Comparison of protective media and freezing techniques for cryopreservation of human semen

To evaluate the influence of cryopreservation medium and freezing-thawing techniques on human sperm motility and morphology.

63 semen samples were obtained from 39 donors to the artificial insemination programme. Possible effects of the sperm dilution with cryomedium on the motility were examined 10 min after exposure of 24 high initial quality semen samples to TEST-yolk ¿zwitterion-citrate-egg yolk extender containing TES [N-Tris (hydroxymethyl) methylaminoethane sulfonic acid] and Tris [(hydroxymethyl) aminomethane]¿ and human sperm preservation medium (HSPM). Post-thaw sperm motility from 24 frozen semen samples was examined comparing the cryoprotective efficacy of TEST-yolk and HSPM following different freezing techniques (vapour freezing, fast programmable freezing and slow programmable freezing). The relationship of sperm morphology to the effects of freezing was investigated on 39 semen samples following different freezing techniques. Post-thaw sperm motility from 39 frozen semen samples was compared among three groups divided according to the percentage of morphologically normal cells (<40, 40-50 and >50%) in fresh semen.

Exposure of spermatozoa to cryomedia for 10 min at room temperature significantly reduced motility in TEST-yolk treatment group for 9% and in HSPM treatment group for 18% (P<0.01). The recovery of motile sperms (mean+/-standard deviation) was 49+/-15.7, 43+/-15.2 and 52+/-16.8% when TEST-yolk was used and 34+/-17.8, 32+/-18.2 and 50+/-13.6% when HSPM was used as a cryopreservative following vapour freezing, and fast and slow programmable freezing, respectively. Following vapour freezing and also following fast programmable freezing, the recovery of motile sperm was significantly higher (P<0.05) after addition of TEST-yolk medium than after addition of HSPM. Post-thaw motility of the sperm cryopreserved in HSPM showed significant differences (P<0.05) after three different freezing techniques. The recovery of motile sperms was 57+/-26.4, 38+/-8.6 and 38+/-17.3% in groups with >50, 40-50 and <40% morphologically normal cells, respectively. The percentage of morphologically normal spermatozoa was reduced 8% after vapour freezing and 6 and 3% after fast and slow programmable freezing, respectively. The results were statistically analysed using SAS/STAT software.

Slow programmable freezing was superior to vapour freezing and fast programmable freezing as a method for sperm cryopreservation. However, none of these methods of freezing had discernible effects on sperm morphology. Motility of spermatozoa decreased due to the exposure of semen to cryomedium. TEST-yolk was a superior cryomedium to HSPM. Fresh semen with more than 50% of morphologically normal cells showed the best recovery of motile cells after freezing and thawing.