Sperm DNA integrity assessment in prediction of assisted reproduction technology outcome

Sperm chromatin structure assay as an independent predictor of fertility in vivo: a case-control study

Standard sperm parameters have a limited power for prediction of the chance of natural conception. Recent studies have indicated that the sperm chromatin structure assay (SCSA) DNA fragmentation index (DFI), a measure for the fraction of sperms with DNA damage, is associated with fertility in vivo. The aim of this study was to evaluate the value of this parameter for prediction of infertility. One hundred and twenty-seven men from infertile couples with no known female factor and 137 men with proven fertility were included. Semen analysis was performed as recommended by the WHO. DFI was assessed using SCSA. Logistic binary regression was used to compute the odds ratios (OR) for infertility. As compared with men with a DFI <10%, men with a DFI between 10% and 20% had an increased risk for infertility (OR 2.5, 95% CI: 1.0-6.1). This was also true for men with a DFI >20% (OR 8.4; 95% CI: 3.0-23). In men with normal standard semen parameters (sperm concentration, motility and morphology) the OR for infertility was increased with DFI >20% (OR 5.1, 95% CI: 1.2-23), whereas if one of the standard semen parameters was abnormal, the OR for infertility was increased already at DFI above 10% (OR 16, 95% CI: 4.2-60). We conclude that SCSA DFI adds to the value of semen analysis in prediction of the chance of natural conception.

Sperm DNA fragmentation: mechanisms of origin, impact on reproductive outcome, and analysis

OBJECTIVE

To review the mechanisms responsible for DNA fragmentation in human sperm, including those occurring during spermatogenesis and transport through the reproductive tract. The mechanisms examined include: apoptosis in the seminiferous tubule epithelium, defects in chromatin remodeling during the process of spermiogenesis, oxygen radical-induced DNA damage during sperm migration from the seminiferous tubules to the epididymis, the activation of sperm caspases and endonucleases, damage induced by chemotherapy and radiotherapy, and the effect of environmental toxicants. The different tests currently used for sperm DNA fragmentation analysis and the factors that determine the predictive value of sperm DNA fragmentation testing and their implications in the diagnosis and treatment of infertility are also discussed. Finally, we also scrutinize how the presence in the embryonic genome of DNA strand breaks or modifications of DNA nucleotides inherited from the paternal genome could impact the embryo and offspring. In particular we discuss how abnormal sperm could be dealt with by the oocyte and how sperm DNA abnormalities, which have not been satisfactorily repaired by the oocyte after fertilization, may interfere with normal embryo and fetal development.

CONCLUSION(S)

Sperm DNA can be modified through various mechanisms. The integrity of the paternal genome is therefore of paramount importance in the initiation and maintenance of a viable pregnancy both in a natural conception and in assisted reproduction. The need to diagnose sperm at a nuclear level is an area that needs further understanding so that we can improve treatment of the infertile couple.

Genetic polymorphisms influence the susceptibility of men to sperm DNA damage associated with exposure to air pollution

The purpose of the present study was to investigate the impact of carcinogenic polycyclic aromatic hydrocarbons and volatile organic compounds on sperm quality in a group of city policemen in Prague during a period of increased concentrations of ambient air-pollutants (winter season) compared to a period of low exposure (spring). Polymorphisms in metabolic genes (CYP1A1, EPHX1, GSTM1, GSTP1, GSTT1), folic acid metabolism genes (MTR, MTHFR) and DNA repair genes (XRCC1, XPD6, XPD23, hOGG1) were evaluated in these men as potential modifiers of associations between air pollution exposure and changes in sperm quality. The study population was a group of 47 policemen working in the center of the city. Seasonal differences in exposure were verified by ambient and personal monitoring. Markers of sperm injury included semen volume, sperm concentration, sperm morphology, sperm motility, and sperm DNA damage measured with the sperm chromatin structure assay The sperm chromatin structure assay (SCSA) includes a measure of DNA damage called DNA Fragmentation Index (DFI). The % of cells with detectable DFI (detDFI) by this assay includes sperm with either medium or high DNA damage; the term hDFI is used to define the % of sperm with only high DNA damage. The assay also detects immature sperm defined by high density staining (HDS). No significant differences were found in any of the standard semen parameters between the sampling periods except for vitality of sperms. Both DFI and HDS were significantly higher in winter than in spring samples for all men and for non-smokers. At the bivariate level, significant associations between hDFI or detDFI and polymorphisms of the repair genes XRCC1, XPD6 and XPD23 were observed. In multivariate models, polymorphisms of the genes XPD6, XPD23 and CYP1A1MspI were associated with hDFI and HDS. Moreover, HDS was significantly associated with polymorphisms in GSTM1 gene.

