One important reason for male infertility is oxidative stress and its destructive effects on sperm structures and functions. The particular composition of the sperm membrane, rich in polyunsaturated fatty acids, and the easy access of sperm DNA to oxidative damage due to sperm cell specific cytologic and metabolic features (no cytoplasm left and cells unable to mount stress responses) make it the cell type in metazoans most susceptible to oxidative damage. In particular, oxidative damage to the spermatozoa genome is an important issue and a cause of male infertility, usually associated with single- or double-strand paternal DNA breaks. Various methods of detecting sperm DNA fragmentation have become important diagnostic tools in the prognosis of male infertility and such assays are available in research laboratories and andrology clinics. However, to date, there is not a clear consensus in the community as to their respective prognostic value. Nevertheless, it is important to understand that the effects of oxidative stress on the sperm genome go well beyond DNA fragmentation alone. Oxidation of paternal DNA bases, particularly guanine and adenosine residues, the most sensitive residues to oxidative alteration, is the starting point for DNA damage in spermatozoa but is also a danger for the integrity of the embryo genetic material independently of sperm DNA fragmentation. Due to the lack of a spermatozoa DNA repair system and, if the egg is unable to correct the sperm oxidized bases, the risk of de novo mutation transmission to the embryo exists. These will be carried on to every cell of the future individual and its progeny. Thus, in addition to affecting the viability of the pregnancy itself, oxidation of the DNA bases in sperm could be associated with the development of conditions in young and future adults. Despite these important issues, sperm DNA base oxidation has not attracted much interest among clinicians due to the lack of simple, reliable, rapid and consensual methods of assessing this type of damage to the paternal genome. In addition to these technical issues, another reason explaining why the measurement of sperm DNA oxidation is not included in male fertility is likely to be due to the lack of strong evidence for its role in pregnancy outcome. It is, however, becoming clear that the assessment of DNA base oxidation could improve the efficiency of assisted reproductive technologies and provide important information on embryonic developmental failures and pathologies encountered in the offspring. The objective of this work is to review relevant research that has been carried out in the field of sperm DNA base oxidation and its associated genetic and epigenetic consequences.

Objective: This study was performed to evaluate the correlation of hyaluronic acid binding assay (HBA) with conventional semen parameters, lipid peroxidation (LPO), intracellular reactive oxygen species (ROS), DNA fragmentation (DF), DNA maturity and mitochondrial membrane potential (MMP) level in human spermatozoa. Methods: The semen samples were obtained from 98 patients. The seminal plasma was separated for the study of LPO, and the pellet was employed for evaluation of intracellular ROS, DF, nuclear maturity (sperm chromatin structure assay) and MMP through flowcytometry. Results: The correlation and strength of HBA with respect to the studied parameters were estimated by the Pearson coefficient and multiple liner regression tests. While HBA indicated a positive correlation with progressive motility (β-coefficients = 0.449, p < 0.05) and normal morphology (β-coefficients = 2.722, p < 0.01), it had only negative relationship with DNA integrity (high DNA stain ability; β-coefficients = -0.517, p < 0.05). HBA also did not show any important correlation with other conventional and intracellular sperm parameters. Conclusions: The HBA is sensitive to morphological integrity, high progressive motility and nuclear maturation. Nonetheless, HBA is not a reliable test for prediction of sperm intracellular ROS, DF and MMP risks and healthy spermatozoa selection.

This study evaluates the relationship between sperm intracellular reactive oxygen species (ROS; H2 O2 , O2 ), DNA fragmentation (DF), low mitochondria membrane potential (MMP) of sperm and normal pronuclear formation among intracytoplasmic sperm injection (ICSI) patients. Semen samples were obtained from 62 infertile male who were candidates for ICSI treatment. After sperm processing, metaphase II (MII) oocytes were injected, and the mean percentages of intracellular ROS, MMP and DF were evaluated using flow cytometry. The mean percentages of pronuclear formation and zygote score (Z) were also recorded, and Pearson, Spearman's rank correlation coefficient and Kruskal-Wallis tests were applied to analyse the data. The amounts of sperm intracellular H2 O2 and O2-˙ had significant positive correlation with low MMP (P < 0.01). The intracellular ROS had a negative correlation with pronuclear formation (P < 0.05), and its effect was higher than 66.66%. In addition, the mean percentages of neither H2 O2 nor O2-˙ affected the quality of pronuclear embryos (Z-score). This study shows that although high levels of both sperm intracellular H2 O2 and O2-˙ in ICSI patients have deleterious effect on sperm MMP, only H2 O2 may interfere in pronuclear formation.