Analysis of the relationship between reactive oxygen species production and leucocyte infiltration in fractions of human semen separated on Percoll gradients

A comparison between the Felix™ electrophoretic system of sperm isolation and conventional density gradient centrifugation: a multicentre analysis

PURPOSE

Developing optimized techniques for the isolation of human spermatozoa possessing low levels of DNA damage is an important objective for the ART industry. The purpose of this study was to compare a novel electrophoretic system (Felix™) of sperm isolation with a conventional method involving density gradient centrifugation (DGC).

METHODS

Five international ART Centres in Australia, India, Sweden, the USA, and China have collaborated in order to compare the quality of the sperm populations isolated by Felix™ and DGC in terms of processing time, sperm concentration, motility, vitality, and DNA integrity as assessed by 3 methods: SCSA, Halo, and TUNEL.

RESULTS

Across all centers, 112 comparisons were performed. Although significant differences were noted between centers in terms of the quality of the semen samples subjected for analysis, overall, both methods were equally capable of isolating populations of spermatozoa exhibiting high levels of vitality and progressive motility. The absolute numbers of spermatozoa recovered were significantly (p < 0.001) lower with the Felix™ device although sperm quality was higher with 4/5 centers reporting a significant improvement in DNA integrity relative to DGC (p < 0.01-p < 0.001). In practical terms, the Felix™ device featured a standardized 6 min preparation time whereas clinical DGC protocols varied from center to center but generally took around 40 min to complete.

CONCLUSIONS

The Felix™ device is a positive technical development capable of isolating suspensions of highly motile spermatozoa exhibiting low levels of DNA damage in a fraction of the time taken by conventional procedures such as DGC.

Antioxidant Intervention against Male Infertility: Time to Design Novel Strategies

Infertility is a highly prevalent condition, affecting 9-20% of couples worldwide. Among the identifiable causes, the male factor stands out in about half of infertile couples, representing a growing problem. Accordingly, there has been a decline in both global fertility rates and sperm counts in recent years. Remarkably, nearly 80% of cases of male infertility (MI) have no clinically identifiable aetiology. Among the mechanisms likely plausible to account for idiopathic cases, oxidative stress (OS) has currently been increasingly recognized as a key factor in MI, through phenomena such as mitochondrial dysfunction, lipid peroxidation, DNA damage and fragmentation and finally, sperm apoptosis. In addition, elevated reactive oxygen species (ROS) levels in semen are associated with worse reproductive outcomes. However, despite an increasing understanding on the role of OS in the pathophysiology of MI, therapeutic interventions based on antioxidants have not yet provided a consistent benefit for MI, and there is currently no clear consensus on the optimal antioxidant constituents or regimen. Therefore, there is currently no applicable antioxidant treatment against this problem. This review presents an approach aimed at designing an antioxidant strategy based on the particular biological properties of sperm and their relationships with OS.

Mitochondria-Targeted Compounds to Assess and Improve Human Sperm Function

Significance: Currently 10%-15% of couples in reproductive age face infertility issues. More importantly, male factor contributes to 50% of these cases (either alone or in combination with female causes). Among various reasons, impaired sperm function is the main cause for male infertility. Furthermore, mitochondrial dysfunction and oxidative stress due to increased reactive oxygen species (ROS) production, particularly of mitochondrial origin, are believed to be the main contributors. Recent Advances: Mitochondrial dysfunction, particularly due to increased ROS production, has often been linked to impaired sperm function/quality. For decades, different methods and approaches have been developed to assess mitochondrial features that might correlate with sperm functionality. This connection is now completely accepted, with mitochondrial functionality assessment used more commonly as a readout of sperm functionality. More recently, mitochondria-targeted compounds are on the frontline for both assessment and therapeutic approaches. Critical Issues: In this review, we summarize the current methods for assessing key mitochondrial parameters known to reflect sperm quality as well as therapeutic strategies using mitochondria-targeted antioxidants aiming to improve sperm function in various situations, particularly after sperm cryopreservation. Future Directions: Although more systematic research is needed, mitochondria-targeted compounds definitely represent a promising tool to assess as well as to protect and improve sperm function. Antioxid. Redox Signal. 37, 451-480.

Mesenchymal Stem-Cell Derived Exosome Therapy as a Potential Future Approach for Treatment of Male Infertility Caused by Chlamydia Infection

Some microbial sexually transmitted infections (STIs) have adverse effects on the reproductive tract, sperm function, and male fertility. Given that STIs are often asymptomatic and cause major complications such as urogenital inflammation, fibrosis, and scarring, optimal treatments should be performed to prevent the noxious effect of STIs on male fertility. Among STIs, Chlamydia trachomatis is the most common asymptomatic preventable bacterial STI. C. trachomatis can affect both sperm and the male reproductive tract. Recently, mesenchymal stem cells (MSCs) derived exosomes have been considered as a new therapeutic medicine due to their immunomodulatory, anti-inflammatory, anti-oxidant, and regenerative effects without consequences through the stem cell transplantation based therapies. Inflammation of the genital tract and sperm dysfunction are the consequences of the microbial infections, especially Chlamydia trachomatis. Exosome therapy as a noninvasive approach has shown promising results on the ability to regenerate the damaged sperm and treating asthenozoospermia. Recent experimental methods may be helpful in the novel treatments of male infertility. Thus, it is demonstrated that exosomes play an important role in preventing the consequences of infection, and thereby preventing inflammation, reducing cell damage, inhibiting fibrogenesis, and reducing scar formation. This review aimed to overview the studies about the potential therapeutic roles of MSCs-derived exosomes on sperm abnormalities and male infertility caused by STIs.

The Sixth Edition of the WHO Manual for Human Semen Analysis: A Critical Review and SWOT Analysis

Semen analysis is the cornerstone of male fertility evaluation with WHO guidelines providing the basis for procedural standardization and reference values worldwide. The first WHO manual was published in 1980, and five editions have been subsequently released over the last four decades. The 6th Edition was published in July 2021. In this review, we identify the key changes of this 6th Edition. Additionally, we evaluate the utility of this 6th Edition in clinical practice using SWOT (strengths, weaknesses, opportunities, and threats) analysis. This new Edition has made the analysis of basic semen parameters more robust, taking into account the criticisms and grey areas of the previous editions. The tests assessing sperm DNA fragmentation and seminal oxidative stress are well-described. The main novelty is that this latest edition abandons the notion of reference thresholds, suggesting instead to replace them with “decision limits”. While this seems attractive, no decision limits are proposed for either basic semen parameters, or for extended or advanced parameters. This critical review of the 6th Edition of the WHO laboratory manual combined with a SWOT analysis summarizes the changes and novelties present in this new Edition and provides an in-depth analysis that could help its global use in the coming years.

