DNA hypomethylation predisposes sperm to DNA damage in individuals with varicocele

Abstract

This study aimed to assess and compare global DNA methylation (GDM) between fertile men and infertile men with varicocele. In addition, we evaluated the correlations between DNA methylation with reactive oxygen species (ROS), protamine deficiency, and DNA integrity. Semen samples were collected from 44 men with grades II and III varicocele, and 15 fertile men for assessment of semen parameters, DNA methylation, DNA fragmentation, oxidative stress, and protamine deficiency. Samples were evaluated by the World Health Organization (WHO) criteria, immunostaining, the TUNEL assay, 2′, 7′-dichlorodihydrofluorescein diacetate (DCFH-DA) staining, and chromomycin A3 (CMA3) staining. Semen parameters were significantly lower in individuals with varicocele compared to fertile men. The percentage of GDM and intensity of DCFH were reduced and the percentages of DCFH, TUNEL, and CMA3 positive sperm significantly increased in individuals with varicocele compared to fertile men. Correlation analysis revealed a negative significant relation between DNA methylation and DNA fragmentation, but not with the degree of protamine deficiency and ROS production. The results have shown that individuals with varicocele show increased DNA susceptibility to damage when DNA is hypomethylated. This phenomenon appears to be independent of ROS production.

• DNA fragmentation
• global DNA methylation
• oxidative stress
• protamine deficiency
• varicocele

Acknowledgments

This study was supported by Royan Institute. We would like to express our appreciation to the staff of Isfahan Fertility and Infertility Center for their full support.

Declaration of interest

The authors have no financial or commercial conflicts with this project. Royan Institute is a nongovernment organization (NGO) that belongs to the Iranian Academic Center for Education, Culture & Research (ACECR). None of the authors are employed in any respect by the Government of Iran.

Author contributions

Collection and/or assembly of data, and manuscript writing; MB; Collection and/or assembly of data, interpretation, manuscript writing, and final approval of the manuscript: MT; Urologist: HA; Flow cytometry analyses: AK; Student supervisor: AHS; Experimental design, student supervisor, interpretation, manuscript writing, and final approval of the manuscript: MHN-E.