Effect of Paraoxonase 1 (PON1) During Oocyte Maturation and Subsequent Development of IVP Bovine Embryos

Some studies suggest that the enzyme paraoxonase 1 (PON1) may exert an antioxidant effect on cell membranes. Therefore, it could improve oocyte competence by minimizing oxidative stress. The aim of this study was to evaluate the effect of different levels of PON1 added to the IVM medium on both cleavage and blastocyst rates at D2 and D7 post IVF. Biotecnologia Animal® provided the media used for IVP (Brazilia, DF, Brazil). In 8 replicates, a total of 1600 cumulus oocyte complexes (COCs) were collected from bovine abattoir-derived ovaries and randomly divided into four groups of 50: T0 = 0.0 mg/mL, T1 = 0.02 mg/mL, T2 = 0.04 mg/mL and T3= 0.08 mg/mL of recombinant PON1 (Chesapeake PERL Inc., Savage, USA). Maturation of COCs took place in an incubator with 5% CO2 at 39˚C for 24 hours. To analyze the activity of PON1 at IVM, 15 µL of media were collected at times 0 and 24 h of maturation. Sperm were recovered by minipercoll density gradient centrifugation and IVF wells were inseminated at a concentration of 1x106 sperm/mL. After 18 hours, presumptive zygotes were cultured for 7 days in SOFaa with FCS under controlled conditions (5% CO2, 5 % O2 and 90% N2 at 39˚C). Statistical analysis was performed using the GLM procedure of SAS software (SAS Institute, Cary, NC, USA) to account for possible linear, quadratic and cubic effects of exogenous PON1 on enzyme activity, cleavage and blastocyst rates. Any effect between level of PON1 activity and the blastocyst rate was accounted by Pearson correlation test. There was a linear effect for average activity of PON1 in IVM medium, which was 2.1 ± 2, 15.2 ± 2, 28.5 ± 2 and 52.4 ± 2 U/mL for T0, T1, T2 and T3, respectively (P 0.05). However, adding PON1 to IVM medium improved linearly embryo development by D7 as shown: 22.1% (T0), 29.2% (T1), 32.6% (T3) and 34.4% (T4) (P < 0.0001). Moreover the latter effect was supported by a positive correlation between the level of PON1 in the IVM media and blastocyst rate at D7 (r = 0.35 and P = 0.04). In sum, PON1 supplementation has a positive effect on the bovine embryo development, possible via improved in vitro maturation.