effect of voltage and duration of electrical stimulus on fusion and cleavage of electrofused two-cell bovine embryos

ABSTRACT

The value of embryonic stem-like cells in cloning is obvious. Production of cloned animals can be achieved by introduction of these cells into a tetraploid embryo. Tetraploid embryo is used as a feeder for development of embryonic stem-like cells and can be produced in vitro by electro-fusion of 2-cell embryos. The aim of this study was to assess the effect of voltage alteration and duration on fusion and cleavage rates of bovine tetraploid embryo produced by electrofusion. After in vitro maturation and fertilization of cumulus oocyte complexes, two-cell embryos were categorized into three groups 1- Fused group [FG] include two-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 micro s]. 2- Exposed control group [ECG] two-cell embryos that remained unfused after electrofusion. 3- Unexposed control group [UCG] two-cell embryos cultured without exposure to any voltage. The embryos from each group were cultured in SOF1. The fusion and cleavage rates were compared in each group. Increase in voltage resulted in significantly higher fusion and lower cleavage rate. The increased duration had no significant effect on fusion rate. The increased duration of high voltages caused decreased cleavage rate significantly, and in low voltage resulted in increased cleavage rate. The cleavage rate in ECG group followed the same as FG group, and they were lower when compared to UCG. Best fusion and cleavage rate was obtained at 0.75-1 kV/cm for 60 micro s duration