Integrating new tests of sperm genetic integrity into semen analysis: breakout group discussion

A Review of Semen Analysis: Updates From the WHO Sixth Edition Manual and Advances in Male Fertility Assessment

Semen analysis is essentially used to check the fertility of a man, especially when couples are having difficulties conceiving. Studies concerning male fertility, testicular factors, and seminal characteristics have been under investigation for the last few decades. In 1980, the World Health Organization (WHO) started reaching out to scientists in order to set standards for high-quality semen and develop a semen manual. From this point to the present, six editions of this manual have been produced, delineating the characteristics of semen and reporting protocols for semen analysis. Sperm morphology is analyzed as per WHO norms to measure the biological capacity of a male for reproduction. Both national and international manuals have been developed, with the latest, the sixth edition, produced in July 2021. This review paper conveys the current WHO publication's updates and identifies the clinical recommendations for proper evaluations. The publication considers the characteristics of semen in order to discuss the content of the previous editions of the WHO. It is also utilized to assess the method applied to determine the DNA presence of sperm fragmentation.

Heavy metal and metalloid - induced reproductive toxicity

Heavy metals and metalloid exposure are among the most common factors responsible for reproductive toxicity in human beings. Several studies have indicated that numerous metals and metalloids can display severe adverse properties on the human reproductive system. Metals like lead, silver, cadmium, uranium, vanadium, and mercury and metalloids like arsenic have been known to induce reproductive toxicity. Moderate to minute quantities of lead may affect several reproductive parameters and even affect semen quality. The ecological and industrial exposures to the various heavy metals and metalloids have disastrous effects on the reproductive system ensuing in infertility. This work emphasizes the mechanism and pathophysiology of the aforementioned heavy metals and metalloids in reproductive toxicity. Additionally, this work aims to cover the classical protective mechanisms of zinc, melatonin, chelation therapy, and other trending methods to prevent heavy metal-induced reproductive toxicity.

Peak retrograde flow a potential objective management tool to identify young adults with varicocele 'at risk' for a high sperm DNA fragmentation

INTRODUCTION

Determining which patients are negatively affected by varicocele would enable clinicians to better select those men who would benefit most from surgery. Since conventional semen parameters, have been limited in their ability to evaluate the negative effects of varicocele on fertility, specialized laboratory tests have emerged.

OBJECTIVE

To identify clinical and ultrasound parameters (including PRF) which would negatively influence standard and functional semen variables in young adults with a varicocele.

DESIGN

Prospective, cross-sectional observational study.

SETTING

Antwerp University Hospital, Belgium.

PATIENT(S)

Young volunteers between 16 and 26 years, Tanner 5, were recruited.

INTERVENTION(S)

Every participant had a scrotal ultrasound to calculate testicular volumes. If a varicocele was present, the grade, vein diameter, peak retrograde flow (PRF) in supine position and spontaneous reflux in standing position were measured. All participants provided a semen sample. Standard semen parameters were analyzed and sperm DNA fragmentation.

MAIN OUTCOME MEASURE(S)

Of all clinical and ultrasound parameters tested, PRF was an objective tool identifying young adults with a varicocele. PRF was highlighted by the prevalence of SDF, both in the total and vital fractions of the spermatozoa, providing opportunities to manage such 'at-risk' adolescents/young adults.

RESULT(S)

Total SDF was significantly increased in grade 3 varicocele compared to grade 1 and 2 but no significant difference with vital SDF or standard descriptive semen parameters was seen. Total and vital SDF on the other hand were significantly increased when PRF was above 38.4 cm/s. Standard semen analysis showed no difference with PRF as an independent predictor. Testicular atrophy index, varicocele vein diameter and spontaneous reflux revealed no significant differences in both the descriptive and functional semen variables.

DISCUSSION

Descriptive semen parameters showed no significant difference between the non-varicocele controls and the varicocele group with low and high PRF. Increased PRF negatively influenced sperm quality via increased DNA fragmentation both in the total as in the vital fractions of the semen.

CONCLUSION(S)

Of all clinical and ultrasound parameters tested, PRF was an objective non-invasive tool to identify varicocele patients at risk for a high SDF.

Current mechanistic perspectives on male reproductive toxicity induced by heavy metals

Environmental and occupational exposures to heavy metals have led to various deleterious damages to the biological system of which infertility is one of them. Infertility is a global public health concern, affecting 15% of all couples of reproductive age. Out of the 100% cases of reported infertility among couples, 40% of the cases are related to male factors; including decreased semen quality. This review focuses on the recent mechanistic perspectives of heavy metal-induced male reproductive toxicity. The associated toxic metal-mediated mechanisms of male reproductive toxicity include ion mimicry, disruption of cell signaling pathways, oxidative stress, altered gene expression, epigenetic regulation of gene expression, apoptosis, disruption of testis/blood barrier, inflammation and endocrine disruption. The current literature suggests that non-coding RNAs (ncRNAs) mediate paternal intergenerational epigenetic inheritance and thus has a direct functional importance, as well as possess novel biomarker potential, for male reproductive toxicity. To identify the specific ncRNAs with the most profound impacts on heavy metal-induced male reproductive toxicity should be thrust of further research.

Can the SCD test and terminal uridine nick-end labeling by flow cytometry technique (TUNEL/FCM) be used interchangeably to measure sperm DNA damage in routine laboratory practice?

