results showed that, eCG priming increased significantly the rate of blastocyst development as compared to the control group (37.9 and 25.6%, respectively) (P < 0.05). No differences were observed in total cell number of blastocysts and hatching blastocysts (mean ± SD) between the eCG and control groups (420.6 ± 193.6 and 347.0 ± 237.1, respectively) (P > 0.05). In the gene expression analysis, blastocysts generated in the eCG group had higher expression of OCT4 than blastocysts from the control group (P < 0.05). However, no significant differences were observed in the relative expression of SOX2, NANOG, CDX2 and GATA6 (P > 0.05). Additionally, six embryo transfer (ET) procedures were done, three with Day 5 embryos and three with Day 7 or 8 embryos. Recipients from both ET groups delivered live kittens. The total pregnancy rate was 4/6 (67%), meanwhile the live birth rate was 2/6 (33%). In conclusion, eCG priming improved the rate of blastocyst development in vitro and increased relative expression of OCT4. These results demonstrate that eCG priming of oocytes donors before IVM improves oocyte competence, enhance in vitro embryo development and allows live births of healthy offspring after ET.

Production of cloned cats using additional complimentary cytoplasm

Somatic cell nuclear transfer (SCNT) is an important technique for producing cloned animals. It, however, is inefficient when there is use of SCNT for cloned animal production. Cytoplasm injection cloning technology (CICT) was developed to overcome the inefficiencies of SCNT use of this purpose. The use of CICT involves additional cytoplasm fusing with enucleated oocytes to restore the cytoplasmic volume, thus improving the in vitro developmental competence and quality of cloned embryos. In this study, there was application of CICT in cats to improve the in vitro developmental competence of cloned embryos, as well as the production of the offspring. The results of this study were that fusion rate of the cloned embryos with use of the CICT method was greater than that with SCNT (80.0 ± 4.8% compared with 67.8 ± 11.3%, respectively), and more blastocysts developed with use of CICT than SCNT (20.0 ± 2.0% compared with 13.5 ± 5.0%, respectively). The 62 cloned embryos that were produced with use of CICT were transferred into five estrous synchronized recipients, and 151 cloned embryos produced using SCNT were transferred to 13 estrous-synchronized recipients. After the embryo transfer, there was birth from surrogate mothers of one live-born kitten that resulted using SCNT compared with three live-born kittens using CICT. The number of CICT-cloned embryos born was greater than that of SCNT-cloned embryos (4.8 ± 2.3% compared with 0.7 ± 1.3%, P <  0.05). These results indicate that the CICT technique can be used to produce cloned kittens, including endangered feline species.

Equine chorionic gonadotrophin improved vascularization of feline ovarian tissue xenografted into immunosuppressed mice

The objective of this study was to evaluate effects of eCG on vascularization and development of feline ovarian tissue xenografted to immunosuppressed mice. Feline ovarian fragments (∼1 mm³) were transplanted under the renal capsule of 20 adult, ovariectomized, C57BL/6 SCID female mice. At 45 d after transplantation, 10 mice (controls) were euthanized and the remainder given 10 IU of eCG (and sacrificed 48 h later). Transplants were recovered immediately after death, fixed, sectioned, and stained with periodic acid-Schiff (PAS). Fragment volume (Cavallieri principle) and vascularization were assessed. Mean xenotransplant volume for control and treatment groups was 0.17 ± 0.03 and 0.37 ± 0.13 mm³, respectively (P = 0.0952); vascular volume density, 30.3 ± 11.3 and 49.1 ± 8.9% (P = 0.0281); surface density, 4.1 ± 2.4 and 6.2 ± 1.7 μm^-1 (P = 0.2222); and vessel total surface, 0.63 ± 0.24 μm² and 2.28 ± 1.05 μm² (P = 0.0079). In conclusion, eCG significantly increased vascular volume density of xenotransplanted ovarian tissue and improved its development.