Sperm chromatin structure assay: its clinical use for detecting sperm DNA fragmentation in male infertility and comparisons with other techniques

Sperm DNA damage assessment: a test whose time has come

Multiple techniques have been developed to measure the amount of sperm DNA damage in an effort to identify more objective parameters for evaluation of infertile men. We now have evidence to support that integrity of sperm DNA influences a couple's fertility and helps predict the chances of pregnancy and its successful outcome. The available tests of sperm DNA damage require additional large-scale clinical trials before their integration into routine clinical practice.

Lonidamine transiently affects spermatogenesis in pubertal CD1 mice

Lonidamine (LND) [1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid], a well-known antispermatogenic drug, was studied for the first time in pubertal mice to assess its possible effects on spermatogenesis. Male CD1 mice were orally treated on Postnatal Day (PND) 28 with a single dose of LND (100 mg/kg body weight) and sacrificed on PND30, PND42, PND74 and PND123. On PND30 (48 h after dosing), severe testicular effects were evidenced in the treated animals: (a) reduction of the testicular sperm head concentration (approximately 50% of the control value); (b) changes in the spermatogenic cell type distribution (mild decrease of the elongated spermatids and S-phase cells fractions); and (c) morphological alterations of the Sertoli cell cytoplasm and germ cell exfoliation. These changes were recovered in adulthood, on PND74 and PND123. However, no effect on sperm chromatin structure was detected on the epididymal sperm of mature mice by sperm chromatin structure assay, suggesting that LND did not interfere with the process of chromatin reorganization and DNA packaging.

Episodic air pollution is associated with increased DNA fragmentation in human sperm without other changes in semen quality

BACKGROUND

This study examined potential associations between exposure to episodes of air pollution and alterations in semen quality. The air pollution, resulting from combustion of coal for industry and home heating in the Teplice district of the Czech Republic, was much higher during the winter than at other times of year with peaks exceeding US air quality standards.

METHODS

Young men from Teplice were sampled up to seven times over 2 years allowing evaluation of semen quality after periods of exposure to both low and high air pollution. Routine semen analysis (sperm concentration, motility and morphology) and tests for sperm aneuploidy and chromatin integrity were performed, comparing measurements within each subject. Exposure was classified as high or low based on data from ambient air pollution monitoring.

RESULTS

Using repeated measures analysis, a significant association was found between exposure to periods of high air pollution (at or above the upper limit of US air quality standards) and the percentage of sperm with DNA fragmentation according to sperm chromatin structure assay (SCSA). Other semen measures were not associated with air pollution.

CONCLUSION

Exposure to intermittent air pollution may result in sperm DNA damage and thereby increase the rates of male-mediated infertility, miscarriage, and other adverse reproductive outcomes.

A carbohydrate-antioxidant hybrid polymer reduces oxidative damage in spermatozoa and enhances fertility

Gamete-gamete interactions are critically modulated by carbohydrate-protein interactions that rely on the carbohydrate-selective recognition of polyvalent carbohydrate structures. A galactose-binding protein has been identified in mammalian spermatozoa that has similarity to the well-characterized hepatic asialoglycoprotein receptor. With the aim of exploiting the ability of this class of proteins to bind and internalize macromolecules displaying galactose, we designed hybrid carbohydrate-antioxidant polymers to deliver antioxidant vitamin E (alpha-tocopherol) to porcine spermatozoa. Treatment of sperm cells with one hybrid polymer in particular produced large increases in intracellular sperm levels of alpha-tocopherol and greatly reduced endogenous fatty acid degradation under oxidative stress. The polymer-treated spermatozoa had enhanced physiological properties and longer half-lives, which resulted in enhanced fertilization rates. Our results indicate that hybrid polymer delivery systems can prolong the functional viability of mammalian spermatozoa and improve fertility rates, and that our functionally guided optimization strategy can be applied to the discovery of active glycoconjugate ligands.

Infection du tractus génital masculin : le point de vue du bactériologiste

Male genital tract infection and inflammation have been associated to 8 to 35% of male infertility cases in various studies. Their investigation is part of a multi-disciplinary process including new techniques as DNA integrity study. Bacterial seminal infection can cause transient or chronic persistent inflammation, and the microbiological investigations, as well as leukospermia, secretory chlamydial IgA and inflammatory cytokines help to approach the responsibility of inflammation in infertility or pathological condition, leading to antibiotic and anti-inflammatory treatment. In Assisted Reproductive Techniques (ART), bacteriospermia must be eradicated for a safe semen preparation to inseminate or to fertilize oocytes. Leukocytes cannot be completely eliminated by sperm preparation and the presence of antibiotics and antioxydants in the culture media is questionned.

La fragmentation de l'ADN du spermatozoïde : impact en Assistance médicale à la procréation

We have used the sperm chromatin structure assay (SCSA) test in order to determine if correlations can be found between sperm DNA fragmentation and spermogram parameters. Only necrospermia and DNA fragmentation index are strongly correlated (P<0.0001). Neither fertilization rates for ICSI and IVF, nor blastocyst formation rates are impaired by a high DFI. However when the critical DFI>30% is reached, the chances of having ongoing pregnancies after blastocyst transfer are reduced by three. Treatments with antioxidants are of limited efficacy even though we obtained 2 deliveries after DFI treatments with such treatments. New strategies in order to improve the pregnancy rates for these peculiar cases of reduced fertility are discussed.

Sperm DNA fragmentation: threshold value in male fertility

BACKGROUND

The extent of sperm DNA fragmentation, which can be measured by the TUNEL assay, is one of the determinants of male fertility. However, the clinical application of this test to in-vivo situations is difficult owing to the absence of a statistically validated threshold value.

METHODS

The aim of this study was to compare the results of TUNEL assay applied to semen samples from men of proven fertility (n = 47) and patients from an infertile population (n = 66), in order to establish a discriminating threshold value.

RESULTS

Infertile patients had a higher mean level of DNA fragmentation than men of proven fertility (40.9 +/- 14.3% versus 13.1 +/- 7.3%, respectively; P < 0.001). The area under the receiver operating characteristics curve was 0.93 for 20% sperm DNA fragmentation. The calculated threshold value for TUNEL assay to distinguish between fertile controls and infertile men was 20%. At this threshold, specificity was 89.4 [95% confidence interval (CI) 83.7-95.1] and sensitivity was 96.9% (95% CI 93.8-100). The positive and negative predictive values of the 20% sperm DNA fragmentation threshold were high: 92.8% (95% CI 87.9-97.5) and 95.5% (95% CI 91.6-99.3), respectively.

CONCLUSION

This study demonstrates that sperm DNA fragmentation, as measured by TUNEL assay, is a highly valuable indicator of male fertility.

