Sperm DNA damage in men from infertile couples

Aim： To investigate the prevalence of high levels of sperm DNA damage among men from infertile couples with both normal and abnormal standard semen parameters. Methods： A total of 350 men from infertile couples were assessed. Standard semen analysis and sperm chromatin structure assay （SCSA） were carried out. Results： Ninety-seven men （28% of the whole study group） had a DNA fragmentation index （DFI） 〉 20%, and 43 men （12%） had a DFI 〉 30%. In the group of men with abnormal semen parameters （n = 224）, 35% had a DFI 〉 20%, and 16% had a DFI 〉 30%, whereas these numbers were 15% and 5%, respectively, in the group of men with normal semen parameters （n = 126）. Men with low sperm motility and abnormal morphology had significantly higher odds ratios （ORs） for having a DFI 〉 20% （4.0 for motility and 1.9 for morphology） and DFI 〉 30% （6.2 for motility and 2.8 for morphology） compared with men with normal sperm motility and morphology. Conclusion： In almost one-third of unselected men from infertile couples, the DFI exceeded the level of 20% above which, according to previous studies, the in vivo fertility is reduced. A significant proportion of men with otherwise normal semen parameters also had high sperm DNA damage levels. Thus, the SCSA test could add to explaining causes of infertility in cases where semen analysis has not shown any deviation from the norm. We also recommend running the SCSA test to choose the appropriate assisted reproductive technique （ART）.     

Oxidative stress status and sperm DNA fragmentation in fertile and infertile men

Evidence suggests that disturbing the balance between reactive oxygen species levels and antioxidant contents in seminal plasma leads to oxidative stress resulting in male infertility. This study was carried out to identifying clinical significance of seminal oxidative stress and sperm DNA fragmentation in treatment strategies of male infertility in southwest Iran. Sperm parameters, lipid peroxidation and activity of antioxidant enzymes were assessed in fertile (n = 105) and infertile (n = 112) men. Malondialdehyde (MDA) levels in seminal plasma were found to be higher significantly (p < .001) in patients. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in seminal plasma were significantly (p < .001) lower in infertile men. Significant negative correlations were observed between MDA levels and sperm motility and normal morphology. Spermatozoa with fragmented DNA were higher (p < .001) in infertile men and significantly correlated with MDA levels and SOD and GPx activities. MDA of 4.2 nmol/ml, SOD of 4.89 U/ml and GPx of 329.6 mU/ml were optimum cut‐off limits to discriminate infertile patients from fertile men. The results show the leading role of oxidative stress in aetiology of male infertility in southwest Iran and indicate that evaluation of seminal antioxidant status and DNA integrity can be helpful in men attending infertility clinics during fertility assessment.     

TUNEL assay: Establishing a sperm DNA fragmentation cut‐off value for Egyptian infertile men

Male factor infertility is responsible for half of all infertility cases. Conventional semen analysis is inadequate to evaluate male fertility. Sperm DNA fragmentation (SDF) test can be done by: direct methods such as Terminal deoxynucleotidyl transferase dUTP Nick‐End Labeling (TUNEL) and Comet assay, or indirect like Sperm Chromatin Structure Assay (SCSA) and Sperm Chromatin Dispersion (SCD). TUNEL assay measures both single‐ and double‐strand breaks and is technically less demanding, while SCSA tests for the susceptibility for nuclear DNA denaturation and samples should be sent to the reference lab. Studies showed that a single cut‐off value does not fit all. Therefore, this study aimed at establishing a cut‐off value to discriminate between fertile and infertile Egyptian men. We enrolled 354 infertile men and 40 proven fertile volunteers.TUNEL assay was performed using Apo‐Direct kit and bench top flow cytometer.The calculated SDF cut‐off value was 20.3% with a sensitivity of 96.6% and specificity of 87.5%, and the overall accuracy of the test was 95.7%. Sperm DNA fragmentation Test using TUNEL assay is valuable tool for male infertility evaluation, and it assists in offering the best treatment options based on it's results.     

