The partial head decondensation test is a new, quick method to assess acrosome status in human spermatozoa

OBJECTIVE: To develop a fast method for assessing acrosome status in human spermatozoa. DESIGN: Development of a new in vitro test to assess acrosome reaction in human spermatozoa. SETTING: Academic medical institution. PATIENT(S): Normozoospermic subjects. INTERVENTION(S): Spermatozoa were isolated from fresh semen samples, capacitated, and stimulated or not with P or ionomycin. Acrosome reactions were evaluated by phase-contrast microscopy after a brief sperm incubation in a decondensing solution. The results were compared with those obtained by scanning electron microscopy and fluoresceinated lectin staining. MAIN OUTCOME MEASURE(S): Percentage of intact acrosomes. RESULT(S): The new procedure allowed intact acrosomes to be easily identified and quantified by phase-contrast microscopy. In unstimulated and ionomycin-treated spermatozoa, a very good agreement was found among the new test, scanning electron microscopy, and fluoresceinated lectin staining. In P-treated spermatozoa, the proposed method allowed a significantly higher percentage of reacted acrosomes to be resolved, likely due to its ability to detect the very initial stages of the acrosome reaction. CONCLUSION(S): The new test allows acrosome-intact and acrosome-reacted spermatozoa to be unambiguously singled out and quantified. The method is rapid, reliable, sensitive, and easy to perform, which makes it of profitable use in both basic research and diagnostic practice.