Influence of semen processing technique on human sperm DNA integrity

Objectives. To compare the effects of density-gradient centrifugation and s wim-up technique on sperm DNA integrity. Methods. Semen samples (n = 22) were obtained from consecutive nonazoosperm ic men presenting for infertility evaluation. Individual samples were divid ed into three aliquots (whole semen, density-gradient centrifugation, and s wim-up) for subsequent analysis of sperm motility and DNA integrity. Sperm DNA integrity was evaluated by flow cytometry analysis of acridine orange-t reated spermatozoa and expressed as the percentage of spermatozoa demonstra ting denatured DNA. Results. Mean sperm motility (+/-SEM) improved significantly after processi ng with two-layer density-gradient and swim-up compared with whole semen (6 5.6% +/- 4.0% and 73.0% +/- 3.0% versus 52.0% +/- 3.6%, respectively, P <0. 005), with no significant difference in motility between Percoll-treated an d swim-uptreated spermatozoa. In contrast, the percentage of spermatozoa wi th denatured DNA was reduced significantly in swim-up-treated but not in Pe rcoll-treated spermatozoa compared with whole semen (4.8% +/- 1.2% and 13.6 % +/- 3.6% versus 10.1% +/- 2.3%, respectively, P <0.0001). Conclusions. Although density-gradient centrifugation is comparable to swim -up technique in recovering spermatozoa with enhanced motility, spermatozoa recovered after swim-up possess higher DNA integrity. These data urge us t o reexamine our current sperm processing techniques in order to minimize sp erm DNA damage. UROLOGY 56: 1081-1084, 2000. (C) 2000, Elsevier Science Inc .