OPTIMAL UTILIZATION OF CRYOPRESERVED HUMAN SEMEN FOR ASSISTED REPRODUCTION - RECOVERY AND MAINTENANCE OF SPERM MOTILITY AND VIABILITY

Purpose: Our purpose was to evaluate sperm motility and viability and the maintenance of these parameters in already cryopreserved semen sam ples following repeated freezing/thawing cycles. Methods: Human sperma tozoa were subjected to five cycles of cryopreservation/thawing. Recov ery of sperm motility and viability and the proportion of viable nonmo tile sperm were determined up to 6 hr after thaw Results: Sperm motili ties (prefreeze motility: 70.1%; n = 9 samples) after each of five fre eze/thaw cycles were 24.4, 8.0, 3.5, 1.5, and 1.8%. The recovery of sp erm viability was higher than that of motility after each cycle: 39.1, 25.3, 22.6 17.8, and 16.5%. Recoveries of motility and viability were improved if the thawed samples were left in the original cryopreserva tion medium prior to refreezing vs. if a washing/ resuspension step,wa s included. The recovery of sperm motility in the first thawing cycle was indicative of the expected motile sperm recovery in the second tha wing cycle. Conclusions: Cryopreserved semen that is intended to be re used in future assisted reproduction treatments should be thawed only once and aliquoted in the original freezing medium before refreezing. The recovery of sperm motility and viability in the second thawing cyc le, thus the applicability of the sample in conventional in vitro fert ilization or intracytoplasmic sperm injection may be anticipated in >9 0% of the samples. In view of intracytoplasmic sperm injection it is i mportant that sperm viability is maintained better than motility; afte r the first, second, and third thawing cycles the ratios of motile:non motile viable sperm were 1:1, 1:4, and 1:7 respectively.