Embryo recovery from superovulated mouflons (Ovis gmelini musimon) and viability after transfer into domestic sheep

The effect of glucocorticoids on ERK-1/2 phosphorylation during maturation of lamb oocytes and their subsequent fertilization and cleavage ability in vitro

High levels of glucocorticoids may alter reproduction, but little is known about their direct actions on oocyte maturation, fertilization and subsequent development. Earlier work suggested negative effects of cortisol or dexamethasone on oocyte maturation but differences were noted between animal models. Both glucocorticoids reduce the p34(cdc2)-cyclin B1 complex but it is unknown if other signaling pathways important for meiosis progression are affected. In this study, using sheep oocytes as a model system, we assessed in vitro the effects of increasing concentration of glucocorticoids (0-250 microM) on oocyte maturation and underlying changes in the MAP kinase pathway, and the ability of oocytes to undergo fertilization and embryo development. Cortisol decreased oocyte maturation but only at the highest concentration, whereas dexamethasone had no effect. Fertilization and cleavage were not affected. On the other hand, both cortisol and dexamethasone inhibited ERK-1/2 activation in a concentration-dependent manner. It thus seems that oocytes can overcome deleterious effects of glucocorticoids during maturation despite the decrease in ERK-1/2 activity, but repercussions in vivo should be further explored.

The effect of glucocorticoids on mouse oocyte in vitro maturation and subsequent fertilization and embryo development

Increased glucocorticoid levels, due to medical therapy or stress-related, may affect reproduction via the hypothalamus-pituitary-axis or directly at the oocyte level. We examined the effects of natural (corticosterone) or synthetic (dexamethasone) glucocorticoids on mouse oocyte maturation and underlying changes in extracellular signal-regulated kinase (ERK) phosphorylation patterns. Fertilization and progression up to the blastocyst stage were also evaluated. Oocytes were exposed to corticosterone or dexamethasone (0, 0.25, 2.5, 25 or 250microM) for 17h during in vitro maturation. After maturation, ERK-1/2 activation in oocytes was assessed by SDS-PAGE and immunoblotting, and fertilization and developmental capacity were examined in vitro. Corticosterone exposure during oocyte maturation significantly decreased progression to metaphase II, fertilization and embryo development at the highest concentration. Corticosterone caused a concentration-dependent inhibition of ERK-1/2 activation, with the highest concentration resulting in considerable inhibition of oocyte ERK-1/2 phosphorylation and no blastocyst development. In contrast, dexamethasone had no effect on maturation, fertilization and cleavage, and no effect was seen on ERK-1/2 phosphorylation. Based on these in vitro findings, high glucocorticoid levels may have consequences for subsequent development, although a short exposure to physiologic or stress-related glucocorticoid levels may not represent a hazard to meiosis progression of the oocyte.

Interspecific embryo transfer from mouflon (Ovis gmelini musimon) to domestic Corriedale sheep in Argentina

An interspecific embryo transfer program was conducted for genetic improvement and increasing the number of offspring from a flock of mouflon sheep in Argentina. The female donor mouflons were divided into three groups, G1 (n=5), G2 (n=4) and G3 (n=5). The total NIH-FSH-P1 dose given to each donor on the superovulatory treatment was 260, 200 and 160 mg for G1, G2 and G3, respectively. The mouflons in G3 were maidens, while the others were multiparous. Domestic Corriedale ewes (n=60) were synchronized and used as recipients. The embryo recovery and transfer was performed by a surgical method. Mouflons (n=13) responded to the superovulatory treatment with an average of 9.1+/-2.8 ovulations. A low incidence of early luteal regression was found (1 out of 14 donors). Embryo recovery rates were 60, 31 and 76% in groups G1, G2 and G3, respectively. The percentage of transferable embryos obtained in G1 and in G2 exceeded 80%. None of the embryos obtained from G3 were of transferable quality. In G1, 25 transferable embryos were recovered and transferred to 13 recipients, resulting in a pregnancy rate of 76.9% (10/13). In G2, 10 embryos were transferred to 5 recipients, resulting in a 60% pregnancy rate (3/5). Lambing rate was 60% (15/25) and 30% (3/10) for G1 and G2, respectively. Thirteen lambs were born to the 14 donors following natural service after the embryo recoveries. This study demonstrates that the application of IET technology would have great reproductive impact, especially when the donor mouflon hinds are selected according to age and reproductive history.

