Removal of DNA-fragmented spermatozoa using flow cytometry and sorting does not improve the outcome of intracytoplasmic sperm injection

PURPOSE

The DNA fragmentation in sperm is associated with reduced outcome in assisted reproduction. Using YoPro1 as the staining dye and flow cytometry and sorting (FACS), the number of spermatozoa with DNA fragmentation can be lowered to 5%. Can the cumulative outcome of ICSI be improved using FACS?

METHODS

A prospective, randomized, double-blind clinical trial was conducted in 104 infertile couples with male infertility based on abnormal conventional semen analysis results. Cumulative ongoing pregnancy rate was the primary outcome parameter. In 52 cases, semen was processed for ICSI using swim-up. In another 52 cases, spermatozoa with fragmented DNA were removed with FACS.

RESULTS

The cumulative pregnancy rate at 12 weeks of gestation (51.9% versus 46.2%) and live birth rate (42.3% versus 34.6%) were higher and the miscarriage rate was lower (27.8% versus 35.3%) after FACS-sorting as compared with swim-up. An interim analysis scheduled before initiation of the study after 100 cases demonstrated that the aim of a 20% gain in pregnancy rate could not be achieved. For that reason, the prospective study was stopped prematurely.

CONCLUSIONS

A trend towards consistently better results was achieved by removing spermatozoa with fragmented DNA. The fragmentation of the DNA in sperm is the end stage of apoptosis. Sorting of spermatozoa may be improved by selecting parameters of processes active more upstream of apoptosis, such as chromatin decondensation.

TRIAL REGISTRATION

NCT02166567 . June 14, 2014.

Soy Isoflavones Improve the Spermatogenic Defects in Diet-Induced Obesity Rats through Nrf2/HO-1 Pathway

Soy isoflavones (SIF) are biologically active compounds of non-steroidal and phenolic properties that are richly present in soybeans, which can reduce the body weight and blood lipids of obese animals. Recently, SIF have been reported to affect reproductive ability in obese male rats. However, the specific mechanism has not been well defined. The aim of the current study was to study the possible mechanisms for the effect of SIF administration on obesity induced spermatogenic defects. Obese rats model induced by high-fat diets were established and gavage treated with 0, 50,150 or 450 mg of SIF/kg body weight/day for 4 weeks. Here, our research shows that obesity resulted in spermatogenic degeneration, imbalance of reproductive hormone, testicular oxidative stress and germ cell apoptosis, whereas evidently recovery effects were observed at 150 and 450 mg/kg SIF. We also have discovered that 150 and 450 mg/kg SIF can activate Nrf2/HO-1 pathway in control of Bcl-2, BAX and cleaved caspase-3 expression with implications in antioxidant protection. Our study indicates the potential mechanism of SIF regulating spermatogenic function in obese rats, and provides a scientific experimental basis for the regulation of biological function of obese male reproductive system by SIF.

Investigating the level of DNA double-strand break in human spermatozoa and its relation to semen characteristics and IVF outcome using phospho-histone H2AX antibody as a biomarker

BACKGROUND

Sperm DNA fragmentation and its relation to conventional semen parameters are well studied. However, there is limited information regarding the rate of DNA double-strand breaks (DSBs) and its correlation to basic semen parameters and IVF outcome.

OBJECTIVES

The present study aimed to investigate the rate of DNA DSBs in human spermatozoa and its correlation to basic semen parameters and IVF outcome.

MATERIALS AND METHODS

The prospective study includes 60 assisted reproductive treatment cycles (52 autologous and eight donors) in which the semen profiles and sperm DNA DSBs have been assessed. The level of sperm DNA DSBs in each sample has been evaluated by using a method to detect histone H2AX phosphorylation. The results were compared with basic semen values and IVF outcomes.

RESULTS

No significant correlation was observed between phospho-histone H2AX (γH2AX) levels and basic semen parameters such as semen volume (p = 0.129), sperm count (p = 0.454), total motility (p = 0.934), progressive motility (p = 0.314) and normal sperm morphology (p = 0.720). Similarly, the mean values of γH2AX did not differ with regard to the age of male participants (p = 0.300). However, cycles that resulted in live birth exhibited lower levels of γH2AX (p = 0.007). Accordingly, the level of γH2AX (p < 0.004) and rate of normal sperm morphology (p = 0.015) were found to be variables that affect the live birth outcomes.

DISCUSSION AND CONCLUSION

The low levels of γH2AX in sperm cells may be an indicator to IVF outcome independently from the conventional semen parameters and male age.

Transgenerational inheritance: how impacts to the epigenetic and genetic information of parents affect offspring health

BACKGROUND

A defining feature of sexual reproduction is the transmission of genomic information from both parents to the offspring. There is now compelling evidence that the inheritance of such genetic information is accompanied by additional epigenetic marks, or stable heritable information that is not accounted for by variations in DNA sequence. The reversible nature of epigenetic marks coupled with multiple rounds of epigenetic reprogramming that erase the majority of existing patterns have made the investigation of this phenomenon challenging. However, continual advances in molecular methods are allowing closer examination of the dynamic alterations to histone composition and DNA methylation patterns that accompany development and, in particular, how these modifications can occur in an individual’s germline and be transmitted to the following generation. While the underlying mechanisms that permit this form of transgenerational inheritance remain unclear, it is increasingly apparent that a combination of genetic and epigenetic modifications plays major roles in determining the phenotypes of individuals and their offspring.

OBJECTIVE AND RATIONALE

Information pertaining to transgenerational inheritance was systematically reviewed focusing primarily on mammalian cells to the exclusion of inheritance in plants, due to inherent differences in the means by which information is transmitted between generations. The effects of environmental factors and biological processes on both epigenetic and genetic information were reviewed to determine their contribution to modulating inheritable phenotypes.

SEARCH METHODS

Articles indexed in PubMed were searched using keywords related to transgenerational inheritance, epigenetic modifications, paternal and maternal inheritable traits and environmental and biological factors influencing transgenerational modifications. We sought to clarify the role of epigenetic reprogramming events during the life cycle of mammals and provide a comprehensive review of how the genomic and epigenomic make-up of progenitors may determine the phenotype of its descendants.