Evaluation of sperm DNA fragmentation index,Zinc concentration and seminal parameters from infertile men with varicocele

The aim of this study was to investigate the effect of varicocele on DNA fragmentation index (DFI), zinc concentration and seminal parameters in infertile patients. In this prospective study, 179 men with at least 1‐year history of infertility and varicocele were examined for semen quality at Hanoi Medical University Hospital (HMUH), Hanoi, Vietnam. In addition, an inverse correlation between zinc concentration and the degree of sperm DNA fragmentation in patients with clinical varicocele was found. The difference in mean values of sperm DNA fragmentation index in patients with various grades of varicoceles can be neglected, whereas most patients with varicocele of grades II and III had DFI >30%. Varicocele is associated with high levels of DNA damage in spermatozoa and reduced zinc levels that correlate with different grades of disease. Therefore, DNA fragmentation index and zinc concentration can be used as essential additional diagnostic test for patients with clinical varicocele. A study should be conducted to evaluate the benefits of zinc supplementation to improve seminal parameters in patients with varicocele.     

精子染色质扩散实验检测精索静脉曲张及不明原因不育患者精子DNA碎片

目的了解精索静脉曲张(VC)及不明原因不育患者精子DNA碎片的发生比例。方法改进的精子染色质扩散(SCD)实验分析精子DNA碎片。检测VC不育患者39例,不明原因不育患者57例。以生育健康成年男性32例为对照组。结果VC不育患者SCD小光晕和无光晕精子(精子DNA碎片)比值平均为(36.6±18.9)%,VC不育组明显高于对照组(12.1±5.2)%(P<0.001),而大光晕和中光晕精子比值VC不育组明显低于对照组(P<0.01);不明原因不育患者精子DNA碎片比值平均为(26.8±10.2)%,与对照组[(12.1±5.2)%]比较有显著性差异(P<0.001)。结论SCD实验表明,VC及不明原因不育患者精子DNA碎片比值增高。     

精索静脉曲张对精子染色质结构及运动能力的影响

目的:探讨精索静脉曲张对精子染色质结构及运动能力的影响。方法:对精索静脉曲张组(无慢性疾病及生殖系统病史者,n=74)和对照组(n=89)进行精子染色质结构分析(SCSA)和精液常规分析(精液量、粘稠度、pH值、精子顶体完整率、精子存活率、畸形率、精子密度、活动率及各运动参数)。结果:精索静脉曲张组精子密度、a+b级精子百分率和精子存活率[分别为(41.4±38.7)×106/ml,(31.7±16.9)%,(62.8±22.2)%]显著低于对照组[分别为(80.9±63.1)×106/ml,(46.8±20.5)%,(77.2±17.5)%],P均<0.05;精子运动参数VCL、VSL、VAP精索静脉曲张组分别为(37.4±12.5)、(23.4±7.8)、(26.5±8.2)μm/s,对照组分别为(42.4±10.7)、(27.3±7.3)、(30.7±7.8)μm/s,精索静脉曲张组与对照组相比显著降低(P均<0.05),而MAD显著增加(P<0.01),SCSACOMPαt值精索静脉曲张组(为23.2±16.2)明显高于对照组(为14.1±11.8)(P<0.05)。结论:精索静脉曲张引起精子DNA损伤和精子运动能力的改变,可能是导致男性不育的主要原因之一。     

Relationship between seminal ascorbic acid and sperm DNA integrity in infertile men

Ascorbic acid has recently been reported to protect sperm DNA from the damage induced by exogenous oxidative stress in vitro. But, there is no report on seminal ascorbic acid and sperm DNA fragmentation in infertile men. In this study, we asked whether sperm DNA damage correlates with seminal ascorbic acid levels. Sperm DNA fragmentation index (DFI) was analysed in 75 men by flow cytometry after acridine orange staining. We also measured the levels of seminal plasma ascorbic acid and total antioxidant capacity. Abnormal sperm DNA integrity (DFI >or= 30%) was observed in 12% of the patients with normal semen parameters and in 52% of the patients with abnormal semen parameters. There were significant correlations between the level of DFI and conventional semen parameters including sperm count, motility and morphology (r = -0.29, -0.55 and -0.53 respectively; p < 0.05). Seminal ascorbic acid level was significantly lower in the patients with leucospermia than the patient with normal semen parameters. Interestingly, a significantly greater percentage of men with abnormal DFI were observed in the patients with low levels of seminal ascorbic acid compared with those with normal or high levels of ascorbic acid (59% vs. 33%, p < 0.05). Men with insufficient seminal ascorbic acid frequently have sperm DNA damage.     