Background

Numerous tests have been proposed to evaluate sperm DNA integrity. To assess the sperm chromatin dispersion (SCD) test in an andrology laboratory, twenty-five men attending Clermont-Ferrand (France) University Hospital’s Center for Reproductive Medicine were recruited. Sperm DNA damage was measured in the same semen samples using the SCD test and the Terminal Uridine Nick-end Labeling by flow cytometry technique (TUNEL/FCM) after density gradient centrifugation.

Results

SCD test reliability between readings, readers or slides was clearly established with very high agreement between measurements (Intraclass correlation coefficient (ICC) at 0.97, 0.95 and 0.98 respectively). Despite very good agreement between the SCD test and TUNEL/FCM (ICC at 0.94), the SCD test tended to slightly but significantly underestimate DNA damage compared with TUNEL (p = 0.0127). This systematic difference between the two techniques was − 3.39 ± 1.45% (mean ± SE).

Conclusions

Andrology laboratories using the SCD test to measure sperm DNA damage need to know that it appears to give slightly underestimated measurements compared to TUNEL/FCM. However, this systematic underestimation is very small in amplitude. Both techniques give almost perfectly congruent results. Our study underlines the importance for each laboratory to validate its method to assess sperm DNA damage before implementing it in routine andrology lab practice.

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

BACKGROUND

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

DISCUSSION AND CONCLUSION

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

Associations of sperm DNA fragmentation with lifestyle factors and semen parameters of Saudi men and its impact on ICSI outcome

BACKGROUND

Male factor infertility is quite common as 30-50% of infertility cases are due to sperm defects. The high sperm DNA fragmentation is one of the causes of male factor infertility. Many factors cause sperm DNA fragmentation and could be testicular or post-testicular. The purpose of this study was to assess relationships among sperm DNA fragmentation, lifestyle factors and semen values of Saudi men and to determine impact of sperm DNA fragmentation on ICSI cycle outcome.

METHODS

The duration of this study was from January 2015 to June 2016. The cases with female factor infertility were excluded. In total 94 couples were selected for investigation. The study parameters were male age, body mass index, smoking, semen values, % sperm DNA fragmentation, fertilization rate and pregnancy outcome. The ICSI procedure was performed in all patients per standard protocol. The semen samples were grouped based on % sperm DNA fragmentation into < 15%, 15-30 and > 30% which corresponded to low, moderate and high sperm DNA fragmentation, respectively.

RESULTS

There was no difference in ICSI outcome in low and moderate sperm DNA fragmentation, however, in high sperm DNA fragmentation no patient achieved pregnancy. In this study, 53.19% Saudi men had low, 32.98% moderate and 13.83% high DFI. Semen volume, sperm morphology and fertilization rate did not show any correlation trend with DNA fragmentation, however, sperm concentration and motility were negatively correlated in all DFI categories. The BMI was positively correlated in moderate DFI category and smoking was positively correlated with low DFI category. The age was positively correlated in moderate and high DFI categories.

CONCLUSIONS

The results of this study indicated that 14% Saudi men had high DNA fragmentation. The BMI was positively correlated in moderate DFI category and smoking was positively correlated with low DFI category. The age was positively correlated in moderate and high DFI categories.

Application of Fluorescence In Situ Hybridization (FISH) Technique for the Detection of Genetic Aberration in Medical Science

Fluorescence in situ hybridization (FISH) is a macromolecule recognition technique, which is considered as a new advent in the field of cytology. Initially, it was developed as a physical mapping tool to delineate genes within chromosomes. The accuracy and versatility of FISH were subsequently capitalized upon in biological and medical research. This visually appealing technique provides an intermediate degree of resolution between DNA analysis and chromosomal investigations. FISH consists of a hybridizing DNA probe, which can be labeled directly or indirectly. In the case of direct labeling, fluorescent nucleotides are used, while indirect labeling is incorporated with reporter molecules that are subsequently detected by fluorescent antibodies or other affinity molecules. FISH is applied to detect genetic abnormalities that include different characteristic gene fusions or the presence of an abnormal number of chromosomes in a cell or loss of a chromosomal region or a whole chromosome. It is also applied in different research applications, such as gene mapping or the identification of novel oncogenes. This article reviews the concept of FISH, its application, and its advantages in medical science. 

Relationship between pregnancy, embryo development, and sperm deoxyribonucleic acid fragmentation dynamics

The way the dynamics of DNA fragmentation affects the growth of embryos in real time, and effectiveness of infertility treatment using the ICSI procedure were determined in 148 couples treated with the ICSI technique. The percentage of sperm with fragmented DNA (known as the DNA fragmentation index [DFI]) in semen samples was determined at 3, 6 and 12 h. Embryo culture was assessed continuously during 12 h of observation monitoring.

Statistically significant difference was found in DFI at 12 h and outcome of treatment. For the remaining time intervals, no statistically significant differences were noted. An analysis of relationship between the DFI dynamics over time at individual measurements and achievement of pregnancy, confirmed a statistically significant relationship between the rate measured at 6–12 h of observations of DFI changes (DFI 12 h%/h), and achieving pregnancy. Correlation was observed between DFI (during 0, 3, 6 and 12 h), the growth rate in DFI, and time of embryo development. A statistically significant relationship was found between the rate from the start to the end of observations of the DFI, and outcome of treatment.

