Media Supplementation With Gamma‐Oryzanol Improves the Outcome of Ovine Oocyte Maturation In Vitro

Abstract

BackgroundThe process of maturing ovine oocyte in vitro has not yet been raised with acceptable results.ObjectiveThis study was designed to evaluate the γ‐oryzanol effect as a supplement of maturation media on the development of ovine oocytes to blastocyst.MethodsAspirated from ovine ovaries, morphologically normal cumulus‐oocyte complexes (COCs) were matured in media supplemented with or without 5 µM γ‐oryzanol. Matured oocytes were divided into two parts: one evaluated for their nuclear maturation, the level of GSH and ROS, mitochondrial membrane potential (MMP) and the pattern of transcription in oocytes and respective cumulus cells (CCs), and another subjected to fertilisation and culture to assess the development of oocytes to the blastocyst.Resultsγ‐Oryzanol improved the proportion of cleaved embryos and total blastocysts in the treated group, which was linked to improved MMP, higher levels of intracellular GSH and lower levels of ROS. A lower proportion of MI and GVBD was recorded for treated oocytes in comparison with control, although the proportion of MII oocytes was not different between groups. The treated oocytes and CCs showed downregulation of genes related to apoptosis (BAX and CASP‐9) and upregulation of genes related to antioxidative status (NRF2, CAT and SOD). In conclusion, our results demonstrated the improved developmental outcome of supplemented oocytes so that the antioxidant response and higher enzymatic activity were maintained, and the generation of ROS was turned off; therefore, a novel alternative for counteracting oxidative stress in ovine oocytes undergoing maturation was offered by γ‐oryzanol through an antioxidative pathway.