Specialized sperm function tests in varicocele and the future of andrology laboratory

Varicocele is a common medical condition entangled with many controversies. Though it is highly prevalent in men with infertility, still it marks its presence in males who do have normal fertility. Determining which patients are negatively affected by varicocele would enable clinicians to better select those men who benefitted the most from surgery. Since conventional semen analysis has been limited in its ability to evaluate the negative effects of varicocele on fertility, a multitude of specialized laboratory tests have emerged. In this review, we examine the role and significance of specialized sperm function tests with regards to varicocele. Among the various tests, analysis of sperm DNA fragmentation and measurements of oxidative stress markers provide an independent measure of fertility in men with varicocele. These diagnostic modalities have both diagnostic and prognostic information complementary to, but distinct from conventional sperm parameters. Test results can guide management and aid in monitoring intervention outcomes. Proteomics, metabolomics, and genomics are areas; though still developing, holding promise to revolutionize our understanding of reproductive physiology, including varicocele.     

精子DNA碎片指数和精子畸形率对ICSI临床结局的影响

目的:通过评估ICSI治疗前的精子畸形率(SMR)和精子DNA碎片指数(DFI),探讨精子DFI和SMR对卵胞浆内单精子注射(ICSI)助孕结局的影响。方法:共入组79对因少弱精子症实施第一周期ICSI治疗的不孕夫妇,在进入治疗周期前3⁶个月,评价精子浓度、前向运动精子百分率、SMR及DFI。主要观察SMR和DFI与ICSI结局参数的关系。结果:79例少弱精子症患者DFI正常51例,异常28例,异常组的DFI值明显升高(14.18%vs 41.47%);巧合的是,SMR正常组同样为51例,异常组28例,异常组的SMR值亦明显升高(87.88%vs98.46%)。按DFI正常(DFI≤25%)与异常(DFI>25%)分组,或按SMR正常(≤96%)与异常(>96%)分组,组间的双方年龄、女方BMI、获卵数、移植胚胎数等基本情况差异无统计学意义。DFI正常和异常组间,SMR正常和异常组间的受精卵子数、可移植胚胎数、早期流产率无显著差异;异常组生化妊娠率(43.5%vs 61.5%)和临床妊娠率(39.1%vs 56.4%)降低,但差异无统计学意义(P=0.19及0.10)。精子DFI与SMR呈显著正相关(r=0.231,P<0.05)。结论:精子DFI增高(>25%),与按严格标准检测的SMR增高(>96%)男性行ICSI治疗,生化妊娠率和临床妊娠率降低,但与正常者比较未发现有统计学差异,可能与样本量小有关,有必要深入研究。     

Sperm DNA fragmentation in subfertile men: the effect on the outcome of intracytoplasmic sperm injection and correlation with sperm variables

OBJECTIVE

To present the first UK data on sperm DNA fragmentation levels in subfertile men and fertile controls, the correlation with semen variables, and to assess the effect on the outcome of intracytoplasmic sperm injection (ICSI).

PATIENTS, SUBJECTS AND METHODS

In all, 56 subfertile men undergoing ICSI (28 with positive and 28 with a negative outcome for paternity) and 10 control fertile semen donors were recruited. The sperm DNA fragmentation index (DFI) was assessed on raw pre‐preparation samples using the sperm chromatin structure assay. A mean of 5212 sperm were analysed per sample and DFI data are presented by fertility status, ICSI outcome and correlated with semen variables (assessed using World Health Organisation criteria).

RESULTS

Total DFI was significantly higher in subfertile men than in fertile controls (mean and median of 22.8% and 17.0% vs 8.4% and 5.0%; P < 0.001), as was the proportion of both moderate DFI (16.4% and 13.0% vs 6.4% and 4.0%; P = 0.001) and high DFI (6.2% and 6.1 vs 2.0% and 1.0%; P = 0.01). This difference remained significant when the control men were compared only with the subfertile men with successful paternity. There was no significant difference in DFI in the subfertile men when analysed by ICSI outcome (mean and median of 24.5% and 17.0% vs 22.3% and 21.0% for successful and unsuccessful cycles, respectively; P = 0.94). There was a positive statistically significant correlation (r = 0.37; P = 0.02) between the DFI and sperm morphology.

CONCLUSIONS

This study confirms a relationship between male subfertility and sperm DFI; we discuss the correct role for genetic testing of sperm in the evaluation of subfertile men. Although DNA fragmentation data might help to decide a suitable treatment, once it is decided to proceed with ICSI, DFI levels have no effect on the outcome.     