On the Nature and Origin of DNA Strand Breaks in Elongating Spermatids1

Transient DNA strand breaks are generated in the whole population of elongating spermatids and are perfectly coincident with histone H4 hyperacetylation at chromatin-remodeling steps. Given the limited DNA repair capacity of elongating spermatids, chromatin remodeling may present a threat to genetic integrity of the male gamete. The nature of the DNA strand breakage, the enzymes involved, and the role of H4 hyperacetylation in the process must be determined to further investigate the potential mutagenic consequences of this important transition. We used the metachromatic dye acridine orange in combination with fluorescence-activated cell sorting to achieve separation of spermatids according to their condensation state. Using single-cell electrophoresis (comet assay), in both alkaline and neutral conditions, we demonstrated that double-stranded breaks account for most of the DNA fragmentation observed in purified elongating spermatids. DNA strand breaks were generated in round spermatids as a result of de novo histone hyperacetylation induced by trichostatin A, whereas an increase in endogenous DNA strand breaks was observed in elongating spermatids. Using a short-term culture of testicular cells, we demonstrated that DNA strand breaks in spermatids were abolished on incubation with two functionally different topoisomerase II inhibitors. Hence, topoisomerase II appears as the unique enzyme responsible for the transient double-stranded breaks in elongating spermatids but depends on histone hyperacetylation for its activity.

A new method to analyze boar sperm DNA fragmentation under bright-field or fluorescence microscopy

We present a new, rapid and simple method to study DNA Fragmentation Index (DFI) in sperm samples from boar under bright-field and fluorescence microscopy. Discrimination of sperm cells containing fragmented DNA relies on the extreme peripheral diffusion of their chromatin fragments, whereas those sperm nuclei without DNA fragmentation do not disperse or show very restricted spreading of DNA loops close to the flagellum. The basic methodology provided in the commercial kit Sperm-Sus-Halomax allows, in addition to a direct estimation of DFI in a sperm sample under bright field microscopy, a direct visualization of DNA breaks by incorporation of labelled nucleotides using the DNA polymerase I following the in situ nick translation assay (ISNT methodology not provided in the kit). An external control using DBD-FISH (DNA breakage detection-fluorescence in situ hybridization) on human and boar sperm samples was used in this experiment. The results obtained show (i) low levels of background DNA fragmentation (from 0.7 to 10%), (ii) no significant differences for DFI after the application of Sperm-Sus-Halomax and ISNT, with a tendency to be underestimated after using DBD-FISH and (iii) a characteristic chromatin organization in boar sperm nucleus, with a particular response to chromatin loop relaxation and preferential DNA labelling by ISNT at the proximal nuclear area, close to the flagellum. This methodology allows the routine assessment of boar sperm samples for DFI, as well as basic and clinical research on this relevant topic in any laboratory of semen analysis.

Assessment of the in vivo genotoxicity of vanadate: Analysis of micronuclei and DNA damage induced in mice by oral exposure

Vanadium compounds are able to interact with living cells exerting a variety of biological effects. The pentavalent form is the most stable and toxic form of the element. In systems in vitro pentavalent vanadium is an effective genotoxic agent, inducing DNA damage and chromosome malsegregation at low doses. On the other hand, no adequate in vivo data are available for the characterization of the genotoxic hazard following oral intake, the most relevant route of human exposure. In this study, the genotoxic effects produced by the oral intake of sodium ortho-vanadate (Na(3)VO(4)) were investigated. Male CD-1 mice were treated for 5 weeks with a range of concentrations of Na(3)VO(4) in drinking water (0.75-1500 mg/l). Both micronuclei and primary DNA lesions as detected by comet assay were assessed in several tissues. Statistically significant increases of micronuclei in bone marrow were observed in mice receiving the two highest concentrations of Na(3)VO(4) (750 and 1500 mg/l). A significant increase of comet tail length was observed in splenocytes of mice receiving Na(3)VO(4) at 1500 mg/l, whereas no effect was observed in bone marrow and testis cells. No treatment-related effect on sperm chromatin structure or on testis cell population was observed. The determination of vanadium content in mouse tissues at the end of treatment highlighted a very low internal exposure, especially in soft tissues. Overall, the results obtained indicate that the genotoxic activity of pentavalent vanadium is expressed in vivo only following high dose exposure, possibly as a consequence of the poor bioavailability of the element.

Increasing storage time of extended boar semen reduces sperm DNA integrity

There is an extensive use of artificial insemination (AI) in the pig industry. Extended liquid boar semen may be used for insemination for up to 5 days after collection. The objective of this study was to determine the changes in sperm quality, when boar semen was extended and stored at 18 degrees C for up to 72 h post-collection. The study included three ejaculates from five boars, for each of the four breeds: Duroc, Hampshire, Landrace and Danish Large White (n=60 ejaculates). The sperm chromatin structure assay (SCSA) showed an increase in DNA fragmentation index (DFI) after 72 h of incubation (P<0.001), with no differences between breeds (P=0.07). For two Hampshire boars, all ejaculates had a large increase in DFI after 24 h of incubation. The standard deviation of DFI (SD-DFI) differed between breeds, with the SD-DFI for Hampshire being significantly greater than for the other breeds. The SD-DFI did not change during the 72 h of storage. Sperm viability was determined using SYBR-14 and propidium iodide in combination with flow cytometry. The sperm viability did not differ between breeds (P=0.21), but a difference in viability during storage (P<0.001) was detected. In conclusion, the SCSA cytogram patterns were consistent for different ejaculates within boars and storage of extended boar semen at 18 degrees C for 72 h significantly decreased the integrity of sperm DNA.

ICSI in cases of sperm DNA damage: beneficial effect of oral antioxidant treatment

BACKGROUND

Most studies examining the use of ICSI for cases of elevated sperm DNA fragmentation report poor pregnancy and implantation rates. ICSI with testicular sperm samples has recently been suggested for these cases. Here we test a less invasive approach based on oral antioxidant treatment prior to ICSI with ejaculated spermatozoa.

METHODS

Thirty-eight men with an elevated (> or =15%) percentage of DNA-fragmented spermatozoa in the ejaculate were treated with antioxidants (1 g vitamin C and 1 g vitamin E daily) for 2 months after one failed ICSI attempt. In 29 (76%) of these cases this treatment led to a decrease in the percentage of DNA-fragmented spermatozoa, and a second ICSI attempt was performed. Outcomes of the two attempts were compared.

RESULTS

No differences in fertilization and cleavage rates or in embryo morphology were found between the ICSI attempts performed before and after the antioxidant treatment. However, a marked improvement of clinical pregnancy (48.2% versus 6.9%) and implantation (19.6% versus 2.2%) rates was observed after the antioxidant treatment as compared with the pretreatment ICSI outcomes.

CONCLUSIONS

Oral antioxidant treatment appears to improve ICSI outcomes in those patiens with sperm DNA damage, in whom this treatment reduces the percentage of damaged spermatozoa.

The significance of sperm nuclear DNA strand breaks on reproductive outcome

PURPOSE OF REVIEW

A growing body of evidence indicates that ejaculated spermatozoa from men being treated with intracytoplasmic sperm injection contain nuclear abnormalities. Many of these nuclear anomalies manifest themselves as breaks in the sperm nuclear DNA. This review examines the mechanisms involved in generating DNA strand breaks during spermatogenesis in the human, the main techniques used to assess the sperm nucleus and the evidence, in relation to assisted reproduction, showing that sperm nuclear DNA strand breaks may impact on reproductive outcome.

RECENT FINDINGS

Techniques such as the TUNEL assay and the sperm chromatin structure assay both show increased levels of DNA abnormalities in spermatozoa from men who have poor semen parameters. The reproductive parameters affected by an increased presence of DNA abnormalities in ejaculated spermatozoa include fertilization, blastocyst development, and pregnancy rates.

