Search Results (5)

Reproductive success is dependent on gamete integrity, and oxidative stress alters male nuclei, meaning that no DNA repair is possible due to chromatin compaction. The composition of sperm makes it highly sensitive to reactive oxygen species (ROS) but, at the same time, ROS are needed for sperm physiology. Over the past 30 years, much attention has been paid to the consequences of oxidative stress on sperm properties and the protective effects of antioxidant formulations to help fertility. Spermatozoa also carry epigenetic marks, critical for embryo development and the health of offspring. As DNA oxidative damage may disturb the sperm epigenome, we used an established mouse model of post-testicular sperm DNA oxidation to investigate sperm DNA methylation and hydroxymethylation. We also analyzed the potential corrective effect of oral antioxidant supplementation, proven to reduce sperm DNA oxidative damage, on sperm DNA methyl/hydroxymethyl marks. We show that sperm DNA oxidation is associated with a significant increase in overall hydroxymethylation. Oral antioxidant supplementation led to unexpected mild epigenetic changes. Antioxidant supplementation should not be proposed without proper clinical evaluation as it may alter sperm epigenetic marks, leading to a risk of paternally inherited epigenetic alterations. Full article

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. Full article

Advanced age has been reported to negatively affect sperm parameters and spermatozoa DNA integrity. A decline in sperm criteria was also associated with altered epigenetic marks such as DNA methylation with a potential downstream impact on in vitro fertilization success and clinical outcomes. The aim of the present retrospective study was to clarify the association between advanced paternal age (APA) and sperm parameters, DNA integrity and DNA methylation profile. A total of 671 patients consulting for infertility underwent sperm analysis, sperm DNA integrity assessment and methylation level measurement. The principal finding was that individuals over 40 years of age exhibit a significant increase in DNA fragmentation levels compared to the younger group (15% versus 9%, respectively, p = 0.04). However, there was no significant difference in DNA decondensation and sperm parameters in association with APA. In addition, a drop in the global methylation level was also found in men over 40 years (6% in the young group versus 2% in the old group, p = 0.03). As a conclusion, men over 40 years are at higher risk of elevated sperm DNA fragmentation and lower methylation level. Based on these observations, it is recommended that the assessment of sperm DNA fragmentation should be taken into consideration particularly after the age of 40. Our findings support the idea that paternal age is a crucial factor that should not be neglected during fertility evaluation and treatment since it is associated with epigenetics changes in sperm. Although the underlying mechanism remains to be clarified, we believe that environmental and professional exposure factors are likely involved in the process. Full article

In this study, we explore the effects of Poria cocos mushroom polysaccharides (PCPs) on the quality and DNA methylation of the cryopreserved spermatozoa of Shanghai white pigs. A total of 24 ejaculates (three ejaculate samples per boar) from eight Shanghai white pigs were manually collected. The pooled semen was diluted with a based extender supplemented with different concentrations of PCPs (0, 300, 600, 900, 1200, and 1500 μg/mL). Once thawed, the quality of the spermatozoa and their antioxidant function were assessed. In the meantime, the effect of spermatozoa DNA methylation was also analyzed. The results show that compared with the control group, 600 μg/mL of PCPs significantly improves the spermatozoa viability (p < 0.05). The motility and plasma membrane integrity of the frozen–thawed spermatozoa are significantly higher after treatment with 600, 900, and 1200 μg/mL of PCPs compared with the control group (p < 0.05). In comparison with the control group, the percentages of acrosome integrity and mitochondrial activity are significantly enhanced after the application of 600 and 900 μg/mL PCPs (p < 0.05). The reactive oxygen species (ROS), the malondialdehyde (MDA) levels, and the glutathione peroxidase (GSH-Px) activity, in comparison with the control group, are significantly decreased in all groups with PCPs (all p < 0.05). The enzymatic activity of superoxide dismutase (SOD) in spermatozoa is significantly higher in the treatment with 600 μg/mL of PCPs than in the other groups (p < 0.05). As compared with the control group, a significant increase in the catalase (CAT) level is found in the groups with PCPs at 300, 600, 900, and 1200 μg/mL (all p < 0.05). In comparison with the control group, the 5-methylcytosine (5-mC) levels are significantly decreased in all groups with PCPs (all p < 0.05). As a result of these findings, a certain amount of PCPs (600–900 μg/mL) added to the cryodiluent can significantly improve the quality of Shanghai white pig spermatozoa and can also reduce the methylation of spermatozoa DNA caused by cryopreservation. This treatment strategy may establish a foundation for the cryopreservation of semen from pigs. Full article

Epigenetic modifications play a special role in the male infertility aetiology. Published data indicate the link between sperm quality and sperm chromatin protamination. This study aimed to determine the relationship between methylation (5mC) and hydroxymethylation (5hmC) in sperm DNA, with respect to sperm chromatin protamination in three subpopulations of fertile normozoospermic controls and infertile patients with oligo-/oligoasthenozoospermia. For the first time, a sequential staining protocol was applied, which allowed researchers to analyse 5mC/5hmC levels by immunofluorescence staining, with a previously determined chromatin protamination status (aniline blue staining), using the same spermatozoa. TUNEL assay determined the sperm DNA fragmentation level. The 5mC/5hmC levels were diversified with respect to chromatin protamination status in both studied groups of males, with the highest values observed in protaminated spermatozoa. The linkage between chromatin protamination and 5mC/5hmC levels in control males disappeared in patients with deteriorated semen parameters. A relationship between 5mC/5hmC and sperm motility/morphology was identified in the patient group. Measuring the 5mC/5hmC status of sperm DNA according to sperm chromatin integrity provides evidence of correct spermatogenesis, and its disruption may represent a prognostic marker for reproductive failure. Full article