Obesity leads to higher risk of sperm DNA damage in infertile patients

There has been a growing interest over the past few years in the impact of male nutrition on fertility. Infertility has been linked to male overweight or obesity, and conventional semen parameter values seem to be altered in case of high body mass index （BMI）. A few studies assessing the impact of BMI on sperm DNA integrity have been published, but they did not lead to a strong consensus. Our objective was to explore further the relationship between sperm DNA integrity and BMI, through a 3-year multicentre study. Three hundred and thirty male partners in subfertile couples were included. Using the terminal uridine nick-end labelling （TUNEL） assay, we observed an increased rate of sDerm DNA damage in obese men （odds ratio （95% confidence interval）： 2.5 （1.2-5.1））.     

Novel insights into the pathophysiology of varicocele and its association with reactive oxygen species and sperm DNA fragmentation

Varicocele has been associated with reduced male reproductive potential. With the advances in biomolecular techniques, it has been possible to better understand the mechanisms involved in testicular damage provoked by varicocele. Current evidence suggests the central role of reactive oxygen species (ROS) and the resultant oxidative stress (OS) in the pathogenesis of varicocele-associated male subfertility although the mechanisms have not yet been fully described and it is likely to be multifactorial. Excessive ROS is associated with sperm DNA fragmentation, which may mediate the clinical manifestation of poor sperm function and fertilization outcome related to varicocele. Testing of ROS/OS and DNA fragmentation has the potential to provide additional diagnostic and prognostic information compared to conventional semen analysis and may guide therapeutic management strategies in individual patient.     

DNA fragmentation assessment by flow cytometry and Sperm-Bos-Halomax (bright-field microscopy and fluorescence microscopy) in bull sperm

The aim of this study was to find the relationship between fertility (as 90-day non-return rates) and DNA fragmentation assessed by two techniques [sperm chromatin structure assay (SCSA) and Sperm-Bos-Halomax (SBH)]. Furthermore, other quality parameters were achieved (motility, morphological abnormalities, cytoplasmic droplets, viability, capacitation and acrosomal and mitochondrial status) and their correlations with fertility were analysed. Bulls were divided into three fertility groups: high [non-return rate (NRR) >or= 80], medium (80 < NRR >or= 70) and low (70 < NRR > 40). The results of this study indicate that there is a good correlation between fertility and different parameters of sperm quality (SBH and SCSA parameters, % of spermatozoa with head, neck and total abnormalities, and % of spermatozoa with proximal cytoplasmic droplets) and differences between fertility groups were observed in some of them (SBH and SCSA parameters and % of spermatozoa with head, neck and total abnormalities). In this sense, SBH parameters rendered good correlations with fertility (r = -0.42 using bright light microscope and r = -0.47 with fluorescence). Also, standard deviation of DNA fragmentation index (SD-DFI) and DFIh (cells with High DNA fragmentation index) showed good correlations with fertility (r = -0.41 and r = -0.29). No correlations were observed between SCSA and SBH parameters. A multiple regression shows that four parameters (% of proximal cytoplasmic droplets, % of intact acrosomes in total population, SD-DFI and percentage of fragmented DNA detected by bright light microscope) present a good predictive value of the fertility of sperm samples (r(2) = 0.34, p < 0.001).     

Comparative analysis of tests used to assess sperm chromatin integrity and DNA fragmentation

Male infertility has a complex etiology, and many times, the cause is unknown. While routine semen analysis provides an overview of basic semen parameters, such as sperm concentration, motility, viability and morphology, a significant overlap of these parameters has been reported in fertile and infertile men. Moreover, conventional semen parameters do not reveal the cellular or molecular mechanisms of sperm dysfunctions leading to infertility. Therefore, sperm functional parameters, including sperm chromatin integrity, are evaluated to provide information on subtle sperm defects that are not routinely identified. Incomplete or defective sperm chromatin condensation increases the susceptibility of the sperm DNA to oxidative damage or other factors. To evaluate sperm chromatin integrity, different methods with varying degrees of diagnostic and prognostic capabilities are available. Among these assays, SCSA, TUNEL and SCD assays are most commonly used. While these assays rather evaluate the DNA directly for damages, the aniline blue and chromomycin A3 stains test for the quality of chromatin condensation. Thus, this review discusses and compares different methods used to evaluate sperm chromatin integrity and condensation, and their inclusion in the routine evaluation of the male infertility.     

