Cerium oxide nanoparticles (CeO₂ NPs) improve the developmental competence of in vitro-matured prepubertal ovine...

The present study investigated whether supplementation with different doses of cerium dioxide nanoparticles (CeO₂ NPs) during in vitro maturation (IVM) of prepubertal ovine oocytes influenced their embryonic development in vitro. Cumulus-oocyte complexes derived from the ovaries of slaughtered prepubertal sheep underwent IVM with CeO₂NPs (0, 44, 88 or 220µg mL^-1). Matured oocytes were fertilised in vitro and zygotes were cultured for 7 days. The results demonstrated that CeO₂NPs were internalised in the cumulus cells and not in the oocyte. The treatment with CeO₂NPs did not affect nuclear maturation or intracellular levels of reactive oxygen species of the oocytes. The percentage of oocytes with regular chromatin configuration and cytoskeleton structures when treated with 44µg mL^-1 CeO₂NPs was similar to oocytes matured in the absence of CeO₂NPs and significantly higher than those treated with 88 or 220µg mL^-1 CeO₂NPs. The relative quantification of transcripts in the cumulus cells of oocytes matured with 44µg mL^-1 CeO₂NPs showed a statistically lower mRNA abundance of BCL2-associated X protein (BAX), B-cell CLL/lymphoma 2 (BCL2) and superoxide dismutase 1 (SOD1) compared with the 0µg mL^-1 CeO2 NPs group. A concentration of 44µg mL^-1 CeO₂NPs significantly increased the blastocyst yield and their total, inner cell mass and trophectoderm cell numbers, compared with the 0 and 220µg mL^-1 groups. A low concentration of CeO₂NPs in the maturation medium enhanced in vitro embryo production of prepubertal ovine oocytes.