EVALUATION OF CHROMATIN CONDENSATION IN HUMAN SPERMATOZOA - A FLOW CYTOMETRIC ASSAY USING ACRIDINE-ORANGE STAINING

The quality of sperm chromatin is an important factor in fertilization and is especially critical where one spermatozoon is artificially sel ected for fertilizing an egg (as in intracytoplasmic sperm injection), In this study, flow cytometry after staining of human spermatozoa wit h Acridine Orange was used to study chromatin structure. A method is d escribed for estimating the percentage of cells in a human sperm sampl e that have completed epididymal maturation in regard to chromatin con densation. Of the 121 samples of semen that were examined, nine contai ned a higher percentage of hypocondensed spermatozoa and six samples c ontained elevated amounts of hypercondensed spermatozoa. In addition t o aberrancies in chromatin condensation other defects showed up as sat ellite populations of spermatozoa with higher than normal ratios of re d/green fluorescence after Acridine Orange staining. Such defects were found in 15 semen samples. The use of swim-up and Percoll gradient ce ntrifugation methods was shown to improve the percentage of spermatozo a with normal chromatin structure in some samples with poor initial qu ality.