OUTCOMES

We found strong evidence supporting the role of DNA methylation patterns, histone modifications and even non-protein-coding RNA in altering the epigenetic composition of individuals and producing stable epigenetic effects that were transmitted from parents to offspring, in both humans and rodent species. Multiple genomic domains and several histone modification sites were found to resist demethylation and endure genome-wide reprogramming events. Epigenetic modifications integrated into the genome of individuals were shown to modulate gene expression and activity at enhancer and promoter domains, while genetic mutations were shown to alter sequence availability for methylation and histone binding. Fundamentally, alterations to the nuclear composition of the germline in response to environmental factors, ageing, diet and toxicant exposure have the potential to become hereditably transmitted.

WIDER IMPLICATIONS

The environment influences the health and well-being of progeny by working through the germline to introduce spontaneous genetic mutations as well as a variety of epigenetic changes, including alterations in DNA methylation status and the post-translational modification of histones. In evolutionary terms, these changes create the phenotypic diversity that fuels the fires of natural selection. However, rather than being adaptive, such variation may also generate a plethora of pathological disease states ranging from dominant genetic disorders to neurological conditions, including spontaneous schizophrenia and autism.

Silver nanoparticles testicular toxicity in rat

To evaluate the potential testicular toxicity induced by silver nanoparticles (AgNPs) in Sprague Dawley rate. The protocol study was designed as follows: G1: 30 adult male rats were kept as control. G2: 30 adult male rats were administered 5.36 mg/kg of AgNPs orally, twice weekly for six months. G3: 30 adult male rats were administered 13.4 mg/kg of AgNPs orally, twice weekly for six months. The results of hormonal assay revealed that a significant decrease in testosterone level while a significant increase in LH level was obtained. The testicular homogenate showed a significant decrease in SOD activity accompanied by a significant increase in MDA level in both G2 and G3 in comparison with the control in a dose-response relationship. Sperm viability indicates a significant decrease in rats in G2 and G3 groups. A significant decrease in DNA chromatin integrity % was obtained in rats of G3 in comparison with G2 and control. The semithin and TEM sections of the testis of G2 and G3 groups showed Sertoli cells have vacuolations with a disturbance in the arrangement and the staining affinity of spermatogenic cells. The spermatogonia appeared with a moderate electron density of the nucleus and cytoplasm. The acrosome and its cap become oval and light electron dens of spermatid cells.

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.

Distribution of DNA damage in the human sperm nucleus: implications of the architecture of the sperm head

The sperm nucleus is prone to sustain DNA damage before and after ejaculation. Distribution of the damage is not homogeneous, and the factors determining differential sensitivity among nuclear regions have not yet been characterized. Human sperm chromatin contains three structural domains, two of which are considered the most susceptible to DNA damage: the histone bound domain, harboring developmental related genes, and the domain associated with nuclear matrix proteins. Using a quantitative polymerase chain reaction (qPCR) approach, we analyzed the number of lesions in genes homeobox A3 (HOXA3), homeobox B5 (HOXB5), sex-determining region Y (SRY)-box 2 (SOX2), β-GLOBIN, rDNA 18S, and rDNA 28S in human sperm after ultraviolet irradiation (400 μW cm⁻², 10 min), H₂O₂ treatment (250 mmol l⁻¹, 20 min), and cryopreservation, which showed differential susceptibility to genetic damage. Differential vulnerability is dependent on the genotoxic agent and independent of the sperm nuclear proteins to which the chromatin is bound and of accessibility to the transcription machinery. Immunodetection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) showed that the highest level of oxidation was observed after H₂O₂ treatment. The distribution of oxidative lesions also differed depending on the genotoxic agent. 8-OHdG did not colocalize either with histone 3 (H3) or with type IIα + β topoisomerase (TOPO IIα + β) after H₂O₂ treatment but matched perfectly with peroxiredoxin 6 (PRDX6), which is involved in H₂O₂ metabolism. Our study reveals that the characteristics of the sperm head domains are responsible for access of the genotoxicants and cause differential degree of damage to nuclear areas, whereas chromatin packaging has a very limited relevance. The histone-enriched genes analyzed cannot be used as biomarkers of oxidative DNA damage.

Sperm DNA damage has a negative effect on early embryonic development following in vitro fertilization

Sperm DNA damage is recognized as an important biomarker of male infertility. To investigate this, sperm DNA damage was assessed by the sperm chromatin dispersion (SCD) test in semen and motile spermatozoa harvested by combined density gradient centrifugation (DGC) and swim-up in 161 couples undergoing in vitro fertilization (IVF). Semen analysis and sperm DNA damage results were compared between couples who did or did not achieve pregnancy. The sperm DNA damage level was significantly different between the two groups (P < 0.05) and was negatively correlated with IVF outcomes. Logistic regression analysis confirmed that it was an independent predictor for achieving clinical pregnancy. The effects of different levels of sperm DNA damage on IVF outcomes were also compared. There were significant differences in day 3 embryo quality, blastocyst formation rate, and implantation and pregnancy rates (P < 0.05), but not in the basic fertilization rate between the two groups. Thus, sperm DNA damage as measured by the SCD appears useful for predicting the clinical pregnancy rate following IVF.

A key role for sex chromosomes in the regulation of parthenogenesis in the brown alga Ectocarpus

Although evolutionary transitions from sexual to asexual reproduction are frequent in eukaryotes, the genetic bases of these shifts remain largely elusive. Here, we used classic quantitative trait analysis, combined with genomic and transcriptomic information to dissect the genetic basis of asexual, parthenogenetic reproduction in the brown alga Ectocarpus. We found that parthenogenesis is controlled by the sex locus, together with two additional autosomal loci, highlighting the key role of the sex chromosome as a major regulator of asexual reproduction. We identify several negative effects of parthenogenesis on male fitness, and different fitness effects of parthenogenetic capacity depending on the life cycle generation. Although allele frequencies in natural populations are currently unknown, we discuss the possibility that parthenogenesis may be under both sex-specific selection and generation/ploidally-antagonistic selection, and/or that the action of fluctuating selection on this trait may contribute to the maintenance of polymorphisms in populations. Importantly, our data provide the first empirical illustration, to our knowledge, of a trade-off between the haploid and diploid stages of the life cycle, where distinct parthenogenesis alleles have opposing effects on sexual and asexual reproduction and may help maintain genetic variation. These types of fitness trade-offs have profound evolutionary implications in natural populations and may structure life history evolution in organisms with haploid-diploid life cycles.

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.

