The Impact of Heavy Smoking on Male Infertility and Its Correlation with the Expression Levels of the PTPRN2 and PGAM5 Genes.

Smoking has been linked to male infertility by affecting the sperm epigenome and genome. In this study, we aimed to determine possible changes in the transcript levels of PGAM5 (the phosphoglycerate mutase family member 5), PTPRN2 (protein tyrosine phosphatase, N2-type receptor), and TYRO3 (tyrosine protein kinase receptor) in heavy smokers compared to non-smokers, and to investigate their association with the fundamental sperm parameters. In total, 118 sperm samples (63 heavy-smokers (G1) and 55 non-smokers (G2)) were included in this study. A semen analysis was performed according to the WHO guidelines. After a total RNA extraction, RT-PCR was used to quantify the transcript levels of the studied genes. In G1, a significant decrease in the standard semen parameters in comparison to the non-smokers was shown (p < 0.05). Moreover, PGAM5 and PTPRN2 were differentially expressed (p ≤ 0.03 and p ≤ 0.01, respectively) and downregulated in the spermatozoa of G1 compared to G2. In contrast, no difference was observed for TYRO3 (p ≤ 0.3). In G1, the mRNA expression level of the studied genes was correlated negatively with motility, sperm count, normal form, vitality, and sperm membrane integrity (p < 0.05). Therefore, smoking may affect gene expression and male fertility by altering the DNA methylation patterns in the genes associated with fertility and sperm quality, including PGAM5, PTPRN2, and TYRO3.

Alterations in sperm DNA methylation patterns of oligospermic males.

Aberrant in sperm DNA methylation patterns and histone modification play a role in male fecundity decline. This study was prepared to determine whether sperm DNA methylation at CpG dinucleotides is different in oligospermic males compared to proven fertile males and then to evaluate the correlation between the changes in sperm DNA methylation patterns and semen parameters of oligospermic males. A total of 165 males (64 proven fertile males "controls" and 101 oligospermic males "cases") were included in the study. Three CpG sites have the highest difference in methylation levels (cg23081194, cg25750688, and cg04807108) were underwent to further analysis using deep bisulfite sequencing in 125 samples (44 controls and 81 cases). The results of a validation study showed that variation in methylation levels was found in more than one CpG site: there was a significant alteration in methylation levels at all CpGs tested within the UBE2G2 and cg25750688 site related amplicon (p≤0.0001), and at eight CpGs (CpG1, CpG3, CpG6, CpG8, CpG11, CpG13, CpG14, and CpG15) within the cg04807108 site related amplicon (p≤0.0001) in cases compared to controls. Besides, a significant correlation was found between the changes in the methylation levels at different CpGs and semen parameters of case group. In conclusion, this study showed that these sites have a significant alteration in sperm DNA methylation levels in oligospermic males compared to proven fertile males, and these changes correlated with semen parameters.