SUMMARY

There is accumulating evidence linking sperm nuclear DNA anomalies to poor reproductive outcome in relation to assisted reproduction technologies. The tests currently available only provide an inkling of the impact of sperm nuclear DNA abnormalities on reproductive outcomes. Although the impact an abnormal paternal genome may have on reproductive outcome is unquestionably less than that of its female counterpart, it cannot be ignored.

DNA damage to spermatozoa has impacts on fertilization and pregnancy

DNA damage in the male germ line has been associated with poor semen quality, low fertilization rates, impaired preimplantation development, increased abortion and an elevated incidence of disease in the offspring, including childhood cancer. The causes of this DNA damage are still uncertain but the major candidates are oxidative stress and aberrant apoptosis. The weight of evidence currently favours the former and, in keeping with this conclusion, positive results have been reported for antioxidant therapy both in vivo and in vitro. Resolving the causes of DNA damage in the male germ line will be essential if we are to prevent the generation of genetically damaged human embryos, particularly in the context of assisted conception therapy.

Effects of PCB99 and PCB153 exposure on spermatogenesis in young adult C57BL6 mice

This study examined the effects of acute exposure to PCB99 (2,2',4,4',5-pentachlorobiphenyl), and PCB153 (2,2',4,4'5,5'-hexachlorobiphenyl), on spermatogenesis in 8-week-old C57BL6 mice. The mice were randomly allocated to PCB99 and PCB153 and a single dose of respectively 10 and 100 mg/kg was given by oral gavage. During the 6-week experiment, six mice per treatment group were sacrificed weekly, body weights were recorded and samples with respect to the male reproductive system were collected until further analysis. None of the treatments, showed changes in body weight or reproductive endpoints. Flow cytometric analysis revealed spermatogenesis to be unaffected. However, PCB99 and PCB153 showed a significant increase in Leydig cell apoptosis. The results from the present study indicate that the male reproductive system is relatively refractory to PCB99 and PCB153 at levels exceeding those of wildlife and humans, when exposed during adult life. However, the finding of apoptotic Leydig cells merits further investigation.

DNA integrity in sexed bull sperm assessed by neutral Comet assay and sperm chromatin structure assay

During the production of sex-sorted spermatozoa from bull semen, the cells are exposed to a number of potential hazards including: dilution, centrifugation, incubation, exposure to DNA stains and laser light. These factors may affect the survival capacity and fertilization potential of the sperm. The objective of this study was to determine whether sex-sorted bull spermatozoa have more DNA damage than sperm from conventional processed bull semen. Two methods were used to determine DNA integrity: the neutral Comet assay (NCA) and the sperm chromatin structure assay (SCSA). The NCA showed that the conventional samples had a higher tail moment (TM) (P < 0.017) than the sorted samples and that there was no difference between the samples in tail length (TL) (P = 0.36). The SCSA showed that the DNA fragmentation index (DFI) was higher for conventional than the sorted samples (P = 0.011), but the standard deviation of DFI (SD-DFI) was higher for the sorted samples (P < 0.001). We conclude that the NCA and SCSA can be used in assessing DNA integrity in bovine sperm and that cell sorting by flow cytometry improves the integrity of the sperm cell population. Additionally the results from the SCSA indicated that the sex-sorted sperm had less homogenous sperm chromatin. In the future assessment of sperm DNA integrity may be used to select bulls for sperm sex sorting and optimizing sperm sex sorting procedures.

Impact of a mild scrotal heat stress on DNA integrity in murine spermatozoa

An increase in scrotal temperature can lead to the production of poor quality spermatozoa and infertility. In the present study we have used mice to examine the impact of mild, scrotal heat stress (42 °C for 30 min) on numbers of spermatozoa as well as on the integrity of their DNA. Spermatozoa recovered from the epididymides hours (1 to 24) or days (7 to 32) after treatment were analysed using COMET and sperm chromatin structure (SCSA) assays. The treatment induced a stress response in both the testis and the epididymis that was associated with reduced expression of the cold inducible RNA binding protein (Cirp) and an increase in germ cell apoptosis (Apotag positive cells). Although spermatozoa present in the epididymis at the time of heating contained correctly packaged DNA, its integrity was compromised by heat stress. In addition, although some germ cells, which were present within the testis at the time of heat stress, were removed by apoptosis, many germ cells completed their development and were recovered as motile spermatozoa with damaged DNA. In conclusion, these data demonstrate that scrotal heat stress can compromise the DNA integrity of spermatozoa and this may have clinical implications for patients undergoing IVF and intra-cytoplasmic sperm injection (ICSI).

Intégrité de l'ADN des spermatozoïdes comme élément diagnostique et pronostique de la fertilité masculine

Recent progress in reproductive biology has improved comprehension physiology of the spermatozoa and on the fertilization mechanisms. This new knowledge has carried out the elaboration of tests on male fertility based on sperm genomic integrity. This review presents some of these techniques and brings a reflexion element on the application and use of sperm DNA integrity in the investigation of male fertility. The single cell gel electrophoresis (COMET assay), Sperm Chromatin Structure Assay (SCSA), In Situ Nick Translation (NT: Nick Translation) and Terminal Uridine Nick-End Labelling (TUNEL assay) are actually the most currently used techniques for the measure of sperm DNA integrity in research clinic. From a certain point of view, TUNEL assay, SCSA, COMET assay and NT assay are complementary. The TUNEL and COMET can measure single and double strand breaks of DNA, the SCSA can detect the abnormalities in the chromatin compaction and the NT assay can detect the single strand breaks of DNA. The exact origin of sperm DNA fragmentation is not established yet. However, several mechanisms have been proposed: defect in the chromatin compaction during spermiogenesis; reactive oxygen species production by immature spermatozoa; apoptosis during spermatogenesis. It becomes important to consider the possible consequences of the oocyte fertilization by a spermatozoon having a high degree of DNA fragmentation. The use in routine of some of these tests must however pass by a standardization of the inter laboratory protocols and obviously, by the establishment of both in vivo and in vitro discriminating threshold values in order for these tests to present a good predictive value for pregnancy outcome.

Effect of an abnormal sperm chromatin structural assay (SCSA) on pregnancy outcome following (IVF) with ICSI in previous IVF failures

A high DNA fragmentation index (DFI) when performing the sperm chromatin structural (SCSA) assay was claimed to be so specific for male subfertility that even IVF and ICSI did not result in live pregnancies. The present study was designed to corroborate or refute these findings. The SCSA test was performed on the male partner from couples failing to have a successful pregnancy despite at least 2 previous IVF attempts. In contrast to the aforementioned studies, ongoing pregnancies were found despite working with a group of recalcitrant patients. Nevertheless, a high DFI score was associated with a trend for lower ongoing pregnancy rates especially related to a high miscarriage rate. Other more recent studies seem to support our conclusions. A high DFI score should influence a patient to choose IVF as a therapeutic modality sooner, especially with ICSI.

