Sperm DNA damage in men with spinal cord injury: the relative incidence of single- and double-strand DNA breaks

Abstract

Background: Men with spinal cord injury (SCI) show a high proportion of sperm DNA damage in their ejaculate but the underlying pathology remains elusive. Objective: To investigate the relative incidence of single (SSBs) and double-strand DNA breaks (DSBs) and DNase activity in men with SCI. Materials and methods: This study included ejaculates of 20 men with SCI and 27 normozoospermic (sperm donors). A TwoTails comet assay (TTComet) allowed visualization of three categories of sperm DNA damage corresponding to SSBs, DSBs and those with a combination of SSBs and DSBs, facilitating accurate calculation of the total proportion of SSBs and DSBs. A subset of 15 individuals (sperm donors and SCI patients) was used to test for DNase activity in the seminal plasma. Results: While the proportion of DSBs in men with SCI (median-57.5%) was higher (P = 0.000) than normozoospermic samples (median-4.6%), the proportion of SSBs was higher (P = 0.022) in the normozoospermic ejaculates (median-6.0%) compared to men with SCI (median-2.5%). The relative proportion of the total DSBs with respect to the total SSBs was 3.3× in men with SCI but 0.9× in normozoospermic samples. We further confirmed the high DNase activity in the seminal plasma of men with SCI. Discussion: The TTComet assay provided new insights to the pathology of sperm DNA in men with SCI and may have diagnostic value in developing sperm selection methodologies to reduce DSBs prior to ART. Conclusion: Men with SCI are characterized by a high proportion of sperm with DSBs and high levels of DNase activity in the seminal plasma compared to normozoospermic men.