Effect of recombinant human FSH and LH on in vitro maturation of sheep oocytes; embryo development and viability

The objective of this work was to study the effect of a preparation of human recombinant gonadotrophins (r-FSH and r-LH) on the in vitro maturation (IVM) and development of sheep oocytes. In addition, the viability of fresh and vitrified blastocysts obtained after transfer was tested. Oocytes collected from slaughtered animals were divided into five different maturation groups. All groups were matured in a medium containing TCM199 with 4 mg/ml BSA, 100 microM cysteamine and 1 microg/ml estradiol-17beta. Each group was also treated with one of the following: 0.1 UI/ml r-FSH (r-FSH group), 0.1UI/ml r-LH (r-LH group), 0.1 UI/ml r-FSH and 0.1 UI/ml r-LH (r-FSH/r-LH group), 5 microg/ml FSH and 5 microg/ml LH hypophysial gonadotrophins (h-G group) as a control, or no gonadotrophins (no-G group). After in vitro fertilization with fresh ram semen, presumptive zygotes were cultured in vitro for 6-7 days and a total of 109 blastocysts were then transferred in pairs into synchronized ewes. To determine the viability of embryos after vitrification, 36 blastocysts from the r-FSH/r-LH group and 30 from the h-G group were vitrified in 10% ethylene glycol (EG) and 10% dimethylsulphoxide (DMSO) for 5min, followed by 20% EG, 20% DMSO and 0.5M Sucrose (S) for <45 s. They were loaded into open pulled straws (OPS) and plunged into LN(2). After warming, the blastocysts were transferred in pairs into synchronized ewes.The highest maturation rate was reached in the r-FSH/r-LH group (91.9%). However, no statistical difference was found when this group was compared with the h-G group (84.0%). Likewise, the cleavage rate of the r-FSH/r-LH group (81.4%) was not significantly different from that of the h-G group (82.3%). The cleavage rates of all other groups, however, were significantly lower than the r-FSH/r-LH and h-G groups. The blastocyst rate was highest in the h-G group (53.6%), and it was statistically higher than in the r-FSH/r-LH group (41.5%). The blastocyst rate was very similar between groups r-FSH and r-FSH/r-LH (42.0 and 41.5%, respectively). The lowest lambing rate (31.8%) was in the no-G group. The highest lambing rate was achieved in the r-FSH/r-LH group (66.6%). The vitrified embryos of h-G and r-FSH/r-LH groups had a very similar lambing rate (16.6% and 19.4%). In conclusion, these data provide support for the hypothesis that sheep oocytes respond to human recombinant gonadotrophins used for in vitro embryo production.