Sperm Metabolomics through Nuclear Magnetic Resonance Spectroscopy

Simple Summary

Proton nuclear magnetic resonance spectroscopy (¹ H-NMR) is of special interest for the analysis of metabolites present in seminal plasma and spermatozoa. This metabolomic approach has been used to identify the presence of new biomarkers or their proportions in a non-invasive manner and is, therefore, an interesting tool for male fertility diagnosis. In this paper, we review current knowledge of the use of ¹ H-NMR to examine sperm metabolomics in different species with special attention paid to humans and farm animals. We also describe the use of ¹ H-NMR to establish a possible relationship between the mammalian diet and the presence of certain hydrophilic and lipophilic metabolites in spermatozoa.

Abstract

This report reviews current knowledge of sperm metabolomics analysis using proton nuclear magnetic resonance spectroscopy (¹ H-NMR) with particular emphasis on human and farm animals. First, we present the benefits of NMR over other techniques to identify sperm metabolites and then describe the specific methodology required for NMR sperm analysis, stressing the importance of analyzing metabolites extracted from both the hydrophilic and lipophilic phases. This is followed by a description of advances produced to date in the use of NMR to diagnose infertility in humans and to identify metabolic differences among the sperm of mammalian herbivore, carnivore, and omnivore species. This last application of NMR mainly seeks to explore the possible use of lipids to fuel sperm physiology, contrary to previous theories that glycolysis and oxidative phosphorylation (OXPHOS) are the only sources of sperm energy. This review describes the use of NMR to identify sperm and seminal plasma metabolites as possible indicators of semen quality, and to examine the metabolites needed to maintain sperm motility, induce their capacitation, and consequently, to predict animal fertility.

Mitochondrial Reactive Oxygen Species (ROS) Production Alters Sperm Quality

Besides ATP production, mitochondria are key organelles in several cellular functions, such as steroid hormone biosynthesis, calcium homoeostasis, intrinsic apoptotic pathway, and the generation of reactive oxygen species (ROS). Despite the loss of the majority of the cytoplasm occurring during spermiogenesis, mammalian sperm preserves a number of mitochondria that rearrange in a tubular structure at the level of the sperm flagellum midpiece. Although sperm mitochondria are destroyed inside the zygote, the integrity and the functionality of these organelles seem to be critical for fertilization and embryo development. The aim of this review was to discuss the impact of mitochondria-produced ROS at multiple levels in sperm: the genome, proteome, lipidome, epigenome. How diet, aging and environmental pollution may affect sperm quality and offspring health—by exacerbating oxidative stress—will be also described.

The role of infections and leukocytes in male infertility

Declining birth rates are one of the problems facing society today. Male counterparts are responsible for about half of the infertility cases, and genitourinary tract infections may play a contributing role in approximately 15% of male infertility cases. Leukocytospermia is an established indicator of infection in the male urogenital tract, although other microorganisms such as bacteria and virus may also be contributors to the etiology of male infertility. The pathophysiology of these infectious agents may be initiated by a local inflammatory reaction resulting in an increase in reactive oxygen species (ROS). This results in testicular injury, thereby affecting sperm morphology, sperm motility, sperm viability and elevation of the seminal leukocyte as a result of the genital tract infection. The infectious and inflammatory changes can result in male infertility. It is proposed that high concentrations of seminal leukocyte and infectious agents may affect sperm function resulting in clumping of motile spermatozoa, decreasing acrosomal functionality and also causing alterations in sperm morphology. However, the literature has poorly clarified the role of infection in male infertility, provoking further debate and research on this topic.

Probing human sperm metabolism using 13C-magnetic resonance spectroscopy

STUDY QUESTION

Can 13C-Magnetic Resonance Spectroscopy (MRS) of selected metabolites provide useful information about human sperm metabolism and how glycolysis or oxidative phosphorylation are used by different sperm populations?

SUMMARY ANSWER

Sperm populations, prepared by density gradient centrifugation (DGC) and incubated with either 13Cu-glucose, 13Cu-fructose or 13C1-pyruvate, showed consistent evidence of metabolism generating principally lactate and more intermittently bicarbonate, and significantly more lactate was produced from 13Cu-glucose by vital or motile sperm recovered from the 40/80% interface compared to those from the pellet, which could not be accounted for by differences in the non-sperm cells present.

WHAT IS KNOWN ALREADY

Previous studies have focused on CO2 or other specific metabolite production by human sperm and there remains considerable debate about whether glycolysis and/or oxidative phosphorylation is the more important pathway for ATP production in sperm.

STUDY DESIGN, SIZE, DURATION

Sperm populations were prepared by DGC and subjected to 13C-MRS to answer the following questions. (i) Is it possible to detect human sperm metabolism of 13C substrates implicated in energy generation? (ii) What are the kinetics of such reactions? (iii) Do different sperm populations (e.g. '80%' pellet sperm and '40%' interface sperm) utilise substrates in the same way? Semen samples from 97 men were used in these experiments; 52 were used in parallel for aims (i) and (ii) and 45 were used for aim (iii).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sperm populations were prepared from ejaculates of healthy men using a Percoll/Phosphate Buffered Saline (PBS) DGC and then incubated with a range of 13C-labelled substrates (13Cu-glucose, 13Cu-fructose, 13C1-pyruvate, 13C1-butyrate, 13C3-lactate, 13C2,4-D-3-hydroxybutyrate, 13C5-l-glutamate, 13C1,2-glycine or 13Cu-galactose) along with penicillin/streptomycin antibiotic at 37°C for 4 h, 24 h or over 48 h for an estimated rate constant. Sperm concentration, vitality and motility were measured and, for a subset of experiments, non-sperm cell concentration was determined. A 9.4 T magnetic resonance spectrometer was used to acquire 1D 13C, inverse gated 1H decoupled, MRS spectra. Spectrum processing was carried out using spectrometer software and Matlab scripts to determine peak integrals for each spectrum.

