Double probing of human spermatozoa for persistent histones, surplus cytoplasm, apoptosis and DNA fragmentation

Advances in human In vitro spermatogenesis: A review

Recent advances surrounding in vitro spermatogenesis (IVS) have shown potential in creating a new paradigm of regenerative medicine in the future of fertility treatments for males experiencing non-obstructive azoospermia (NOA). Male infertility is a common condition affecting approximately 15% of couples, with azoospermia being present in 15% of infertile males (Cocuzza et al., 2013; Esteves et al., 2011a). Treatment for patients with NOA has primarily been limited to surgical sperm retrieval combined with in vitro fertilization intracytoplasmic sperm injection (IVF-ICSI); however, sperm retrieval is successful in only half of these patients, and live birth rates typically range between 10 and 25% (Aljubran et al., 2022). Therefore, a significant need exists for regenerative therapies in this patient population. IVS has been considered as a model for further understanding the molecular and cellular processes of spermatogenesis and as a potential regenerative therapeutic approach. While 2D cell cultures using human testicular cells have been attempted in previous research, lack of proper spatial arrangement limits germ cell differentiation and maturation, posing challenges for clinical application. Recent research suggests that 3D technology may have advantages for IVS due to mimicry of the native cytoarchitecture of human testicular tissue along with cell-cell communication directly or indirectly. 3D organotypic cultures, scaffolds, organoids, microfluidics, testis-on-a-chip, and bioprinting techniques have all shown potential to contribute to the technology of regenerative treatment strategies, including in vitro fertilization (IVF). Although promising, further work is needed to develop technology for successful, replicable, and safe IVS for humans. The intersection between tissue engineering, molecular biology, and reproductive medicine in IVS development allows for multidisciplinary involvement, where challenges can be overcome to realize regenerative therapies as a viable option.

Investigation on the origin of sperm morphological defects: oxidative attacks, chromatin immaturity, and DNA fragmentation

DNA fragmentation can be deleterious on spermatozoon morphology but the pathogenesis of teratozoospermia associated with DNA breaks is not fully understood, even if oxidative attacks and defects in chromatin maturation are hypothesized. Therefore, this study is one of the first to clarify on the underlying hypothesizes behind such observations. The objectives of our study were to assess the role of oxidative attacks in DNA damage pathogenesis in ejaculated spermatozoa from patients with isolated teratozoospermia. We aimed to assess the correlation of DNA breaks with morphologically abnormal spermatozoa, as well as ROS level and impairment chromatin condensation. A total of 90 patients were divided into two groups, men with isolated teratozoospermia (n = 60) and men with normal semen parameters (n = 30) as controls. DNA fragmentation was evaluated by TUNEL assay; chromatin immaturity was studied using acridine orange and toluidine blue staining. We evaluated the ability of spermatozoa to produce reactive oxygen species with nitro blue tetrazolium staining. Patient with teratozoospermia when compared to fertile men showed significantly higher rates of semen ROS production, sperm hypocondensated chromatin, denaturated DNA, and fragmented DNA. All these parameters were positively correlated with abnormal sperm morphology. The studied DNA integrity markers were also correlated with ROS production. Fragmented DNA is the main pathway leading to morphology defects in the sperm. In fact, impaired chromatin compaction may induce DNA breaks and free radicals, which can break the DNA backbone indirectly, by reducing protamination and disulphide bond formation, as oxidative attack appears to be the major cause of poor semen morphology.

Effect of erythrocyte-sperm separation medium on nuclear, acrosomal, and membrane maturity parameters in human sperm

PURPOSE

The purpose of this study is to investigate whether erythrocyte-sperm separation medium (ESSM) has effects on human sperm motility, morphology, viability, membrane maturity, acrosome integrity, and nuclear attributes before and after cryopreservation.

METHODS

Semen samples from normozoospermic (n = 36) and oligozoospermic (n = 9) patients were analyzed. Samples from the same patient were divided into three aliquots: group 1 and group 2 were resuspended in sperm washing media and ESSM, respectively. Group 3 was resuspended in ESSM with blood sample to mimic the extensive number of erythrocytes in the testicular sperm extraction (TESE) material. All groups were evaluated for sperm concentration, motility, Kruger/Tygerberg strict morphology, viability by eosin-nigrosin staining, membrane maturity by hyaluronic acid-binding assay (HBA), acrosomal integrity by Pisum sativum lectin staining, chromatin maturity by aniline blue staining, and DNA integrity by TUNEL assay before and after cryopreservation.