Sperm DNA fragmentation valued by SCSA and its correlation with conventional sperm parameters in male partner of recurrent spontaneous abortion couple

The objective of this study is to evaluate the predictive value of sperm DNA fragmentation Index (DFI) in unexplained recurrent spontaneous abortion (RSA) and to investigate its correlation with conventional sperm parameters. Besides, we aimed to reveal the necessity of establishing a DFI clinical threshold of each laboratory for the prognostic diagnosis of RSA and establish our own DFI threshold. Semen samples were collected from male partners of RSA patients (n = 139) and healthy recent fathers (control, n = 200). DFI was tested using SCSA and conventional semen analysis was performed using an automatic semen analyzer. The DFI value and distribution were compared between the two groups using corresponding statistical software. The diagnostic threshold value was established by ROC curve. The correlation between DFI and the conventional semen parameters of the 139 cases was further analyzed using Student's t test and Mann-Whitney U test. Our result showed that DFI was significantly higher in RSA patients compared with normal donor controls. We established our own DFI threshold at 13.59%. There was only a weak partial correlation between DFI values and conventional sperm analysis parameters. Our present study suggested that DFI might be used as a valuable predictor for RSA independent of conventional sperm parameters. Additionally, we recommend that each laboratory should establish its own clinical DFI threshold for more precise prediction of RSA and we recommend that sperm DNA fragmentation test should be included in complete sperm quality assessment in addition to conventional semen analysis for RSA male partners.

A RNA-Seq Analysis to Describe the Boar Sperm Transcriptome and Its Seasonal Changes

Understanding the molecular basis of cell function and ultimate phenotypes is crucial for the development of biological markers. With this aim, several RNA-seq studies have been devoted to the characterization of the transcriptome of ejaculated spermatozoa in relation to sperm quality and fertility. Semen quality follows a seasonal pattern and decays in the summer months in several animal species. The aim of this study was to deeply profile the transcriptome of the boar sperm and to evaluate its seasonal changes. We sequenced the total and the short fractions of the sperm RNA from 10 Pietrain boars, 5 collected in summer and 5 five sampled in winter, and identified a complex and rich transcriptome with 4,436 coding genes of moderate to high abundance. Transcript fragmentation was high but less obvious in genes related to spermatogenesis, chromatin compaction and fertility. Short non-coding RNAs mostly included piwi-interacting RNAs, transfer RNAs and microRNAs. We also compared the transcriptome of the summer and the winter ejaculates and identified 34 coding genes and 7 microRNAs with a significantly distinct distribution. These genes were mostly related to oxidative stress, DNA damage and autophagy. This is the deepest characterization of the boar sperm transcriptome and the first study linking the transcriptome and the seasonal variability of semen quality in animals. The annotation described here can be used as a reference for the identification of markers of sperm quality in pigs.

The progesterone-induced sperm acrosome reaction is a good option for the prediction of fertilization in vitro compared with other sperm parameters

Progesterone (P₄ ) is crucial for the physiological function of spermatozoa. In the study, we investigated the correlation between P₄ -induced sperm acrosome reaction (AR) and parameters including sperm progressive motility, normal morphology and sperm DNA fragmentation (SDF), and compared the in vitro fertilization (IVF) predictive values of these indicators based on the multivariate regressions analysis and receiver operator characteristics (ROC) curve analyses. The results demonstrated a negative correlation between P₄ -induced sperm AR and the SDF, with the correlation -9.05 (-17.25 to -0.84), p<0.05, n = 47). No relationship was found between the sperm progressive motility, normal morphology and the induced AR. The P₄ -induced AR and SDF were both significantly correlated to the fertilization rate. ROC curve analyses indicated that P₄ -induced AR was a better prognostic predictor for the fertilization rate compared with the SDF, with the areas under the curve 0.729 (0.580-0.849), p<0.01 and 0.637 (0.484-0.772), p=0.16 respectively. The cut-off value for P₄ -induced AR to predict "50% fertilization rate" was 23.4% with sensitivity and specificity of 63.3% and 88.2% respectively. The overall results indicated that the assessment of P₄ -induced AR seemed to be a more sensitive indicator for fertilization rate in vitro compared with other sperm parameters.

Detection of protamine 2 in bovine spermatozoa and testicles

BACKGROUND

Sperm DNA integrity is crucial for transmission of genetic information to future generations and DNA damage can occur during chromatin packaging. Chromatin packaging involves the replacement of somatic nucleosomal histones by nuclear proteins called protamines. Protamine 1 (PRM1) is transcribed and translated in spermatids of all mammals; however, protamine 2 (PRM2) is transcribed in low levels in spermatids and it is not yet described in bull mature spermatozoa.

OBJECTIVES

The aim of this study was to assess gene and protein expression of PRM2 and corroborate gene and protein expression of PRM1 in bull spermatozoa and testis.

MATERIALS AND METHODS

For this purpose, absolute q-RT-PCR was performed to calculate the number of copies of PRM1 and PRM2 mRNAs in bovine epididymal spermatozoa and testicular tissue. Western blot and mass spectrometry were performed to identify PRM1 and PRM2 in samples of bovine epididymal spermatozoa. Samples of bovine testicular tissue were collected to identify PRM1 and PRM2 by immunohistochemistry.

RESULTS

We evaluated that the number of PRM1 mRNA copies was about hundred times higher than PRM2 mRNA copies in sperm and testicular samples (p < 0.0001). In addition, we estimated the PRM1: PRM2 ratio based on mRNA number of copies. In spermatozoa, the ratio was 1: 0.014, and in testicle, the ratio was 1: 0.009. We also evaluated the immunolocalization for PRM1 and PRM2 in bovine testis, and both proteins were detected in spermatids. Western blot and mass spectrometry in bovine epididymal spermatozoa confirmed these results.

CONCLUSION

Our work identifies, for the first time, PRM2 in bovine epididymal spermatozoa and in testis. Further studies are still needed to understand the role of PRM2 on the chromatin of the spermatozoa and to verify how possible changes in PRM2 levels may influence the bull fertility.