Exposure to PCBs and p,p'-DDE and human sperm chromatin integrity

Persistent organochlorine pollutants (POPs) such as polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (p,p'-DDE), the major metabolite of dichlorodiphenyltrichloroethane (DDT), are stable lipophilic compounds widely found in the environment and in the general population. They can enter the food chain, and their negative impact on male reproduction is currently under active scrutiny. To explore the hypothesis that environmental exposure to these compounds is associated with altered sperm chromatin structure integrity in human sperm, we conducted a study of 176 Swedish fishermen (with low and high consumption of fatty fish, a very important exposure source of POPs). We determined serum levels of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and p,p'-DDE, and we used the sperm chromatin structure assay (SCSA) to assess sperm DNA/chromatin integrity. When CB-153 serum levels (individual dose range, 39-1,460 ng/g lipid) were categorized into equally sized quintiles, we found an association with the DNA fragmentation index (%DFI). A significantly lower %DFI was found in the lowest CB-153 quintile (< 113 ng/g lipid) compared with the other quintiles; there was a similar tendency, although not statistically significant, between %DFI and p,p'-DDE. These results suggest that POP exposure may have a slight negative impact on human sperm chromatin integrity.

Sperm survival and heterogeneity are correlated with fertility after intrauterine insemination in superovulated ewes

Efficient animal production involves accurate estimations of fertilizing ability. One key factor is the plasma membrane of the sperm cell, which is actively involved in the cascade of events before oocyte fusion. Many methods are used to analyze the characteristics of this membrane, including partition in aqueous two-phase systems which is an efficient method to analyze sperm surface changes accounting for loss of viability and different functional states. Centrifugal countercurrent distribution (CCCD) analysis can also be used in an aqueous two-phase system to determine the relationship between sperm parameters and in vivo fertility in ewes. In a previous work, we found a significant correlation between two post-CCCD parameters (heterogeneity and recovered viability) and field fertility when the same sample was used after cervical AI. The present study was intended to find out whether the control of several external factors that affect reproductive efficiency is able to increase the correlation coefficient between post-CCCD parameters and fertility. Thus, 90 Rasa aragonesa ewes were controlled on the same farm and received intrauterine inseminations using the same technical equipment. The fertilizing ability of the raw semen and sperm samples selected by a dextran/swim-up process was compared using a low number of spermatozoa per insemination (7 x 10(7)) to enhance possible fertility differences. A new post-CCCD parameter was considered; the loss of viability (LV) occurred during the CCCD process. This variable denotes the sperm surviving ability and corresponds to the difference between the total number of viable cells loaded and recovered after the CCCD run. The mean fertility of eight sperm control samples was 60% (range: 25-76%), and there was no significant correlation between standard parameters and in vivo fertility. LV ranged from 2 to 69% (average 27%) and was negatively correlated with fertility (r = -0.914, P < 0.01). Ejaculate heterogeneity (H) ranged from 20 to 47% and was positively, but not significantly, correlated with fertility (r = 0.391). A predictive equation for fertility was deduced by multiple analysis with a very high correlation coefficient (r = 0.967), and level of significance (P < 0.005): predictive fertility PF = 52.546 - 0.594 LV + 0.665 H. The mean fertility of 13 swim-up selected samples was 63% (range: 25-86%). Again, only parameters derived from the CCCD analysis were highly correlated with fertility, especially LV and H (P < 0.05).

Clinical Laboratory Evaluation of Male Subfertility

Male subfertility is a common problem with a complex etiology, requiring a complete andrological work-up for proper diagnosis. The male reproductive tract is controlled by a well-balanced hormonal system, in which hypothalamic (GnRH), pituitary (LH, FSH) and testicular hormones (androgens, inhibin B) participate. Any disturbance of this hormonal system may therefore lead to testicular dysfunction and interfere with the spermatogenesis process. In addition, also other components along the ductal system, such as epididymis, prostate and seminal vesicles, that improve sperm fertility by contributing their secretions to the semen, might function inadequately and thus fail to enhance the fertilizing capacity of the sperm cells. External factors (heat, chemicals, life style) and anatomical abnormalities (varicocele) were shown to have a negative influence on male fertility. In a number of patients genetic defects can be identified as the cause of their infertility. Laboratory tests are available to assess hormone concentrations, semen composition, accessory gland function and sperm cell function. Conventional semen analysis includes the determination of sperm concentration, semen volume, sperm motility (qualitative and quantitative), sperm morphology, sperm cell vitality, pH, leucocytes and antibodies. The usefulness of the determination of these parameters as predictor of fertility appears to be rather limited, however. Therefore, alternative tests, some based on more functional aspects (sperm penetration, capacitation, acrosome reaction), have been developed. Furthermore, there is an increasing attention for the assessment of DNA integrity, for instance by the flowcytometer-based Sperm Chromation Structure Assay (SCSA), as an additional or alternative parameter of sperm quality. It is likely and desirable that further assays with better predictive value are being developed in the near future.

Effect of sperm DNA damage and sperm protamine deficiency on fertilization and embryo development post-ICSI

The aim of this study was to evaluate the effect of sperm DNA damage and protamine deficiency on fertilization and embryo development post-intracytoplasmic sperm injection (ICSI), and also to assess the effect of protamine deficiency on DNA damage. Semen samples were collected from 28 patients participating in the ICSI programme. Following sperm preparation and ICSI, the remaining processed semen samples were used to assess protamine deficiency and DNA damage employing chromomycin A3 (CMA3) staining and comet assay, respectively. Comet parameters, CMA3 percentage positivity, fertilization rate, embryo cleavage score and embryo quality score were assessed. Except for CMA3, none of the comet parameters showed significant correlation with fertilization rate. However, among comet parameters, head area and head intensity showed positive correlation with the embryo cleavage score, while comet mean intensity and head mean intensity showed a significant negative correlation with CMA3 positivity. Results of this study demonstrate that DNA fragmentation is more frequent in protamine-deficient spermatozoa. Unlike protamine deficiency, sperm DNA fragmentation does not preclude fertilization. Nonetheless, embryos derived from spermatozoa with high DNA damage have a lower potential to reach blastocyst stage.

[Genomic instability and male infertility]

Knowledge of the human genome has opened the genomic era. The genome instability, its causes and the possible consequences especially about fertility start to be understood. This instability can be observed on chromosome structure but also on genes. Different chromosomes rearrangements involved in infertility including translocations and Y chromosome deletions are described. The Y chromosome is a model of instability, and this instability is the source of its evolution. All those rearrangements are the results of illegitimate recombinations between homologous sequences. On genes we find punctual and dynamic mutations, polymorphisms and epigenetic abnormalities. They all are the results of ADN replication mistakes not corrected by the cellular machine. This machinery is the guardian of the genome integrity and in case of abnormality the programmed cellular death is induced. The knowledge of all these instability mechanisms is essential to appreciate the risk for the offspring after intracytoplasmic sperm injection. Indeed we go round physiological barriers without a complete understanding of the mechanisms involved. Thus, this is an important challenge for research teams but also for all assisted reproduction centers, dealing with ART. Genome is unstable - the very basis of its evolution. But this is also the cause of mistakes with pathological consequences like infertility and mental retardation.

Reduced senescence and retained nuclear DNA integrity in human spermatozoa prepared by density gradient centrifugation

PURPOSE

To investigate whether removal of extraneous cells and immotile spermatozoa from a sperm preparation by density gradient centrifugation could help to maintain normal spermatozoa in a viable state and retain their deoxyribonucleic acid integrity.

METHODS

Sperm motility was assessed on a daily basis in aliquots of neat semen, extended semen, and spermatozoa prepared on a PureSperm density gradient. At the same time, aliquots of each sperm sample were preserved for TUNEL assay and nick translation.

