Chromatin condensation and DNA damage of human epididymal spermatozoa in obstructive azoospermia

Abstract

Obstructive azoospermia (OA) includes patients with different aetiologies of obstruction such as congenital bilateral absence of vas deferens (CBAVD), post-vasectomy/failed vaso–vasostomy, or unknown (idiopathic). The frequency of DNA-damaged spermatozoa and abnormal chromatin condensation in epididymal spermatozoa of OA patients was investigated for the different aetiology subgroups. DNA damage in caput epididymis spermatozoa was assessed with the TdT-UTP nick-end labelling (TUNEL) assay and chromatin condensation status was measured with chromomycin A3 (CMA3) stain ( n = 60 patients). All epididymal sperm samples showed high levels of TUNEL positivity (mean and SD, 43 ± 17%). CMA3 rates showed large variation within the samples (mean and SD, 53 ± 21%, range 7–97%); however, a significant difference in chromatin condensation was found between the different aetiologies of obstruction. The highest percentage of CMA3 positivity was found in the CBAVD and idiopathic groups (60 ± 17 and 65 ± 18% respectively) compared with the post-vasectomy samples (37 ± 17%) or ejaculated spermatozoa from normozoospermic males (29 ± 12%). In conclusion, despite the normal testicular histology in OA men, chromatin condensation differed between OA patients. The physiological heterogeneity found in chromatin condensation between patient subgroups is probably influenced by the aetiology of the obstruction.