The influence of homogenous zona pellucida on human spermatozoa hyperactivation, acrosome reaction and zona binding
The study aimed to evaluate the changes in sperm motion characteristics and the occurrence of hyperactivation among sperm populations after exposure to human zona pellucida. Motile spermatozoa samples were used to evaluate the sperm-zona binding capacity, zona-induced acrosome reaction and changes in sperm motion characteristics. Sperm motion characteristic changes studied included straight line velocity, curvilinear velocity, amplitude of lateral head displacement, straightness and beat cross frequency. Recordings were performed on semen immediately after liquefaction, 3 h capacitation and after exposure to solubilised human zona pellucida. The semen samples were divided into morphology categories, namely six (16 ± 1.4% normal forms, normal patterns), 31 (8 ± 1.7% normal forms, G-pattern) and 27 (3 ± 1.3% normal forms, P-pattern). The Hemizona Indices for the three morphology groups namely normal, G-patterns and P-patterns, were 77 ± 6%, 61 ± 5% and 41 ± 5% respectively (P ≤ 0.05). The zona-induced acrosome reaction for the three groups were 25.0 ± 2% (normal group), 18.0 ± 2% (G-patterns) and 14.1 ± 0.6% (P-pattern) (P ≤ 0.05). The number of hyperactivated sperm showed an increase in the ejaculates (1%), after capacitation (2%) and exposure to zona pellucida (5%) (P ≤ 0.05). When divided into the three morphology groups, the number of spermatozoa with hyperactivated motility was more profound in men with normal morphology compared with G- and P-pattern men. Human zona pellucida is a strong inducer of hyperactivated motility among spermatozoa and the effect is more profound among sperm populations with normal morphology. © 2007 The Authors.