RESULTS

No significant difference was determined between ESSM-treated and ESSM-untreated sperm samples for the sperm parameters tested (p > 0.05). After cryopreservation, total sperm motility and viability decreased regardless of ESSM used. The percentages of sperm with Tygerberg normal morphology, intact acrosome, and HA-bound sperm were found to be lower in oligozoospermic samples before cryopreservation in each group. However, no statistically significant differences were found between oligozoospermic and normozoospermic samples when all groups were compared. Thus, ESSM treatment did not cause a significant change on sperm motility, normal morphology, viability, HA-binding capacity, chromatin maturity, and DNA fragmentation.

CONCLUSION

ESSM can enhance the efficiency of sperm retrieval protocol and can also decrease the time required to collect spermatozoa while not affecting sperm morphogenetic properties.

DNA fragmentation in spermatozoa: a historical review

Sperm DNA Fragmentation has been extensively studied for more than a decade. In the 1940s the uniqueness of the spermatozoa protein complex which stabilizes the DNA was discovered. In the fifties and sixties, the association between unstable chromatin structure and subfertility was investigated. In the seventies, the impact of induced DNA damage was investigated. In the 1980s the concept of sperm DNA fragmentation as related to infertility was introduced as well as the first DNA fragmentation test: the Sperm Chromatin Structure Assay (SCSA). The terminal deoxynucleotidyl transferase nick end labelling (TUNEL) test followed by others was introduced in the nineties. The association between DNA fragmentation in spermatozoa and pregnancy loss has been extensively investigated spurring the need for a therapeutic tool for these patients. This gave rise to an increased interest in the aetiology of DNA damage. The present decade continues within this research area. Some of the more novel methods recently submerging are sorting of cells with increased DNA fragmentation and hyaluronic acid (HA) binding techniques. The clinical value of these tests remains to be elucidated. In spite of half a century of research within the area, this analysis is not routinely implemented into the fertility clinics. The underlying causes are multiple. The abundance of methods has impeded the need for a clinical significant threshold. One of the most promising methods was commercialized in 2005 and has been reserved for larger licensed laboratories. Myriads of reviews and meta‐analyses on studies using different assays for analysis of DNA fragmentation, different clinical Artificial Reproductive Treatments (ART), different definitions of successful ART outcome and small patient cohorts have been published. Although the area of DNA fragmentation in spermatozoa is highly relevant in the fertility clinics, the need for further studies focusing on standardization of the methods and clinical implementation persists.

TUNEL labeling with BrdUTP/anti-BrdUTP greatly underestimates the level of sperm DNA fragmentation in semen evaluation

Many studies have now confirmed that sperm DNA fragmentation (SDF) is associated with a poorer outcome of some forms of assisted reproduction technology. For this reason, SDF is an important parameter to evaluate in male fertility assessment. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay coupled to flow cytometry is one of the most promising methods for SDF quantification. Several kits for the detection of DNA fragmentation are currently available on the market and all are recommended as equally appropriate to quantify SDF. In this work we compared for the first time the efficacy of two different types of TUNEL kits for SDF quantification: one using an indirect antibody-based labeling system (BrdUTP/fluorescein-anti-BrdUTP) and another using a direct labeling system (fluorescein-dUTP). We demonstrated that TUNEL indirect labeling system largely underestimates SDF when compared with the direct labeling, the differences ranging from 19.2% to 85.3% (p<0.05, n = 22). We observed that these differences were most pronounced among dead spermatozoa where indirect labeling stained 40.1% [23.6%, 58.2%] and the direct system 65.7% [36.5%, 90.9%] (n = 10, p<0.05). Interestingly, we found that both systems stained the living spermatozoa with the same efficiency. We showed that the differences are due to the steric hindrance of the antibody during its binding to the BrdUTP. Indeed, after sperm DNA decondensation, the percentages of TUNEL positivity increased significantly from 46.3% [31.8%, 61.7%] to 97.5% [96.1%, 98.8%] (p<0.05, n = 5). Our results are important for future use of TUNEL in clinical practice. Laboratories relying on the use of an antibody-based system heavily underestimate SDF, most particularly in infertile patients with reduced sperm motility. As a consequence, the kit using BrdUTP/fluorescein-anti-BrdUTP should not be recommended as a method to assay DNA damage in semen. This study represents one further step in the standardization of TUNEL among laboratories.

