Localization of single-stranded DNA in human sperm nuclei.

OBJECTIVE To localize foci of single-stranded (ss) DNA in sperm nuclei of fertile and infertile men. DESIGN Prospective, observational study. SETTING University infertility clinic. PATIENT(S) Semen samples from 12 consecutive asthenoteratospermic men presenting for infertility evaluation and 5 consecutive fertile men presenting for vasectomy. INTERVENTION(S) Semen analysis, semen processing, and immunocytochemistry using an antibody targeting ssDNA. MAIN OUTCOME MEASURE(S) Sperm nuclear ssDNA immunostaining pattern in whole and processed semen samples. RESULT(S) Immunocytochemistry (using ssDNA antibody) demonstrated one of two sperm nuclear staining patterns: [1] faint punctated staining, and [2] diffuse nuclear staining. Infertile men had a higher proportion of spermatozoa exhibiting diffuse ssDNA staining than did fertile men (52 +/- 19 vs. 14 +/- 13, respectively). The proportion of spermatozoa exhibiting diffuse ssDNA staining was significantly higher in whole compared with processed semen. Positive (DNAse-treated nuclei) and negative controls (S1 nuclease-treated nuclei) were obtained to validate the specificity of the antibody. CONCLUSION(S) Human sperm nuclei generally exhibit discrete (presumably peripheral) foci of ssDNA. The data also show that infertile men have a higher proportion of sperm nuclei with diffuse areas of ssDNA than do fertile men, and suggest that spermatozoa with diffuse nuclear staining are abnormal.