Ovarian transport temperature (4 vs 33 °C) impacts differently the in vitro development of isolated goat preantral and antral follicles

Abstract

The aim of the present study was to determine the effect of transport temperature of goat ovaries on the in vitro survival and development of preantral follicles and early antral follicles. From each ovarian pair, the ovaries were individually transported in HEPES-buffered MEM at two different temperatures (4 vs 33 °C). The follicles were isolated at the same temperature that the ovary was transported and subsequently cultured in vitro for 18days. After follicle culture, the cumulus-oocyte complexes were recovered and submitted to in vitro maturation for 32h followed by the evaluation of oocyte viability and chromatin configuration. Our results showed that there was no effect of transport temperature (4 vs 33°C) on the percentage of morphologically normal follicles regardless of the evaluated follicular category. Preantral follicles from ovaries transported at 4°C showed a delay in the antrum formation at day 12 (78.33%) in relation to 33°C (91.94%). The overall growth rates for the two tested follicular categories (Preantral follicles and Early antral follicles) transported at 33°C was higher than those transported at 4°C. Zona pellucida thickness values were lower (P<0.05) in the oocytes from early antral follicles transported at 4°C compared to oocytes harvested from preantral follicles and early antral follicles transported at 33°C. Oocyte diameter of early antral follicles transported at 4°C was significantly higher after culture. Meiotic resumption rate was higher when preantral follicles were obtained from ovaries transported at 4°C than transported at 33°C. Finally, it was observed a significant higher ROS production only for early antral follicles at day 6 when the ovaries were previously transported at 4°C than transported at 33°C. In conclusion, the transport temperature differentially impacts the in vitro development of goat preantral follicles and early antral follicles. Even though high transport temperature (33°C) improves antrum formation and follicular growth irrespective of follicular category (Preantral follicles and Early antral follicles); the best outcome for fully grown oocyte production and meiotic resumption were obtained using low (4°C) and high (33°C) temperature for preantral follicles and early antral follicles, respectively.