Sperm DNA damage in male infertility: etiologies, assays, and outcomes

Male factor infertility is the sole cause of infertility in approximately 20% of infertile couples, with an additional 30% to 40% secondary to both male and female factors. Current means of evaluation of male factor infertility remains routine semen analysis including seminal volume, pH, sperm concentration, motility, and morphology. However, approximately 15% of patients with male factor infertility have a normal semen analysis and a definitive diagnosis of male infertility often cannot be made as a result of routine semen analysis. Attention has focused on the role of sperm nuclear DNA integrity in male factor infertility. Here we review the structure of human sperm chromatin, the etiology and mechanisms of sperm DNA damage, current tests available to assess sperm DNA integrity, and effect of sperm DNA integrity on reproductive outcomes.

Sperm chromatin structure is associated with the quality of spermatogenesis in infertile patients

OBJECTIVE

To establish the diagnostic value of sperm chromatin structure assessment for the evaluation of male factor infertility, in addition to conventional andrological workup.

DESIGN

Cross-sectional controlled study.

SETTING

A tertiary referral andrology clinic.

PATIENT(S)

Two hundred seventy-nine male partners of infertile couples.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The DNA fragmentation index (DFI) determined by the sperm chromatin structure assay (SCSA), semen parameters, serum levels of reproductive hormones, and World Health Organization (WHO) classification of male factor subfertility.

RESULT(S)

In all patient categories, except those including patients with hypogonadotrophic hypogonadism, sperm antibodies, or normospermia, DFI was significantly higher compared with in proven fertile controls. After classification of the quality of spermatogenesis based on mean testicular volume (<10 ml vs. >15 ml), follicle stimulating hormone (FSH; > 10 U/L vs. <5 U/L), and inhibin-B (<100 nmol/L vs. >150 nmol/L), the DFI was significantly higher in patients with poor spermatogenesis (35.9%) than in patients with normal spermatogenesis (25.9%). In a multiple regression analysis, the teratozoospermia index, sperm vitality, and FSH were significant determinants of the DFI level. Male age was associated with DFI, but leukocytospermia, body mass index, and smoking were not confounders of DFI.

CONCLUSION(S)

Impaired spermatogenesis, irrespective of the WHO classification of male factor subfertility, is generally associated with an increase of sperm DNA damage.

Advances in the management of male infertility

Male infertility can be treated by surgical procedures (e.g., varicocelectomy) or by administration of drugs if causal factors (e.g., seminal tract infections) are detected. In more severe cases, methods of assisted fertilization often have to be applied, but even these have only a limited success rate. Recent studies have demonstrated that disturbances of sperm DNA integrity (determined by the acridine orange test) can explain certain cases of fertilization failure and failure to achieve pregnancy following in vitro fertilisation with intracytoplasmic sperm injection. The evaluation of DNA integrity should be considered when diagnosing male infertility as it has been shown to be an independent factor and can be used as a supplement to standard semen analysis. Analysis of DNA integrity may, therefore, provide further information about altered male fertility and lead to administration of more appropriate therapy.

