Effect of Follicular Fluid on the Kinetics of Human Sperm Acrosome Reaction in Vitro

Abstract

The purpose of the present study was to evaluate the kinetics of human sperm acrosome reaction in vitro using the triple stain technique. Acrosome reaction was studied in sperm samples from 16 fertile men 2, 6, and 9 h after ejaculation, following incubation in culture medium (CM; Ham's F-10), with a mixture of CM and follicular fluid (FF), or with FF only. Incubation of sperm samples without the influence of any medium served as control. The highest proportion of living acrosome-reacted sperm after a 2-h incubation period occurred in samples incubated with FF (18%), followed by samples incubated with the mixture (15.2%), and then with CM (11.8%). The proportion of living sperm that had undergone the acrosome reaction in the control group was significantly lower (5.7%, p < 0.05). After 6 h of incubation, live acrosome-reacted sperm in FF had increased to 39%, in the mixture to 35.5%, and in CM to 30.5%, whereas in the control group the increase was only 6.3% (p < 0.05). After 9 h of incubation, the percentage of living reacted sperm showed a decline compared with the percentage at 6 h. This decline was greater in samples incubated with FF (from 39 to 19.8%) than in samples incubated with the mixture (from 35.5 to 23.6%). Samples incubated in CM only showed a small decrease from 30.5 to 28.4%, while in the control group this percentage decreased from 6.3 to 2.3%. In conclusion, incubation of sperm in suitable media favorably influences the acrosome reaction, inducing an increase in the percentage of live acrosome-reacted sperm. The most beneficial effect on the induction of acrosome reaction is exercised by FF, followed by the mixture, and then the CM after 6 h of incubation. The study of the acrosome reaction in vitro could be helpful in assessing more accurately the fertilizing potential of human sperm.

Key Words:

• Acrosome reaction
• Follicular fluid
• Human sperm