MAIN RESULTS AND THE ROLE OF CHANCE

13Cu-glucose, 13Cu-fructose and 13C1-pyruvate were consistently converted into lactate and, to a lesser extent, bicarbonate. There was a significant correlation between sperm concentration and lactate peak size for 13Cu-glucose and 13Cu-fructose, which was not observed for 13C1-pyruvate. The lactate peak did not correlate with the non-sperm cell concentration up to 6.9 × 106/ml. The concentration of 13Cu-glucose, 13Cu-fructose or 13C1-pyruvate (1.8, 3.6, 7.2 or 14.4 mM) had no influence on the size of the observed lactate peak over a 4 h incubation. The rate of conversion of 13C1-pyruvate to lactate was approximately three times faster than for 13Cu-glucose or 13Cu-fructose which were not significantly different from each other. After incubating for 4 h, the utilisation of 13Cu-glucose, 13Cu-fructose or 13C1-pyruvate by sperm from the '40%' interface of the DGC was no different from those from the pellet when normalised to total sperm concentration. However, after normalising by either the vital or motile sperm concentration, there was a significant increase in conversion of 13Cu-glucose to lactate by '40%' interface sperm compared to pellet sperm (Vital = 3.3 ± 0.30 × 106 vs 2.0 ± 0.21 × 106; P = 0.0049; Motile = 7.0 ± 0.75 × 106 vs 4.8 ± 0.13 × 106; P = 0.0032. Mann-Whitney test P < 0.0055 taken as statistically significant). No significant differences were observed for 13Cu-fructose or 13C1-pyruvate.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

Only 13C labelled metabolites that accumulate to a sufficiently high concentration can be observed by 13C MRS. For this reason, intermediary molecules in the metabolic chain are difficult to observe without trapping the molecule at a particular step using inhibitors. Non-sperm cell concentration was typical of the general population and no link was found between these cells and the magnitude of the 13C-lactate peak. However, it is possible that higher concentrations than the maximum observed (6.9 × 106/ml) may contribute to exogenous substrate metabolism in other experiments.

WIDER IMPLICATIONS OF THE FINDINGS

13C-MRS can provide information on the underlying metabolism of multiple pathways in live sperm. Dysfunction in sperm metabolism, as a result of either impaired enzymes of lack of metabolisable substrate, could be detected in sperm by a non-destructive assay, potentially offering new treatment options to improve overall sperm quality and outcomes for reproduction.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by the Medical Research Council Grant MR/M010473/1. The authors declare no conflicts of interest.

The Role of Genetics and Oxidative Stress in the Etiology of Male Infertility-A Unifying Hypothesis?

Despite the high prevalence of male infertility, very little is known about its etiology. In recent years however, advances in gene sequencing technology have enabled us to identify a large number of rare single point mutations responsible for impeding all aspects of male reproduction from its embryonic origins, through the endocrine regulation of spermatogenesis to germ cell differentiation and sperm function. Such monogenic mutations aside, the most common genetic causes of male infertility are aneuploidies such as Klinefelter syndrome and Y-chromosome mutations which together account for around 20-25% of all cases of non-obstructive azoospermia. Oxidative stress has also emerged as a major cause of male fertility with at least 40% of patients exhibiting some evidence of redox attack, resulting in high levels of lipid peroxidation and oxidative DNA damage in the form of 8-hydroxy-2'-deoxyguanosine (8OHdG). The latter is highly mutagenic and may contribute to de novo mutations in our species, 75% of which are known to occur in the male germ line. An examination of 8OHdG lesions in the human sperm genome has revealed ~9,000 genomic regions vulnerable to oxidative attack in spermatozoa. While these oxidized bases are generally spread widely across the genome, a particular region on chromosome 15 appears to be a hot spot for oxidative attack. This locus maps to a genetic location which has linkages to male infertility, cancer, imprinting disorders and a variety of behavioral conditions (autism, bipolar disease, spontaneous schizophrenia) which have been linked to the age of the father at the moment of conception. We present a hypothesis whereby a number of environmental, lifestyle and clinical factors conspire to induce oxidative DNA damage in the male germ line which then triggers the formation de novo mutations which can have a major impact on the health of the offspring including their subsequent fertility.

DNA fragmentation in concert with the simultaneous assessment of cell viability in a subfertile population: establishing thresholds of normality both before and after density gradient centrifugation

PURPOSE

TUNEL assay is the most common, direct test for sperm chromatin integrity assessment. But, lack of standardized protocols makes interlaboratory comparisons impossible. Consequently, clinical thresholds to predict the chance of a clinical pregnancy also vary with the technique adopted. This prospective study was undertaken to assess the incidence of sperm DNA fragmentation in a subfertile population and to establish threshold values of normality as compared to a fertile cohort, both before and after density gradient centrifugation in the total and vital fractions.

METHOD

Men presenting at a university hospital setup for infertility treatment. DNA damage via TUNEL assay was validated on fresh semen samples, as conventional semen parameters, to reduce variability of results.

RESULTS

Total DNA fragmentation in the neat semen was significantly higher in the subfertile group, but the vital fraction was not significantly different between the two cohorts. After gradient centrifugation, DNA fragmentation increased significantly in the total fraction of the subfertile group but decreased significantly in the vital fraction. In the fertile cohort, there was a non-significant increase in total fragmentation and in the vital fraction the trend was unclear.

CONCLUSIONS

Estimating total and vital sperm DNA fragmentation, after density gradient centrifugation, increased both the sensitivity and the specificity, thereby lowering the number of false negatives and false positives encountered. These findings provide opportunities to investigate the significance of the total and the vital fractions after different assisted reproductive technologies.

Relationship between leukocytospermia, reproductive potential after assisted reproductive technology, and sperm parameters: a systematic review and meta-analysis of case-control studies

BACKGROUND

The association of leukocytospermia with male fertility is still under debate.

OBJECTIVE

To evaluate the impact of leukocytospermia (≥1 × 10⁶  white blood cells/mL of semen, according to the World Health Organization) in men attending a fertility clinic for couple subfertility, on fertility outcomes after assisted reproductive technology (ART) and on semen quality.

MATERIALS AND METHODS

A systematic review with meta-analysis of case-control studies reporting mean ± standard deviation for values of different seminal parameters (sperm concentration, progressive motility, sperm morphology, sperm DNA fragmentation, semen volume, and Ph) and fertilization rate (FR), or the odds ratio (OR) for clinical pregnancy rate (PR) per cycle after ART in leukocytospermic and non-leukocytospermic patients was performed. A literature search was carried out in MEDLINE and SCOPUS for English-language studies published till June 2018.