Potential biological role of poly (ADP-ribose) polymerase (PARP) in male gametes

Maintaining the integrity of sperm DNA is vital to reproduction and male fertility. Sperm contain a number of molecules and pathways for the repair of base excision, base mismatches and DNA strand breaks. The presence of Poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme, and its homologues has recently been shown in male germ cells, specifically during stage VII of spermatogenesis. High PARP expression has been reported in mature spermatozoa and in proven fertile men. Whenever there are strand breaks in sperm DNA due to oxidative stress, chromatin remodeling or cell death, PARP is activated. However, the cleavage of PARP by caspase-3 inactivates it and inhibits PARP's DNA-repairing abilities. Therefore, cleaved PARP (cPARP) may be considered a marker of apoptosis. The presence of higher levels of cPARP in sperm of infertile men adds a new proof for the correlation between apoptosis and male infertility. This review describes the possible biological significance of PARP in mammalian cells with the focus on male reproduction. The review elaborates on the role played by PARP during spermatogenesis, sperm maturation in ejaculated spermatozoa and the potential role of PARP as new marker of sperm damage. PARP could provide new strategies to preserve fertility in cancer patients subjected to genotoxic stresses and may be a key to better male reproductive health.

Semen molecular and cellular features: these parameters can reliably predict subsequent ART outcome in a goat model

Currently, the assessment of sperm function in a raw or processed semen sample is not able to reliably predict sperm ability to withstand freezing and thawing procedures and in vivo fertility and/or assisted reproductive biotechnologies (ART) outcome. The aim of the present study was to investigate which parameters among a battery of analyses could predict subsequent spermatozoa in vitro fertilization ability and hence blastocyst output in a goat model. Ejaculates were obtained by artificial vagina from 3 adult goats (Capra hircus) aged 2 years (A, B and C). In order to assess the predictive value of viability, computer assisted sperm analyzer (CASA) motility parameters and ATP intracellular concentration before and after thawing and of DNA integrity after thawing on subsequent embryo output after an in vitro fertility test, a logistic regression analysis was used. Individual differences in semen parameters were evident for semen viability after thawing and DNA integrity. Results of IVF test showed that spermatozoa collected from A and B lead to higher cleavage rates (0 < 0.01) and blastocysts output (p < 0.05) compared with C. Logistic regression analysis model explained a deviance of 72% (p < 0.0001), directly related with the mean percentage of rapid spermatozoa in fresh semen (p < 0.01), semen viability after thawing (p < 0.01), and with two of the three comet parameters considered, i.e tail DNA percentage and comet length (p < 0.0001). DNA integrity alone had a high predictive value on IVF outcome with frozen/thawed semen (deviance explained: 57%). The model proposed here represents one of the many possible ways to explain differences found in embryo output following IVF with different semen donors and may represent a useful tool to select the most suitable donors for semen cryopreservation.

Single semen analysis as a predictor of semen quality: clinical and epidemiological implications

It is generally thought that a single ejaculate is a bad predictor of semen quality of a subject, because of significant intra-individual variation. Therefore, we investigated the degree to which the results of a first semen analysis differ from that of a second analysis among men from a general population in Norway. In addition, we analysed how the two different semen results mirrored the overall semen quality assessment. A total of 199 volunteers participated in the study and delivered two semen samples with an interval of 6 months. The semen parameters were determined according to the World Health Organization (WHO) 1999 guidelines, which were also used to determine whether semen quality was normal or abnormal. In addition, the DNA fragmentation index (DFI) was determined using the Sperm Chromatin Structure Assay. The two samples from each individual were very similar with regard to standard semen parameters and DFI (r(s:) 0.67-0.72), and there were no significant systematic differences between the two samples. The result of the first sample (normal/abnormal) was highly predictive of the overall conclusion based on the two samples (sperm concentration: in 93% of the cases (95% confidence interval [CI]: 89%-96%); sperm motility: in 85% of the cases (95% CI: 79%-89%); overall semen quality: in 85% of the cases (95% CI: 80%-90%). In epidemiological studies, one ejaculate is a sufficient indicator of semen quality in a group of subjects. In a clinical situation, when the question is whether the semen quality is normal or not, the first ejaculate will, in at least 85% of cases, give a correct overall conclusion.

