The effects of electric field-mediated transfer of nonpermeable molecules of meiosis, fertilization, and early embryo development

Currently there is no simple method of introducing nonpermeable molecules into oocytes or embryos. A technique that would allow direct access to the cytosol with minimal cell damage would be an extremely useful tool in gamete and embryo research. This study investigates the use of electric field-mediated transfer of nonpermeable molecules into mouse oocytes and embryos. Meiosis II stage oocytes, pronuclear stage zygotes, and two-cell embryos were used to determine optimal voltage settings needed for molecular transfer, viability, and blastocyst transformation in culture. Our highest voltage setting (7.0 kV) yielded molecular transfer, viability, and blastocyst transformation rates of 68%, 73%, and 46%, respectively, in two-cell embryos, whereas our lowest setting (3.75 kV) yielded rates of 28%, 90%, and 47%, respectively. Blastocyst transformation rates for control embryos not exposed to the electric field were significantly higher at 69% ( p < 0.01). Meiosis, as assessed by germinal vesicle breakdown, was not affected when compared with controls, 78% versus 83%, respectively. We conclude that electric field-mediated transfer of nonpermeable molecules into oocytes and embryos is a simple, relatively atraumatic technique that can be used to study intraoocyte physiologic characteristics and embryo development.