Vitrified sperm banks: the new aseptic technique for human spermatozoa allows cryopreservation at -86 °C

The vitrification technique is simple, quick, cost-effective and has showed a significantly stronger cryoprotective effect in contrast to conventional freezing. The method is based on the rapid cooling of the cell by direct immersion in liquid nitrogen (LN (2) ), thereby avoiding the formation of ice crystals, due to the lower risk of water thawing, which impairs cell function. The aim of this study was to evaluate the effect of storage at -86 °C compared to the conventional -196 °C (under LN (2) ) on essential parameters of the functioning of aseptically vitrified human sperm. Sperm motility, integrity of mitochondrial membrane potential and the rate of DNA fragmentation were determined. The comparison of -86 °C and -196 °C demonstrated no statistical difference in sperm progressive motility (73% vs. 77%), integrity of mitochondrial membrane potential (71% vs. 74%) or DNA fragmentation (3.1% vs. 2.9%). In conclusion, aseptically vitrified sperm can be preserved at -86 °C; eliminating the use of LN (2) simplifies and significantly reduces the costs associated with storage in sperm banks by decreasing the time and space needed for storage, the effort in finding stored samples, and by improving safety for the operator. However, for prolonged storage further studies are needed.