Biologic variability of sperm DNA denaturation in infertile men

Abstract

Objectives. To examine sperm DNA denaturation (DD) in fertile and infertile men and assess the variability of conventional semen parameters and sperm DD in repeated semen samples from infertile men. Methods. Twenty-one consecutive nonazoospermic, infertile men each submitted two semen samples, 2 to 6 weeks apart. We examined semen samples from consecutive fertile men (n = 10) presenting for vasectomy as controls. Standard semen parameters (World Health Organization criteria) and sperm chromatin structure (evaluated by flow cytometry analysis of acridine orange-treated spermatozoa and expressed as the percentage of spermatozoa with denatured DNA) were monitored. Results. Fertile men had a significantly higher sperm concentration and percentage of sperm motility and a significantly lower percentage of sperm with DD than did infertile men (36 ± 5.2 × 10 6/mL versus 12.5 ± 2.2 × 10 6/mL, 60.0% ± 5.2% versus 30.1% ± 4.1%, and 8.9% ± 1.9% versus 20.3% ± 2.5%, respectively, P <0.05). The sperm concentration, sperm motility, and percentage of spermatozoa with DD were not significantly different between the first and second semen samples from the infertile men. Sperm DD showed the lowest average within-subject coefficient of variation (SD/mean), followed by motility and concentration (coefficient of variation 21%, 24%, and 35%, respectively). Conclusions. Our data demonstrate that infertile men have significantly higher sperm DD compared with fertile men and that sperm DD exhibits a low coefficient of variation (∼20%) on repeated assessment. These data suggest that sperm DD has a relatively low degree of biologic variability.