Sperm DNA fragmentation (SDF) has been generally acknowledged as a valuable tool for male fertility evaluation. While its detrimental implications on sperm function were extensively investigated, little is known about the actual indications for performing SDF analysis. This review delivers practice based recommendations on commonly encountered scenarios in the clinic. An illustrative description of the different SDF measurement techniques is presented. SDF testing is recommended in patients with clinical varicocele and borderline to normal semen parameters as it can better select varicocelectomy candidates. High SDF is also linked with recurrent spontaneous abortion (RSA) and can influence outcomes of different assisted reproductive techniques. Several studies have shown some benefit in using testicular sperm rather than ejaculated sperm in men with high SDF, oligozoospermia or recurrent in vitro fertilization (IVF) failure. Infertile men with evidence of exposure to pollutants can benefit from sperm DNA testing as it can help reinforce the importance of lifestyle modification (e.g., cessation of cigarette smoking, antioxidant therapy), predict fertility and monitor the patient’s response to intervention.

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In conclusion, sperm DNA damage is associated with a significantly increased risk of pregnancy loss after IVF and ICSI. These data provide a clinical indication for the evaluation of sperm DNA damage prior to IVF or ICSI and a rationale for further investigating the association between sperm DNA damage and pregnancy loss.

Although high concentrations of reactive oxygen species (ROS) cause sperm pathology (ATP depletion leading to insufficient axonemal phosphorylation, lipid peroxidation and loss of motility and viability), recent evidence demonstrates that low and controlled concentrations of these ROS play an important role in sperm physiology. Reactive oxygen species, such as the superoxide anion, hydrogen peroxide and nitric oxide, induce sperm hyperactivation, capacitation or the acrosome reaction in vitro. The ROS involved in these processes may vary depending on experimental conditions, but all the evidence converges to describe these events as 'oxidative' or 'redox regulated'. Human sperm capacitation and acrosome reaction are associated with extracellular production of a superoxide anion that is thought to originate from a membrane 'oxidase'. The enzymes responsible for tyrosine phosphorylation-dephosphorylation of sperm proteins are possible targets for ROS since mild oxidative conditions cause increases in protein tyrosine phosphorylation and acrosome reaction. The lipid peroxidation resulting from low concentrations of ROS promotes binding to the zona pellucida and may trigger the release of unesterified fatty acids from the sperm plasma membrane. The fine balance between ROS production and scavenging, as well as the right timing and site for ROS production are of paramount importance for acquisition of fertilizing ability.

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Despite advances in the field of male reproductive health, idiopathic male infertility, in which a man has altered semen characteristics without an identifiable cause and there is no female factor infertility, remains a challenging condition to diagnose and manage. Increasing evidence suggests that oxidative stress (OS) plays an independent role in the etiology of male infertility, with 30% to 80% of infertile men having elevated seminal reactive oxygen species levels. OS can negatively affect fertility via a number of pathways, including interference with capacitation and possible damage to sperm membrane and DNA, which may impair the sperm's potential to fertilize an egg and develop into a healthy embryo. Adequate evaluation of male reproductive potential should therefore include an assessment of sperm OS. We propose the term Male Oxidative Stress Infertility, or MOSI, as a novel descriptor for infertile men with abnormal semen characteristics and OS, including many patients who were previously classified as having idiopathic male infertility. Oxidation-reduction potential (ORP) can be a useful clinical biomarker for the classification of MOSI, as it takes into account the levels of both oxidants and reductants (antioxidants). Current treatment protocols for OS, including the use of antioxidants, are not evidence-based and have the potential for complications and increased healthcare-related expenditures. Utilizing an easy, reproducible, and cost-effective test to measure ORP may provide a more targeted, reliable approach for administering antioxidant therapy while minimizing the risk of antioxidant overdose. With the increasing awareness and understanding of MOSI as a distinct male infertility diagnosis, future research endeavors can facilitate the development of evidence-based treatments that target its underlying cause.

The advent of assisted reproductive technologies, particularly intracytoplasmic sperm injection (ICSI), has revolutionized the treatment of male-factor infertility. However, there are many unanswered questions regarding the safety of these techniques. These safety concerns are relevant because 1) these technologies often bypass the barriers to natural selection; 2) infertile men, particularly those with severe male-factor infertility, possess substantially more sperm DNA damage than do fertile men; and 3) experimentally, sperm DNA damage has been shown to adversely affect the developing embryo. This review discusses the etiology of sperm DNA damage, describes the individual tests of sperm DNA damage, and explores the relationship between sperm DNA damage and pregnancy outcomes. Based on a systematic review of the literature, sperm DNA damage is associated with lower natural, intrauterine insemination (IUI), and in vitro fertilization (IVF) pregnancy rates, but not with ICSI pregnancy rates. The literature also suggests that that sperm DNA damage is associated with an increased risk of pregnancy loss in those couples undergoing IVF or ICSI. Nonetheless, the true clinical utility of sperm DNA damage tests remains to be established, because the available studies are small and few in number and the study characteristics are heterogeneous. Although current data suggest that impaired sperm DNA integrity may have the greatest effect on IUI pregnancy rates and pregnancy loss by IVF and ICSI, further prospective studies are needed before testing should become a routine part of patient management.

Reactive oxygen species (ROS) can be detected in the semen of 40% of infertile men, whereas none is detected in semen from normal men. The ROS detected in semen are a reflection of the imbalance between ROS production and degradation. The aim of the present study was to determine whether a lowered scavenging capacity or an increased production of ROS was responsible for the ROS detected in semen samples from infertile men. Two activities were investigated: (1) catalase-like activity, which is responsible for the degradation of H2O2 and (2) superoxide dismutase-like (SOD-like) activity which is responsible for the degradation of .O2-. Catalase-like and SOD-like activities were found in whole seminal plasma, in dialyzed seminal plasma (> 12 kD), in an ultrafiltrate of seminal plasma (< 5 kD) and in spermatozoa. There was no significant difference in the SOD-like activities measured in spermatozoa, or in seminal plasma (whole or fractionated) from samples that did or did not produce ROS. SOD-like activity originated mostly from the high molecular weight components of seminal plasma. However, the catalase-like activity of whole seminal plasma and of spermatozoa was significantly greater (P = 0.01) in those samples that produced ROS as compared to those that did not. The catalase-like activity in dialyzed seminal plasma, and an ultrafiltrate of seminal plasma from semen samples that did or did not produce ROS were not statistically different. The catalase-like activity of the seminal plasma originated equally from high and low molecular weight components.(ABSTRACT TRUNCATED AT 250 WORDS)