RESULTS

Spermatozoa prepared using density gradient centrifugation survived three times as long as spermatozoa in neat semen or in extended semen. Both deoxyribonucleic acid integrity and sperm motility were retained in the gradient preparations.

CONCLUSIONS

Preparing spermatozoa by density gradient centrifugation is advantageous in prolonging sperm survival and maintaining deoxyribonucleic acid integrity, presumably by removing sources of reactive oxygen species. Stored spermatozoa could be used for a second attempt at fertilization if oocyte immaturity was suspected.

Should cryopreserved epididymal or testicular sperm be recovered from obstructive azoospermic men for ICSI?

OBJECTIVE

To determine the effect of the anatomical site of sperm recovery on intracytoplasmic sperm injection (ICSI) embryo implantation, pregnancy and live birth rates in couples with isolated obstructive azoospermia as the sole cause of infertility.

DESIGN

Controlled, single centre, retrospective clinical study.

SETTING

University Hospital, Centre for Reproductive Medicine.

SAMPLE

One hundred and fifty-one cycles of ICSI were performed, using surgically recovered sperm, between August 1996 and March 2002.

METHODS

The outcome of ICSI, with surgically recovered sperm, was compared between epididymal (Group E) and testicular (Group T) derived sperm. Inclusion was limited to couples undergoing their first treatment cycle, where female age was < or =39 years and a minimum of five oocytes were available for injection. Women with a history of ovarian surgery, ultrasonic evidence of polycystic ovaries, uterine anomalies or hydrosalpinx were excluded.

MAIN OUTCOME MEASURES

Clinical pregnancy, implantation and live birth rate.

RESULTS

Forty-two of 151 cycles met the strict inclusion criteria. Groups E and T were comparable with respect to age, basal serum FSH, ovarian response; number of oocytes injected and number of embryos available and transferred. No difference existed between Groups E and T in implantation, clinical pregnancy or live birth rate (28.8% vs 25.8%, 42.9% vs 42.9% and 39.3% vs 42.9%, respectively).

CONCLUSIONS

Cryopreserved epididymal and testicular sperm, from men with obstructive azoospermia, appear equally effective in ICSI. Epididymal recovery should remain the method of first choice for obstructive azoospermic men but further study of sperm DNA damage rates in different testicular sites is required.

Comparison between the toluidine blue stain and the Feulgen reaction for evaluation of rabbit sperm chromatin condensation and their relationship with sperm morphology

Sperm chromatin alteration is an important feature that can affect fertility of the male rabbit. This study compared toluidine blue staining with Feulgen reaction (as methods for evaluating chromatin alteration) and investigated the relationship between sperm morphology and chromatin alteration. Seven hundred rabbit ejaculates of animals with unknown fertility were used. Primary and secondary morphological sperm abnormalities were evaluated in semen smears with phase-contrast microscopy. Chromatin alterations were evaluated in semen smears stained with toluidine blue (pH 4.0 and 5.0) and with the Feulgen reaction. While the three methods were equally efficacious for identification of chromatin alterations, toluidine blue staining was more appropriate to characterize the intensity of chromatin alterations. The correlation between primary sperm defects and chromatin alteration was high and positive, suggesting that sperm chromatin structure affected sperm head morphology. The correlation between secondary sperm defects and chromatin alteration was also positive, but lower. The final chromatin compaction occurs in the epididymus, where secondary sperm defects originate. Therefore, the causes of secondary sperm defects could also intervene with final chromatin compaction. In summary, the toluidine blue stain was an effective means of evaluating the sperm chromatin alteration in rabbit spermatozoa.

Evaluation of chromatin integrity in human sperm using acridine orange staining with different fixatives and after cryopreservation

Staining of cells with acridine orange (AO) has been widely accepted as a predictor of DNA damage in many cell types. Because of variability of protocols used in previous studies, the AO staining technique has not been widely accepted as a screening test to predict DNA damage in human sperm. In order to further validate the use of AO staining, sperm were evaluated using numerous variations in the staining protocol. This study also elucidated the effects of cryopreservation on sperm DNA. Sperm fixation in Carnoy's solution showed significantly (P < 0.05) more DNA damage (29.9 +/- 4.5%) than 2% glutaraldehyde (14.4 +/- 2.1%), 4% paraformaldehyde (5.5 +/- 1.7%), no fixation (15.8 +/- 4.3%) but did not differ from Diff Quik solution (19.2 +/- 5.8%). No difference was observed for sperm DNA damage assessment using a 0.2 m (15.5 +/- 3.2%) or 0.3 m (14.9 +/- 3.3%) concentration of Na(2)HPO(4).7H(2)O in the AO staining solution. Frozen-thawed semen samples showed increased damage to sperm DNA under both Carnoy's (fresh: 10.9 +/- 1.3%; frozen: 30.8 +/- 2.9%; P < 0.05) and Diff Quik fixation (fresh: 6.2 +/- 0.8; frozen: 17.1 +/- 2.5%P < 0.05). Present data also showed that spermatozoa from some individuals are more prone to DNA damage after freezing and thawing procedures than others. In conclusion, Carnoy's fixative provides a better predictive value for DNA damage to sperm using AO staining. Additionally, cryopreservation increased damage to the sperm DNA.

Extent of nuclear DNA damage in ejaculated spermatozoa impacts on blastocyst development after in vitro fertilization

OBJECTIVE

To determine whether the extent of ongoing apoptotic cell death measured as the presence of DNA strand breaks in spermatozoa affects embryo development to the blastocyst stage in IVF.

DESIGN

A prospective comparative study.

SETTING

A university IVF clinic and a private IVF clinic.

PATIENT(S)

Men (n = 49) undergoing infertility treatment with IVF.

INTERVENTION(S)

After density gradient centrifugation preparation, part of the sperm sample was used for infertility treatment, and the rest was fixed in paraformaldehyde. Strand breaks in DNA that are indicative of apoptosis were detected by the in situ DNA nick end labeling (TUNEL) technique. A total of 15,000 spermatozoa from each sample were evaluated for TUNEL reactivity by flow cytometry.

MAIN OUTCOME MEASURE(S)

Percentage of ejaculated spermatozoa with DNA strand breaks indicative of apoptosis, blastocyst development rate, and pregnancy rate.

RESULT(S)

Blastocyst development showed a significant negative correlation with percentage TUNEL positivity in spermatozoa. When 20% was used as a cutoff for TUNEL positivity in sperm samples, the percentage of blastocyst development was 50% higher in the <20% TUNEL-positivity group (n = 27) compared with those with >/=20% TUNEL positivity (n = 22; 44.7% blastocyst development vs. 29.8%). Clinical pregnancy rates in these two groups were 52% vs. 44%, respectively.

CONCLUSION(S)

The extent of nuclear DNA fragmentation in prepared ejaculated spermatozoa used in IVF negatively correlates with blastocyst development. A larger series of patients needs to be assessed to determine whether this paternal effect on blastocyst development may also affect pregnancy outcome.

Toluidine blue cytometry test for sperm DNA conformation: comparison with the flow cytometric sperm chromatin structure and TUNEL assays

BACKGROUND

Sperm DNA integrity (SDI) is an important factor in the prognosis of male fertility. Here we compare the toluidine blue (TB) image cytometry test, recently proposed by us for SDI assessment, with two other tests-the sperm chromatin structure assay (SCSA) and the terminal nick-end labelling (TUNEL) assay.