Hyaluronic Acid Binding Sperm Selection for assisted reproduction treatment (HABSelect): study protocol for a multicentre randomised controlled trial

INTRODUCTION

The selection of a sperm with good genomic integrity is an important consideration for improving intracytoplasmic sperm injection (ICSI) outcome. Current convention selects sperm by vigour and morphology, but preliminary evidence suggests selection based on hyaluronic acid binding may be beneficial. The aim of the Hyaluronic Acid Binding Sperm Selection (HABSelect) trial is to determine the efficacy of hyaluronic acid (HA)-selection of sperm versus conventionally selected sperm prior to ICSI on live birth rate (LBR). The mechanistic aim is to assess whether and how the chromatin state of HA-selected sperm corresponds with clinical outcomes-clinical pregnancy rate (CPR), LBR and pregnancy loss (PL).

METHODS AND ANALYSIS

Couples attending UK Centres will be approached, eligibility screening performed and informed consent sought. Randomisation will occur within 24 hours prior to ICSI treatment. Participants will be randomly allocated 1:1 to the intervention arm (physiological intracytoplasmic sperm injection, PICSI) versus the control arm using conventional methods (ICSI). The primary clinical outcome is LBR ≥37 weeks' gestation with the mechanistic study determining LBR's relationship with sperm DNA integrity. Secondary outcomes will determine this for CPR and PL. Only embryologists performing the procedure will be aware of the treatment allocation. Steps will be taken to militate against biases arising from embryologists being non-blinded. Randomisation will use a minimisation algorithm to balance for key prognostic variables. The trial is powered to detect a 5% difference (24-29%: p=0.05) in LBR ≥37 weeks' gestation. Selected residual sperm samples will be tested by one or more assays of DNA integrity.

ETHICS AND DISSEMINATION

HABSelect is a UK NIHR-EME funded study (reg no 11/14/34; IRAS REF. 13/YH/0162). The trial was designed in partnership with patient and public involvement to help maximise patient benefits. Trial findings will be reported as per CONSORT guidelines and will be made available in lay language via the trial web site (http://www.habselect.org.uk/).

TRIAL REGISTRATION NUMBER

ISRCTN99214271; Pre-results.

Impact of sperm DNA chromatin in the clinic

The paternal contribution to fertilization and embryogenesis is frequently overlooked as the spermatozoon is often considered to be a silent vessel whose only function is to safely deliver the paternal genome to the maternal oocyte. In this article, we hope to demonstrate that this perception is far from the truth. Typically, infertile men have been unable to conceive naturally (or through regular IVF), and therefore, a perturbation of the genetic integrity of sperm heads in infertile males has been under-considered. The advent of intracytoplasmic sperm injection (ICSI) however has led to very successful treatment of male factor infertility and subsequent widespread use in IVF clinics worldwide. Until recently, little concern has been raised about the genetic quality of sperm in ICSI patients or the impact genetic aberrations could have on fertility and embryogenesis. This review highlights the importance of chromatin packaging in the sperm nucleus as essential for the establishment and maintenance of a viable pregnancy.

Confrontation, Consolidation, and Recognition: The Oocyte's Perspective on the Incoming Sperm

From the oocyte's perspective, the incoming sperm poses a significant challenge. Despite (usually) arising from a male of the same species, the sperm is a "foreign" body that may carry with it additional, undesirable factors such as transposable elements (mainly retroposons) into the egg. These factors can arise either during spermatogenesis or while the sperm is moving through the epididymis or the female genital tract. Furthermore, in addition to the paternal genome, the sperm also carries its own complex repertoire of RNAs into the egg that includes mRNAs, lncRNAs, and sncRNAs. Last, the paternal genome itself is efficiently packaged into a protamine (nucleo-toroid) and histone (nucleosome)-based chromatin scaffold within which much of the RNA is embedded. Taken together, the sperm delivers a far more complex package to the egg than was originally thought. Understanding this complexity, at both the compositional and structural level, depends largely on investigating sperm chromatin from both the genomic (DNA packaging) and epigenomic (RNA carriage and extant histone modifications) perspectives. Why this complexity has arisen and its likely purpose requires us to look more closely at what happens in the oocyte when the sperm gains entry and the processes that then take place preparing the paternal (and maternal) genomes for syngamy.