Sperm DNA damage: correlation to severity of semen abnormalities

OBJECTIVES

To analyze the relationship between DNA damage and standard semen parameters (SSP) in patients who present for fertility evaluation. Evaluation of male fertility includes assessment of the SSP and increasingly sperm DNA damage. However, the relationship between DNA damage and SSP remains controversial.

METHODS

Following Institutional Research Ethics Board approval, semen samples from 2586 unselected nonazoospermic patients were subjected to computer-assisted semen analysis and flow cytometry-based sperm DNA damage assessment expressed as the DNA fragmentation index.

RESULTS

Sperm DNA damage was significantly negatively correlated to sperm SSP (concentration, motility, and normal morphology) and positively correlated to patient's age. DNA damage increased in association with the number of abnormalities in SSP. Patients with oligoasthenoteratozoospermia had significantly higher DNA damage and more frequent DNA damage over 30% compared with normozoospermic patients and patients with abnormalities in 1 or 2 SSP.

CONCLUSIONS

Our results indicate that DNA damage is significantly correlated to SSP as well as age. In addition, the degree of DNA damage increases with the number of abnormal parameters in a sample and is most severe in patients with oligoasthenoteratozoospermia. Complex and possibly age-related mechanisms of DNA damage in human spermatozoa may be responsible for the strong relationship between SSP and DNA fragmentation index.

Antioxidants and sperm DNA damage: a clinical perspective

PURPOSE

Infertile men possess substantially more sperm DNA damage than do fertile men, damage that may impact negatively on reproductive outcomes. In this era of assisted reproductive technologies there is mounting concern regarding the safety of utilizing DNA-damaged spermatozoa in this setting. Therefore, it is important to identify strategies that may reduce sperm DNA damage. The purpose of this review is to discuss the rationale for antioxidant therapy in men with sperm DNA damage and to evaluate the data on the efficacy of dietary and in vitro antioxidant preparations on sperm DNA damage.

METHODS

We reviewed the literature on antioxidants and sperm DNA damage.

RESULTS

To date, the data suggest that dietary antioxidants may be beneficial in reducing sperm DNA damage, particularly, in men with high levels of DNA fragmentation. However, the mechanism of action of dietary antioxidants has not been established and most of the clinical studies are small. A beneficial effect of in vitro antioxidant supplements in protecting sperm DNA from exogenous oxidants has been demonstrated, however, the effect of these antioxidants in protecting sperm from endogenous ROS, gentle sperm processing and cryopreservation has not been established.

Cause-specific treatment in patients with high sperm DNA damage resulted in significant DNA improvement

Assessment of sperm DNA damage has been suggested as a negative predictor of fertility potential. Multiple pathological factors acting at both the intra-testicular and post-testicular levels may contribute to sperm DNA damage. The relative contribution of each of these factors in an individual with high DNA damage (>30%) is unclear. The management of patients with elevated DNA damage is also challenging. The purpose of our retrospective study was to evaluate the clinical course of patients with sperm DNA damage over 30% and to assess the effect of non-specific (oral antioxidant) and cause-specific treatments on the quality of their sperm DNA. Results of our retrospective study suggest that the evaluated group with high DNA damage was diagnostically heterogeneous and comprised patients with varicoceles, bacteriospermia and idiopathic infertility. A three month course of antioxidant therapy reduced sperm DNA damage in only 30/61 (49%) patients with significant improvement between the initial and post-treatment DNA Fragmentation Index (DFI) results (46.8%+/-14.1 vs. 36.7%+/-16.6, p < .001). The positive effect of antioxidants could be age-dependent, as patients older that 40 years of age showed no improvement after such treatment. The cause-specific treatments showed superior results compared to antioxidants alone. Improvement was observed in 7/9 (78%) of patients after surgical varicocele repair between the initial and post-treatment DFI results (44.7%+/-12.8 vs. 28.4%+/-9.5, p < .03). The majority of the patients 13/14 (93%) with bacteriospermia had improvement in sperm DFI results after antibiotic treatment (50.4%+/-19.1 vs. 38.6%+/-18.7, p < .001).

