Association between freezing agent and acrosome damage of human spermatozoa from subnormal and normal semen

This experimental study compares the effects of human sperm preservation me dium (HSPM) with TEST-yolk buffer (TYB) as cryoprotectants of human spermat ozoa with respect to the integrity of the acrosome after the freeze thawing procedure. Fifty-six semen samples were included in this study; 18 were su bnormal (G1) and 38 were normal (G2) based on World Health Organization cri teria, except for morphology, which was evaluated according to strict crite ria. Each semen sample was divided into two parts: the first part was prepa red for cryopreservation by the addition of HSPM (1:1) and the second by ad dition of TYB (1:1). Freezing was performed in liquid nitrogen vapour. Smea rs were made before freezing and after the thawing process for evaluation o f acrosome integrity using fluorescent-lectin labelling. The mean percentag e of spermatozoa with intact acrosomes in the subnormal group was 77.0 +/- 7.2% before freezing and decreased significantly (P < 0.001) after thawing: to 63.7 +/- 8.2% with the use of HSPM and 66.8 +/- 8.7% with the use of TY B. The corresponding values in the normal semen samples were 83.4 +/- 9.2%, 76.0 +/- 8.8% and 77.9 +/- 9.2%, respectively. It is obvious that the decr ease in the mean percentage of spermatozoa with intact acrosome was signifi cantly higher when using HSPM in comparison with TYB, not only for G1 (-14. 9 +/- 1.9 % versus -11. 8 +/- 1.4%) but also for G2 samples (-13.8 +/- 1.5% versus -11.9 +/- 1.3%). In conclusion, TYB should be recommended for freez e-thawing of human spermatozoa as the first-choice cryoprotectant, for norm al as well as subnormal semen samples, in order to protect the sperm acroso me from the deleterious effects of the freeze-thawing procedure.