Investigation on the Origin of Sperm DNA Fragmentation: Role of Apoptosis, Immaturity and Oxidative Stress

Sperm DNA fragmentation (sDF) represents a threat to male fertility, human reproduction and the health of the offspring. The causes of sDF are still unclear, even if apoptosis, oxidative assault and defects in chromatin maturation are hypothesized. Using multicolor flow cytometry and sperm sorting, we challenged the three hypothesized mechanisms by simultaneously evaluating sDF and signs of oxidative damage (8-hydroxy, 2'-deoxyguanosine [8-OHdG] and malondialdehyde [MDA]), apoptosis (caspase activity and cleaved poly[ADP-ribose] polymerase [cPARP]) and sperm immaturity (creatine phosphokinase [CK] and excess of residual histones). Active caspases and c-PARP were concomitant with sDF in a high percentage of spermatozoa (82.6% ± 9.1% and 53.5% ± 16.4%, respectively). Excess of residual histones was significantly higher in DNA-fragmented sperm versus sperm without DNA fragmentation (74.8% ± 17.5% and 37.3% ± 16.6%, respectively, p < 0.005), and largely concomitant with active caspases. Conversely, oxidative damage was scarcely concomitant with sDF in the total sperm population, at variance with live sperm, where 8-OHdG and MDA were clearly associated to sDF. In addition, most live cells with active caspase also showed 8-OHdG, suggesting activation of apoptotic pathways in oxidative-injured live cells. This is the first investigation on the origin of sDF directly evaluating the simultaneous presence of the signs of the hypothesized mechanisms with DNA breaks at the single cell level. The results indicate that the main pathway leading to sperm DNA breaks is a process of apoptosis, likely triggered by an impairment of chromatin maturation in the testis and by oxidative stress during the transit in the male genital tract. These findings are highly relevant for clinical studies on the effects of drugs on sDF and oxidative stress in infertile men and for the development of new therapeutic strategies.

Assessment of chromatin maturity in human spermatozoa: useful aniline blue assay for routine diagnosis of male infertility

During spermatogenesis, sperm chromatin undergoes structural changes and results in a high condensation. This nuclear compaction would be useful as a predictor of sperm fertilization capacity and pregnancy outcome. We purpose to evaluate firstly the relationship among chromatin maturity assessed by aniline blue staining (AB) and the semen parameters in infertile men. Secondly, we analyzed whether the sperm gradient density centrifugation is effective to select mature spermatozoa. Fifty-one ejaculates were investigated by semen analysis and stained for chromatin condensation with AB to distinguish between unstained mature sperm and stained immature sperm. AB was applied also on 12 ejaculates which proceeded by density gradient centrifugation to compare the rates of immature sperm before and after selection. Neat semen were divided into two groups: G1 (n = 31): immature sperm <20% and G2 (n = 20): immature sperm ≥20%. No significant differences were detected in sperm concentration, motility, and normal morphology between G1 and G2. However, the rates of some morphology abnormalities were higher in G2: head abnormalities (P = 0.01) and microcephalic sperm (P = 0.02). We founded significant correlation between sperm immaturity and acrosome abnormalities (r = 0.292; P = 0.03). Sperm selection has significantly reduced the rates of immature sperm. A better understanding of chromatin structure and its impact on the sperm potential is needed to explore male infertility.

The pattern of tyrosine phosphorylation in human sperm in response to binding to zona pellucida or hyaluronic acid

In mammalian species, acquisition of sperm fertilization competence is dependent on the phenomenon of sperm capacitation. One of the key elements of capacitation is protein tyrosine phosphorylation (TP) in various sperm membrane regions. In previous studies performed, the pattern of TP was examined in human sperm bound to zona pellucida of oocytes. In the present comparative study, TP patterns upon sperm binding to the zona pellucida or hyaluronic acid (HA) were investigated in spermatozoa arising from the same semen samples. Tyrosine phosphorylation, visualized by immunofluorescence, was localized within the acrosomal cap, equatorial head region, neck, and the principal piece. Tyrosine phosphorylation has increased in a time-related manner as capacitation progressed, and the phosphorylation pattern was identical within the principal piece and neck, regardless of the sperm bound to the zona pellucida or HA. Thus, the data demonstrated that the patterns of sperm activation-related TP were similar regardless of the spermatozoa bound to zona pellucida or HA. Further, sperm with incomplete development, as detected by excess cytoplasmic retention, failed to exhibit TP.