Fertile bull sperm aneuploidy and chromatin integrity in relationship to fertility

Aneuploidy is associated with spontaneous abortions, perinatal mortality, mental retardation and with embryonic and foetal mortality. Most of these abnormalities originate as a result of meiosis errors during gametogenesis. The main purpose of the study was to analyse frequency of aneuploidies of sex chromosomes and chromosome 6 by three-colour fluorescence in situ hybridization (FISH) in 47 young bulls, candidates for artificial insemination programme with cryopreserved semen and to investigate the influence of aneuploidies and disturbed sperm chromatin integrity on non-return rates, the frequencies of abortions, perinatal mortality and stillbirths. The average frequencies of spermatozoa with disomy for chromosomes X, Y, XY and 6 were 0.032, 0.005, 0.003 and 0.039% respectively. The incidence of XX66, YY66 and XY66 diploidy was 0.017, 0.006 and 0.015% respectively. Frequencies of meiotic II errors were significantly higher than meiotic I errors (p < 0.01). More X bearing spermatozoa than Y bearing spermatozoa were detected (5151 vs. 5022; p < 0.01). Sperm chromatin damage expressed by DNA fragmentation index (DFI) was 5.3 +/- 3.7 and percentage of cells with defective chromatin condensation (HDS) was 1.4 +/- 0.8. No correlation was found between sperm aneuploidy and basic sperm analysis. The relationship was found between non-return rate and total aneuploidy (r = -0.310; p = 0.036). Significant correlation was found between sex disomy, total aneuploidy (disomy of chromosomes 6, X, Y and XY spermatozoa and diploidy) and stillbirths (r = 0.390; p = 0.013; and r = 0.331; p = 0.037). Chromosome 6 disomy correlated with perinatal mortality (r = 0.317; p = 0.047). HDS correlated significantly with total aneuploidy (r = 0.449; p = 0.002). Our study indicated that aneuploidy frequencies in young fertile bull spermatozoa are relatively low. Nevertheless, there exists a variability in aneuploidy frequencies amongst bulls, which appears to be able to have an influence on the fertility of these animals.

Differential sensitivity of male germ cells to mainstream and sidestream tobacco smoke in the mouse

Cigarette smoking in men has been associated with increased chromosomal abnormalities in sperm and with increased risks for spontaneous abortions, birth defects and neonatal death. Little is known, however, about the reproductive consequences of paternal exposure to second-hand smoke. We used a mouse model to investigate the effects of paternal exposure to sidestream (SS) smoke, the main constituent of second-hand smoke, on the genetic integrity and function of sperm, and to determine whether male germ cells were equally sensitive to mainstream (MS) and SS smoke. A series of sperm DNA quality and reproductive endpoints were investigated after exposing male mice for two weeks to MS or SS smoke. Our results indicated that: (i) only SS smoke significantly affected sperm motility; (ii) only MS smoke induced DNA strand breaks in sperm; (iii) both MS and SS smoke increased sperm chromatin structure abnormalities; and (iv) MS smoke affected both fertilization and the rate of early embryonic development, while SS smoke affected fertilization only. These results show that MS and SS smoke have differential effects on the genetic integrity and function of sperm and provide further evidence that male exposure to second-hand smoke, as well as direct cigarette smoke, may diminish a couple's chance for a successful pregnancy and the birth of a healthy baby.

Sperm chromatin integrity in young men with no experiences of infertility and men from idiopathic infertility couples

Damage to the genetic component of spermatozoa seems to play the main role in a majority of cases where current approaches fail to reveal the specific cause of male infertility. In this study, we compared semen quality in men assigned to two defined groups: men from couples with unexplained infertility - idiopathic infertility (A) and young men with no experiences of infertility (B). All samples were examined by standard ejaculate analysis and sperm chromatin structure assay (SCSA). Sperm chromatin damage was significantly higher in men from group A than in those from group B. Similar results were obtained by comparison of men from group A (all men were normozoospermic) with normozoospermic men from group B. According to these results, we can suppose that chromatin disorders may be the causal factor of subfertility or infertility in some of these men. No evidence for a strong association between chromatin disorders and standard parameters of ejaculates was found. We failed to confirm a relationship between smoking and sperm quality in men from any of the investigated groups. SCSA is a method that facilitates the identification of infertile men who otherwise show normal semen variables.