Intensity level regarding fragmentation of sperm DNA and its growth rate affected the time of embryo development in the ICSI procedure. The most significant prognostic factor for achieving pregnancy was intensification of sperm DNA fragmentation after 12 h.

Evaluating γH2AX in spermatozoa from male infertility patients

OBJECTIVE

To investigate whether γH2AX levels were different in the spermatozoa of healthy men compared with infertility patients, and to assess the possible correlations between γH2AX and conventional semen parameters and double-stranded breaks (DSBs) identified with the use of comet assay.

DESIGN

Prospective study.

SETTING

Clinical laboratory.

PATIENT(S)

Semen from 100 male infertile patients and 100 healthy sperm donors.

INTERVENTION(S)

Human sperm samples were analyzed in terms of World Health Organization parameters. The γH2AX levels were detected by means of flow cytometry. DSBs of sperm were detected by means of comet assay. Morphology slides were made and the sperm morphology assessed according to strict criteria.

MAIN OUTCOME MEASURE(S)

Conventional semen analyses, γH2AX levels in sperm, DNA DSBs in sperm, and correlations among γH2AX, conventional semen analyses, and DSBs.

RESULT(S)

Concentration, viability, motility, and normal sperm morphology were significantly lower in male infertility patients compared with healthy men. Also, γH2AX levels and the number of DSBs were significantly higher in the sperm of infertile subjects compared with healthy men. γH2AX levels correlated negatively with conventional semen parameters and positively with DSBs. A threshold γH2AX level of 18.55% was identified as a cutoff value to discriminate infertile subjects from fertile control subjects with a specificity of 86.0% and a sensitivity of 83.0%. The positive and negative predictive values of the 18.55% γH2AX threshold were high: 87.7% and 85.5%, respectively.

CONCLUSION(S)

γH2AX levels were higher in the sperm of male infertility patients than in healthy men. γH2AX levels in sperm, as evaluated with the use of flow cytometry, might be a useful biomarker for evaluating DSBs in human spermatozoa.

The effect of sperm DNA fragmentation on the dynamics of the embryonic development in intracytoplasmatic sperm injection

The genetic integrity of sperm DNA can contribute to the infertility problems experienced by couples. Sperm DNA fragmentation (SDF) is the most common DNA abnormality in male gametes, and yet its effect on embryo kinetics has not been widely studied. Embryo morphokinetic parameters during the first days of embryo culture after intracytoplasmatic sperm injection (ICSI) are weakly predictive of both embryo development and pregnancy outcome. This study investigated the effect of SDF on embryo morphokinetic parameters following ICSI. The DNA fragmentation index (DFI) in spermatozoa from all males in the study (n = 165) was determined before ICSI and the morphokinetic parameters of the embryos (n = 165) were monitored via time-lapse recording. We found that a low DFI index in spermatozoa corresponded with embryos that reached the blastocyst stage at a faster rate after ICSI. Overall, lower SDF levels were also found in the group of patients that achieved pregnancy. Thus, higher SDF levels can slow down embryo morphokinetic parameters, and may be predictive of pregnancy outcomes after ICSI.

Next day determination of ejaculatory sperm motility after overnight shipment of semen to remote locations

PURPOSE

To develop a method for delayed assessment of sperm motility, after shipment of semen to a remote laboratory. Sperm in semen were labeled with the MitoTracker(®) Red CM-H(2)XRos reagent, and fixed with 3.7 % formaldehyde by the laboratory technicians at the origin of the semen. This treatment reflected well sperm mitochondrial activity, and the MitoTracker(®) signal was related to sperm motility and velocity for 2-3 days following ejaculation.

METHODS

Sperm motility and velocity were evaluated manually and by computer assisted semen analysis (CASA), respectively. Fluorescence assessment of individual sperm was carried out with the computer assisted Metamorph v4.6.9 program. Emission levels of MitoTracker(®) spermatozoa were studied in room temperature and cooled semen, or in the respective room temperature swim-up sperm fractions following ejaculation, and on the second day (N = 103 samples, 89 men) and third day (N = 10 samples, 8 men).

RESULTS

Sperm with optical density (O.D.) ≥0.7 showed close correlations with ejaculatory sperm motility and velocity even after second day (r = 0.92, p < 0.001, N = 103 samples). Further, the multiple of sperm motility and velocity was also related to the proportion of high MitoTracker(®) reagent emission sperm (r = 0.83, p < 0.001, N = 103 samples). MitoTracker(®) dye fluorescence on the second day accurately reflected the ejaculatory sperm motility (r = 0.90, p < 0.001). Thus, a shipping delay would not adversely affect the results.

CONCLUSIONS

The delayed assessment of sperm motility in samples treated with MitoTracker(®) Red CM-H(2)XRos reagent and shipped to remote laboratory truly reflects the level of sperm motility at the time of the ejaculation.

Fragmentation of sperm DNA using the TUNEL method

OBJECTIVES

To establish the validity of the TUNEL assay in determining sperm DNA fragmentation, the relationship between the degree of fragmentation and the seminal parameters and the sample needed to conduct the test.

MATERIAL AND METHODS

We used semen samples from healthy fertile men (n=33), patients who consulted for infertility with a prescription for the TUNEL assay (n=77) and patients with intracytoplasmic sperm injection failure (n=20), analyzed according to the 2010 WHO. The TUNEL/propidium iodide test was performed by flow cytometry, on baseline and post-swim-up samples.