RESULTS

Twenty-eight case-controlled retrospective studies met the inclusion criteria, comparing fertility outcomes after ART or semen parameters in men with or without leukocytospermia. FR and PR after ART were not significantly different in the two groups. Leukocytospermic samples showed a lower sperm concentration (pooled SMD = -0.14; 95% CI: -0.28, -0.01, I²  = 71%, p_{for heterogeneity}  < 0.00001) and a lower progressive motility (pooled SMD = -0.18; 95% CI: -0.29, -0.06; I²  = 59%, p_{for heterogeneity}  < 0.0001). However, the significant differences disappeared, along with the large inter-study heterogeneity, when analyses were restricted to studies clearly reporting the inclusion of men without clinical evidence of seminal tract infection.

DISCUSSION AND CONCLUSION

Leukocytospermia in men seeking consultation for couple subfertility is not associated with a reduced fertility after ART and with altered semen quality in populations asymptomatic for genital tract infection. Therefore, the current clinical criteria for definition of leukocytospermia should be re-assessed in subfertile couples attending a fertility clinic.

The association between iron, calcium, and oxidative stress in seminal plasma and sperm quality

The present study aimed to determine the level of iron and calcium in the seminal plasma of men with different fertility potentials and to examine its relationship with oxidative stress. Seventy-nine sub-fertile patients with asthenoteratozoospermia (AT), n 27; teratoleucozoospermia (TL), n 20; teratozoospermia (Terato), n 32; and 29 healthy donors were included. The ability of spermatozoa to produce reactive oxygen species (ROS) was evaluated by using nitroblue tetrazolium (NBT) staining. The lipid peroxidation end product, malondialdehyde (MDA), and the trace element levels (iron and calcium) were measured spectrophotometrically. Iron and calcium concentrations in seminal plasma of the patient groups were significantly more elevated than the normal group. Nevertheless, both calcium and iron showed strong negative correlations with the total sperm motility and normal sperm morphology, but only iron was positively and significantly associated with multiple anomalies index and seminal leucocyte concentration. On the other hand, the rates of MDA and ROS production in semen were significantly higher in the three abnormal groups than in controls. These two oxidative stress biomarkers were significantly associated with the percentage of atypical forms in semen. However, only semen ROS level was significantly associated with the decreased sperm motility and the sperm leucocytes concentration. Meanwhile, there are positive correlations between seminal iron and calcium content and the studied oxidative stress biomarkers. Oxidative stress and trace element excess are implicated in low sperm quality. Iron and calcium might be the mediators of the effects of oxidative damage and induces lipid peroxidation.

Antioxidants for male subfertility

BACKGROUND

The inability to have children affects 10% to 15% of couples worldwide. A male factor is estimated to account for up to half of the infertility cases with between 25% to 87% of male subfertility considered to be due to the effect of oxidative stress. Oral supplementation with antioxidants is thought to improve sperm quality by reducing oxidative damage. Antioxidants are widely available and inexpensive when compared to other fertility treatments, however most antioxidants are uncontrolled by regulation and the evidence for their effectiveness is uncertain. We compared the benefits and risks of different antioxidants used for male subfertility. This review did not examine the use of antioxidants in normospermic men.

OBJECTIVES

To evaluate the effectiveness and safety of supplementary oral antioxidants in subfertile men.

SEARCH METHODS

The Cochrane Gynaecology and Fertility (CGF) Group trials register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, and two trials registers were searched on 1 February 2018, together with reference checking and contact with study authors and experts in the field to identify additional trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared any type, dose or combination of oral antioxidant supplement with placebo, no treatment or treatment with another antioxidant, among subfertile men of a couple attending a reproductive clinic. We excluded studies comparing antioxidants with fertility drugs alone and studies that included fertile men attending a fertility clinic because of female partner infertility.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. The primary review outcome was live birth. Clinical pregnancy, adverse events and sperm parameters were secondary outcomes.

MAIN RESULTS

We included 61 studies with a total population of 6264 subfertile men, aged between 18 and 65 years, part of a couple who had been referred to a fertility clinic and some of whom were undergoing assisted reproductive techniques (ART). Investigators compared and combined 18 different oral antioxidants. The evidence was of 'low' to 'very low' quality: the main limitation was that out of the 44 included studies in the meta-analysis only 12 studies reported on live birth or clinical pregnancy. The evidence is current up to February 2018.Live birth: antioxidants may lead to increased live birth rates (OR 1.79, 95% CI 1.20 to 2.67, P = 0.005, 7 RCTs, 750 men, I2 = 40%, low-quality evidence). Results suggest that if in the studies contributing to the analysis of live birth rate, the baseline chance of live birth following placebo or no treatment is assumed to be 12%, the chance following the use of antioxidants is estimated to be between 14% and 26%. However, this result was based on only 124 live births from 750 couples in seven relatively small studies. When studies at high risk of bias were removed from the analysis, there was no evidence of increased live birth (Peto OR 1.38, 95% CI 0.89 to 2.16; participants = 540 men, 5 RCTs, P = 0.15, I2 = 0%).Clinical pregnancy rate: antioxidants may lead to increased clinical pregnancy rates (OR 2.97, 95% CI 1.91 to 4.63, P < 0.0001, 11 RCTs, 786 men, I2 = 0%, low-quality evidence) compared to placebo or no treatment. This suggests that if in the studies contributing to the analysis of clinical pregnancy, the baseline chance of clinical pregnancy following placebo or no treatment is assumed to be 7%, the chance following the use of antioxidants is estimated to be between 12% and 26%. This result was based on 105 clinical pregnancies from 786 couples in 11 small studies.Adverse eventsMiscarriage: only three studies reported on this outcome and the event rate was very low. There was no difference in miscarriage rate between the antioxidant and placebo or no treatment group (OR 1.74, 95% CI 0.40 to 7.60, P = 0.46, 3 RCTs, 247 men, I2 = 0%, very low-quality evidence). The findings suggest that in a population of subfertile men with an expected miscarriage rate of 2%, the chance following the use of an antioxidant would result in the risk of a miscarriage between 1% and 13%.Gastrointestinal: antioxidants may lead to an increase in mild gastrointestinal upsets when compared to placebo or no treatment (OR 2.51, 95% CI 1.25 to 5.03, P = 0.010, 11 RCTs, 948 men, I2 = 50%, very low-quality evidence). This suggests that if the chance of gastrointestinal upsets following placebo or no treatment is assumed to be 2%, the chance following the use of antioxidants is estimated to be between 2% and 9%. However, this result was based on a low event rate of 35 out of 948 men in 10 small or medium-sized studies, and the quality of the evidence was rated very low and was high in heterogeneity.We were unable to draw any conclusions from the antioxidant versus antioxidant comparison as insufficient studies compared the same interventions.