METHODS

Sperm samples from 35 men were evaluated for standard sperm parameters and subjected to the TB test and SCSA. Eighteen of the 35 samples were also subjected to the TUNEL assay.

RESULTS

The proportion of sperm cells with abnormal DNA integrity assayed by the TB test correlated strongly with the proportion of abnormal cells detected by the SCSA and TUNEL assay (rho=-0.84 and rho=0.80, P<0.001, respectively). Furthermore, the fractions of abnormal cells by the TB test corresponded closely to the sum of two SCSA parameters, the DNA fragmentation index (DFI) and the fraction of highly DNA-stainable cells (HDS) (medians 33.0 versus 32.0%, P=0.6).

CONCLUSIONS

Abnormal cells in a TB test correspond to the sum of DFI and HDS fractions in the SCSA. TB-positive cells may represent sperm with fragmented DNA and/or abnormal chromatin structure. Because the TB test is an easy and inexpensive method, its potential use as a routine test for sperm DNA integrity, complementary to standard semen parameters, should be investigated further.

Semen analysis in laboratory practice: an overview of routine tests

Semen analysis is a basic step in the investigation of several disturbances affecting the male genital tract. Analysis of seminal parameters provides important clinical information on the spermatogenesis and functional competence of spermatozoa, as well as on the secretory pattern of the accessory genital glands. Semen analysis is particularly useful in the evaluation of couples requiring fertility investigation (to detect genital infections and pathologies) and in verifying the influence of environmental factors, drugs, lifestyle, chemical products, and professional activities on several diseases affecting male reproductive health. Measure of semen quality is of substantial interest for diagnoses in clinical urology, andrology, and gynecology. Currently, basic requirements for semen analysis are standardized by World Health Organization (WHO) guidelines that describe several procedures for an objective evaluation of the semen quality with diagnostic purposes. These guidelines include: parameters for the physical and biochemical evaluation of semen; parameters for the analysis of sperm characteristics; and other seminal parameters that can be easily adopted in any laboratory. This report summarizes current concepts on semen analysis and the significance of the seminal parameters for reaching a diagnosis based on the procedures recommended by WHO guidelines.

Influence of the abstinence period on human sperm quality

OBJECTIVE

To determine the influence of ejaculatory abstinence on within-subject semen parameters and DNA fragmentation.

DESIGN

Prospective study.

SETTING

Private infertility institute and university-based research laboratory.

PATIENT(S)

Sixteen consenting male volunteers undergoing infertility investigation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Within-subject analysis of World Health Organization semen parameters and sperm DNA fragmentation and chromatin packaging after 1, 3, 5, and 8 days' abstinence.

RESULT(S)

Of 16 men recruited, data for 11 men were included for statistical analysis because 5 men did not strictly comply with abstinence criteria. Duration of abstinence had a statistically significant positive influence on sperm concentration and semen volume. Abstinence had no statistically significant influence on pH, viability, total and grade A motility, or morphology. The percentage of DNA fragmentation remained unchanged relative to abstinence. The percentage of sperm with immature chromatin was statistically significantly increased with 1 day of abstinence.

CONCLUSION(S)

This is the first study to report on within-subject semen parameter, DNA fragmentation, and chromatin packaging variations after specified target days of abstinence. Sperm numbers and semen volume increased with duration of abstinence. Abstinence did not influence pH, viability, morphology, total or grade A motility, or sperm DNA fragmentation. A short (24-hour) abstinence period negatively influenced chromatin quality.

Sperm chromatin structure assay (SCSA) parameters are related to fertilization, blastocyst development, and ongoing pregnancy in in vitro fertilization and intracytoplasmic sperm injection cycles

OBJECTIVE

To determine the relationship between sperm chromatin structure assay (SCSA) parameters (DNA fragmentation index [DFI] and high DNA stainability [HDS]), and conventional IVF and IVF/intracytoplasmic sperm injection (ICSI) outcomes.

DESIGN

Retrospective review and prospective study.

SETTING

Private IVF clinic.

PATIENT(S)

Two hundred forty-nine couples undergoing first IVF and/or ICSI cycle.

INTERVENTION(S)

IVF, ICSI, blastocyst culture.

MAIN OUTCOME MEASURE(S)

DFI, HDS, conventional semen parameters, IVF, ICSI.

RESULT(S)

IVF and ICSI fertilization rates were not statistically different between high- and low-DFI groups. More men with > or =15% HDS had lower (<25% and <50%) IVF fertilization rates. High DNA stainability was not related to ICSI fertilization rates. High DNA stainability did not affect blastocyst rates or pregnancy outcomes. Men with > or =30% DFI were at risk for low blastocyst rates (<30%) and no ongoing pregnancies. Men with > or =30% DFI had more male factors. World Health Organization thresholds were not predictive of ongoing pregnancy.

CONCLUSION(S)

The relationship between HDS and poor IVF fertilization rates provides preliminary evidence that ICSI may be indicated in men with > or =15% HDS. Men with high levels of DNA fragmentation (> or =30% DFI) were at greater risk for low blastocyst rates and failure to initiate an ongoing pregnancy. The SCSA provides valuable prognostic information to physicians counseling couples before IVF and/or ICSI cycles.

The neutral comet assay detects double strand DNA damage in selected and unselected human spermatozoa of normospermic donors

The occurrence of DNA breaks in human sperm is of concern to genetic safety in artificial reproduction techniques. Here, we have explored the neutral comet assay (NCA) for evaluating the frequency of spermatozoa with double strand (ds) DNA breaks in normospermic donors. The NCA results into DNA tail formation by fibre extension and by the separation of DNA fragments. Gamma-irradiated native, lysed and lysed plus RNA and protein degraded human sperm nuclei have been used to assess sensitivity and specificity of fragment formation as an indication for ds DNA breaks. At 5 and 10 Gy gamma irradiation, the sensitivity increases in the order: native, lysed, lysed plus RNA and protein degraded. At 10 Gy, a uniform response between donors was obtained. For technical and biological reasons, the NCA underestimates the true incidence of ds DNA breaks by an unknown factor. Semen samples of six healthy normospermic donors were differentiated by swim up and by Percoll density centrifugation, followed by the NCA. In native semen, percentages of sperm nuclei with ds DNA breaks ranged from 15 to 25%. Swim up and selection for high-density sperm nuclei (high Percoll fraction) reduced the frequency of sperm with ds DNA breaks by about one third, whereas an increased frequency was found in the low Percoll fraction. In conclusion, the response to gamma irradiation of DNA fragment formation indicates the NCA to demonstrate ds DNA breaks which is in keeping with theory and experimental results from somatic cells. Ds DNA breaks are a characteristic of the sperm population of normal donors. Current sperm selection procedures reduce the fractions of sperm with ds DNA breaks, yet are not effective in eliminating these cells.

