A polyphenol-rich extract from an oenological oak-derived tannin influences in vitro maturation of porcine oocytes

Abstract Tannins have been demonstrated to have antioxidant and various health benefit properties. The aim of this study was to determine the effect of an ethanol extract (TRE) of a commercial oenological tannin ( Quercus robur toasted oak wood, Tan’Activ R ® ) on female gamete using an in vitro model of pig oocyte maturation (IVM) and examining nuclear maturation, cytoplasmic maturation, intracellular GSH and ROS levels and cumulus cell steroidogenesis. To this aim, during IVM performed in medium either supplemented (IVM A) or not supplemented (IVM B) with cysteine and β-mercaptoethanol, TRE was added at different concentrations (0, 1, 5, 10, 20 μg/ml). The addition of TRE at all the concentration tested to either IVM A or IVM B, did not influence oocyte nuclear maturation. When IVM was performed in IVM A, no effect was induced on cytoplasmic maturation by TRE at the concentration of 1, 5 and 10 μg/ml, while TRE 20 μg/ml significantly reduced the penetration rate after IVF (p  TRE addition at all the concentration tested to both IVM A and IVM B, did not induce any effect on E2 and P4 secretion by cumulus cells suggesting that the biological effect of the ethanol extract is not exerted thought a modulation of cumulus cell steroidogenesis. In conclusion, TRE, thanks to its antioxidant activity, was partially able to reduce the negative effect of the absence of cysteine and β-mercaptoethanol in IVM B, while TRE at high concentration in IVM A was detrimental for oocyte cytoplasmic maturation underlying the importance of maintaining a balanced redox environment during oocyte maturation.