AUTHORS' CONCLUSIONS

In this review, there is low-quality evidence from seven small randomised controlled trials suggesting that antioxidant supplementation in subfertile males may improve live birth rates for couples attending fertility clinics. Low-quality evidence suggests that clinical pregnancy rates may also increase. Overall, there is no evidence of increased risk of miscarriage, however antioxidants may give more mild gastrointestinal upsets but the evidence is of very low quality. Subfertilte couples should be advised that overall, the current evidence is inconclusive based on serious risk of bias due to poor reporting of methods of randomisation, failure to report on the clinical outcomes live birth rate and clinical pregnancy, often unclear or even high attrition, and also imprecision due to often low event rates and small overall sample sizes. Further large well-designed randomised placebo-controlled trials reporting on pregnancy and live births are still required to clarify the exact role of antioxidants.

Role of Oxidative Stress and Antioxidants in Male Infertility: An Interventional Study

Aims:

The study aims, in infertile men, (i) to assess oxidative stress parameters in semen plasma and (ii) to study the effect of antioxidants in those with abnormal semen parameters.

Settings and Design:

This was an interventional study.

Population:

Ninety men attending and infertility clinic in a tertiary center were enrolled in the study.

Materials and Methods:

The present study was conducted in the departments of obstetrics and gynecology and biochemistry in a tertiary center. Ethical approval was obtained from the institute ethics subcommittee, and the study was conducted between July 2014 and July 2016. The study was conducted on two groups of 45 men with normal semen parameters in group 1 and 45 men with abnormal semen parameters in group 2.

Results:

Malondialdehyde (MDA) value was higher in men with abnormal semen parameters, which was statistically significant. The total antioxidant assay was higher in men with abnormal semen parameters, which was not statistically significant. Oxidative stress index (OSI) value was higher in men with normal semen parameters, which was not statistically significant. After 90 days of antioxidants therapy to men with abnormal semen parameters, MDA value decreased, total antioxidant assay increased, and OSI value decreased, which were statistically significant. Semen parameters such as sperm concentration, motility, and normal morphology improved after 90 days of antioxidant therapy, which were statistically significant.

Conclusions:

Oxidative stress is increased in men with abnormal semen parameters. Antioxidant therapy improves sperm concentration and motility and decreases oxidative stress in the semen plasma.

1H Magnetic Resonance Spectroscopy of live human sperm

STUDY QUESTION

Can ¹H Magnetic Resonance Spectroscopy (MRS) be used to obtain information about the molecules and metabolites in live human spermatozoa?

SUMMARY ANSWER

Percoll-based density gradient centrifugation (DGC) followed by a further two washing steps, yielded enough sperm with minimal contamination (<0.01%) from seminal fluid to permit effective MRS which detected significant differences (P < 0.05) in the choline/glycerophosphocholine (GPC), lipid and lactate regions of the ¹H MRS spectrum between sperm in the pellet and those from the 40%/80% interface.

WHAT IS KNOWN ALREADY

Current methods to examine sperm are either limited in their value (e.g. semen analysis) or are destructive (e.g. immunohistochemistry, sperm DNA testing). A few studies have previously used MRS to examine sperm, but these have either looked at seminal plasma from men with different ejaculate qualities or at the molecules present in pooled samples of lyophilized sperm.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Sperm suspended in phosphate buffered saline (PBS) at 37°C were examined by ¹H MRS scanning using a ¹H excitation-sculpting solvent suppression sequence after recovery from fresh ejaculates by one of three different methods: (i) simple centrifugation; (ii) DGC with one wash; or (iii) DGC with two washes. In the case of DGC, sperm were collected both from the pellet (‘80%’ sperm) and the 40/80 interface (‘40%’ sperm). Spectrum processing was carried out using custom Matlab scripts to determine; the degree of seminal plasma/Percoll contamination, the minimum sperm concentration for ¹H MRS detection and differences between the ¹H MRS spectra of ‘40%’ and ‘80%’ sperm.

MAIN RESULTS AND THE ROLE OF CHANCE

DGC with two washes minimized the ¹H MRS peak intensity for both seminal plasma and Percoll/PBS solution contamination while retaining sperm specific peaks. For the MRS scanner used in this study, the minimum sperm concentration required to produce a choline/GPC ¹H MRS peak greater than 3:1 signal to noise ratio (SNR) was estimated at ~3 × 10⁶/ml. The choline/GPC and lactate/lipid regions of the ¹H spectrum were significantly different by two-way ANOVA analysis (P < 0.0001; n = 20). ROC curve analysis of these region showed significant ability to distinguish between the two sperm populations: choline/GPC ROC AUC = 0.65–0.67, lactate/lipid ROC AUC = 0.86–0.87.

LIMITATIONS, REASONS FOR CAUTION

Only 3–4 semen samples were used to assess the efficacy of each sperm washing protocol that were examined. The estimated minimum sperm concentration required for MRS is specific to the hardware used in our study and may be different in other spectrometers. Spectrum binning is a low resolution analysis method that sums MRS peaks within a chemical shift range. This can obscure the identity of which metabolite(s) are responsible for differences between sperm populations. Further work is required to determine the relative contribution of somatic cells to the MRS spectrum from the ‘40%’ and ‘80%’ sperm.

WIDER IMPLICATIONS OF THE FINDINGS

¹H MRS can provide information about the molecules present in live human sperm and may therefore permit the study of the underlying functional biology or metabolomics of live sperm. Given the relatively low concentration of sperm required to obtain a suitable MRS signal (~3 × 10⁶/ml), this could be carried out on sperm from men with oligo-, astheno- or teratozoospermia. This may lead to the development of new diagnostic tests or ultimately novel treatments for male factor infertility.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by the Medical Research Council Grant MR/M010473/1. The authors declare no conflicts of interest.

Protective effect of Lespedeza cuneata ethanol extract on Bisphenol A-induced testicular dysfunction in vivo and in vitro

PURPOSE

Bisphenol A (BPA) has been regarded as a possible risk factor for reproductive health. We examined potential reproductive health benefits of Lespedeza cuneata ethanol extract (LCE). Previously, Lespedeza cuneata showed many therapeutic effects. However, the protective effect of LCE on BPA-induced testicular dysfunction and its mechanisms have not been precisely studied.