Correlation between DNA damage and sperm parameters: a prospective study of 1,633 patients

OBJECTIVE

To investigate DNA fragmentation by using terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling in relation to World Health Organization parameters and computer-aided sperm analysis (CASA) in sperm to determine the possibility of obtaining a correlation among CASA parameters, sperm morphology, and DNA fragmentation.

DESIGN

Sperm analysis according to World Health Organization parameters, terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) for sperm DNA fragmentation, and CASA for sperm movement. Prospective study.

SETTING

All the patients were under clinical management, consulting for hypofertility at a fertility center in France.

PATIENT(S)

One thousand six hundred thirty-three men who were referred for infertility investigation, including a complete sperm analysis.

INTERVENTION(S)

Sperm analysis and DNA damage testing.

MAIN OUTCOME MEASURE(S)

Sperm morphology, DNA fragmentation, and movement characteristics.

RESULT(S)

One third of the patients had a TUNEL rate of >30%. Analysis of the 21 semen parameters tested revealed that 7 of them were significantly correlated with the TUNEL results.

CONCLUSION(S)

World Health Organization sperm parameters and DNA damage are complementary, rather than strongly linked. This should be considered to more fully understand the paternal contribution in assisted reproductive technologies failures.

Testicular spermatozoa have statistically significantly lower DNA damage compared with ejaculated spermatozoa in patients with unsuccessful oral antioxidant treatment

OBJECTIVE

To compare DNA damage in ejaculated and testicular spermatozoa in patients with previously unsuccessful oral antioxidant treatment.

DESIGN

Prospective clinical study.

SETTING

University-affiliated teaching hospital.

PATIENT(S)

Twelve men with persistently high sperm DNA damage.

INTERVENTION(S)

Evaluation of DNA damage of ejaculated and testicular spermatozoa by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay.

MAIN OUTCOME MEASURE(S)

The DNA damage of ejaculated spermatozoa compared with that of testicular spermatozoa, both samples collected on the day of intracytoplasmic sperm injection.

RESULT(S)

Ejaculated spermatozoa showed a threefold higher DNA damage when compared with testicular samples (39.7% +/- 14.8 vs. 13.3% +/- 7.3).

CONCLUSION(S)

Our results indicated that in patients with previously unsuccessful oral antioxidant treatment the retrieved testicular spermatozoa had a lower degree of DNA damage compared with ejaculated sperm collected on the same day.

Effect of maternal and paternal age on pregnancy and miscarriage rates after intrauterine insemination

More than 17,000 intrauterine insemination (lUI) cycles were analysed retrospectively with respect to outcome according to differing aetiologies of infertility. The quantity and motility of spermatozoa in the final preparation used for insemination had a positive effect on the outcome, as classically observed in the past. It was found that advanced maternal age had a negative effect on the pregnancy rate and was associated with increased miscarriage rate. More interestingly, an exactly parallel effect was found for paternal age. The impact of increased age on necrospermia and sperm DNA structure is discussed as a probable direct cause of this paternal effect.

Sperm chromatin: fertile grounds for proteomic discovery of clinical tools

Sperm are remarkably complex cells with a singularly important mission: to deliver paternal DNA and its associated factors to the oocyte to start a new life. The integrity of sperm DNA is a keystone of reproductive success, which includes fertilization and embryonic development. In addition, the significance in these processes of proteins that associate with sperm DNA is increasingly being appreciated. In this review, we highlight proteomic studies that have identified sperm chromatin proteins with fertility roles that have been validated by molecular studies in model organisms or correlations in the clinic. Up to 50% of male-factor infertility cases in the clinic have no known cause and therefore no direct treatment. In-depth study of the molecular basis of infertility has great potential to inform the development of sensitive diagnostic tools and effective therapies that will address this incongruity. Because sperm rely on testis-specific protein isoforms and post-translational modifications for their development and function, sperm-specific processes are ideal for proteomic explorations that can bridge the research lab and fertility clinic.