The effects of male social environment on sperm phenotype and genome integrity

Sperm function and quality are primary determinants of male reproductive performance and hence fitness. The presence of rival males has been shown to affect ejaculate and sperm traits in a wide range of taxa. However, male physiological conditions may not only affect sperm phenotypic traits but also their genetic and epigenetic signatures, affecting the fitness of the resulting offspring. We investigated the effects of male‐male competition on sperm quality using TUNEL assays and geometric morphometrics in the zebrafish, Danio rerio. We found that the sperm produced by males exposed to high male–male competition had smaller heads but larger midpiece and flagellum than sperm produced by males under low competition. Head and flagella also appeared less sensitive to the osmotic stress induced by activation with water. In addition, more sperm showed signals of DNA damage in ejaculates of males under high competition. These findings suggest that the presence of a rival male may have positive effects on sperm phenotypic traits but negative effects on sperm DNA integrity. Overall, males facing the presence of rival males may produce faster swimming and more competitive sperm but this may come at a cost for the next generation.

A Comparison Between Two Assays for Measuring Seminal Oxidative Stress and their Relationship with Sperm DNA Fragmentation and Semen Parameters

Oxidative stress (OS) is a significant cause of DNA fragmentation and is associated with poor embryo development and recurrent miscarriage. The aim of this study was to compare two different methods for assessing seminal OS and their ability to predict sperm DNA fragmentation and abnormal semen parameters. Semen samples were collected from 520 men attending for routine diagnostic testing following informed consent. Oxidative stress was assessed using either a chemiluminescence assay to measure reactive oxygen species (ROS) or an electrochemical assay to measure oxidation reduction potential (sORP). Sperm DNA fragmentation (DFI) and sperm with immature chromatin (HDS) were assessed using sperm chromatin structure assay (SCSA). Semen analysis was performed according to WHO 2010 guidelines. Reactive oxygen species sORP and DFI are negatively correlated with sperm motility (p = 0.0012, 0.0002, <0.0001 respectively) and vitality (p < 0.0001, 0.019, <0.0001 respectively). The correlation was stronger for sORP than ROS. Reactive oxygen species (p < 0.0001), sORP (p < 0.0001), DFI (p < 0.0089) and HDS (p < 0.0001) were significantly elevated in samples with abnormal semen parameters, compared to those with normal parameters. Samples with polymorphonuclear leukocytes (PMN) have excessive ROS levels compared to those without (p < 0.0001), but sORP and DFI in this group are not significantly increased. DNA fragmentation was significantly elevated in samples with OS measured by ROS (p = 0.0052) or sORP (p = 0.004). The results demonstrate the multi-dimensional nature of oxidative stress and that neither assay can be used alone in the diagnosis of OS, especially in cases of leukocytospermia.

Double-stranded sperm DNA damage is a cause of delay in embryo development and can impair implantation rates

OBJECTIVE

To analyze the effect of single- and double-stranded sperm DNA fragmentation (ssSDF and dsSDF) on human embryo kinetics monitored under a time-lapse system.

DESIGN

Observational, double blind, prospective cohort study.

SETTING

University spin-off and private center.

PATIENT(S)

One hundred ninety-six embryos from 43 infertile couples were included prospectively.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

SsSDF and dsSDF were analyzed in the same semen sample used for intracytoplasmic sperm injection. Embryo kinetics was then monitored using time-lapse technology, and the timing of each embryo division was obtained.

RESULT(S)

When comparing embryos obtained from semen samples with low dsSDF and high dsSDF, splitting data using a statistically significant delay in high dsSDF was observed in second polar body extrusion, T4, T8, morula, and starting blastocyst and embryo implantation rates were impaired. Embryo kinetics and implantation rates are not significantly affected when high values of ssSDF are present. Different patterns of delay in embryo kinetics were observed for these different types of DNA damage: dsSDF caused a delay along all stages of embryo development; however, its major effect was observed at the second polar body extrusion and morula stages, coinciding with embryo DNA damage checkpoint activation as described before; ssSDF had its major effect at the pronucleus stage, but embryo kinetics was then restored at all following stages. The results show that dsSDF could be the main type of DNA damage that affects embryo development in intracytoplasmic sperm injection cycles, probably due to motility-based sperm selection in this assisted reproduction procedure.

CONCLUSION(S)

Double-stranded sperm DNA damage caused a delay in embryo development and impaired implantation, while single-stranded DNA damage did not significantly affect embryo kinetics and implantation.

Insights into soy lecithin and egg yolk-based extenders for chilling canine spermatozoa

SummaryThe aim of this study was to compare different concentrations of soy lecithin (LEC0.01%, LEC0.05% and LEC0.1%) with egg yolk (Control) in cooling extenders during the storage of semen at 5ºC for 5 days. Twelve dogs (n = 12) were selected, and semen was cooled and assessed after 2, 24, 48, 72, 96 or 120 h. At each time point, sperm were analyzed for kinetic patterns (using computer-assisted sperm analysis), mitochondrial activity (3'3- diaminobenzidine assay), lipid peroxidation (TBARS assay), DNA fragmentation (SCSA®) and plasma and acrosome membrane integrity (eosin/nigrosin and fast green/rose Bengal stains, respectively). The Control group (1814.4 ± 197.2) presented the highest rates of lipid peroxidation at 120 h. Conversely, progressive motility (42.8 ± 4%), linearity (45.4 ± 1%), and VAP (88 ± 3%) were higher in the Control group. In addition, there was lower mitochondrial activity in the Control group at 72 h. Therefore, our data show that lecithin used at these concentrations was not able to maintain sperm viability at as high qualities as would egg yolk. Moreover, the decrease in high mitochondrial activity and the persistence of sperm motility may indicate a compensatory mechanism in canine spermatozoa (i.e., glycolytic pathway). Furthermore, these higher lipid peroxidation indexes could indicate the necessity for future therapy using extenders and antioxidants over a long cooling time for dog sperm.

Single and Double Strand Sperm DNA Damage: Different Reproductive Effects on Male Fertility

Reproductive diseases have become a growing worldwide problem and male factor plays an important role in the reproductive diagnosis, prognosis and design of assisted reproductive treatments. Sperm cell holds the mission of carrying the paternal genetic complement to the oocyte in order to contribute to an euploid zygote with proper DNA integrity. Sperm DNA fragmentation had been used for decades as a male fertility test, however, its usefulness have arisen multiple debates, especially around Intracytoplasmic Sperm Injection (ICSI) treatments. In the recent years, it has been described that different types of sperm DNA breaks (single and double strand DNA breaks) cause different clinical reproductive effects. On one hand, single-strand DNA breaks are present extensively as a multiple break points in all regions of the genome, are related to oxidative stress and cause a lack of clinical pregnancy or an increase of the conception time. On the other hand, double-strand DNA breaks are mainly localized and attached to the sperm nuclear matrix as a very few break points, are possibly related to a lack of DNA repair in meiosis and cause a higher risk of miscarriage, low embryo quality and higher risk of implantation failure in ICSI cycles. The present work also reviews different studies that may contribute in the understanding of sperm chromatin as well as treatments to prevent sperm DNA damage.

