Dynamics of human sperm acrosome reaction: relation with in vitro fertilization

OBJECTIVE: Acrosomal status has been studied on human sperm prepared for in vitro fertilization (IVF) and related to the rate of fertilization. DESIGN AND PATIENTS: A group of 41 men with normal classical semen parameters, included in the IVF program of University of Nice for feminine tubal obstruction (n = 37) or unexplained infertility (n = 4), were evaluated in a prospective study and compared with a control group of 10 fertile donors. MAIN OUTCOME MEASURES: Evaluation of acrosome status (spontaneous and A23187-induced acrosome loss) after 6 hours incubation in Ménézo's B2 medium was made by flow cytometry on suspended cells with a new immunofluorescence test recently reported by the authors based on a monoclonal antibody GB24. RESULTS: Spontaneous acrosome loss remained low even after 6 hours capacitation (mean + 1 SD, 6.5% + 4.9%). Response to A23187 increased with the duration of preincubation with a marked response after 6 hours (29.5% + 8.9%). Low spontaneous acrosome loss (less than mean + 1 SD) and high response to A23187 (greater than mean - 1 SD) were observed in 25 out of 26 cases of group A with a high fertilization rate (greater than 50% fertilized oocytes). A high level of spontaneous acrosome loss and/or a lack of response to A23187 was observed in 2 of 7 cases of group B (fertilization rate less than 50%) and 6 of 8 cases of group C (unexplained unsuccessful fertilization). CONCLUSION: Impaired acrosomal status can be associated with unexplained unsuccessful fertilization.