METHODS

Mice were randomly divided into six groups (n = 7). Sperm counts and motility were measured by light microscope. Testosterone, total cholesterol, triglycerides, HDL, LDL-cholesterol, glucose, free fatty acids, hs-CRP, Angiotensinogen, Angiotensin II, GOT, GPT, TBARS, GSH, CAT, and SOD1 were measured in mouse serum. The potential protective effects of the LCE on mouse sertoli cells were evaluated.

RESULTS

Oral administration of LCE in BPA-exposed male mice restored testis weight, sperm count, motility, and testosterone levels by inhibiting markers in serum. In addition, treatment with LCE in BPA-treated TM4 sertoli cells recovered cell viability by attenuating Bax expression and activating caspase 3 and PARP.

CONCLUSIONS

These results indicate that LCE prevented BPA-induced testicular dysfunction and cell viability in BPA-treated TM4 sertoli cells. Our study also suggests that LCE has the potential to protect male reproductive health.

Relationship of antioxidant system and reactive oxygen species with clinical semen parameters in infertile men

Aims and Objectives:

To determine the correlation of antioxidant system and reactive oxygen species with clinical parameters in infertile semen samples.

Materials and Methods:

Semen sample of fifty infertile men were divided into three groups: (1) Group I - Normospermic (count >15 million/ml), Group II - Asthenospermic (motility <32%), and Group III - Oligospermic (counts <15 million/ml) subjects based on the sperm count and sperm motility. The samples were also divided into two groups: (1) Group IV with semen pH >7.2 (25 samples) and Group V - Semen pH <7.2 (25 samples). The grouping was based on the WHO guideline for semen analysis (12). The semen antioxidant parameters like glucose-6-phosphate dehydrogenase (G-6-PDH) (spectrophotometric method Kornberg and Horecker, 1955). Catalase (Maehly and Chance 1954), glutathione peroxidase (GPX) (Rotruck method), glutathione (GSH) (dithiobisnitro-benzoate method), superoxide dismutase (SOD) (direct method), and malondialdehyde (MDA) (thiobarbituric acid reactive substances assay kit method) were investigated. Mann–Whitney U-test was applied to compare the findings.

Results:

Of fifty semen samples there were 12 normospermic (sperm concentration ≥15 × 10⁶/ml of ejaculates), 24 asthenospermic (sperm motility ≤32%), and 14 oligospermic (sperm concentration ≤15 × 10⁶/ml of ejaculates) subjects. Results suggested that all asthenospermic males were found to have reduced motility and viability when compared with normospermic and oligospermic subjects. Activity of antioxidant parameters such as G-6-PDH, GPX, GSH, and SOD was decreased in case of asthenospermic subjects. The concentration of MDA was increased significantly (P < 0.001) in semen of asthenospermic subjects compared to normospermic and oligospermic subjects.

Conclusion:

The current study concludes that there is a significant relationship of ROS and semen parameters. Further studies will be needed in such subjects regarding role of effectiveness of dietary antioxidants in improving semen qualities.

New Approaches to Boar Semen Evaluation, Processing and Improvement

The improvement of boar reproductive performance may be the next frontier in reproductive management of swine herd in Unites States, facilitated by better understanding of boar sperm function and by the introduction of new advanced instrumentation in the andrology field. Objective single ejaculate evaluation and individual boar fertility prediction may be possible by introducing automated flow cytometric semen analysis with vital stains (e.g. acrosomal integrity and mito-potential), DNA fragmentation analysis and biomarkers (ubiquitin, PAWP, ALOX15, aggresome) associated with normal or defective sperm phenotypes. Measurement of sperm-produced reactive oxygen species (ROS) is a helpful indicator of normal semen sample. Semen ROS levels could be managed by the addition of ROS-scavenging antioxidants. Alternative energy regeneration substrates and sperm stimulants such as inorganic pyrophosphate and caffeine could increase sperm lifespan in extended semen and within the female reproductive system. Such technology could be combined with timed sperm release in the female reproductive system after artificial insemination. Sperm phenotype analysis by the image-based flow cytometry will go hand in hand with the advancement of swine genomics, linking aberrant sperm phenotype to the fertility influencing gene polymorphisms. Finally, poor-quality ejaculates could be rescued and acceptable ejaculates improved by semen purification methods such as the nanoparticle-based semen purification and magnetic-activated sperm sorting. Altogether, these scientific and technological advances could benefit swine industry, provided that the challenges of new technology adoption, dissemination and cost reduction are met.

Reactive Oxygen Species (ROS) in human semen: determination of a reference range

PURPOSE

High levels of reactive oxygen species (ROS) are a leading cause of male factor infertility. Measurement of ROS has been hampered by a lack of standardisation and confounding variables including choice of controls and sample selection. This study aimed to determine a reference range for ROS in human semen.

METHODS

Semen samples were obtained from men attending for routine semen analysis who gave informed consent for the study. Samples were assigned groups: Group 1 (N = 94) normal semen parameters, no leucocytospermia; Group 2 (N = 100) abnormal semen parameters, no leucocytospermia; Group 3 (N = 41) any semen parameters with leucocytospermia. ROS levels were assayed in fresh neat semen using a chemiluminescence assay measured in a single tube luminometer. Data are reported in relative light units (RLU)/sec/10(6) sperm

RESULTS

ROS levels were significantly different between Groups 1, 2 and 3 (19.75 ± 8.12, 95.03 ± 33.63, 890.17 ± 310.23 RLU/sec/10(6) sperm respectively; p < 0.001). Group 3 gave the highest value confirming this group as the optimum choice for positive controls. The reference range < 24.1 RLU/sec/10(6) sperm was determined by ROC analysis that differentiates a reference population (Group 1) from a positive control group (Group 3), optimising the sensitivity and specificity (80.5 and 87.2% respectively) of the test.

CONCLUSIONS

We have determined a reference range for ROS in human semen and identified a patient population that falls outside the normal range. This simple, cost effective assay can be incorporated into routine diagnostic testing to aid in the diagnosis of male infertility, especially with regard to unexplained infertility.

Treatment of aromatase (CYP19A1) inhibitor reduces fertility in porcine sperm

To ascertain whether aromatase (CYP19A1) expression is linked to sperm fertility of pigs, the present study determined the expression of the CYP19A1 gene in porcine sperm and its relationship with fertilization in vitro. First, to investigate its role in fertility, the presence of CYP19A1 of mRNA and protein expression in porcine sperm were confirmed by real-time (RT) or quantitative polymerase chain reaction (q-PCR) and by western blots. The expression levels were determined quantitatively using two sperm groups recovered by a Percoll gradient, which revealed that the sperm group with a low density had a higher penetration rate than that of the high-density group (P < 0.05). However, the expression level of CYP19A1 was not significantly different between the two groups. Secondly, to examine the effect of aromatase activity on fertilization, fresh semen was treated with a steroidal inhibitor, exemestane (50 μM for 0.5 h), followed by the dose- and time-dependent viability test. Our results clearly showed that an exemestane treatment effect (P < 0.05) was found for both the sperm-penetration rate and the oocyte cleavage rate. These results indicated that CYP19A1 could be involved in sperm fertility and its expression in sperm plays an important role in fertilization.