45,X/46,XY Mosaicism and Normozoospermia in a Patient with Male Phenotype

The phenotypic spectrum of 45,X/46,XY mosaic males varies greatly. Previous reports have only described cases with either oligozoospermia, growth retardation, or elevated gonadotropins. However, the present case presented with normozoospermia, and normal height, sperm DNA fragmentation index (DFI), and gonadotropins. The male and his spouse were referred to The Fertility Clinic, Skive Regional Hospital, due to 2 years of infertility. After failure of several attempts of assisted reproductive treatment (ART), the male underwent genetic analysis. Conventional karyotyping in peripheral lymphocytes yielded a low-grade 45,X/46,XY mosaicism, confirmed by fluorescence in situ hybridization (FISH) showing 6% 45,X cells. A FISH test performed on interphase nuclei from buccal mucosal cells yielded one cell with only one X-signal (0.6%), explaining the normal phenotype of the patient, but not the infertility. FISH test for sperm aneuploidy showed normal range parameters, except for a 10-fold elevated gonosomal nullisomy rate (2.1%). Hence, germinal mosaicism may be an explanation of the infertility of the case. Increased sex nullisomy levels may reflect an aberrant testicular environment compromising fertility even though sperm euploidy rates and other sperm parameters do not preclude a successful treatment with ART. Based on these results, the couple decided to use donor semen for their subsequent intrauterine insemination treatment and obtained a successful pregnancy.

Evidence that fertility trades off with early offspring fitness as males age

Models of ageing predict that sperm function and fertility should decline with age as sperm are exposed to free radical damage and mutation accumulation. However, theory also suggests that mating with older males should be beneficial for females because survival to old age is a demonstration of a male's high genetic and/or phenotypic quality. Consequently, declines in sperm fitness may be offset by indirect fitness benefits exhibited in offspring. While numerous studies have investigated age-based declines in male fertility, none has taken the integrated approach of studying age-based effects on both male fertility and offspring fitness. Here, using a cohort-based longitudinal study of zebrafish (Danio rerio), we report a decline in male mating success and fertility with male age but also compensating indirect benefits. Using in vitro fertilization, we show that offspring from older males exhibit superior early survival compared to those from their youngest counterparts. These findings suggest that the high offspring fitness observed for the subset of males that survive to an old age (approx. 51% in this study) may represent compensating benefits for declining fertility with age, thus challenging widely held views about the fitness costs of mating with older males.

DNA Damage and Repair in Human Reproductive Cells

The fundamental underlying paradigm of sexual reproduction is the production of male and female gametes of sufficient genetic difference and quality that, following syngamy, they result in embryos with genomic potential to allow for future adaptive change and the ability to respond to selective pressure. The fusion of dissimilar gametes resulting in the formation of a normal and viable embryo is known as anisogamy, and is concomitant with precise structural, physiological, and molecular control of gamete function for species survival. However, along the reproductive life cycle of all organisms, both male and female gametes can be exposed to an array of “stressors” that may adversely affect the composition and biological integrity of their proteins, lipids and nucleic acids, that may consequently compromise their capacity to produce normal embryos. The aim of this review is to highlight gamete genome organization, differences in the chronology of gamete production between the male and female, the inherent DNA protective mechanisms in these reproductive cells, the aetiology of DNA damage in germ cells, and the remarkable DNA repair mechanisms, pre- and post-syngamy, that function to maintain genome integrity.

IUI: review and systematic assessment of the evidence that supports global recommendations

BACKGROUND

IUI with or without ovarian stimulation (OS) has become a first-line treatment option for many infertile couples, worldwide. The appropriate treatment modality for couples and their clinical management through IUI or IUI/OS cycles must consider maternal and perinatal outcomes, most notably the clinical complication of higher-order multiple pregnancies associated with IUI-OS. With a current global emphasis to continue to decrease maternal and perinatal mortality and morbidity, the World Health Organization (WHO) had established a multi-year project to review the evidence for the establishment of normative guidance for the implementation of IUI as a treatment to address fertility problems, and to consider its cost-effectiveness for lower resource settings.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a review of the evidence of 13 prioritized questions that cover IUI with and without OS. We provide summary recommendations for the development of global, evidence-based guidelines based upon methodology established by the WHO.

SEARCH METHODS

We performed a comprehensive search using question-specific relevant search terms in May 2015. For each PICO (Population, Intervention, Comparison and Outcomes) drafted by WHO, specific search terms were used to find the available evidence in MEDLINE (1950 to May 2015) and The Cochrane Library (until May 2015). After presentation to an expert panel, a further hand search of references in relevant reviews was performed up to January 2017. Articles that were found to be relevant were read and analysed by two investigators and critically appraised using the Cochrane Collaboration's tool for assessing risk of bias, and AMSTAR in case of systematic reviews. The quality of the evidence was assessed using the GRADE system. An independent expert review process of our analysis was conducted in November 2016.

OUTCOMES

This review provides an assessment and synthesis of the evidence that covers 13 clinical questions including the indications for the use of IUI versus expectant management, the sperm parameters required, the best and optimal method of timing and number of inseminations per cycle, prevention strategies to decrease multiple gestational pregnancies, and the cost-effectiveness of IUI versus IVF. We provide an evidence-based formulation of 20 recommendations, as well as two best practice points that address the integration of methods for the prevention of infection in the IUI laboratory. The quality of the evidence ranges from very low to high, with evidence that may be decades old but of high quality, however, we further discuss where critical research gaps in the evidence remain.

WIDER IMPLICATIONS

This review presents an evidence synthesis assessment and includes recommendations that will assist health care providers worldwide with their decision-making when considering IUI treatments, with or without OS, for their patients presenting with fertility problems.

