Final maturation of bovine oocytes in a Fert-TALP medium increased their quality and competence to in vitro embryo development

In vitro maturation (IVM) of the oocytes is an important step for in vitro embryo production (IVP). In vitro culture during maturation decreases oocyte quality and therefore, IVM conditions need to be improved. Routinely, IVM of bovine oocytes is performed using one-step medium, the TC-199 complemented with fetal bovine serum (FBS) and gonadotropins. However, the asynchrony of oocyte nuclear and cytoplasm maturation processes may require the differential hormonal environment during IVM. In the present work, for the first time we have compared the efficiency of the two-step IVM protocols, which include the first step in standard conditions and final maturation in hormone-free mediums TC-199 or Fert-TALP; the last one is a routine medium for in vitro fertilization (IVF). The objective was to study the effects of two-step IVM protocols to chromosome modifications and apoptotic events in mature oocytes and a quality of in vitro produced embryos. Oocyte-cumulus cells complexes (ОСС) were in vitro matured during 16 h in medium TC-199 complemented with 10 % FBS, 10 mg/ml follicle-stimulating hormone and 10 mg/ml luteinizing hormone, and then transferred to either medium TC-199 without gonadotropins (System 1) or Fert-TALP medium (System 2) for additional 8 h of IVM. After final IVM, nuclear state and apoptosis were checked in a part of the mature oocytes. IVF was performed on remaining OCC to analyze in vitro embryo development. No difference was observed in nuclear maturation rates between the systems 1 and 2 after 24 h IVM: 83.3 % and 84.7 % of the oocytes reached metaphase-II. Apoptosis rate were significantly lower (p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }