Effect of resveratrol supplementation during culture on the quality and cryotolerance of bovine in vitro produced embryos

• Resveratrol is an antioxidant polyphenolic compound found in many vegetal sources.
• The effects of resveratrol during bovine in vitro embryo culture were evaluated.
• Low resveratrol concentrations increased significantly the embryo cryotolerance.
• Hatching rate at 48 h post-warming culture was 2-fold higher than in the control.
• Improved embryo cryotolerance is critical for the IVEP success.

The aim of the study was to evaluate whether resveratrol supplementation of bovine culture medium improves in vitro blastocyst development, embryo cryotolerance and cell numbers. Abattoir-derived oocytes were matured and fertilized in vitro according to standard procedure. Twenty hours after IVF, zygotes were cultured in SOF medium, supplemented with 0 (control, n = 439), 0.25 μM (n = 422), 0.5 μM (n = 447) and 1 μM resveratrol (n = 416). On Day 7 (IVF = Day 0) blastocysts were vitrified by cryotop in 16.5% ethylene glycol, 16.5% dimethyl sulfoxide and 0.5 M sucrose. Development rate, i.e. the percentage of embryos resuming development to reach a more advanced stage, and hatching rate were evaluated after 24 and 48 h culture. Blastocysts cultured with (0.5 μM) and without resveratrol underwent differential staining to count inner cell mass (ICM) and trophectoderm (TE) cells. Resveratrol during culture did not increase blastocyst yields (57.1, 57.7, 59.2 and 46.6%, respectively in 0, 0.25, 0.5 and 1 μM resveratrol). However, 0.5 μM resveratrol improved embryo cryotolerance compared to the control, as indicated by higher development rates (67.3% vs 50.3%, respectively; P < 0.01) and hatching rates (58.9% vs 30.9%, respectively; P < 0.01) recorded after 48 h post-warming culture. Blastocysts produced in the control and in 0.5 μM resveratrol groups had similar numbers of ICM (34.1 and 36.4, respectively), TE (88.1 and 85.3, respectively) and total (122.2 and 121.7, respectively) cells. In conclusion, low levels of resveratrol during in vitro culture improve the quality of IVP bovine embryos, as indicated by their increased resistance to cryopreservation.