In vivo and in vitro fertilizing capacity of cryopreserved European mouflon [Ovis gmelini musimon] spermatozoa used to restore genetically rare and isolated populations

European mouflon sheep are an endangered species of ovidae residing primarily in the mountenous habitat of the islands of Sardinia and Corsica. The purpose of this study was to assess the fertilizing capacity of cryopreserved European mouflon spermatozoa after AI in synchronized mouflon and domestic ewes and after IVF in in vitro matured mouflon and domestic ewe oocytes collected by OPU technique. Domestic ram (Ovis aries) spermatozoa served as control. Semen was collected by artificial vagina from three mouflons and three domestic rams during the breeding season and was cryopreserved. At thawing, no significant differences in sperm viability were found between the wild and the domestic species (53.1 +/- 4.6% versus 56.0 +/- 4.7%) whereas the percentage of acrosome-intact sperm was lower in mouflon (55.5 +/- 4.6%) than in ram semen (62.7 +/- 3.1%; P < 0.05). Lambing rate did not differ between synchronized mouflon and domestic ewes (5/11 versus 8/12) after 150 and 156 days of pregnancy, respectively. After two OPU sessions, 87 and 132 oocytes were collected from three hyperstimulated mouflon and three domestic ewes. Cryopreserved/thawed semen was inseminated with an endoscope into the uterus of corresponding species during the non-breeding season. The oocytes were matured and fertilized in vitro; 61/73 mouflon and 81/101 domestic ewe oocytes were found to be fertilized. From these, we obtained 6/61 and 17/81 blastocysts. After vitrification and thawing, the hatching rate showed no significant difference between mouflon and sheep blastocysts (4/6 versus 14/17). In conclusion, our data showed that cryopreserved mouflon spermatozoa can be successfully used to carry out a genuine and complete program of genetic restoration in small and isolated groups of European mouflons.

Ovum pick-up in sheep: efficiency of in vitro embryo production, vitrification and birth of offspring

The production of offspring involving available technologies like ovum pick-up, in vitro embryo production and cryopreservation has not been fully described in the sheep. We tested the overall efficiency of these procedures on 20 Sarda dairy ewes that were twice stimulated for recovery of follicular oocytes. In total, 415 oocytes were aspirated from 522 follicles (11.5 oocytes/ewe), and 328 of them (9.1 oocytes/ewe) were selected for in vitro embryo production procedure. Development into blastocysts occurred in 98 embryos (2.7 blastocysts/ewe), of which 64 were vitrified and 34 were transferred, in pairs, directly to recipients. The pregnancy rate, diagnosed at 80 d for fresh and vitrified embryos, did not differ significantly (47.1 vs 42.8%, respectively), but there were significant differences in lambing rates between the 2 groups (41.2 vs 23.8%, respectively). Overall, 24 lambs were born; all weighed within the range for the breed, but head deformities were observed in 2 cases. The results of this study show that with application of the above techniques, it is possible to obtain repeatedly embryos and viable offspring.

Membrane integrity and fertilizing potential of cryopreserved spermatozoa in European mouflon

There is a pressing need to develop and use assisted reproductive techniques in wildlife species living in small and captive groups. We evaluated the effect of freezing on membrane integrity and fertilizing capacity of European mouflon (Ovis gmelini musimon) spermatozoa collected during the breeding season. After thawing, the percentage of live spermatozoa, stained with fluorescein isothiocynate labeled Pisum Sativum agglutinin and propidium iodide, was 47% of which 19% showed intact acrosomal membrane. After culture in TCM 199 + 10% FCS, the number of live spermatozoa was significantly (P < 0.01) lower than in a medium with oviductal epithelial cells. The absence of oviductal cells decreased significantly the fertilization rates (P < 0.05), 24.0 vs. 63.1 with oviductal epithelial cells and 59.1 in vivo of in vitro matured ovine oocytes. Polyspermic fertilization rate of oocytes was lower (P < 0.05) with oviductal epithelial cells (1.6) than in absence of cells (12.8). However, the percentage of embryos that reached blastocyst stage was significantly higher in vivo than in vitro. These results provide interesting preliminary data for the development of genetic resource banks for European mouflon.