Predicting fertility

Various predictors of fertility have been described, suggesting that none are ideal. The literature on tests of ovarian reserve is largely limited to women undergoing in vitro fertilization, and is reliant on the use of surrogate markers, such as cycle cancellation and number of oocytes retrieved, as reference standards. Currently available prediction models are far from ideal; most are applicable only to subfertile women seeking assisted reproduction, and lack external validation. Systematic reviews and meta-analyses of predictors of fertility are limited by their heterogeneity in terms of the population sampled, predictors tested and reference standards used. There is an urgent need for consensus in the design of these studies, definition of abnormal tests, and, above all, a need to use robust outcomes such as live birth as the reference standard. There are no reliable predictors of fertility that can guide women as to how long childbearing can be deferred.

Sperm DNA damage in men from infertile couples

AIM

To investigate the prevalence of high levels of sperm DNA damage among men from infertile couples with both normal and abnormal standard semen parameters.

METHODS

A total of 350 men from infertile couples were assessed. Standard semen analysis and sperm chromatin structure assay (SCSA) were carried out.

RESULTS

Ninety-seven men (28% of the whole study group) had a DNA fragmentation index (DFI)> 20%, and 43 men (12%) had a DFI>30%. In the group of men with abnormal semen parameters (n = 224), 35% had a DFI>20%, and 16% had a DFI>30%, whereas these numbers were 15% and 5%, respectively, in the group of men with normal semen parameters (n=126). Men with low sperm motility and abnormal morphology had significantly higher odds ratios (ORs) for having a DFI>20% (4.0 for motility and 1.9 for morphology) and DFI>30% (6.2 for motility and 2.8 for morphology) compared with men with normal sperm motility and morphology.

CONCLUSION

In almost one-third of unselected men from infertile couples, the DFI exceeded the level of 20% above which, according to previous studies, the in vivo fertility is reduced. A significant proportion of men with otherwise normal semen parameters also had high sperm DNA damage levels. Thus, the SCSA test could add to explaining causes of infertility in cases where semen analysis has not shown any deviation from the norm. We also recommend running the SCSA test to choose the appropriate assisted reproductive technique (ART).

[Could apoptotic markers help the exploration of male infertility?]

Apoptosis is a cell death program involved in different steps of spermatogenesis, first at puberty, at the beginning of spermatogenesis, then in adult testicles by controlling normal spermatogenesis. As a result, apoptosis deregulation can affect spermatogenesis. Many studies have provided evidence that apoptosis deregulation in germinal cells resulted in male infertility. In addition, apoptosis detection in ejaculated spermatozoa arouses a growing interest in research as a reliable marker of spermatozoon quality. The aim of this review is to summarize our knowledge on physiological apoptosis during spermatogenesis, and then analyse the possibility of using apoptotic markers as selective markers of spermatozoon quality to optimize the rate of success of in vitro fertilization.

Modern andrology: from semen analysis to postgenomic studies of the male gametes

A male factor is implicated in about 50% of couples treated with advanced assisted reproductive techniques (in vitro fertilization [IVF] or intracytoplasmic sperm injection [ICSI]). An important function of spermatozoa is to deliver the paternal genome to the oocyte. However, neither the routine testing of male fertility potential, nor its treatment, addresses the specific mechanisms by which spermatozoal factors may impact reproductive outcome. Recently, a number of screening tests for DNA integrity have been proposed to assess sperm chromatin abnormalities. These include nonspecific DNA strand breaks, numerical abnormalities in spermatozoal chromosome content, and alterations in the epigenetic regulation of the paternal genome. This minireview discusses methods to assess the influence of the paternal genome on reproduction beyond that which can be appreciated by simple quantitative and morphologic evaluation of spermatozoa. Finally, new data on how to select the "best fit" sperm for ICSI will be presented.

[Which technique is best for which male infertility?]