RESULTS

The cutoff value for the TUNEL assay (ROC curves) was 26%, with a sensitivity and specificity of 85% and 89%, respectively. The pre-swim-up and post-swim-up medians of the results from the TUNEL assay showed no significant differences (17.0% vs. 12.9%, respectively). However, 39.1% of the samples showed a difference greater than 15 in absolute value between the results of the baseline and post-swim-up TUNEL assays. The linear correlation study of the morphology, mobility and vitality using the post-swim-up TUNEL assay showed a greater correlation than preselection, with significant results (r: -0.394, P<.0001; r: -0.461, P<.0001; r: -0.526, P<.0001).

CONCLUSIONS

The TUNEL assay is a valid test for clinical use. DNA fragmentation is a factor independent from traditional semen tests. We found a greater susceptibility to damage generated in the laboratory procedures in the samples with lower quality. The sample of choice for evaluating DNA fragmentation will depend on whether the clinician is treating a natural or assisted fertilization.

In vitro effects of nonylphenol on motility, mitochondrial, acrosomal and chromatin integrity of ram and boar spermatozoa

The objective of this study was to determine the effects of nonylphenol (NP) on viability of ram and boar sperm in vitro. Ram or boar spermatozoa were exposed to 1, 10, 100, 250 and 500 μg NP ml(-1) for 1, 2, 3 or 4 h. Computer-assisted sperm motility analysis (CASA) system was used to evaluate sperm motility characteristics. Flow cytometry was used to determine mitochondrial membrane potential (MMP) and chromatin integrity, while epifluorescent microscopy was used to determine sperm acrosomal status. Exposure of both species spermatozoa to 250 and 500 μg NP ml(-1) was detrimental to progressive motility (P < 0.05), and its adverse effect was significant at lower (100 μg NP ml(-1) ) concentration (P < 0.05). The percentages of ram and boar spermatozoa with high MMP declined drastically after exposures to ≥250 μg ml(-1) NP (P < 0.05). Unlike chromatin integrity, which did not appear to be altered by NP exposure, there were dose-dependent NP effects (P < 0.05) on acrosomal integrity of both species at as low as 1 μg ml(-1) NP for boar spermatozoa and 10 μg ml(-1) NP for ram spermatozoa. These data show adverse effects of NP on ram and boar spermatozoa and thus its potential harmful effects on male reproduction as NP is found in fruits, vegetables, human milk, fish and livestock products.

Lifestyle factors and sperm aneuploidy

Different environmental and lifestyle factors may interfere with the normal disjunction of sister chromatids/chromosomes during meiosis and may cause aneuploidy. The aim of the study was to examine the association between lifestyle factors and sperm aneuploidy. The study population consisted of 212 healthy men under 45 years of age attending an infertility clinic for diagnostic purposes and who had a normal semen concentration of 20-300×10⁶mL or slight oligozoospermia (semen concentration of 15-20×10⁶/mL). All participants were interviewed and provided a semen sample. Sperm aneuploidy was assessed using multicolor FISH (DNA probes specific for chromosomes X, Y, 18, 13, 21). Results from the study suggest that lifestyle factors are related to sperm aneuploidy. A positive relationship was found between coffee drinking everyday and the lack of chromosome X or Y, as well as coffee drinking 1-6 times per week and additional chromosome 18. Wearing boxer shorts decrease the copy number changes in the whole chromosome 18, the number of additional chromosome 18 and the lack of chromosome 13. Additionally, obesity (BMI 30-40 kg/m²) was positively associated with additional chromosome 21 after being adjusted for potential confounders. These findings demonstrate that changing the men's lifestyle habits may contribute to reduction of the incidence of sperm aneuploidy. It is necessary that men continue to follow sensible health advice concerning excess weight, coffee drinking and wearing tight fitting underwear. As this is the first such study to examine different lifestyle factors and sperm aneuploidy, the results need to be confirmed on larger population.

Evaluation of human sperm chromatin status after selection using a modified Diff-Quik stain indicates embryo quality and pregnancy outcomes following in vitro fertilization

Sperm chromatin/DNA damage can be measured by a variety of assays. However, it has been reported that these tests may lose prognostic value in Assisted Reproductive Technology (ART) cycles when assessed in post-prepared samples, possibly due to the normalizing effect promoted by sperm preparation procedures. We have recently implemented a modified version of the Diff-Quik staining assay that allows for the evaluation of human sperm chromatin status in native samples, together with standard sperm morphology assessment. However, the value of this parameter in terms of predicting in vitro fertilization (IVF) and Intracytoplasmic sperm injection (ICSI) outcomes after sperm selection is unknown. In this study, data from 138 couples undergoing in vitro fertilization (IVF) or Intracytoplasmic sperm injection (ICSI) treatments showed that sperm chromatin integrity was significantly improved after density gradient centrifugation and swim up (p < 0.001), but no correlations were found with fertilization or embryo development rates (p > 0.05). However, sperm samples presenting lower percentages of damaged chromatin were associated with better quality (Grade I) embryos in both ART procedures (p < 0.05) and clinical pregnancy among IVF couples (p < 0.05). Furthermore, regression analysis confirmed the clinical value of Diff-Quik staining in predicting IVF (but not ICSI) clinical pregnancy (OR: 0.927, 95% CI: 0.871-0.985, p = 0.015), and a threshold value of 34.25% for this parameter was established. The proportion of IVF couples achieving a clinical pregnancy was reduced 1.9-fold when the percentage of abnormal dark staining was ≥34.25% (p = 0.05). In conclusion, the Diff-Quik staining assay provides useful information regarding ART success, particularly in IVF cycles, where some degree of 'natural' sperm selection may occur; but not in ICSI, where sperm selection is operator dependent. This quick and low-cost assay is suggested as an alternative method to detect sperm chromatin status in minimal clinical settings, when no other well-established and robust assays (e.g. Sperm chromatin structure assay, terminal deoxynucleotidyl transferase-mediated dUDP nick-end labelling) are available.

