The effect of elevated temperatures on the development of cattle embryos cocultured with bovine oviduct epithelial cells (BOECs) and a KSOMaa medium

The aim of this study was to compare the effect of elevated temperatures on the development of cattle embryos cocultured with bovine oviduct epithelial cells (BOECs) and cultured in a KSOMaa medium. Zygotes obtained in vitro were cocultured with BOECs and cultured in KSOMaa (potassium simplex optimised medium modified by amino acids) at a control temperature (38.5 degrees C), and elevated temperatures (40.5 degrees C and 41 degrees C) for 168 hours. At 38.5 degrees C there was no significant difference in embryo development between BOEC and KSOMaa treatments. At 40.5 degrees C embryos cocultured with BOECs developed significantly better compared to the KSOMaa system, as observed at the cleavage rate (73.45 +/- 2.45 vs 66.75 +/- 1.34%), minimum 8 cell rate (20.36 +/- 1.42 vs 16.78 +/- 1.48%) and the blastocyst rate (3.13 +/- 3.25 vs 0%), (P<0.001). At 41 degrees C there were significant differences in the cleavage rate (62.25 +/- 1.72 vs 56.313.47%) and the minimum 8 cell rate (13.06 +/- 1.97 vs 9.64 +/- 2.14%) in the BOEC coculture system compared to the KSOMaa system (P<0.001), at no differences in the blastocyst rate. In embryos cocultured with BOECs, the hsp70 mRNA expression was higher than in embryos cultured in KSOMaa: 38.5 degrees C-1.42 +/- 0.05 vs 0.77 +/- 0.04; 40.5 degrees C-3.82 +/- 0.04 vs 1.92 +/- 0.24; 41 degrees C-6.74 +/- 0.20 vs 2.14 +/- 0.13, (P<0.001). Also, the HSP70 protein level was higher in embryos cocultured with BOECs than those cultured in KSOMaa: 38.5 degrees C-0.98 +/- 0.01 vs 0.17 +/- 0.02; 40.5 degrees C-1.96 +/- 0.01 vs 0.82 +/- 0.01; 41 degrees C-2.45 +/- 0.01 vs 1.30 +/- 0.01, (P<0.001). This data indicates that bovine embryos cultured at elevated temperatures in the presence of BOECs develop better than embryos cultured in KSOMaa and also that BOECs stimulate embryos to switch on their defence mechanisms to a significantly higher level than in embryos cultured in KSOMaa.