Optimal utilization of cryopreserved human semen for assisted reproduction: recovery and maintenance of sperm motility and viability.
OBJECTIVE
Our purpose was to evaluate sperm motility and viability and the maintenance of these parameters in already cryopreserved semen samples following repeated freezing/thawing cycles.


METHODS
Human spermatozoa were subjected to five cycles of cryopreservation/thawing. Recovery of sperm motility and viability and the proportion of viable nonmotile sperm were determined up to 6 hr after thaw.


RESULTS
Sperm motilities (prefreeze motility, 70.1%; n = 9 samples) after each of five freeze/thaw cycles were 24.4, 8.0, 3.5, 1.5 and 1.8%. The recovery of sperm viability was higher than that of motility after each cycle: 39.1, 25.3, 22.6, 17.8, and 16.5%. Recoveries of motility and viability were improved if the thawed samples were left in the original cryopreservation medium prior to refreezing vs. if a washing/ resuspension step was included. The recovery of sperm motility in the first thawing cycle was indicative of the expected motile sperm recovery in the second thawing cycle.


CONCLUSIONS
Cryopreserved semen that is intended to be reused in future assisted reproduction treatments should be thawed only once and aliquoted in the original freezing medium before refreezing. The recovery of sperm motility and viability in the second thawing cycle, thus the applicability of the sample in conventional in vitro fertilization or intracytoplasmic sperm injection may be anticipated in > 90% of the samples. In view of intracytoplasmic sperm injection it is important that sperm viability is maintained better than motility; after the first, second, and third thawing cycles the ratios of motile:nonmotile viable sperm were 1:1, 1:4, and 1:7, respectively.
Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
T E
TE
Polcz
J
J
Stronk
C
C
Xiong
E E
EE
Jones
D L
DL
Olive
G
G
Huszar
D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology; D005307:Fertilization in Vitro; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence; D009930:Organic Chemicals; D011419:Propidium / Q000737:chemistry; D012661:Semen / Q000502:physiology*; D012662:Semen Preservation; D013081:Sperm Motility / Q000502:physiology*
D003451:Cryoprotective Agents; D005456:Fluorescent Dyes; D009930:Organic Chemicals; C093207:SYBR-14; D011419:Propidium