Male infertility workup needs additional testing of expressed prostatic secretion and/or post-massage urine

The male factor accounts for almost 50% of infertility cases. Inflammation may reduce semen quality via several pathways, including oxidative stress (OxS). As male infertility routinely is assessed using semen analysis only, the possible presence of non-leukocytospermic asymptomatic inflammatory prostatitis may be overlooked. We compared local and systemic OxS levels in male partners of infertile couples with different inflammation patterns in their genital tract and/or oligospermia. Subjects (n=143) were grouped according to inflammation in their semen, expressed prostatic secretion (EPS), and/or post-massage urine (post-M). Systemic (8-isoprostanes in urine) and local (diene conjugates and total antioxidant capacity in seminal plasma) OxS was measured The levels of OxS markers were significantly elevated in both severe inflammation groups--leukocytospermic men and subjects whose inflammation was limited only to EPS and/or post-M. Comparison between oligospermic and non-oligospermic men with genital tract inflammation, and oligozoospermic men with or without inflammation in the genital tract indicated that inflammation but not oligospermia status had significant impact on the measured OxS markers. Hence, a high leukocyte count in prostate-specific materials (EPS, post-M), even in absence of clear leukocytopsermia, is an important source of local and systemic OxS that may be associated with male infertility and affect general health. We suggest including the tests for detection of inflammation of the prostate into the workup of infertile men as was suggested in the WHO 1993 recommendation.

Cytosolic and mitochondrial ROS: which one is associated with poor chromatin remodeling?

The aim of this study was to determine if there are any associations between impaired chromatin packaging and the origin of reactive oxygen species (ROS) production. Cytosolic ROS, mitochondrial ROS, DNA protamination, and apoptosis were evaluated with dichlorofluoresceindiacetate (DCFH-DA), dihydrorhodamine 123 (DHR123), chromomycin A3 (CMA3), and YO-Pro-1 (Y1)/propidium iodide (PI), respectively, by flow cytometry (FCM) in 40 infertile individuals. Percentages DCF+ and R123+ sperm were positively associated with percentage CMA3+ sperm and negatively associated with percentage apoptotic sperm. No correlation was observed between CMA3+ sperm and the percentage of apoptotic sperm. Under protamination of sperm is not associated with the origin of ROS production, but their relationship may suggest an association with general physiological dysfunction of sperm. Furthermore, under protamination does make sperm prone to apoptosis. Rather, it is likely that apoptosis is induced by ROS production. Considering that these conclusions are derived from correlative analyses, additional studies including an interventive approach are required.

On methods for the detection of reactive oxygen species generation by human spermatozoa: analysis of the cellular responses to catechol oestrogen, lipid aldehyde, menadione and arachidonic acid

Oxidative stress is known to have a major impact on human sperm function and, as a result, there is a need to develop sensitive methods for measuring reactive oxygen species (ROS) generation by these cells. A variety of techniques have been developed for this purpose including chemiluminescence (luminol and lucigenin), flow cytometry (MitoSOX Red, dihydroethidium, 4,5-diaminofluorescein diacetate and 2',7'-dichlorodihydrofluorescein diacetate) and spectrophotometry (nitroblue tetrazolium). The relative sensitivity of these assays and their comparative ability to detect ROS generated in different subcellular compartments of human spermatozoa, have not previously been investigated. To address this issue, we have compared the performance of these assays when ROS generation was triggered with a variety of reagents including 2-hydroxyestradiol, menadione, 4-hydroxynonenal and arachidonic acid. The results revealed that menadione predominantly induced release of ROS into the extracellular space where these metabolites could be readily detected by luminol-peroxidase and, to a lesser extent, 2',7'-dichlorodihydrofluorescein. However, such sensitivity to extracellular ROS meant that these assays were particularly vulnerable to interference by leucocytes. The remaining reagents predominantly elicited ROS generation by the sperm mitochondria and could be optimally detected by MitoSOX Red and DHE. Examination of spontaneous ROS generation by defective human spermatozoa revealed that MitoSOX Red was the most effective indicator of oxidative stress, thereby emphasizing the general importance of mitochondrial dysregulation in the aetiology of defective sperm function.

Utility of the Nitroblue Tetrazolium Reduction Test for Assessment of Reactive Oxygen Species Production by Seminal Leukocytes and Spermatozoa

The purpose of this study was to evaluate the ability of spermatozoa and leukocytes in semen to produce reactive oxygen species (ROS) by using nitroblue tetrazolium (NBT) staining and to examine the association between NBT staining and levels of ROS as measured by chemiluminescence. Twenty-one infertility patients (leukocytospermia; n = 8; nonleukocytospermia, n = 13) and 9 healthy donors were included. Standard semen analysis and density gradient centrifugation were performed to test NBT staining, ROS, and total antioxidant capacity. A ROS-total antioxidant capacity (ROS-TAC) score was calculated by using principal component analysis. In the leukocytospermic group, after separation on a density gradient, the percentage of NBT-positive staining was significantly higher in sperm suspensions contaminated with leukocytes (median [25th, 75th percentiles]; 70% [61%, 79%]) compared to the nonleukocytospermic group (14.5% [9%, 25.5%]; P =.03) and donors (7% [3%, 11%]; P =.02), respectively. A strong positive correlation was seen between levels of ROS in whole ejaculates and NBT-positive staining in leukocytes (r = 0.59; P <.0006) and in leukocyte fractions (r = 0.72; P <.0001) after density gradient separation. Similarly, ROS was positively correlated with excessive cytoplasmic retention in spermatozoa from whole ejaculates and abnormal spermatozoa after separation on density gradients (r = 0.72; P <.0001). The ROS-TAC score was inversely correlated with NBT staining in leukocytes in whole ejaculates (r = -0.960, P <.0007) and in both leukocyte fractions (r = -0.39; P <.04) and spermatozoa with cytoplasmic retention (r = -0.38; P <.04). Our results indicate that the NBT reduction test can be used to assess the contribution of seminal leukocytes and defective spermatozoa towards ROS generation in semen. Levels of ROS assessed by chemiluminescence assay are strongly correlated with the results of NBT staining.

