Objective
Cryopreservation causes deleterious effects on human spermatozoa due to freezing and thawing, leading to decreased cryosurvival rates (CSR). The objectives of this study were to assess levels of oxidation-reduction potential (ORP) in cryopreserved semen of infertile men, and to determine their relationship to post-thaw sperm parameters.
Design
A prospective cohort study.
Materials and Methods
The study included 28 semen samples obtained from men who were evaluated for an infertility problem between November, 2016 and April, 2017. Standard semen analysis was performed according to the WHO guidelines (fifth edition, 2010). Fresh seminal ORP was measured using the MiOXSYS system (Aytu BioScience, Inc., Englewood, CO, USA). Recorded ORP values were adjusted for sperm concentration and final results were expressed as mv/106 sperm/ml. Semen samples with azoospermia, sperm concentration < 1 million/ml or leukocytospermia were excluded. Aliquots of 0.5 ml semen were cryopreserved using slow freezing technique. One week later, frozen samples were thawed at 37 °C, and examined for post-thaw percent of total motility, percent of progressive motility, total motile sperm (TMS) counts and ORP levels. Cryosurvival rate was calculated according to the equation: CSR = post-thaw TMS/pre-freeze TMS X 100. Data were presented as median (25thand 75th percentiles). Paired sample t test was used for comparison of the pre and post-thaw results. P value < 0.05 was considered significant.
Results
Post-thaw percent of total motility [20 (10, 40)], percent of progressive motility [10 (5, 25)] and TMS counts [4.1 (0.6, 6.3) X106 sperm] were significantly lower than pre-freeze values (percent of total motility [50 (40, 55)], percent of progressive motility [30 (24, 35)] and TMS counts [25 (18, 41) X106 sperm); P values < 0.001. Post-thaw levels of seminal ORP [2.8 (2.3, 4.4) mv/106 sperm/ml] were significantly higher than pre-freeze values [0.9 (0.54, 1.34) mv/106 sperm/ml]; P < 0.001. The median percentage of CSR was 10 (5 & 20). A significant (P< 0.05) negative correlation was found between post-thaw levels of seminal ORP and total motility (r = -0.5), progressive motility (r = -0.41), TMS counts (r = -0.60) and CSR (r = -0.52).
Conclusions
Sperm cryopreservation in infertile men was associated with high seminal ORP, low sperm motility and reduced CSR. Sperm cryo-damage is related to high seminal ORP generated during freeze-thaw process. Future efforts should be directed towards reduction in oxidant production to improve sperm recovery following cryopreservation.