DNA strand breaks in human spermatozoa: a possible factor, to be considered in couples suffering from unexplained infertility.

BACKGROUND: The aim of this study was to assess the presence of DNA strand breaks and sperm cell morphology in men suffering from unexplained infertility, and to compare these results with normal fertile and oligozoospermic men. METHODS: One fresh sperm sample from proven fertile sperm donors (n=20) and from infertile men with oligozoospermia, (<20 x 10(6)/ml sperm cells) (n=74), and men suffering from unexplained infertility (>20 x 10(6)/ml sperm cells) (n=39) who delivered two sperm samples with 24 hours interval, were tested for the presence of DNA strand breaks in the spermatozoa by direct immunoperoxidase detection of digoxigenin-labeled genomic DNA. Correlations to other sperm parameters, sperm cell counts, motility, activation and Krüger's strict criteria were performed. RESULTS: DNA strand breaks in sperm cell nuclei were found significantly more often in sperm samples from men suffering from unexplained infertility compared to those from normal fertile men, and significantly more rarely compared with sperm samples from men with oligozoospermia. The percentages of normal spermatozoa (Krüger's strict criteria) were significantly lower in samples from men suffering from unexplained infertility compared to those of normal fertile men, but significantly higher compared to those of men with oligozoospermia. No difference was found between first and second day samples used for insemination, as regards DNA strand breaks, sperm cell morphology, total number of motile sperm cells, activation and motility degree. CONCLUSION: The present data suggest that a subgroup of men suffering from unexplained infertility have DNA strand breaks in their sperm cell DNA. This group might suffer from the same malfunction as many men with oligozoospermia, however, their apoptotic activated sites in the testis are different. Delivery of sperm samples with 24 hours interval does not affect any sperm cell counts, CASA, DNA strand breaks or morphology findings in sperm samples from men suffering from unexplained infertility.