Cold-preserved human spermatozoa in electrolyte-free solution retain their pene-tration capacity

Objective: To evaluate penetration capacity of human sperm preserved in electrolyte-free (EF) solution at 4 ℃.Methods: The motility, acrosomal status penetration rate and fertility index of human sperm were assessed before and after cold-preservation in EF solution, respectively.Results: The motility of human sperm cold-preserved in EF solution for 1 week was significantly higher than that of human sperm cold-preserved in modified human tubal fluid (mHTF) (43.4%±7.9% vs 9.5%±2.5%, P<0.01 ).Although acrosomal status of human sperm cold-preserved in the EF solution before reinitiation was not different from those of the fresh sperm (capacitated sperm: 7.6%±1.8% vs 6.4±1.8%; acrosome-reacted sperm: 3.0%±1.7% vs 2.4±1.1%, P>0.05), the percentage of capacitated and acrosome-reacted sperm in the EF solution significantly increased after reinitiation (capacitated sperm: 16.0%±2.3% vs 7.6±1.8%, acrosome-reacted sperm: 9.4%±2.1% vs 3.0%±1.7%, P<0.01).The penetration rate and fertility index of cool-preserved human sperm in the EF solution were comparable with those of fresh sperm (48.1% vs 50.9%; 1.38±0.16 vs 1.29±0.13, respectively, P>0.05).Conclusion: Cold-preservation did not induce capacitation and acrosome reaction of human sperm in the EF solution, but human sperm cold-preserved in the EF solution for 1 week possesses as much penetration capacity as fresh sperm.