Voltages up to 600V did not affect cryopreserved bovine spermatozoa on capillary-type electroporation

Physical methods such as electroporation have been used to improve the DNA uptake efficiency of sperm cells. This study aims to develop an efficient capillary-type electroporation method for incorporation of exogenous DNA into bovine cryopreserved sperm cells with minimal detrimental effects for later use in SMGT. Electroporation of the samples was performed in 2 different groups (with 1 μg of DNA and without DNA transfection) and under five different voltages: 500 V, 600 V, 700 V, 800 V and 900 V. Non-electroporated sperm cells (with and without DNA) were used as control. Kinetics parameters were determined using computer assisted semen analyses, whereas membrane integrity, fluidity, mitochondrial function and DNA uptake were evaluated by flow cytometry. Results revealed that all tested voltages reduced electroporated sperm motility (P < 0.05) when compared to the control (non-electroporated cells). Mitochondrial function results showed no statistical difference among groups. Similarly, groups electroporated with lower (500 V, 600 V and 700 V) voltages showed no difference in cell membrane integrity and fluidity. Groups electroporated at higher voltages (800 V and 900 V) demonstrated negative effects in cells membrane integrity when compared to other groups and control. Also, all electroporated groups demonstrated significant higher percentages of transfected sperm cells when compared to the control group (P < 0.05). Under the recommendation of using voltages up to 600 V, this method represents a safe and efficient alternative for electroporation of bovine spermatozoa.