Green tea polyphenols added to IVM and IVC media affect transcript abundance, apoptosis, and pregnancy rates in bovine embryos

Three experiments were conducted to examine the effects of green tea polyphenols (GTP) during IVM and IVC on apoptosis and relative transcript abundance (RA) of three genes controlling antioxidant enzymes, as well as subsequent pregnancy rates. In experiment 1, oocytes were matured in the presence of 0, 10, 15, or 25 μM GTP for 24 hours. The GTP dose applied to IVM medium was followed by the same dose supplemented to IVC medium, so oocytes and embryos of a given group were cultured in similar conditions. This resulted in a total of four groups (three experimental groups and the control). After IVF, presumptive zygotes were cultured in medium containing 0 to 25 μM GTP for 8 days. The addition of 15 μM GTP during IVM and IVC increased RA of SOD1, CAT, and GPX genes in blastocysts compared with the control (P < 0.05). Increase in GTP doses from 15 to 25 μM did not further increase the transcript level. In experiment 2, effects of GTP doses on apoptosis were investigated in bovine blastocysts. Two of the applied GTP doses (10 and 15 μM) decreased the apoptotic index (AI) in blastocysts (7.4% and 6.2% respectively) compared with the control (9.3%; P < 0.05). However, the highest GTP dose used (25 μM) caused an increase in AI compared with a dose of 15 μM (P < 0.05). Considering the results of experiment 1 and 2, the effects of 15 μM GTP treatment during IVM and IVC on pregnancy rate was evaluated after embryo transfer in experiment 3. Cows receiving embryos treated with 15 μM GTP had higher pregnancy rates on Day 30 (34.8% vs. 28.6%) and Day 60 (34.8% vs. 23.9%) than those receiving control embryos (P < 0.05). In conclusion, addition of 15 μM GTP during IVM and IVC improved pregnancy rates; this improvement seemed to be associated with the increase of RA of antioxidant enzyme genes and the decrease in AI in bovine blastocysts.