Methodology of aniline blue staining of chromatin and the assessment of the associated nuclear and cytoplasmic attributes in human sperm

In this chapter, the laboratory methods for detection of sperm biomarkers that are aimed at identifying arrested sperm development are summarized. These probes include sperm staining with aniline blue for persistent histones, representing a break in the histone-transition protein-protamine sequence, immunocytochemistry with cytoplasmic sperm proteins, highlighting cytoplasmic retention during spermiogenesis, DNA nick translation testing for DNA chain fragmentation due to various reasons, for instance low HspA2 chaperone protein levels, and consequential diminished DNA repair. Finally, we briefly provide references on our work on sperm hyaluronan binding, abnormal Tybergerg sperm morphology, and the increased levels of chromosomal aneuploidies in sperm with developmental arrest. A very interesting aspect of the biomarker field is the discovery (Sati et al, Reprod Biomed Online 16:570-579, 2008) that the various nuclear and cytoplasmic defects detected by the biomarkers are related, and may simultaneously occur within the same spermatozoa as evidenced by a combination of biomarkers, such as aniline blue staining (persistent histones) coupled with cytoplasmic retention, DNA fragmentation, Caspase-3, Tygerberg abnormal morphology, and increased levels of chromosomal aneuploidies. We show examples of this >80% overlap in staining patterns within the same spermatozoa.

Effects of the insemination of hydrogen peroxide-treated epididymal mouse spermatozoa on γH2AX repair and embryo development

BACKGROUND

Cryopreservation of human semen for assisted reproduction is complicated by cryodamage to spermatozoa caused by excessive reactive oxygen species (ROS) generation.

METHODS AND FINDINGS

We used exogenous ROS (H(2)O(2)) to simulate cryopreservation and examined DNA damage repair in embryos fertilized with sperm with H(2)O(2)-induced DNA damage. Sperm samples were collected from epididymis of adult male KM mice and treated with capacitation medium (containing 0, 0.1, 0.5 and 1 mM H(2)O(2)) or cryopreservation. The model of DNA-damaged sperm was based on sperm motility, viability and the expression of γH2AX, the DNA damage-repair marker. We examined fertility rate, development, cell cleavage, and γH2AX level in embryos fertilized with DNA-damaged sperm. Cryopreservation and 1-mM H(2)O(2) treatment produced similar DNA damage. Most of the one- and two-cell embryos fertilized with DNA-damaged sperm showed a delay in cleavage before the blastocyst stage. Immunocytochemistry revealed γH2AX in the one- and four-cell embryos.

CONCLUSIONS

γH2AX may be involved in repair of preimplantation embryos fertilized with oxygen-stressed spermatozoa.

Is sperm DNA damage associated with IVF embryo quality? A systematic review

PURPOSE

Sperm DNA damage is common amongst infertile men and may adversely impact natural reproduction, IUI-assisted reproduction and to a lesser degree IVF pregnancy. The objective of this study was to examine the influence of sperm DNA damage on embryo quality and/or development at IVF and ICSI.

METHODS

We conducted a systematic review of studies that evaluated sperm DNA damage and embryo development and/or quality after IVF and/or ICSI.

RESULTS

We identified 28 studies (8 IVF, 12 ICSI and 8 mixed IVF-ICSI studies) that evaluated the relationship between sperm DNA damage and embryo quality. These 28 studies evaluated 3226 treatment cycles (1033 IVF and 873 ICSI, 1320 mixed IVF-ICSI cycles) and demonstrated highly variable characteristics. In 11 of the 28 studies (1/8 IVF, 5/12 ICSI and 5/8 mixed IVF-ICSI studies), sperm DNA damage was associated with poor embryo quality and/or development, whereas the remaining 17 studies showed no relationship between sperm DNA damage and embryo quality and/or development.

CONCLUSIONS

This systematic review indicates that the evaluable studies are heterogeneous and that overall, there is no consistent relationship between sperm DNA damage and embryo quality and/or development. The data also suggest that the influence of sperm DNA damage on embryo quality/development may be more significant in ICSI compared to IVF cycles.

The effects of male aging on semen quality, sperm DNA fragmentation and chromosomal abnormalities in an infertile population

PURPOSE

To investigate the effects of male aging on semen quality, DNA fragmentation and chromosomal abnormalities in the spermatozoa of infertile patients and fertile men.

METHODS

Semen samples of 140 infertile patients (24-76 years) and 50 men with proven fertility (25-65 years) were analyzed according to WHO guidelines. DNA fragmentation was detected by TUNEL assay, while aneuploidy was assessed by FISH.