The use of complimentary assays to evaluate the enrichment of human sperm quality in asthenoteratozoospermic and teratozoospermic samples processed with Annexin-V magnetic activated cell sorting

Sperm chromatin integrity may affect the outcomes of assisted reproductive technology (ART). Developing a clinically reliable strategy to enrich sperm samples with high chromatin quality spermatozoa prior to sperm banking or use in ART would thus be advantageous. The objectives of this study were to: (i) assess the sperm chromatin quality in men with different categories of semen parameters; and (ii) evaluate the extents of Annexin-V magnetic-activated cell sorting (MACS) technology coupled with differential density gradient centrifugation (DGC) in improving sperm chromatin quality. Three categories of men from couples attending a university-based fertility clinic were recruited based on their semen parameters: normozoospermic (n = 13), asthenoteratozoospermic (n = 17) and teratozoospermic (n = 12). For each patient, spermatozoa in semen samples were processed first by DGC to enrich the motility and further by MACS to remove spermatozoa showing apoptotic features. The yield and enrichment of sperm quality was evaluated at each step with conventional semen parameters in conjunction with a combination of five complementary assays, to assess sperm maturity, chromatin structure, compaction and DNA integrity (Hyaluronic Binding Assay, SCSA, chromomycine A3 staining and TUNEL and COMET assays). Our results demonstrated that, compared with normozoospermic samples, raw asthenoteratozoospermic and teratozoospermic samples had a higher proportion of spermatozoa containing DNA breaks, but only asthenoteratozoospermic exhibited altered chromatin structure and decreased binding to hyaluronic acid. Interestingly, the DGC appeared to select for more mature spermatozoa with high DNA compaction. More importantly, in all categories of semen samples, Annexin-V MACS allows enrichment of spermatozoa with good chromatin quality as measured by the TUNEL and SCSA. Because effective treatment modalities to improve sperm DNA damage are limited, our results suggest a potential clinical value of MACS as a mean to enhance sperm quality that may improve assisted reproductive outcomes.

Clinical value of DNA fragmentation evaluation tests under ART treatments

Male reproductive health has been under scrutiny recently. Many studies in the literature have concluded that semen quality is declining and that the incidence of testicular cancers is increasing. The reason for this change has been attributed to damage in sperm chromatin. During in vivo reproduction, the natural selection process ensures that only a spermatozoon with normal genomic material can fertilize an oocyte. However, the assisted reproduction technique (ART) is our selection process, leading to the possibility that abnormal spermatozoa could be used to fertilize an oocyte. We could avoid this by quantifying the amount and type of genomic damage in sperm using well-accepted laboratory methods. The sperm deoxyribonucleic acid (DNA) integrity is important for success of natural or assisted fertilization as well as normal development of the embryo, fetus and child. Intra cytoplasmic sperm injection (ICSI) is bypassing natural sperm selection mechanisms, which increases the risk of transmitting damaged DNA. The significance of required investigations and multiple techniques is that they could evaluate DNA defects in human spermatozoa. The ability of these techniques to accurately estimate sperm DNA damage depends on many technical and biological aspects. The aim of this review is to evaluate the most commonly used methods.

Relationship between varicocele and sperm DNA damage and the effect of varicocele repair: a meta-analysis

Varicocele, a cause of male infertility, occurs in nearly 40% of infertile males. It has been postulated that varicoceles may cause sperm DNA damage. Sperm DNA integrity has been recognized as one of the important determinants of normal fertilization and embryo growth in natural and assisted conception. Eighty-three human studies were identified after an extensive literature search involving the role of varicoceles in sperm DNA damage. Of the 83 studies, 12 were selected that measured similar types of reactive sperm DNA damage. Seven studies determined the damage of sperm DNA in varicocele-associated patients and six studies evaluated the efficacy of varicocelectomy. One study was a duplicate because both outcomes were included. Data were analysed using RevMan software. The overall estimate showed that patients with varicoceles have significantly higher sperm DNA damage than controls, with a mean difference of 9.84% (95% CI 9.19 to 10.49; P<0.00001). A varicocelectomy can improve sperm DNA integrity, with a mean difference of -3.37% (95% CI -4.09 to -2.65; P<0.00001). In conclusion, there is increased sperm DNA damage in patients with varicoceles and varicocelectomy may be a possible treatment; however, more studies with appropriate controls are needed to confirm this finding. A varicocele is an important cause of male infertility and occurs in nearly 40% of infertile males. The recent understanding of the effect of varicoceles in male reproduction has led some researchers to postulate varicoceles as the possible cause of sperm DNA damage. Eighty-three human studies were identified after an extensive literature search involving the role of varicoceles in sperm DNA damage. Of the 83 studies, 12 were selected that measured similar types of reactive sperm DNA damage by a similar method. Seven studies determined the damage of sperm DNA in varicocele-associated patients and six studies evaluated the efficacy of varicocelectomy. One study was a duplicate because both outcomes were included. The data were then entered in the RevMan software for analysis. The overall estimate showed that patients with varicoceles have significantly higher sperm DNA damage than controls, with a mean difference of 9.84% (95% CI 9.19 to 10.49; P<0.00001). A varicocelectomy can improve sperm DNA integrity, with a mean difference of -3.37% (95% CI -4.09 to -2.65; P<0.00001). Based on the results, it can be concluded that there is increased sperm DNA damage in patients with varicoceles and that varicocelectomy may be a possible treatment; however, more studies with appropriate controls are needed to confirm this finding.