Relationship of leptin administration with production of reactive oxygen species, sperm DNA fragmentation, sperm parameters and hormone profile in the adult rat

PURPOSE

Leptin, an adipose tissue-derived hormone, plays an important role in energy homeostasis and metabolism, and in the neuroendocrine and reproductive systems. The function of leptin in male reproduction is unclear; however, it is known to affect sex hormones, sperm motility and its parameters. Leptin induces mitochondrial superoxide production in aortic endothelia and may increase oxidative stress and abnormal sperm production in leptin-treated rats. This study aims to evaluate whether exogenous leptin affects sperm parameters, hormone profiles, and the production of reactive oxygen species (ROS) in adult rats.

METHODS

A total of 65 Sprague-Dawley rats were divided into three treated groups and a control group. Treated rats received daily intraperitoneal injections of 5, 10 and 30 μg/kg of leptin administered for a duration of 7, 15, and 42 days. Control rats were given 0.1 mL of 0.9 % normal saline for the same period. One day after final drug administration, we evaluated serum specimens for follicle-stimulating hormone (FSH), leutinizing hormone (LH), free testosterone (FT), and total testosterone (TT) levels. Samples from the rat epididymis were also evaluated for sperm parameters and motility characteristics by a Computer-Aided Semen Analysis (CASA) system. Samples were treated with 2',7'-dichlorofluorescein-diacetate (DCFH-DA) and analyzed using flow cytometry and TUNEL to determine the impact of leptin administration on sperm DNA fragmentation.

RESULTS

According to CASA, significant differences in all sperm parameters in leptin-treated rats and their age-matched controls were detected, except for TM, ALH and BCF. Serum FSH and LH levels were significantly higher in rats that received 10 and 30 μg/kg of leptin compared to those treated with 5 μg/kg of leptin in the same group and control rats (P < 0.05). ROS and sperm DNA fragmentation was significantly higher in rats injected with 10 and 30 μg/kg of leptin for 7 and 15 days compared with rats treated with 5 μg/kg of leptin and the control group (P < 0.05) for the same time period. However, at day 42 of treatment, ROS and sperm DNA fragmentation levels significantly decreased in all groups (P < 0.05).

CONCLUSION

According to these results, leptin can possibly affect male infertility by ROS induction or hormone profile modulation.

Cost-effective diagnosis of male oxidative stress using the nitroblue tetrazolium test: useful application for the developing world

Seminal oxidative stress plays an important role in male factor infertility (MFI), worldwide. A study was thus undertaken for the first time to establish seminal reactive oxygen species (ROS) as a clinical marker of MFI in a cohort of Sri Lankan males. The nitro blue tetrazolium (NBT) assay for ROS estimation and modified Endtz test for detecting leucocytes were carried out on semen samples (N = 102) of subfertile males. Age-matched individuals (N = 30) with proven past paternity served as controls. Significantly higher ROS production was evident in individuals with asthenozoospermia and unexplained infertility (Mann-Whitney U-test, P = 0.000), than in the fertile and the other subfertile groups tested. Receiver operating characteristic plot analysis established cut-off points of 40.57 and 42.02 μg formazan/10(7) spermatozoa for ROS to distinguish fertile males from asthenozoospermics (71.4% sensitivity: 70% specificity; AUC = 0.82), and from unexplained infertile males (74.1 % sensitivity: 73.3% specificity; AUC = 0.85) respectively. As ROS appear to be a potential marker of male infertility, it is imperative to validate this test as a simple, cost-effective hence a widely accessible diagnostic tool to be included in MFI investigations in the developing world.

NOX5 in human spermatozoa: expression, function, and regulation

Physiological and pathological processes in spermatozoa involve the production of reactive oxygen species (ROS), but the identity of the ROS-producing enzyme system(s) remains a matter of speculation. We provide the first evidence that NOX5 NADPH oxidase is expressed and functions in human spermatozoa. Immunofluorescence microscopy detected NOX5 protein in both the flagella/neck region and the acrosome. Functionally, spermatozoa exposed to calcium ionophore, phorbol ester, or H(2)O(2) exhibited superoxide anion production, which was blocked by addition of superoxide dismutase, a Ca(2+) chelator, or inhibitors of either flavoprotein oxidases (diphenylene iododonium) or NOX enzymes (GKT136901). Consistent with our previous overexpression studies, we found that H(2)O(2)-induced superoxide production by primary sperm cells was mediated by the non-receptor tyrosine kinase c-Abl. Moreover, the H(V)1 proton channel, which was recently implicated in spermatozoa motility, was required for optimal superoxide production by spermatozoa. Immunoprecipitation experiments suggested an interaction among NOX5, c-Abl, and H(V)1. H(2)O(2) treatment increased the proportion of motile sperm in a NOX5-dependent manner. Statistical analyses showed a pH-dependent correlation between superoxide production and enhanced sperm motility. Collectively, our findings show that NOX5 is a major source of ROS in human spermatozoa and indicate a role for NOX5-dependent ROS generation in human spermatozoa motility.

Oocyte quality determines bovine embryo development after fertilisation with hydrogen peroxide-stressed spermatozoa

Exposure of gametes to specific stressors at sublethal levels can enhance the gametes’ subsequent performance in processes such as cryopreservation. In the present study, bull spermatozoa were subjected to H2O2 for 4 h at 100-, 200- and 500-μM levels; computer-assisted sperm analysis (CASA) and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay were used for evaluation of subsequent sperm motility and DNA integrity, respectively. Exposure of spermatozoa to H2O2 did not affect sperm motility but DNA integrity was negatively affected by 500 μM H2O2 compared with mock-exposed spermatozoa, whereas both motility and DNA integrity were affected compared with untreated spermatozoa. Nevertheless, insemination of oocytes with spermatozoa exposed to 200 μM H2O2 increased fertilisation, cleavage and blastocyst rates (P < 0.05). Furthermore, the higher blastocyst yield after fertilisation of oocytes with spermatozoa exposed to 200 μM H2O2 was related to oocyte diameter, with large–medium oocytes yielding higher blastocyst rates, while small-diameter oocytes consistently failed to develop into blastocysts. In conclusion, the results indicate that exposure of spermatozoa to 200 μM H2O2 before sperm–oocyte interaction may enhance in vitro embryo production in cattle. However, this increased embryo production is largely dependent on the intrinsic quality of the oocytes.