RESULTS

In the patient group, semen volume and vitality of spermatozoa decreased significantly with age, while sperm concentration showed a statistically significant increase with age. DNA fragmentation as well as disomy of sex chromosomes and disomy 8 did not show a statistically significant change with age. However, the diploidy rate was significantly increased with patient's age. In the control group, conventional semen parameters as well as DNA fragmentation and chromosomal abnormalities did not show a statistically significant with age.

CONCLUSION

Increased age in infertile men is associated with an increase in sperm concentration and diploidy, as well as a decline in semen volume and sperm vitality. However motility, morphology and DNA fragmentation are not affected by male age.

The effect of age on the expression of apoptosis biomarkers in human spermatozoa

OBJECTIVE

To evaluate the impact of age on the expression of apoptotic biomarkers in human spermatozoa.

DESIGN

Cross sectional, prospective study.

SETTING

Academic centers.

PATIENT(S)

Healthy volunteers with proven fertility, stratified by age (n = 25, range: 20-68 years).

INTERVENTION(S)

Examination of serum hormone levels and basic semen parameters, and assessment of early (plasma membrane translocation of phosphatidylserine) and late (DNA fragmentation) sperm apoptotic markers by flow cytometry (using Annexin-V binding and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling).

MAIN OUTCOME MEASURE(S)

Apoptosis markers.

RESULT(S)

Advancing male age was significantly and positively correlated with Annexin-V binding results. Although not significant, there was a clear trend for increased DNA fragmentation in the older groups. The age threshold for these observations appears to be 40 years. Advancing male age was positively correlated with FSH and sex hormone-binding globulin (SHBG) levels, and negatively correlated with sperm concentration.

CONCLUSION(S)

Advancing male age is associated with the expression of early apoptotic markers as evidenced by significantly increased plasma membrane translocation of phosphatidylserine, as well as with a more subtle proportion of sperm carrying DNA fragmentation. This study confirmed that male age is also associated with a decline in sperm concentration.

Impact of caspase activation in human spermatozoa

Caspases are central components in the apoptosis signaling cascade. The family of cysteine proteases transduces and enhances the apoptosis signal, and activation of effector caspases results in controlled cellular degradation. Although initially the presence of caspases in spermatozoa was controversially discussed in recent years, many studies demonstrated their activation in male germ cells. Activated apoptosis signaling results in decreased fertilizing capacity of the sperm. This review presents the current knowledge on the role of caspases in human sperm. Techniques of caspase monitoring are highlighted. With regard to the high impact of caspases on the sperm fertilizing potential, physiological and pathological settings of caspase activation and inactivation are discussed. Finally, the effects of depletion of caspase-positive sperm are shown with various standard and molecular sperm preparation methods.

Tests to measure the quality of spermatozoa at spermiation

This commentary is to critique the revised World Health Organization (WHO) semen analysis manual as it pertains to characteristics of a spermatozoon at spermiation. The aims of the revised WHO manual include improving the 'quality of semen analysis' without any restriction to clinical use. Furthermore, the manual states that semen analysis may be useful for (a) 'investigating male fertility status' and (b) 'monitoring spermatogenesis during and following male fertility regulation.' However, if the analysis of ejaculated spermatozoa is intended for the purposes described in (b), then cells that are abnormal at spermiation must be identified. This paper takes the position that the manual does not identify methods to estimate the quality of spermatozoa at spermiation. Instead, it uses a 'gold standard' of sperm passing through the cervical mucus or arriving near the site of fertilization. Although this standard is appropriate for drawing conclusions regarding the probability that an individual could impregnate his partner, it is not appropriate for studying illness of the testes per se. Herein, the measures of sperm quality presented in the WHO manual are critiqued with respect to the detection of spermatozoa that were abnormal at spermiation vs. those that became abnormal subsequently. Quality assessments based on the percentage of motile or 'viable' spermatozoa are meaningless. Alternative quality attributes defining spermatozoa at spermiation are presented in this paper. In conclusion, assessment of spermatozoal quality at spermiation, on the basis of quality attributes of individual ejaculated spermatozoa, is best achieved through application of (a) a new paradigm for the morphological evaluation of sperm quality and (b) modern analytical techniques to evaluate, in an adequate sample, several appropriate independent attributes in each spermatozoon in order to more accurately identify the proportion of abnormal spermatozoa.

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.