Sperm DNA integrity assays: diagnostic and prognostic challenges and implications in management of infertility

Sperm is not a simple carrier of paternal genetic information but its role extends clearly beyond fertilization. Integrity of sperm genome is an essential pre-requisite for birth of healthy offspring and evaluation of sperm should entail DNA integrity analysis. DNA integrity analysis is a better diagnostic and prognostic marker of sperm reproductive potential. Conventional semen analysis emphasizes on sperm concentration, viability, motility and morphology and has been proven to be a poor indicator of reproductive potential and pregnancy outcome. To overcome the drawbacks associated with conventional semen analysis more useful fertility tests and molecular biomarkers have been explored. Among the different tests which have evolved for assessing the sperm reproductive potential, tests for sperm DNA quality are most promising. Sperm DNA damage has been closely associated with numerous indicators of reproductive health including fertilization, embryo quality, implantation, spontaneous abortion, congenital malformations and childhood diseases. It therefore has great potential as a prognostic test for both in vitro and in vivo conception. This review presents an updated account of tests that have better diagnostic and prognostic implications in the evaluation of sperm DNA damage. The basic principles, outline of methodology, advantage, disadvantage, clinical significance of each technique and implications of these tests have been discussed. The logistics of each test with respect to available resources and equipment in an andrology laboratory, the feasibility of performing these tests in routine diagnostic workup of infertile men and the opportunities and challenges provided by DNA testing in male fertility determination are also presented.

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.

Toxicants and human sperm chromatin integrity

The integrity of the paternal genome is essential as the spermatozoon can bring genetic damage into the oocyte at fertilization and contribute to the development of abnormal pregnancy outcome. During the past two decades, many assays have been developed to measure sperm DNA strand breaks, chromatin structure and compaction and assess the proteins associated with the DNA, as well as epigenetic modifications. Using these assays, it has been shown that exposure to physical agents or chemicals, including therapeutic drugs and environmental toxicants, can affect the integrity of sperm chromatin, inducing structural, genetic and/or epigenetic abnormalities. The mechanisms by which such damage is triggered are still largely unresolved and the susceptibility of each individual will depend on their genetic background, lifestyle and exposure to various insults. Depending on the nature of the chemicals, they may directly target the DNA, induce an oxidative stress, or modify the epigenetic elements. The significance of measuring the sperm chromatin integrity comes from the fact that this end-point correlates well with the low IVF and ICSI outcomes, and idiopathic infertility. Nevertheless, it is hard to establish a direct link between the paternal sperm chromatin integrity and the health of the future generations. Thus, it seems essential to undertake studies that will resolve the impact of chemical and environmental factors on chromatin structure and epigenetic components of human spermatozoa and to elucidate what sperm nuclear end-points are predictors of the quality of progeny outcome.

Human sperm DNA fragmentation: correlation of TUNEL results as assessed by flow cytometry and optical microscopy

An association between DNA fragmentation in sperm determined by the terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay and the incidence of reproductive failure has been reported, either using flow cytometry or optical microscopy. However, the results obtained using each of these two approaches are different. Since there is a relative lack of studies standardizing these two approaches, the direct comparison of the results described in the different articles is difficult at present. To allow the comparison of the TUNEL results obtained using flow cytometry and optical microscopy, we applied these two approaches in a total of 66 human sperm samples. A positive correlation is detected in the TUNEL results as measured by flow cytometry and optical microscopy (Spearman; r = 0.720, P < 0.001). The percentage of TUNEL-positive spermatozoa assessed by flow cytometry is 2.6 times higher than that detected in optical microscopy (39.7% +/- 23.1% versus 15.3% +/- 10.3%). Although there is a good correlation of the TUNEL results obtained by flow cytometry and optical microscopy, the percentages obtained with either technique are different. Therefore, the TUNEL results described in the present work should be valuable to compare the results described in many independent articles, using either optical microscopy or flow cytometry.

Do heat stress and deficits in DNA repair pathways have a negative impact on male fertility?

