[Self-made metal freezing plate for cryopreservation of human epididymal sperm: An experimental study]

To study the effect of a new human sperm freezing method on the sperm recovery rate and search for an optimal method for cryopreservation of human epididymal sperm.

We collected semen samples from 76 men with obstructive azoospermia by percutaneous epididymal sperm aspiration and divided each sample into two parts to be cryopreserved with a self-made metal freezing plate (the experimental group) or by slow freezing (the control group), respectively. We measured the percentage of progressively motile sperm (PMS) with the computer-assisted semen analysis system and compared the membrane function, DNA fragmentation index (DFI), acrosin activity and morphological abnormality of the sperm between the two groups before and after cryopreservation.

After thawing, both the percentages of PMS and hypotonically swollen sperm were significantly higher in the experimental than in the control group (［12.0 ± 7.5］% vs ［8.0 ± 5.1］%, P < 0.05; ［22.0 ± 17.5］% vs ［18.0 ± 20.5］%, P < 0.05), though both decreased in comparison with the pre-freezing parameters (［20.7 ± 8.8］% and ［30.0 ± 13.5］%) (P < 0.05). The sperm acrosin activity was remarkably higher in the experimental than in the control group after thawing (［75.2 ± 9.5］ vs ［55.7 ± 8.3］ μIU/106sperm, P < 0.05), though decreased as compared with the baseline (［120.0 ± 10.5］ μIU/106 sperm, P < 0.05). No statistically significant differences were observed between the experimental and the control groups after thawing in the percentage of morphologically abnormal sperm (［98.7 ± 8.8］% vs ［98.5±9.2］%, P > 0.05) or sperm DFI ［38.2 ± 8.5］% vs ［39.5 ± 10.2］%, P > 0.05), though both markedly elevated in comparison with the pre-freezing parameters (［97.2 ± 9.5］% and ［30.8 ± 9.7］%) (P < 0.05). The post-thaw recovery rate of sperm was significantly higher in the experimental than in the control group (［65.2 ± 12.0］% vs ［52.3 ± 18.0］%, P < 0.05).

The self-made metal freezing plate, with its advantages of low cost, high efficiency, and easy operation, can be used as an effective method for cryopreservation of human sperm to achieve a high post-thaw sperm recovery rate, progressive sperm motility, and sperm acrosin activity.