Canine IVM with SOF medium, insulin-transferrin-selenium and low O2 tension improves oocyte meiotic competence and decreases reactive oxygen species levels

DUQUE RODRIGUEZ, MATTEO; CITTADINI, CAMILA ORNELLA ; TEPLITZ, G. M.; DE STEFANO, ADRINA; LOMBARDO, D. M.; SALAMONE, D.

Frontiers in Cell and Developmental

London Institute of Medical Sciences

Lugar: Londres; Año: 2021

Assisted reproductive technologies in canine species are limited due to the low efficiency of in vitro maturation (IVM). Unlike othermammals, bitches ovulate oocytes in the germinal vesicle stage and complete the Metaphase II (MII) after 48-72 h in the oviductalenvironment and become fertilizable. For this reason, we compared two different IVM media, one mimicking the oviductalenvironment, SOF (Synthetic oviductal fluid) supplemented with 8% BSA, a mixture of 8% BSA- 2.5% FBS, with TCM-199. Additionally,we evaluated the effect of the supplementation with insulin-transferrin-selenium (ITS) and low O2 tension in oocyte maturation,reactive oxygen species (ROS) levels, membrane integrity, and embryo development following parthenogenetic activation (PA).After 72 h of culture, SOF+BSA, SOF+BSA+FBS and TCM-199+FBS show 5%, 7% and 4% of MII respectively without statistical difference.However, SOF+BSA produced significantly higher degeneration rates compared to SOF+BSA+FBS (44% and 23%, respectively).Remarkably, supplementation with 1 µL/mL of ITS under high O2 tension demonstrated a beneficial effect by improving maturationrates up to 20% compared to the other groups. Low O2 tension increased maturation rates to 36.5%, although there were nostatistical differences compared to high O2 tension in the presence of ITS. Lower ROS levels and higher integrity of the cytoplasmicmembrane were found in the presence of ITS despite no differences in maturation rates under low O2 tension groups. Additionally,after PA, 1% development until the 8-cell stage was obtained after activation of in vitro matured oocytes in the presence of ITS.Taken together, these results indicate that SOF, supplemented with 8% BSA and 2.5% FBS is suitable for IVM of canine oocytes and ITSsupplementation was beneficial for both, high and low O2. tension. Furthermore, the addition of ITS in the cultured system lowersROS levels and increases membrane integrity in the domestic dog oocytes after IVM.