Royal jelly protects male rats from heat stress-induced reproductive failure

Royal jelly (RJ) as an antioxidant has been shown to have attenuated oxidative stress damages in reproductive organs. The objective was carried out the effects of RJ on sperm characteristics, sperm malondialdehyde (MDA) concentration and in vitro fertilisation (IVF) outcome in heat stress (HS) exposed male rats. Forty-eight male rats were randomly divided into eight groups; group 1 received normal saline, group 2 received RJ (100 mg kg^-1  day^-1 ; PO), groups 3, 4 and 5 were heat-stressed (43, 39 and 37°C for 20 min per day respectively) and groups 6, 7 and 8 were heat-stressed along with RJ (43, 39 and 37°C for 20 min per day, respectively, plus RJ at a dose of 100 mg kg^-1  day^-1 ; PO). The HS was induced through immersion of experimental rat scrotums in a water bath. After 48 days, the HS induced remarkable diminish in sperm motility, viability and fertilising potential along with reduced blastulation rate and enhanced sperm chromatin abnormality, MDA levels and DNA damage. Nevertheless, RJ co-administration improved sperm characteristics and early embryo development as well as sperm lipid peroxidation level. Our data suggest that RJ can effectively ameliorate the experimental HS-induced infertility in rats through MDA concentration restoration and sperm characteristics and pre-implantation embryo development improvement.

Oxidative stress in sperm affects the epigenetic reprogramming in early embryonic development

Background

Reactive oxygen species (ROS)-induced oxidative stress is well known to play a major role in male infertility. Sperm are sensitive to ROS damaging effects because as male germ cells form mature sperm they progressively lose the ability to repair DNA damage. However, how oxidative DNA lesions in sperm affect early embryonic development remains elusive.

Results

Using cattle as model, we show that fertilization using sperm exposed to oxidative stress caused a major developmental arrest at the time of embryonic genome activation. The levels of DNA damage response did not directly correlate with the degree of developmental defects. The early cellular response for DNA damage, γH2AX, is already present at high levels in zygotes that progress normally in development and did not significantly increase at the paternal genome containing oxidative DNA lesions. Moreover, XRCC1, a factor implicated in the last step of base excision repair (BER) pathway, was recruited to the damaged paternal genome, indicating that the maternal BER machinery can repair these DNA lesions induced in sperm. Remarkably, the paternal genome with oxidative DNA lesions showed an impairment of zygotic active DNA demethylation, a process that previous studies linked to BER. Quantitative immunofluorescence analysis and ultrasensitive LC–MS-based measurements revealed that oxidative DNA lesions in sperm impair active DNA demethylation at paternal pronuclei, without affecting 5-hydroxymethylcytosine (5hmC), a 5-methylcytosine modification that has been implicated in paternal active DNA demethylation in mouse zygotes. Thus, other 5hmC-independent processes are implicated in active DNA demethylation in bovine embryos. The recruitment of XRCC1 to damaged paternal pronuclei indicates that oxidative DNA lesions drive BER to repair DNA at the expense of DNA demethylation. Finally, this study highlighted striking differences in DNA methylation dynamics between bovine and mouse zygotes that will facilitate the understanding of the dynamics of DNA methylation in early development.

Conclusions

The data demonstrate that oxidative stress in sperm has an impact not only on DNA integrity but also on the dynamics of epigenetic reprogramming, which may harm the paternal genetic and epigenetic contribution to the developing embryo and affect embryo development and embryo quality.

Electronic supplementary material

The online version of this article (10.1186/s13072-018-0224-y) contains supplementary material, which is available to authorized users.

Paternal factors and embryonic development: Role in recurrent pregnancy loss

The events occurring at the maternal-foetal interface define a successful pregnancy but the current paradigm has shifted towards assessing the contribution of spermatozoa for embryogenesis. Spermatozoa with defective DNA integrity may fertilise the oocyte but affect subsequent embryonic development. The present case-control study was conducted in male partners of couples experiencing recurrent pregnancy loss (RPL) to assess the gene expression of spermatozoal FOXG1, SOX3, OGG1, PARP1, RPS6, RBM9, RPS17 and RPL29. This was correlated with reactive oxygen species (ROS) levels and DNA Fragmentation Index (DFI). Semen samples were obtained from 60 cases and 30 fertile controls. Gene expression was done by qPCR analysis, and relative quantification was calculated by the 2^-ΔΔCt method. Chemiluminescence and the sperm chromatin structure assay were used to measure the ROS and DFI levels respectively. FOXG1, OGG1, RPS6 and RBM9 were seen to be upregulated, while SOX3 and PARP1 were downregulated. Relative expression of SOX3, OGG1, RPS6 and RPS17 showed a significant difference between patients and controls (p < 0.05). RPL patients were seen to have high ROS (>27.8; p = 0.001) and DFI (>30.7; p < 0.0001) with respect to controls. Sperm transcript dysregulation and oxidative DNA damage can be "carried over" after implantation, thus affecting embryogenesis and health of the future progeny.

Is sperm DNA fragmentation a useful test that identifies a treatable cause of male infertility?

The present-day laboratory methods of sperm analysis are a poor predictor of reproductive outcome, and for many years it has been clear that newer and better tests are required. Although many such tests have been proposed, only those which determine sperm DNA quality are still being considered. Of these, several tests of sperm DNA fragmentation are available, although there is presently no consensus about the most appropriate test, the best test specimen (fresh or washed sperm) or what level of fragmentation is of clinical concern. Moreover, although several strategies have been proposed to reduce DNA fragmentation, there is no universal approach and few randomised trials have tested these in a clinical context. As such, most professional bodies do not presently support the use of sperm DNA fragmentation tests, and it is clear that large randomised trials are still required to further evaluate their clinical effectiveness.

The male contribution to recurrent pregnancy loss

There are several known causes of recurrent pregnancy loss (RPL) in a couple, which include endocrine abnormalities, immunologic abnormalities, structural uterine abnormalities and karyotype abnormalities. The evaluation largely focuses on the female. The male contribution to RPL remains understudied. With the exception of the karyotype analysis, there is currently no other recommended testing for the male partner of a woman who has suffered multiple pregnancy losses. Chromosomal abnormalities are well defined causes of pregnancy losses in the literature. However, despite the fact that abnormal DNA fragmentation has been implicated in the pathogenesis of unexplained RPL, it is not routinely checked during the evaluation of RPL. This is likely due to the fact that abnormal DNA fragmentation is the end result of multiple different mechanisms including environmental exposures, varicoceles, gene alteration and epigenetic changes resulting in an inherent susceptibility to DNA damage? We are just beginning to scratch the surface of our understanding of the male contribution to RPL and more studies especially focusing on epigenetic modifications and gene alterations are needed.

