Semen processing by density gradient centrifugation is useful in selecting sperm with higher double-strand DNA integrity.

The objective of this study was to determine the effects of density gradient centrifugation on sperm cell DNA integrity and to correlate any detected DNA damage with semen analysis parameter. A total of 40 semen samples were collected from nonazoospermic men presenting for infertility evaluation at our department. Individual samples were divided into two parts: one part of the semen was washed and the remainder was prepared using the PureSperm density gradient centrifugation. Sperm DNA fragmentation as evaluated by the terminal desoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick-end labelling assay, was monitored in the initially washed sample and in the different layers of the density gradient centrifugation. No significant correlations were observed between sperm DNA fragmentation, age of patient, concentration and motility. However, a significant correlation existed with strict spermatic morphology. Following density gradient centrifugation, the proportion of spermatozoa with DNA fragmentation decreased significantly when compared with whole semen. In addition, we found that spermatozoa isolated in the 90% layer possessed a significantly lower percentage of DNA damage when compared with those remaining in the 70% and 50% layers. These results demonstrate that semen processing by the PureSperm gradient is useful in selecting sperm with higher double-strand DNA integrity.