Nuclear cytoplasmic maturation of Sus Scrofa Domesticus oocytes at ultralow temperatures

Abstract

Abstract. Vitrification of female gametes is the most important tool for solving the strategic tasks of cellular reproductive technologies in animal husbandry, veterinary medicine and biomedicine: replication of elite individuals (cloning, transgenesis), biodiversity conservation, organ xenotransplantation. The aim of this study was to evaluate the parameters of nuclear cytoplasmic maturation (chromatin status and mitochondrial activity) and developmental competence of donor porcine oocytes subjected to intra- (IOV) or extra-ovarian (EOV) vitrification and cultured in various maturation systems. Methods. Donor pig oocytes (6–8 months old) were vitrified extra- or intraovarially using cryoprotective agents (DMSO, ethylene glycol, trehalose, sucrose). The composition of cryoprotective agents was supplemented with 0.001 % highly dispersed silica nanoparticles (HDSns). Oocytes were thawed in trehalose solutions in TS-199 with 10 % of fetal bovine serum (FBS). Oocytes were cultured for 44 hours in media supplemented with granulosa cells (106 cells per ml of medium) and/or 0.001% of HDSns at 38.5 °C, in an atmosphere of 5 % CO2. Fertilization in vitro was carried out in accordance with the recommendations presented by us earlier [17. p. 17]. The functional activity of mitochondria and the status of chromatin in oocytes were assessed by double staining using MitoTracker Orange CMTMRos and Hoechst 33258 dyes. Results. The level of matured oocytes was 61 % at EOV and 29 % at IOV, and the level of cleavage embryos in EOV was in 11 % (31 % vs. 20 %, P < 0.05) higher than at IOV when HDSns with granulosa cells were added in culture media. The maximum indicators of the functional activity of mitochondria among devitrified oocytes were in the group of EOV oocytes have cultured in media supplemented with HDSns and granulosa cells (152 ± 14.9 μA). Scientific novelty. The protocols for intra- and extra-ovarian vitrification of porcine oocytes have been modernized. Addition to cryoprotective agents and culture media of HDSns and co-culture of devitrified oocytes with granulosa cells significantly increased the fertility rates of devitrified gametes.