In Europe up to one in four couples experience difficulty conceiving and in half of these cases the problem has been attributed to sub or infertility in the male partner. The development of assisted reproductive technologies (ART) such as in vitro fertilization and intra-cytoplasmic spermatozoa injection has allowed some such couples to achieve a pregnancy. Concerns have been raised over the increasing use of ART not least because of the discovery of elevated levels of DNA damage in sperm from subfertile men. The impact of damaged DNA originating in the male germ line is poorly understood, but is thought to contribute to early pregnancy loss (recurrent miscarriage), placental problems and have a long-term impact on the health of the offspring. DNA repair is essential for meiotic recombination and correction of DNA damage in germ cells and proteins involved in all the major repair pathways are expressed in the testis. In this review, we will consider evidence that the production of sperm containing damaged DNA can be the result of suboptimal DNA repair and/or a mild environmental insult, such as heat stress, and how studies in mice may give us insight into the origins and consequences of DNA damage in human sperm.

Deoxyribonucleic acid-damaged sperm in cryopreserved-thawed specimens from cancer patients and healthy men

A similarity was found between the percentage of thawed, DNA-damaged spermatozoa in cancer patients and that in candidates to become sperm bank donors who had low sperm cryofreezability. Both groups were significantly different from the sperm bank donor group. It is suggested that the higher rate of DNA fragmentation in sperm from cancer patients compared with sperm bank donors is apparently a result of selecting donors by the level of sperm cryofreezability (i.e., high), rather than a direct effect of an existing malignancy.

Gender effects on the incidence of aneuploidy in mammalian germ cells

Aneuploidy occurs in 0.3% of newborns, 4% of stillbirths, and more than 35% of all human spontaneous abortions. Human gametogenesis is uniquely and gender-specific susceptible to errors in chromosome segregation. Overall, between 1% and 4% of sperm and as many as 20% of human oocytes have been estimated by molecular cytogenetic analysis to be aneuploid. Maternal age remains the paramount aetiological factor associated with human aneuploidy. The majority of extra chromosomes in trisomic offspring appears to be of maternal origin resulting from nondisjunction of homologous chromosomes during the first meiotic division. Differences in the recombination patterns between male and female meiosis may partly account for the striking gender- and chromosome-specific differences in the genesis of human aneuploidy, especially in aged oocytes. Nondisjunction of entire chromosomes during meiosis I as well as premature separation of sister chromatids or homologues prior to meiotic anaphase can contribute to aneuploidy. During meiosis, checkpoints at meiotic prophase and the spindle checkpoint at M-phase can induce meiotic arrest and/or cell death in case of disturbances in pairing/recombination or spindle attachment of chromosomes. It has been suggested that gender differences in aneuploidy may result from more permissive checkpoints in females than males. Furthermore, age-related loss of chromosome cohesion in oocytes as a cause of aneuploidy may be female-specific. Comparative data about the susceptibility of human male and female germ cells to aneuploidy-causing chemicals is lacking. Increases of aneuploidy frequency in sperm have been shown after exposure to therapeutic drugs, occupational agents and lifestyle factors. Conversely, data on oocyte aneuploidy caused by exogenous agents is limited because of the small numbers of oocytes available for analysis combined with potential maternal age effects. The vast majority of animal studies on aneuploidy induction in germ cells represent cause and effect data. Specific studies designed to evaluate possible gender differences in induction of germ cell aneuploidy have not been found. However, the comparison of rodent data available from different laboratories suggests that oocytes are more sensitive than male germ cells when exposed to chemicals that effect the meiotic spindle. Only recently, in vitro experiments, analyses of transgenic animals and knockdown of expression of meiotic genes have started to address the molecular mechanisms underlying chromosome missegregation in mammalian germ cells whereby striking differences between genders could be shown. Such information is needed to clarify the extent and the mechanisms of gender effects, including possible differential susceptibility to environmental agents.

Clinical relevance of sperm DNA damage in assisted reproduction

Many studies have shown how a 'paternal effect' can cause repeated assisted reproduction failures. In particular, with increasing experience of intracytoplasmic sperm injection (ICSI), it became evident that spermatozoa from some patients repeatedly fail to form viable embryos, although they can fertilize the oocyte and trigger early preimplantation development. Many authors have shown how this paternal effect can be traced back to anomalies in sperm chromatin organization: the spermatozoa of subfertile men are characterized by numerical abnormalities in spermatozoal chromosome content, Y chromosome microdeletions, alterations in the epigenetic regulation of paternal genome and non-specific DNA strand breaks. In particular, pathologically increased sperm DNA fragmentation is one of the main paternal-derived causes of repeated assisted reproduction failures in the ICSI era. The intention of this review is to describe nuclear sperm DNA damage, with emphasis on its clinical significance and its relationship with male infertility. Assessment of sperm DNA damage appears to be a potential tool for evaluating semen samples prior to their use in assisted reproduction, helping to select spermatozoa with intact DNA or with the least amount of DNA damage for use in assisted conception.

