IMPROVEMENT OF POSTTHAW SPERM MOTILITY IN POOR QUALITY HUMAN SEMEN

Objective: To find alternative cryopreservation methods to improve the post-thaw fertilizing capacity of poor quality human sperm. Design: C ontrolled clinical study. Setting: Fertility clinic of a teaching hosp ital. Patients: Men with poor quality semen samples, i.e., asthenozoos permia (<40% motile sperm) and/or oligozoospermia (< 20 X 10(6) sperm/ mL). Fertile sperm donors were used for comparison. Interventions: Sem en samples were divided into four aliquots and slowly diluted 1:1 with : [1] n-tris (hydroxymethyl) methyl-2-amino ethane sulfonic acid (TES) and tris (hydroxymethyl) aminomethane (Tris)-citric acid-egg yolk buf fer with 12% glycerol (TEST), [2] TEST + CryoSeeds (Cell Systems, Ltd. , Cambridge, UK), [3] TEST + 10 mM dithiothreitol (DTT), or [4] TEST CryoSeeds + 10 mM DTT. Cryovials were frozen using slow staged coolin g and static vapor freeze and stored at -196-degrees-C. Main Outcome M easure: The frozen aliquots were randomly thawed and, after 15 minutes at 37-degrees-C, motion analysis was performed. Results: The percent motility after freeze-thaw in TEST was significantly decreased to 42 /- 5% of prefreeze motility (P < 0.001). Addition of CryoSeeds with ho lding at -5-degrees-C for 10 minutes resulted in 47 +/- 6% of prefreez e motility, which was not different than TEST alone. Addition of DTT t o TEST significantly improved post-thaw motility over TEST alone to 71 +/- 7% of initial motility (P < 0.01). The combination of CryoSeeds a nd DTT further improved post-thaw motility to 80 +/- 10% of initial mo tility, which was not different than the neat semen. Conclusion: The p resent results suggest that DTT, a reducing agent that prevents oxidat ion of sulfhydryl groups, protects poor quality spermatozoa from exces sive cryodamage. Thus, DTT along with seeding may be a useful addition when long-term storage of poor quality semen is crucial for maintaini ng reproductive potential.