198 RESVERATROL SUPPLEMENTATION DURING IN VITRO MATURATION AND FERTILISATION ENHANCES DEVELOPMENTAL COMPETENCE OF BOVINE OOCYTES

Abstract

Resveratrol (3,4′,5-trihydroxystilbene) is a phytoalexin identified in various plant species, particularly in grapevine peel. It is a strong antioxidant, induces mitochondrial biogenesis and enhances Sirtuin 1 (SIRT1) activity by inhibiting phosphodiesterase. SIRT1 belongs to the family of NAD⁺-dependent histone deacetylates and has been shown to regulate several key cellular processes, including transcriptional silencing, aging, chromatin remodeling, and genomic stability, via deacetylation of p53, FoxO transcription factors, and nuclear factor kappa B (NF-κB). The aim of this study was to determine whether supplementation of the maturation and fertilisation medium with resveratrol influences bovine oocyte maturation and subsequent embryonic development and whether these effects are mediated via SIRT1 pathway. Three different resveratrol concentrations were used during in vitro maturation (IVM) and IVF. Cumulus-oocyte complexes (n = 2878) were collected from slaughterhouse ovaries and subjected to IVM medium supplemented with 0.2 µM, 1 µM, or 20 µM resveratrol^® (Sigma-Aldrich, Buchs, Switzerland) for 24 h followed by IVF with the same concentrations of resveratrol for 19 h. The IVM and IVF medium without resveratrol (controls) and dimethyl sulfoxide supplementation as vehicle control were also included. Presumptive zygotes were cultured in vitro until Day 8 to assess embryo development, and maturation rates, cleavage, and blastocyst formation were evaluated. Maturation rates as determined by polar body extrusion (0.2 µM: 64.2% ± 7; 1 µM: 82.3% ± 4; 20 µM: 68.8% ± 2; control: 74.6% ± 5 and vehicle control: 70.2% ± 6, respectively; P ≤ 0.05) did not differ dramatically. Oocytes in 1 µM resveratrol supplemented maturation medium showed distinct detachment of cumulus cells in comparison with those in the other treatment and control groups. Cleavage rates were reduced in the 0.2 µM and 20 µM group compared with controls (0.2 µM: 44.21% ± 2; 1 µM: 58.4% ± 3; 20 µM: 40.9% ± 5; control: 56.6% ± 2 and vehicle control: 55.2% ± 6, respectively; P ≤ 0.05). Blastocyst rates were impaired in the low and high resveratrol concentration groups compared to all other groups (0.2 µM: 11.3% ± 1; 1 µM: 33.4% ± 3; 20 µM: 8.2% ± 4; control: 26.7% ± 4 and vehicle control: 20.8% ± 2, respectively; P ≤ 0.05). Relative mRNA abundance of SIRT1 in matured oocytes from the 1 µM group did not differ significantly compared to the controls. Results so far indicate that very low and high concentrations of resveratrol impair development to the blastocyst stage. In conclusion, a 1 µM resveratrol supplementation during IVM and IVF seems to improve the developmental competence of oocytes, which is reflected not only in the elevated blastocyst rates but also in higher degree of expansion of cumulus cells after IVM and maturation rates.