Transient DNA Strand Breaks During Mouse and Human Spermiogenesis:New Insights in Stage Specificity and Link to Chromatin Remodeling1

In the course of mammalian spermiogenesis, a unique chromatin remodeling process takes place within elongating and condensing spermatid nuclei. The histone-to-protamine exchange results in efficient packaging and increased stability of the paternal genome. Although not fully understood, this change in chromatin architecture must require a global but transient appearance of endogenous DNA strand breaks because most of the DNA supercoiling is eliminated in the mature sperm. To establish the extent of DNA strand breakage and the stage specificity at which these breaks are created and repaired, we performed a sensitive terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) assay to detect in situ DNA strand breaks on both mice and human testis cross sections. In the mouse, we established that DNA strand breaks are indeed detected in the whole population of elongating spermatids between stages IX and XI of the seminiferous epithelium cycle perfectly coincident with the chromatin remodeling as revealed by histone H4 hyperacetylation. Similarly, TUNEL analyses performed on human testis sections revealed an elevated and global increase in the levels of DNA strand breaks present in nuclei of round-shaped spermatids also coincident with chromatin remodeling. The demonstration of the global character of the transient DNA strand breaks in mammalian spermiogenesis suggests that deleterious consequences on genetic integrity of the male gamete may arise from any disturbance in the process. In addition, this investigation may shed some light on the origin of the low success rate that has been encountered so far with intracytoplasmic injection procedures making use of round spermatids in humans.

Influence of deoxyribonucleic acid damage on fertilization and pregnancy

OBJECTIVE

To investigate sperm DNA damage in relation to fertilization and pregnancy.

DESIGN

Prospective study.

SETTING

The Institute of Reproductive Medicine, Giessen, Germany.

PATIENT(S)

Semen collected from 249 patients attending the IVF program.

MAIN OUTCOME MEASURE(S)

The percentage of terminal deoxynucleotidyl transferase-mediated dUDP nick-end labeling- (TUNEL-), Fas-, and annexin-V-positive sperm and the proportion of green-fluorescing sperm in the acridine orange stain was determined and correlated with sperm concentration, motility, fertilization, and pregnancy.

RESULT(S)

Significant correlations with the concentration of motile sperm were only found for the acridine orange stain (before and after sperm separation) and for the TUNEL assay (after sperm separation). Moreover, patients whose sperm had a high percentage of DNA fragmentations showed significantly lower pregnancy rates (TUNEL assay: 19.05% vs. 34.65%; acridine orange stain: 24.58% vs. 37.93%). The apoptosis parameters (annexin V binding and Fas expression) showed no statistically significant differences.

CONCLUSIONS

Our data clearly demonstrate that DNA fragmentation, as determined by the TUNEL assay, is predictive for pregnancy in IVF. This implies that spermatozoa with DNA fragmentation can still fertilize an oocyte but that when paternal genes are "switched on," further embryonic development stops, resulting in failed pregnancy. It seems that, at least in the patients we analyzed, apoptosis in the sperm does not play a role for fertilization. This would imply that DNA fragmentation in human spermatozoa is caused by external factors, such as reactive oxygen species, rather than by apoptosis.

Selecting cryopreserved semen for assisted reproductive techniques based on the level of sperm nuclear DNA fragmentation resulted in pregnancy

A cryopreserved sperm sample with a low level of DNA fragmentation was used for intracytoplasmic sperm injection and resulted in a twin birth from a couple with a 10-year history of idiopathic infertility.

Evaluation of nuclear DNA damage in spermatozoa from infertile men with varicocele

OBJECTIVE

To examine levels of sperm DNA damage and oxidative stress (OS) in infertile men with varicocele.

DESIGN

Prospective controlled study.

SETTING

Male infertility clinic, Glickman Urological Institute, Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Thirty-one infertility patients and 16 fertile controls.

INTERVENTION(S)

Sperm DNA fragmentation index (DFI), levels of seminal reactive oxygen species (ROS), and total antioxidant capacity (TAC) were assessed using the sperm chromatin structure assay, chemiluminescence assay, and enhanced chemiluminescence assay, respectively. ROS-TAC score was calculated as a measure of OS.

MAIN OUTCOME MEASURE(S)

Median (interquartile range) DFI and ROS-TAC scores.

RESULT(S)

Sixteen of the 31 patients had left varicocele [grade I (n = 3), grade II (n = 10), and grade III(n = 3)], and the remaining 15 had normal genital examination. Patients with varicoceles had significantly higher percent DFI than controls (25%, range: 20%-35%; vs. 15%, range: 10%-22%). Patients with varicoceles had significantly lower ROS-TAC scores (21, range: 9.5-31) than the infertile patients with normal genital examination (34, range: 28-42) or the controls (40.3, range: 38-44).

CONCLUSION(S)

Infertile men with varicoceles showed significantly increased spermatozoal DNA damage that appears to be related to high levels of OS in semen.

Flow cytometry and microscopic acridine orange test: relationship with standard semen analysis

Improved prediction of male fertility requires advances in semen analysis. This study examined the reproducibility and independence of the flow cytometry acridine orange test (FCM-AOT) of sperm chromatin integrity as an assessment of semen quality. The study found that FCM-AOT results are not significantly affected by up to 6 h delay in semen preparation (n = 9) or contamination of semen with moderate concentrations of bacteria (<10(8)/ml E. coli or Staph. epidermidis, n = 14). The variation of replicate measurements within samples was low (%Abnormal alpha(t): SD = 1.4, 95%CI = 4.6, n = 25) and different samples from the same men were mostly within the range of measurement error (n = 35). FCM-AOT variables, in particular %Abnormal alpha(t), displayed significant correlations with motility (r = -0.557), vitality (r = -0.469) and morphology (r = -0.464, n = 201), which are similar in magnitude to those existing between the standard semen variables. Surprisingly, no correlation was found between %Abnormal alpha(t) and the microscopic acridine orange test (M-AOT) (n = 185), suggesting the FCM results are sensitive to a different aspect of sperm quality. In summary, this study confirms that although not totally independent of standard semen analysis or the M-AOT, it is found to be a robust, sensitive and reproducible measure of semen quality, representative of the individual.

Correlation between sperm motility and sperm chromatin structure assay parameters

OBJECTIVE

To evaluate the association between chromatin structure and sperm motility.

DESIGN

Cross-sectional prospective study.

SETTING

Scanian Andrology Centre, Malmö, Sweden; ENEA Casaccia, Rome, Italy; and Department of Occupational Medicine, Aarhus University, Aarhus, Denmark.

PATIENT(S)

One hundred seventy-one males from Danish first pregnancy planner couples (group 1) and 278 Swedish military conscripts (group 2).

MAIN OUTCOME MEASURE(S)

Sperm chromatin structure assay (SCSA) parameters, DNA fragmentation index (DFI), high DNA stainable (HDS), and sperm motility, which was evaluated manually and by use of computer-aided sperm analysis (CASA).

RESULT(S)

A statistically significant negative correlation between DFI and the CASA percentage of motile sperms (group 1: r = -0.53; group 2: r = -0.38) was found. For the manual motility assessment, the correlation coefficients were slightly lower. Furthermore, HDS correlated negatively with CASA sperm motility (group 1: r = -0.39; group 2: r = -0.36) and percentage of World Health Organization category A motile sperm. In multiple linear regression analysis, concentration and SCSA parameters, but not the time of abstinence, were statistically significant predictors of sperm motility.

CONCLUSION(S)

There is a moderate correlation between sperm motility and SCSA parameters. The study supports the assumption that both SCSA and motility can be relatively independent predictors of male fertility.

