[Prospective comparison of different techniques for cryopreservation of small numbers of human spermatozoa].

This study aimed to determine if vitrification is more efficient than the slow freezing method when cryopreservation of small numbers of human spermatozoa is needed and, if so, which device is the most suitable. This is a prospective experimental study conducted in a university-affiliated assisted reproductive center. Ejaculates were obtained from the same fertile man after written consent. Selected sperm were cryopreserved by slow freezing method or vitrified in two different devices: Cell Sleeper and Stripper tip. Vitrification in Cell Sleeper provided significantly higher recovery, motility and survival rates than slow freezing. Only recovery rate was higher in Cell Sleeper than when using Stripper tip. Moreover, recovery time per spermatozoon was faster in Cell Sleeper than in the two other groups. Furthermore, statistical significance was achieved when comparing the four above parameters between Stripper tip and slow freezing, concluding to the superiority of vitrification in Stripper tip as well. Finally, the theorical time needed per injected oocyte was significantly shorter after vitrification in the two devices than when using slow freezing, and shorter in Cell Sleeper in comparison with Stripper tip. Vitrification, in particular using Cell Sleeper, appears as the most suitable method to cryopreserve small numbers of spermatozoa.

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