Can Advanced paternal age affect global DNA methylation of human spermatozoa and ICSI outcome?

Abstract

This study was performed to (I) evaluate the potential effect of advanced paternal age on global DNA methylation on spermatozoa, and (II) to investigate the association between the intracytoplasmic sperm injection (ICSI) outcomes, semen parameters, and advanced paternal age. This study comprised 230 semen samples collected from males with a mean age of 38.2 ± 8.5 years. The medical records were used to gather the medical information related to the female partner. The participants were divided into three groups depending on males' age: (age < 30; n = 50 "21.8%", age = 30-40; n = 90 "39.1%", and age > 40; n = 90 "39.1%"). The DNA was extracted from purified spermatozoa; then the sperm global DNA methylation, sperm DNA fragmentation, and chromatin decondensation were evaluated by an ELISA, TUNEL, and Chromomycin A3 staining, respectively. A significant variation has been found in the age of males included in this study (P < 0.001). A significant reduction has been observed in sperm count, total motility, and non-progressive motility in the older group compared to the younger group (P < 0.001). Additionally, a significant elevation in chromatin decondensation level, DNA fragmentation level, and global DNA methylation of spermatozoa in the older age group (P < 0.001) has been found. A significant positive correlation has been detected between the percentage of non-motile sperm, sperm chromatin decondensation, DNA fragmentation, global DNA methylation status, and paternal age (P < 0.001). This study pointed out that advanced paternal age increases the DNA fragmentation, chromatin decondensation, and global DNA methylation level in human spermatozoa which negatively affects the ICSI outcomes in couples undergoing ICSI cycles.