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.

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

Methods: 100 sperm samples were collected from candidates for sperm donation and cryopreserved in liquid nitrogen. After thawing, the samples were analyzed for motility, vitality, and DNA fragmentation. Then they were randomized to either Group A or Group B, which underwent either 90 or 180 minutes of incubation at room temperature. The samples were analyzed at the end of their respective incubation periods and once more after an additional freeze-thaw cycle.

Results: Semen analysis of fresh samples showed that both Group A and Group B had similar motility and vitality. After one freeze-thaw cycle, both groups still had comparable parameters.
At the end of their respective incubation periods, there was a statistically significant difference in the mean values of the parameters assessed between the groups (p<0.01). An additional freeze-thaw cycle further exacerbated these sperm parameters. However, Group B had a more substantial decline (p<0.001).

Conclusion: Our data suggests that thawed human spermatozoa has a much more statistically significant decline with longer incubation times at room temperature and is further exacerbated by an additional freeze-thaw cycle.