Numerous studies have shown the presence of DNA lesions in human spermatozoa affecting sperm quality. However, the nature of this anomaly and its relationship with patient etiology are poorly understood since different mechanisms can be involved in the formation of these novel DNA configurations including the action of a seminal plasma nuclease activity. The objective of this study was to assess the capacity of seminal plasma for producing endogenous DNA cleavage using nuclei of peripheral blood leukocytes as external targets. For this purpose, we used seminal plasma from fertile males with normal semen parameters to produce DNA cleavage in a sample of leukocytes. Three different tests were performed to visualize DNA cleavage: (a) DNase activity detection, (b) DNA Breakage Detection-Fluorescence In Situ Hybridization (DBD-FISH), and (c) Two-dimensional comet assay (Two-tail comet assay). Our results demonstrate that: (i) the seminal plasma is able to cleave DNA compacted with histones in the leukocytes; (ii) this DNA cleavage can be associated with DNase activity and (iii) DNA damage mainly corresponds to single-strand DNA breaks. In conclusion, capacity of seminal plasma for producing DNA cleavage represents a solid contribution to expand the analysis of the standard seminal profile and could constitute a putative diagnostic tool for evaluating male infertility.

Purpose To examine the effect of co-incubating spermatozoa with human follicular fluid (HFF) on the rate of sperm DNA fragmentation. Methods This prospective study used semen (n = 23) and HFF from oocyte donors (n = 23). Liquified semen was divided into four aliquots: (1) neat semen (NEAT), (2) seminal plasma removed and replaced with sperm media (HTF) containing 0% (FF0), (3) 20% (FF20), or (4) 50% (FF50) HFF. Sperm motility and DNA fragmentation (SDF) were assessed following 24 h of incubation at 37 °C. Pro-oxidant capacity of HFF and seminal plasma and the effect of HFF on seminal plasma DNase activity was assessed in a sub-sample of 10 ejaculates. Results Sperm motility was higher after 3 h of incubation in media that contained HFF compared to the NEAT sample or when sperm was diluted in media without HFF. r-SDF (increase of SDF per time unit) values after 24 h of incubation for NEAT, FF0, FF20 and FF50 were 0.91, 0.69, 0.25 and 0.36, respectively. While pro-oxidant capacity of seminal plasma samples showed large variation (mean: 94.6 colour units; SD 65.4), it was lower and more homogeneous in FF samples (mean: 29.9 colour units; SD: 6.3). Addition of HFF to seminal plasma appeared to inhibit DNase activity. Conclusion While differences exist in the pro-oxidant capacity of seminal plasma of patients, sperm DNA integrity was preserved with addition of HFF to sperm media, irrespective of the level of pro-oxidant capacity. DNase activity in the original seminal plasma was abolished after HFF co-incubation.

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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.