The kinetics of the acrosome reaction of human spermatozoa and its correlation with in vitro fertilization

OBJECTIVE: To study the reaction pattern of acrosome reaction in human semen and correlate it to the results of in vitro fertilization (IVF). DESIGN: The percentage of acrosome-reacted spermatozoa of 41 IVF semen samples was determined after 0, 2, 4, and 24 hours of incubation in human tubal fluid medium supplemented with 10% human pool serum. SETTING: St. Radboud Hospital, Catholic University of Nijmegen, The Netherlands. PATIENTS: Forty-one IVF couples. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Acrosome reaction was determined using fluorescein isothiocyanate conjugated concanavalin A lectin. To avoid false-positive signals from dead spermatozoa, the sperm viability was determined. RESULTS: Three kinetic patterns of acrosome reaction could be distinguished: (1) normal reacting pattern (percentage of acrosome-reacted spermatozoa less than 10% at 2 hours and greater than 5% at 4 hours; 75% fertilization in IVF); (2) a quickly reacting pattern (percentage of acrosome-reacted spermatozoa greater than 10% at 2 hours; 22% fertilization in IVF); and (3) a nonreacting pattern (percentage of acrosome-reacted spermatozoa less than 5% at all time intervals studied; 15% fertilization in IVF). CONCLUSIONS: The timing of acrosome reaction and the percentage of acrosome-reacted spermatozoa are very important parameters in IVF.