Fusion and development of 2-cell bovine embryos to tetraploid blastocyst with different voltages and durations

The values of embryonic stem cell and cloning are evident. Production of clone from embryonic stem cells can be achieved by introduction of stem cell into a tetraploid blastocyst. Tetraploid blastocyst can be produced in vitro by electrofusion of 2-cell embryos.

The aim of this study was to assess the effect of different voltages and durations on fusion rate of bovine 2-cell embryos and their subsequent development in vitro.

The in vitro produced bovine 2-cell embryos were categorized into 3 groups: (1) fused group (FG); 2-cell embryos fused by exposure to different voltages (0.5, 0.75, 1, 1.25 and 1.5 kV/cm) and durations (20, 40, 60, 80 and 100 μs), (2) exposed control group (ECG); 2-cell embryos exposed to different voltages and durations but remained unfused and (3) unexposed control group (UCG); embryos cultured without exposure to any voltage. The embryos from each group were cultured and fusion, cleavage and developmental rates were compared in each group.

The results show that increased voltage, increases the fusion rate up to 88% for 1.5 kV/cm; however, the rate of cleavage and blastocyst formation decreases significantly to 18% and 10% respectively (p<0.05). Increased duration does not significantly increase fusion rate, however, in high voltage, increased duration decreases cleavage rate and blastocyst formation rate. Blastocyst formation rate in UCG showed a better development (32%) compared to FG (20%) or ECG (22.5%) (p<0.05).

It can be concluded that for optimal fusion, cleavage and development, one pulse of 0.75 kV/cm for 60μs should be applied.