Acrosin activity in human spermatozoa in relation to semen quality and in-vitro fertilization

Acrosin, a sperm proteinase released during acrosomal exocytosis, facilitates penetration through the oocyte vestments. The purpose of this investigation was to determine if a correlation exists between the acrosin activity of ejaculated human spermatozoa, before motility enrichment techniques, and in-vitro fertilization (IVF) success using selected (glass wool or swim-up) spermatozoa. Since all the oocytes were retrieved from women receiving exogenous hormonal stimulation and a mixed population of mature and immature oocytes were encountered, only cases with > or = 50% mature oocytes were analysed. Under these conditions, the acrosin activity was significantly greater (P < 0.01) in the ejaculates in which spermatozoa ultimately fertilized > or = 70% of the mature oocytes, than in the ejaculates in which spermatozoa ultimately fertilized < 70% of the mature oocytes. Furthermore, a strong correlation (r = 0.962, P = 0.0001) was detected between pre-IVF acrosin activity and subsequent high (> or = 70%) IVF success. Acrosin activity from normozoospermic and oligo-asthenozoospermic men was also compared and was significantly (P < 0.01) higher for the normozoospermic group. These data suggest that measurement of acrosin activity may be a valuable clinical laboratory assay for assessing the sperm fertilizing potential and that low acrosin activity is associated with abnormal semen characteristics.