Evaluation of DNA damage in different stages of mouse spermatogenesis after testicular X irradiation

To evaluate whether DNA alterations in mature spermatozoa could stem from DNA damage induced in immature germ cells, testis cells and spermatozoa were analyzed by the comet assay and by the sperm chromatin structure assay 14, 45 and 100 days after in vivo X irradiation of the testes. These times were selected, according to the mouse seminiferous epithelium cycle, to follow the DNA damage induced in different germ cell compartments. The cytotoxic action was assessed by DNA flow cytometric analysis of testicular cells. A dose-dependent increase of DNA damage in testis cells was observed 14 days after irradiation, whereas mature sperm cells were not affected. On the other hand, an increase in DNA strand breaks was seen in spermatozoa 45 days after treatment. DNA damage returned to the control levels 100 days after irradiation. The methods used to evaluate DNA damage gave comparable results, emphasizing the correlation between DNA fragmentation and susceptibility of sperm chromatin to denaturation. Both techniques showed the high radiosensitivity of differentiating spermatogonia. The overall results showed that DNA damage induced in pre-meiotic germ cells is detectable in primary spermatocytes and is still present in mature spermatozoa.

Oxidative stress is associated with increased apoptosis leading to spermatozoa DNA damage in patients with male factor infertility

OBJECTIVE

To evaluate ejaculated spermatozoa from patients with male factor infertility for the role of cytochrome c and caspases 9 and 3 (the proteins known to mediate apoptosis) and to examine association between semen quality and apoptosis in the presence of oxidative stress.

DESIGN

Prospective study.

SETTING

Male infertility clinic at a tertiary health care center.

PATIENT(S)

Semen specimens from 35 patients with idiopathic infertility and 8 normal healthy donors.

MAIN OUTCOME MEASURE(S)

Levels of ROS, cytochrome c, and caspases 9 and 3 and semen variables.

RESULT(S)

Compared with normal donors, infertile patients had significantly higher levels (expressed as median [25th and 75th percentiles]) of ROS (4.15 x 10(6) counted photons per minute [cpm] [0.26, 40.16 x 10(6) cpm] vs. 0.06 x 10(6) cpm [0.02, 0.29 x 10(6) cpm]; P<.01), cytochrome c (2.78 [2.21, 43.65 vs. 1.5 [1.25, 2.2]; P<.01)], caspase 9 (2.52 [0.9, 4.28] vs. 6 [4.85, 7.63]; P<.006), and caspase 3 (0.56 [0.32, 1.02] vs. 1.69 [1.66, 2.67]; P<.01). Semen variables (motility, concentration, and morphology) were negatively correlated with caspase 9 and 3 (P<.05). Reactive oxygen species was positively correlated with cytochrome c (r=.43; P<.03), caspase 9 (r=.56; P<.001), and caspase 3 (r=.65;P<.01).

CONCLUSION(S)

Infertile men have decreased sperm variables induced by higher ROS levels in semen. A positive relationship exists between increased sperm damage by ROS and higher levels of cytochrome c and caspases 9 and 3, which indicate positive apoptosis in patients with male factor infertility.

Protamine 2 deficiency leads to sperm DNA damage and embryo death in mice

Cytokinesis is incomplete in spermatogenic cells, and the descendants of each stem cell form a clonal syncytium. As a result, a heterozygous mutation in a gene expressed postmeiotically affects all of the haploid spermatids within a syncytium. Previously, we have found that disruption of one copy of the gene for either protamine 1 (PRM1) or protamine 2 (PRM2) in the mouse results in a reduction in the amount of the respective protein, abnormal processing of PRM2, and inability of male chimeras to transmit either the mutant or wild-type allele derived from the 129-genotype embryonic stem cells to the next generation. Although it is believed that protamines are essential for compaction of the sperm nucleus and to protect the DNA from damage, this has not been proven experimentally. To test the hypothesis that failure of chimeras to transmit the 129 genotype to offspring was due to alterations in the organization and integrity of sperm DNA, we used the single-cell DNA electrophoresis (comet) assay, ultrastructural analysis, and the intracytoplasmic sperm injection (ICSI) procedure. Comet assay demonstrated a direct correlation between the fraction of sperm with haploinsufficiency of PRM2 and the frequency of sperm with damaged DNA. Ultrastructural analysis revealed reduced compaction of the chromatin. ICSI with PRM2-deficient sperm resulted in activation of most metaphase II-arrested mouse eggs, but few were able to develop to the blastocyst stage. These findings suggest that development fails because of damage to paternal DNA and that PRM2 is crucial for maintaining the integrity of sperm chromatin.

Oxidative stress in the male germ line and its role in the aetiology of male infertility and genetic disease

The human male is characterized by extremely poor semen quality as reflected in the number, morphology and motility of the spermatozoa and a high incidence of nuclear and mitochondrial DNA damage. As a consequence of these factors, defective sperm function is thought to be a major contributor to the aetiology of human infertility, as well as childhood diseases including dominant genetic mutations such as achondroplasia and cancer. Factors associated with the origin of poor semen quality include: (i) a lack of selection pressure for high fecundity genes in developed countries, (ii) an evolutionary lineage associated with the deterioration of several male fertility genes in humans and their close ancestors, (iii) genetic factors including, but not limited to, Y-chromosome deletions (iv) paternal age and (v) environmental factors. A model is proposed whereby factors such as ageing or environmental toxicants initiate DNA strand breakage in the spermatozoa of affected males, eventually leading to a mutation in the embryo. This hypothesis stresses the importance of discovering the identity of those environmental factors that are capable of damaging DNA integrity in the male germ line. Such information could make an important contribution to understanding of the origins of both male infertility and a variety of pathological conditions that affect humans, including cancer and dominant genetic disease.

Negative effects of increased sperm DNA damage in relation to seminal oxidative stress in men with idiopathic and male factor infertility

OBJECTIVE

To examine the effects of increased sperm DNA damage in relation to seminal oxidative stress in men with idiopathic and male factor infertility. Prospective study.

SETTINGS

Infertility clinic at a tertiary care academic institution.

PATIENT(S)

Ninety-two infertile men with normal female partners. Sixteen fertile donors served as the control group.

INTERVENTION(S)

Standard semen analysis and assessment of levels of seminal oxidative stress. Assisted reproductive techniques in 33 of the 92 patients (IUI [n = 19], IVF [n = 10], and intracytoplasmic sperm injection [n = 4]).

MAIN OUTCOME MEASURE(S)

Sperm DNA damage by sperm chromatin structure assay. Results were expressed as DNA fragmentation index.

RESULT(S)

Patients were classified as having either idiopathic (n = 23) or male factor infertility (n = 69). Patients with idiopathic and male factor infertility had significantly higher DNA fragmentation index and oxidative stress compared with the case of fertile donors. A clinical pregnancy was achieved in 9 (27%) of 33 patients with assisted reproductive techniques. Significantly higher DNA fragmentation index and oxidative stress were found in men who failed to initiate a pregnancy after assisted reproductive techniques (n = 24), compared with the cases of those who succeeded and of the fertile donors. DNA fragmentation index was correlated positively with oxidative stress (r = 0.27), and negatively with fertilization (r = -0.70) and embryo quality (r = -0.70).

CONCLUSION(S)

Sperm DNA damage is significantly increased in men with idiopathic and male factor infertility and in men who failed to initiate a pregnancy after assisted reproductive techniques. Such an increase may be related to high levels of seminal oxidative stress.