The specificity of human spermatozoa/zona pellucida interaction under hemizona assay conditions

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Abstract
The objective of this prospective study was to evaluate the specificity of human sperm/zona pellucida interaction under hemizona assay (HZA) conditions in experiments with gametes from the same and different species. Human, cynomolgus monkey and hamster oocytes were used after salt‐storage. Oocytes were bisected into matching hemizonae by micromanipulation and used in the HZA. Semen was obtained from healthy men (donors) and male cynomolgus monkeys and prepared by wash and swim‐up. Sperm binding to matching hemizonae was assessed (tight binding) after 4‐h coincubation in the HZA in homologous and interspecies experiments. Acrosome reaction was evaluated in the sperm droplets using FITC‐PSA and on the hemizonae using the T‐6 monoclonal antibody. On human hemizonae, the number of tightly bound sperm for human and monkey were 93.2 ± 15.8 and 3.9 ± 1.3, respectively (PP = 0.02) respectively. On hamster hemizonae, there was negligible binding of human and monkey sperm. There was a significantly higher incidence of acrosome reacted sperm on the zona pellucida in homologous compared to heterologous experiments. These results demonstrate a high species‐specificity of human gamete functions under HZA conditions, providing further support for the use of this bioassay in infertility and contraception testing.