A comparison of DNA damage in testicular and proximal epididymal spermatozoa in obstructive azoospermia

Testicular and epididymal spermatozoa are used routinely for intracytoplasm ic sperm injection (ICSI) to treat men with obstructive azoospermia. Little is known of the effects of obstruction and stasis on the DNA of these sper matozoa, particularly in the epididymis where spermatozoa have been retaine d for long periods. Surgical epididymal aspiration for ICSI could provide s permatozoa that are senescent or dying. Using the Comet assay, the percenta ge of undamaged DNA of testicular spermatozoa from 20 men with obstructive azoospermia was significantly better (83.0 +/- 1.2%) than from proximal epi didymal spermatozoa (75.4 +/- 2.3%; P < 0.05). There was no difference betw een the percentage of undamaged DNA of testicular spermatozoa from 39 men w ith obstructive azoospermia (84.0 +/- 0.9) or from 10 fertile men at vasect omy (86.8 +/- 1.8) or from ejaculated spermatozoa from five of the controls (78.9 +/- 3.9; P > 0.05). In nine subjects, a second biopsy was carried ou t 6 months later. There was no significant difference in undamaged DNA on t hese two occasions (83.5 +/- 5.6 and 84.1 +/- 4.2; P > 0.05). This confirms the reproducibility of the Comet assay for non-ejaculated spermatozoa. Our data suggest that testicular sperm DNA appears to be significantly less da maged than epididymal sperm DNA, and so testicular spermatozoa should be us ed in preference for ICSI to treat men with obstructive azoospermia.