Morphological, biochemical and functional studies to evaluate bovine oocyte vitrification

GUTNISKY, C.; MORADO, S.; GADZE, T.; DONATO, A.; ALVAREZ, G.; DALVIT, G.; CETICA, P.

THERIOGENOLOGY

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2020 vol. 143 p. 18 - 26

0093-691X

The aim of the present study was to evaluate the effect of vitrification on morphological, biochemical andfunctional parameters of matured bovine oocytes at different recovery times. To this end, matured bovineoocytes were vitrified using the Cryotech® kit (a minimum-volume system) and then incubated inmaturation medium for different post-warming durations (0 h, 3 h or 21 h). Morphology, viability andbiochemical parameters were assessed at each time point mentioned above and the recovery of themetaphase plate was analyzed at 2 h, 3 h and 4 h post-warming. The vitrification-warming process didnot affect the viability or morphology of oocytes at any time point. However, the recovery of themetaphase plate occurred mostly between 3 and 4 h rather than at 2 h after warming (P < 0.05). Bothcontrol and vitrified-warmed oocytes showed changes in cytosolic oxidative activity, quantification ofactive mitochondria, reactive oxygen species (ROS) levels and redox status at the different time pointsstudied (P < 0.05). However, differences between control and vitrified-warmed oocytes were found onlyin the quantification of active mitochondria and ROS production (P < 0.05). Finally, in vitro fertilizationand embryo culture were carried out as functional studies to establish whether vitrification-warmingaffected oocyte competence, and a significant decrease was found both in the cleavage rate and embryodevelopment (P < 0.05). We concluded that major improvements in oocyte vitrification, at list withCryotech® kit, are still needed to avoid variations in oocyte metabolism which could contribute to thereduction in the developmental competence of bovine oocytes.