Time Has its Cost on Freeze-Thawed Sperm Samples

Introduction:

Cryopreserved sperm samples are often refrozen since limited stored samples are available. Several studies have reported on the decreased quality of spermatozoa following repeated cycles of freezing and thawing. These studies, however, had a small sample size and the length of time from when the samples were thawed was not reported. This is especially important because sperm samples remain thawed during the entire ART procedure, which can take several hours.

Aim: To assess the effect of time on sperm parameters in thawed samples which have undergone repeated freezing and thawing.

Methods: Sperm samples were collected from candidates for sperm donation. The sperm was cryopreserved in liquid nitrogen until used. After thawing, the samples were analyzed for motility, vitality and DNA fragmentation. The samples were incubated at room temperature and reanalyzed after 90 or 180 minutes and once again after a repeated cycle of freezing and thawing.

Results: Our preliminary results showed that after the sample was initially thawed, motility and vitality decreased on average by 53.1%±20.5% and 33.7%±15.0%, respectively. The average DNA fragmentation was 27.7%±13.9%.

After incubation for 90 minutes at room temperature, motility and vitality decreased by an additional mean of 19.0%±46.9% and 18.2%±12.2%, respectively, while DNA fragmentation increased by 44.7%±55.0%. With an additional freeze-thaw cycle, the mean motility and vitality decreased by an additional 53.3%±19.2% and 32.6%±12.7%, with DNA fragmentation rising by 24.66%±21.5%.

After incubation for 180 minutes, the motility and vitality decreased by 47.5%±22.7% and 29.9%±10.6%, respectively on average. The mean DNA fragmentation rate was 34.0%±13.5%. With an additional freeze-thaw cycle, the mean motility and vitality decreased by an additional 46.5%±19.2% and 36.7%±13.9, respectively, while DNA fragmentation increased by 25.7%±21.5% on average.

Conclusion: Once a sperm sample has thawed, time becomes essential as an increase in the length of time is correlative with a decrease in the quality of the sperm.