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.