Analysis on the association between sperm DNA fragmentation index and conventional semen parameters, blood microelements and seminal plasma ROS in male patients with infertility

We conducted this study to analyze the sperm DNA fragmentation index, conventional semen parameters, blood microelements and seminal plasma reactive oxygen species (ROS) in patients with male infertility to determine the association between each of the above male physiological parameters and DNA fragmentation index and infertility. Eighty cases of infertile males and 20 cases of normal males with children were divided into the infertility and control groups, respectively. Sperm DNA fragmentation index, conventional semen parameters, serum microelement content and seminal plasma ROS levels were detected, and the existing correlation between sperm DNA fragmentation index and the various physiological parameters were studied. The sperm DNA fragmentation index had no correlation with conventional sperm parameters. Our results demonstrated that zinc, lead and magnesium ions in the serum microelements were correlated with sperm DNA fragmentation (p<0.05). Upon an increase in zinc and lead serum concentration, there was a subsequent increase in sperm DNA fragmentation (p=0.008). Furthermore, when magnesium ion increased, it also caused an increase in sperm DNA fragmentation (p<0.05). The seminal plasma ROS of infertile males was higher than that of males with children (p<0.05). Our results suggest that sperm DNA fragmentation index is closely associated with the infertility rate and microelements of serum and seminal plasma ROS can impact the formation of sperm DNA fragmentation. Therefore, the sperm DNA fragmentation index can serve as an important parameter to assess male infertility.

Expression of selenium-independent glutathione peroxidase 5 (GPx5) in the epididymis of Small Tail Han sheep

OBJECTIVE

Selenium-independent glutathione peroxidase (GPx5) is specifically expressed in the mammalian epididymis and plays an important role in protecting sperm from reactive oxygen species and lipid peroxidation damage. This study investigates GPx5 expression in the epididymis of Small Tail Han sheep.

METHODS

GPx5 expression was studied in three age groups: lamb (2 to 3 months), young (8 to 10 months), and adult (18 to 24 months). The epididymis of each age group divided into caput, corpus and cauda, respectively. Analysis the expression quantity of GPx5 in epididymis and testis by real-time fluorescent quantitative polymerase chain reaction and Western blot. Finally, GPx5 protein locating in the epididymis by immunohistochemical.

RESULTS

The results demonstrate that in the lamb group, the GPx5 mRNA, but not protein, can be detected. GPx5 mRNA and expressed protein were detected in both the young and adult groups. Moreover, both the mRNA and protein levels of GPx5 were significantly higher in the young group than in other two groups. When the different segments of epididymis were investigated, GPx5 mRNA was expressed in each segment of epididymis regardless of age. Additionally, the mRNA level in the caput was significantly higher than that in corpus and cauda within same age group. The GPx5 protein was in the epithelial cells' cytoplasm. However, GPx5 mRNA and protein were not detected in the testis.

CONCLUSION

These results suggest that GPx5 is mainly expressed in the epididymis of Small Tail Han sheep, and that the expression level of GPx5 is associated with age. Additionally, GPx5 was primarily expressed in the epithelial cells of the caput. Taken together, these studies indicate that GPx5 is expressed in the epididymis in all age grades.

Very low concentration of cerium dioxide nanoparticles induce DNA damage, but no loss of vitality, in human spermatozoa

Cerium dioxide nanoparticles (CeO₂NP) are widely used for industrial purposes, as in diesel, paint, wood stain and as potential therapeutic applications. The Organization for Economic Cooperation and Development included CeO₂NP in the priority list of nanomaterials requiring urgent evaluation. As metal nanoparticles can cross the blood-testis barrier, CeO₂NP could interact with spermatozoa. The genotoxicity of CeO₂NP was demonstrated in vitro on human cell lines and mouse gametes. However, the effects of CeO₂NP on human spermatozoa DNA remain unknown. We showed significant DNA damage induced in vitro by CeO₂NP on human spermatozoa using Comet assay. The genotoxicity was inversely proportional to the concentration (0.01 to 10 mg·L^-1). TEM showed no internalization of CeO₂NP into the spermatozoa. This study shows for the first time that in vitro exposure to very low concentrations of cerium dioxide nanoparticles can induce significant DNA damage in human spermatozoa. These results add new and important insights regarding the reproductive toxicity of priority nanomaterials, which require urgent evaluation.

Role of sperm DNA fragmentation in male factor infertility: A systematic review

OBJECTIVE

To summarise the latest evidence on the role of sperm DNA fragmentation (SDF) in male factor infertility, as SDF has been emerging as a valuable tool for male infertility evaluation.

METHODS

A search of PubMed was conducted using the keywords 'sperm DNA fragmentation' and 'male infertility'. Studies in languages other than English were excluded. All identified studies were screened and clinical studies in humans were included.

RESULTS

In all, 150 articles were included for analysis. Current evidence supports the association between high SDF and poor reproductive outcomes for natural conception and intrauterine insemination. Although the relationship between high SDF and in vitro fertilisation and intracytoplasmic sperm injection is less clear, the negative implication of high SDF on pregnancy loss is evident. Various treatment strategies have been attempted with varying success. The predictive value of SDF testing on outcomes of natural pregnancy and assisted reproduction illustrates its value in clinical practice.

CONCLUSION

The significant role of SDF in male factor infertility is supported by current evidence. The beneficial role of SDF testing in selection of varicocelectomy candidates, evaluation of patients with unexplained infertility and recurrent pregnancy loss, selection of the most appropriate assisted reproductive technique with highest success rate for infertile couples, and assessment of infertile men with modifiable lifestyle factors or gonadotoxin exposure has been recently proposed.