Relationships between sperm DNA fragmentation, sperm apoptotic markers and serum levels of CB-153 and p,p′-DDE in European and Inuit populations

Persistent organochlorine pollutants (POPs) are suspected to interfere with hormone activity and the normal homeostasis of spermatogenesis. We investigated the relationships between sperm DNA fragmentation, apoptotic markers identified on ejaculated spermatozoa and POP levels in the blood of 652 adult males (200 Inuits from Greenland, 166 Swedish, 134 Polish and 152 Ukrainian). Serum levels of 2, 2′, 4, 4′, 5, 5′-hexachlorobiphenyl (CB-153), as a proxy of the total POP burden, and of 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p′-DDE), as a proxy of the total DDT exposure were determined. Sperm DNA fragmentation was measured by using the TUNEL assay, whereas immunofluorescence methods were utilized for detecting pro-apoptotic (Fas) and anti-apoptotic (Bcl-xL) markers. Both TUNEL assay and apoptotic markers were statistically differed across the four populations. No correlation between neither sperm DNA fragmentation nor apoptotic sperm parameters and the large variations in POPs exposure was observed for the separate study groups. However, considering the European populations taken together, we showed that both %TUNEL positivity and Bcl-xL were related to CB-153 serum levels, whereas our study failed to demonstrate any relations between DDE and %TUNEL positivity and apoptotic sperm biomarkers (Fas and Bcl-xL) in any region or overall regions. These results suggest that CB-153 and related chemicals might alter sperm DNA integrity and Bcl-xL levels in European adult males, but not in the highly exposed Inuit men. Additional issues (genetic background, lifestyle habits and characterization of total xeno-hormonal activities) need to be investigated in order to fully assess the population variations observed.

Correlation of sperm DNA damage with IVF and ICSI outcomes: a systematic review and meta-analysis

PURPOSE

To assess the effects of sperm DNA damage, as determined by the TUNEL assay and the SCSA respectively, on the outcomes of IVF/ICSI treatment.

METHODS

A Medline search (from Jan 1978 to Apr 2006) was performed, together with a manual search of the bibliographies of retrieved original papers and review articles. 8 articles met all inclusion/exclusion criteria, of which, 5 used the TUNEL assay and the other 3 used the SCSA. All these articles were included in separate meta-analysis. The meta-analysis was conducted using the RevMan software with fixed-effect model or random-effects model.

RESULTS

As for articles using the TUNEL assay, the pooled results of IVF outcomes indicated that the clinical pregnancy rate (RR 0.68, 95% CI 0.54 to 0.85, P = 0.006), but not the fertilization rate (RR 0.79, 95% CI 0.54 to 1.16, P = 0.23) decreased significantly for patients with high degree of sperm DNA damage compared with those with low degree of sperm DNA damage. RRs of the ICSI outcomes indicated that there was no significant difference in either fertilization rate (RR 1.03, 95% CI 0.89 to1.18, P = 0.70) or clinical pregnancy rate (RR 0.76, 95% CI 0.55 to 1.04, P = 0.09) between these two groups. As for the SCSA papers, the pooled results showed no significant effects of sperm DNA damage on the clinical pregnancy rate after IVF (RR 0.58, 95% CI 0.25 to 1.31, P = 0.19) or ICSI (RR 1.18, 95% CI 0.81 to 1.74, P = 0.38).

CONCLUSION(S)

Our meta-analysis indicates that sperm DNA damage, as assessed by the TUNEL assay, significantly decreases only the chance of IVF clinical pregnancy, but not that of either IVF fertilization or ICSI fertilization or ICSI clinical pregnancy. Besides, our results also reveal that sperm DNA damage, when assessed by the SCSA, has no significant effect on the chance of clinical pregnancy after IVF or ICSI treatment.

Sperm DNA integrity in testicular cancer patients

BACKGROUND

We evaluated the impact of testicular germ cell cancer (TGCC), its treatment and length of follow-up on sperm DNA integrity.

METHODS

In 96 TGCC patients, semen was collected at specific intervals until 5 years after treatment. Sperm DNA integrity was assessed by the sperm chromatin structure assay (SCSA, n = 193) and by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL, n = 159) assay. Results were expressed as DNA fragmentation index (DFI). Controls comprised of 278 military conscripts.

RESULTS

Post-surgery testicular cancer (TC) patients did not differ from controls. Compared with pretreatment values, radiotherapy induced a transient increase in SCSA(DFI) (medians: 12 versus 19%; P = 0.03), normalizing after 3-5 years. One year or more after therapy, 5/13 (38%) of normozoospermic, irradiated patients had SCSA(DFI) >27% compared with 7% of normozoospermic controls (P = 0.002). More than two cycles of chemotherapy decreased DFI 3-5 years post-therapy (median SCSA(DFI): 12 versus 9.1%, P = 0.02; median TUNEL(DFI): 11 versus 7.5%, P = 0.03).

CONCLUSION

Irradiation increases sperm DNA damage 1-2 years after treatment, and 38% of irradiated patients with normozoospermia had high (>27%) DNA damage, which may affect the sperm-fertilizing ability. TC per se is not associated with an increase of DFI, and DFI is reduced by three or more cycles of chemotherapy.

Sperm DNA fragmentation

Several 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. The 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 trails before their integration into routine clinical practice. The physiological/molecular integrity of sperm DNA is a novel parameter of semen quality and a potential fertility predictor. Although DNA integrity assessment appears to be a logical biomarker of sperm quality, it is not being assessed as a routine part of semen analysis by clinical andrologists. Extensive investigation has been conducted for the comparative evolution of these techniques. However, some of these techniques require expensive instrumentation for optimal and unbiased analysis, are labor intensive, or require the use of enzymes whose activity and accessibility to DNA breaks may be irregular. Thus, these techniques are recommended for basic research rather than for routine andrology laboratories. Sperm chromatin structure evaluation is applied to detect male factors that may affect the chance of success with IVF as well as natural fertility. Further research is needed to define the optimal test of sperm chromatin structure. The clinical application of this test will evolve as well.