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. 2021 Mar-Apr;47(2):275-283.
doi: 10.1590/S1677-5538.IBJU.2019.0827.

Oxidative origin of sperm DNA fragmentation in the adult varicocele

Jessica Timóteo Jeremias  1 , Larissa Berloffa Belardin  1 , Fatima Kazue Okada  1 , Mariana P Antoniassi  1 , Renato Fraietta  1 , Ricardo Pimenta Bertolla  1 , Paula Intasqui  1
Affiliations

Oxidative origin of sperm DNA fragmentation in the adult varicocele

Jessica Timóteo Jeremias et al. Int Braz J Urol. 2021 Mar-Apr.

Abstract

Purpose: Sperm DNA fragmentation is a major cellular mechanism underlying varicocele-related male infertility. However, the type of DNA fragmentation - whether oxidative or of another nature - remains unknown. Thus, the aim of this study was to evaluate single- and double-stranded sperm DNA fragmentation, and oxidative-induced sperm DNA damage in men with varicocele.

Materials and methods: A cross-sectional study was performed, including 94 normozoospermic adults, of which 39 men without varicocele (controls) and 55 men with varicocele grades II or III, uni- or bilaterally. All men collected semen by masturbation. After semen analysis, the remaining volume was used for evaluation of three types of sperm DNA damage: (i) total DNA fragmentation, using an alkaline comet assay, (ii) double-stranded DNA fragmentation, using a neutral comet assay, and (iii) oxidative DNA damage, using an alkaline comet assay associated with the DNA glycosylase formamidopyrimidine enzyme. In each assay, percentage of sperm with any degree of DNA fragmentation, and with high DNA fragmentation were compared between the groups using an unpaired Student's t test or a Mann-Whitney test.

Results: The varicocele group presented a higher rate of sperm with fragmented DNA (both any and high DNA fragmentation), considering single-stranded DNA fragmentation, double-stranded DNA fragmentation, or a combination of both, as well as oxidative-induced DNA fragmentation.

Conclusions: Patients with varicocele have an increase in sperm DNA fragmentation levels, particularly in oxidative stress-induced sperm DNA damage.

Keywords: DNA Fragmentation; Infertility, Male; Oxidative Stress.

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Conflict of interest statement

None declared.

Figures

Figure 1
Figure 1. Study design, including all performed sperm DNA fragmentation tests, as well as the type of fragmentation detected in each of these tests. Right panel: representative images of cell classification, both for alkaline assays and neutral comet assay. Class I - High DNA integrity (no DNA migration); Class II - Low DNA fragmentation (an intense nucleus with little DNA migration); Class III - Increased DNA fragmentation (an observed nucleus, but with intense DNA migration); Class IV - High DNA fragmentation (an intense DNA migration and no observed nucleus). FPG - DNA glycosylase formamidopyrimidine enzyme.
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