In vitro Developmental Competence of Adult Sheep Oocytes Treated with Roscovitine

Contents The efficiency of invitro sheep embryo production is still low compared to that observed invivo and in other species. In this context, meiotic inhibition strategies emerged as a promising alternative to improve this biotechnology. So, this study aimed to evaluate, for the first time, the effects of roscovitine on invitro maturation of sheep oocytes and their subsequent embryo development. For this, cumulus-oocyte complexes (COCs) were cultured for 6h in the presence (Rosco) or absence (Control) of 75m roscovitine and, subsequently, invitro matured (IVM) for 18h with gonadotropins. At 0 (Immature), 6 and 24h of culture, the nuclear status of oocytes was evaluated by Hoechst staining. Embryo cleavage and blastocyst formation were recorded 30h after invitro fertilization and on day 7 of culture, respectively. Blastocyst quality was evaluated by differential staining. At 6h, the GV rate in the Rosco treatment (93.8%) was similar to that observed in the Immature oocytes (94.9%) and significantly higher compared to Control (41.3%). After IVM for 18h, a high and similar proportion of oocytes from Rosco (93.6%) and Control (88.4%) reached the MII stage. In both treatments, approximately 70% of oocytes cleaved and 50% of them developed up to blastocyst. The mean percentage of blastocyst cells, embryoblast, trophoblast and pyknosis did also not differ between Control and Rosco. In conclusion, roscovitine, at the studied experimental conditions, was efficient to reversibly inhibit the meiosis of adult sheep oocytes without detrimental effect on development and quality of the invitro produced embryos. (AU)