Extender Supplementation with Antioxidants Selected after the Evaluation of Sperm Susceptibility to Oxidative Challenges in Goats

This study aimed to detect the most deleterious ROS for goat sperm and then supplemented the extender with a proper antioxidant. For this, 12 adult goats (aged 1-7) were used. Fresh samples were submitted to challenge with different ROS (superoxide anion, hydrogen peroxide, and hydroxyl radical) and malondialdehyde (MDA-toxic product of lipid peroxidation). After experiment 1, sperms were cryopreserved in extenders supplemented to glutathione peroxidase (Control: 0 UI/mL; GPx1: 1 UI/mL; GPx5: 5 UI/mL, and GPx10: 10 UI/mL) and catalase (Control: 0 UI/mL; CAT60: 60 UI/mL; CAT120: 120 UI/mL, and CAT240: 240 UI/mL). Each sample was evaluated by motility, plasma membrane integrity (eosin/nigrosin), acrosome integrity (fast green/rose bengal), sperm morphology, assay of the sperm chromatin structure, mitochondrial activity (3,3-diaminobenzidine), and measurement of lipid peroxidation (thiobarbituric acid reactive substances [TBARS]). It was possible to observe a mitochondrial dysfunction (DAB-Class IV) and low membrane integrity after hydrogen peroxide action. However, the high rates of TBARS were observed on hydroxyl radical. CAT240 presents the lower percentage of plasma membrane integrity. It was possible to attest that hydrogen peroxide and hydroxyl radical are the more harmful for goat sperm. Antioxidant therapy must be improving perhaps using combination between antioxidants.

Fatherhood and Sperm DNA Damage in Testicular Cancer Patients

Testicular cancer (TC) is one of the most treatable of all malignancies and the management of the quality of life of these patients is increasingly important, especially with regard to their sexuality and fertility. Survivors must overcome anxiety and fears about reduced fertility and possible pregnancy-related risks as well as health effects in offspring. There is thus a growing awareness of the need for reproductive counseling of cancer survivors. Studies found a high level of sperm DNA damage in TC patients in comparison with healthy, fertile controls, but no significant difference between these patients and infertile patients. Sperm DNA alterations due to cancer treatment persist from 2 to 5 years after the end of the treatment and may be influenced by both the type of therapy and the stage of the disease. Population studies reported a slightly reduced overall fertility of TC survivors and a more frequent use of ART than the general population, with a success rate of around 50%. Paternity after a diagnosis of cancer is an important issue and reproductive potential is becoming a major quality of life factor. Sperm chromatin instability associated with genome instability is the most important reproductive side effect related to the malignancy or its treatment. Studies investigating the magnitude of this damage could have a considerable translational importance in the management of cancer patients, as they could identify the time needed for the germ cell line to repair nuclear damage and thus produce gametes with a reduced risk for the offspring.

Update on the proteomics of male infertility: A systematic review

Objective

To assess the role of differentially expressed proteins as a resource for potential biomarker identification of infertility, as male infertility is of rising concern in reproductive medicine and evidence pertaining to its aetiology at a molecular level particularly proteomic as spermatozoa lack transcription and translation. Proteomics is considered as a major field in molecular biology to validate the target proteins in a pathophysiological state. Differential expression analysis of sperm proteins in infertile men and bioinformatics analysis offer information about their involvement in biological pathways.

Materials and methods

Literature search was performed on PubMed, Medline, and Science Direct databases using the keywords ‘sperm proteomics’ and ‘male infertility’. We also reviewed the relevant cross references of retrieved articles and included them in the review process. Articles written in any language other than English were excluded.

Results

Of 575 articles identified, preliminary screening for relevant studies eliminated 293 articles. At the next level of selection, from 282 studies only 80 articles related to male infertility condition met the selection criteria and were included in this review.

Conclusion

In this molecular era, sperm proteomics has created a platform for enhanced understanding of male reproductive physiology as a potential tool for identification of novel protein biomarkers related to sperm function in infertile men. Therefore, it is believed that proteomic biomarkers can overcome the gaps in information from conventional semen analysis that are of limited clinical utility.

Nitric oxide, malondialdheyde and non-enzymatic antioxidants assessed in viable spermatozoa from selected infertile men

There are growing evidences that the semen of infertile male population shows higher reactive oxygen species (ROS) levels concomitant with lower antioxidant capacity compared to those detected in semen of fertile population. The plasma membrane of the sperm cell, which has high levels of polyunsaturated fatty acids, renders it particularly sensitive to ROS. The aim of this study was to compare the sperm parameters (concentration, motility, morphology and vitality) and the levels of malondialdehyde (MDA), as marker of lipid peroxidation (LPO), nitric oxide (NO), ascorbic acid (AA), total (GSHt) and oxidized glutathione (GSSG) in viable sperm in a group of 38 infertile patients and in a group of 55 control subjects with unknown reproductive potential. The comparison between variables in infertile patients and controls revealed that the sperm quality was reduced in the infertile group, whereas the levels of NO, AA and GSH were significantly increased in viable spermatozoa from infertile men; however, the endogenous levels of MDA were similar in infertile and control groups. Based on our results, we could speculate that the rise of GSHt and AA levels in viable sperm of infertile group help partially to counteract the damaging effect of ROS and partly prevent a substantial LPO. The observation of the concomitant increase of NO and antioxidant indices in viable spermatozoa of infertile subjects is a novel finding and we think that these results can be useful since the viable sperm population is conceivably used in assisted reproductive technology.

Reactive oxygen species as mediators of sperm capacitation and pathological damage

Oxidative stress plays a major role in the life and death of mammalian spermatozoa. These gametes are professional generators of reactive oxygen species (ROS), which appear to derive from three potential sources: sperm mitochondria, cytosolic L-amino acid oxidases, and plasma membrane Nicotinamide adenine dinucleotide phosphate oxidases. The oxidative stress created via these sources appears to play a significant role in driving the physiological changes associated with sperm capacitation through the stimulation of a cyclic adenosine monophosphate/Protein kinase A phosphorylation cascade, including the activation of Extracellular signal regulated kinase-like proteins, massive up-regulation of tyrosine phosphorylation in the sperm tail, as well as the induction of sterol oxidation. When generated in excess, however, ROS can induce lipid peroxidation that, in turn, disrupts membrane characteristics that are critical for the maintenance of sperm function, including the capacity to fertilize an egg. Furthermore, the lipid aldehydes generated as a consequence of lipid peroxidation bind to proteins in the mitochondrial electron transport chain, triggering yet more ROS generation in a self-perpetuating cycle. The high levels of oxidative stress created as a result of this process ultimately damage the DNA in the sperm nucleus; indeed, DNA damage in the male germ line appears to be predominantly induced oxidatively, reflecting the vulnerability of these cells to such stress. Extensive evaluation of antioxidants that protect the spermatozoa against oxidative stress while permitting the normal reduction-oxidation regulation of sperm capacitation is therefore currently being undertaken, and has already proven efficacious in animal models.