To what extent are sperm analyses valid? Does a normality benchmark exist? Analysis of the literature suggests that the normal values for semen parameters defined by the WHO may require reassessment. Other criteria should perhaps be taken into account, such as chromatin or DNA abnormalities. The existing studies are contradictory and the DNA fragmentation rate is not used by the ASRM as a predictor of the pregnancy rate. Several teams have attempted to suggest threshold values for semen parameters, both in cases of intrauterine insemination and ICSI. In the case of IUI, the results are highly variable depending on the study in question. As for ICSI, although there is some consensus of opinion in the data, other findings are controversial or debatable. However, there are few properly conducted randomised prospective studies and very few multivariate analyses.

Data analysis of two in vivo fertility studies using Sperm Chromatin Structure Assay-derived DNA fragmentation index vs. pregnancy outcome

The 2006 American Society for Reproductive Medicine Compendium of Practice Report found no significant effects of elevated sperm DNA fragmentation by using a 30% DNA fragmentation index (DFI) threshold for natural fertilization and SCSA data (odds ratio, 1.07; 95% confidence interval, 0.39-2.93). In contrast, it is shown in this article that these two in vivo studies showed significant odds ratios of 6.54 (95% confidence interval, 1.71, 24.91) and 7.58 (95% confidence interval, 2.54, 22.67), which resulted in the conclusion that the pregnancy (PG) rates are statistically significantly higher for the group with DFI below the thresholds of 30% and 40%, respectively. In addition, all the chi(2) statistics used to test the null hypotheses of no association between the pregnancy status and DFI for natural (normal) fertilization confirmed this conclusion that the probability of pregnancy for the group with <30% or <40% DFI was statistically significantly higher than that for the group with >30% or >40% DFI.

GSTM1 genotype influences the susceptibility of men to sperm DNA damage associated with exposure to air pollution

Previous studies have provided evidence for an association between exposure to high levels of air pollution and increased DNA damage in human sperm. In these studies DNA damage was measured using the sperm chromatin structure assay (SCSA) wherein the percentage of sperm with abnormal chromatin/fragmented DNA is determined and expressed as % DNA fragmentation index (%DFI). Here we extend these observations to address the following hypothesis: men who are homozygous null for glutathione-S-transferase M1 (GSTM1-) are less able to detoxify reactive metabolites of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) found in air pollution. Consequently they are more susceptible to the effects of air pollution on sperm chromatin. Using a longitudinal study design in which men provided semen samples during periods of both low (baseline) and episodically high air pollution, this study revealed a statistically significant association between GSTM1 null genotype and increased SCSA-defined %DFI (beta=0.309; 95% CI: 0.129, 0.489). Furthermore, GSTM1 null men also showed higher %DFI in response to exposure to intermittent air pollution (beta=0.487; 95% CI: 0.243, 0.731). This study thus provides novel evidence for a gene-environment interaction between GSTM1 and air pollution (presumably c-PAHs). The significance of the findings in this study with respect to fertility status is unknown. However, it is biologically plausible that increases in %DFI induced by such exposures could impact the risk of male sub/infertility, especially in men who naturally exhibit high levels of %DFI.

Spermatozoal sensitive biomarkers to defective protaminosis and fragmented DNA

Human sperm DNA damage may have adverse effects on reproductive outcome. Infertile men possess substantially more spermatozoa with damaged DNA compared to fertile donors. Although the extent of this abnormality is closely related to sperm function, the underlying etiology of ensuing male infertility is still largely controversial. Both intra-testicular and post-testicular events have been postulated and different mechanisms have been proposed to explain the presence of damaged DNA in human spermatozoa. Three among them, i.e. abnormal chromatin packaging, oxidative stress and apoptosis, are the most studied and discussed in the present review. Furthermore, results from numerous investigations are presented, including our own findings on these pathological conditions, as well as the techniques applied for their evaluation. The crucial points of each methodology on the successful detection of DNA damage and their validity on the appraisal of infertile patients are also discussed. Along with the conventional parameters examined in the standard semen analysis, evaluation of damaged sperm DNA seems to complement the investigation of factors affecting male fertility and may prove an efficient diagnostic tool in the prediction of pregnancy outcome.