Relationships between human sperm acrosin, acrosomes, morphology and fertilization in vitro

Acrosin was measured in the semen used for sperm preparation for in-vitro fertilization (IVF) in 118 patients. Acrosin levels correlated with the proportion of spermatozoa with normal intact acrosomes determined with Pisum sativum agglutinin labelled with fluorescein. However, acrosin levels and the proportion of spermatozoa with normal intact acrosomes in semen were not significantly related to the fertilization rate in vitro. Only the percentage normal morphology and sperm concentration in the insemination medium were independently significantly related to the fertilization rate by logistic regression analysis. In patients with fewer than 30% of spermatozoa with normal morphology, although acrosin levels were not correlated with the fertilization rate, the proportion of spermatozoa with normal intact acrosomes in the insemination medium was the only significant factor in the logistic regression analysis. In conclusion, acrosin levels have no prognostic value for fertilization in vitro but the proportion of spermatozoa with normal intact acrosomes may be a useful clinical marker of fertilizing ability in men with poor sperm morphology.