DNA sperm damage correlates with nuclear ultrastructural sperm defects in teratozoospermic men

Sperm morphology has consistently been the best indicator of male fertility. Transmission electron microscopy currently provides the most information on the subcellular details of sperm structure. Recently, assessment of sperm DNA damage has been employed to assess fertility potential. The purpose of this work was to link sperm DNA damage, evaluated by an intercalated fluorescent dye, with the structural characteristics of sperm. Conventional semen analysis was performed on samples from men undergoing fertility evaluation. Thirty men were evaluated and assigned to three subgroups based on strict criteria for sperm morphology: normal morphology (>14% normal forms), intermediate morphology (5-14% normal forms), and poor morphology (<5% normal forms). By quantifying acridine orange-positive cells and ultrastructural sperm defects, we found that the poor morphology pattern group showed a positive association between sperm carrying damaged DNA and the percentage of sperm nucleus with vacuoles (P = 0.01). No statistically significant correlations were established in other ultrastructural characteristics of sperm, including immature chromatin, lytic changes, or abnormal sperm tails. These results suggest that zones without chromatin in the sperm nucleus reflect underlying chromosomal or DNA defects in severe teratozoospermic men. This association should be considered in the evaluation of male fertility.     

Relationship between sperm telomere length and sperm quality in infertile men

Telomeres, noncoding and repetitive DNA sequences play a significant function in chromatin integrity. Telomere length is age-dependent in somatic cells, while it increases in sperm cell with age. Therefore, we aimed to assess sperm chromatin, leucocyte and sperm telomere length (LTL, STL) in spermatozoon of 38 infertile and 19 fertile men aged between 20 and 50 years. Protamine deficiency (chromomycin A3 test), DNA fragmentation (TUNEL assay), lipid peroxidation (Bodipy probe) and telomere length (quantitative real-time PCR) were assessed. A significant decrease in mean of sperm concentration and motility and a significant increase in means of sperm abnormal morphology, DNA fragmentation, lipid peroxidation and protamine deficiency were observed in infertile compared with fertile men. In addition, the mean of LTL and STL were significantly shorter in infertile men compared with fertile individuals. We observed significant associations between telomere length with sperm concentration, DNA fragmentation and lipid peroxidation. We hypothesised that increased oxidative stress in spermatozoa of infertile men can result in abnormal packaging of chromatin, damage of DNA and shorter sperm telomere length. Together, these anomalies may account for fertility failure in these individuals.     

Poor sperm quality and advancing age are associated with increased sperm DNA damage in infertile men

With increasing evidence for faulty paternal contribution to reproduction, there has been a steady increase in studies highlighting an association between sperm DNA damage, failed/delayed fertilisation and aberrant embryo development. Owing to prevailing ambiguity, the aims of the study were to analyse the genetic integrity of the male gamete and then to understand its association with age, standard semen parameters, lifestyle and occupational factors. The study included 504 subjects, attending university infertility clinic for fertility evaluation and treatment. Semen characteristics were analysed by standard criteria; terminal deoxynucelotidyl transferase-mediated nick end-labelling assay was employed for DNA damage assessment. The average incidence of sperm DNA damage in patients with normozoospermic semen parameters was <10%. Patients with oligozoospermia, severe oligozoospermia, oligoasthenoteratospermia, asthenoteratozoospermia and necrozoospermia had significantly higher level of sperm DNA damage (P < 0.001). Patients above 40 years of age had significantly high levels of DNA damage (P < 0.001) compared with their counterparts. Patients with varicocele and a history of alcohol consumption had higher incidence of spermatozoa with DNA damage (P < 0.01). Poor sperm characteristics in the ejaculate are associated with increased sperm DNA damage. Age-related increase in sperm DNA damage and association of the same with varicocele and alcohol consumption are also demonstrated.     

Prediction of reproductive function recovery after microsurgical varicocelectomy in men from infertile couples: Clinical and laboratory predictors

The objective was to reveal predictors for fertility recovery after varicocelectomy in subfertile men. This retrospective study recruited 93 men with clinical varicocele and pathozoospermia who underwent microsurgical varicocelectomy. Stepwise discriminant analysis was performed to identify predictors of spontaneous pregnancy (SP) after surgery. ‘Clinically significant improvement’ (CSI) following varicocelectomy was defined as an increase in total progressively motile sperm count (TPMSC) by at least 12.5 million (calculated from WHO-2010 reference values). 52% of patients showed CSI, and 28% reported SP after surgery. Patients who reported SP (group II), compared to that remained infertile (group I), were younger (27.3 ± 2.9 versus 30.2 ± 4.2 years; p < .01), had less infertility period (24.1 ± 14.0 versus 44.4 ± 32.9 months; p < .05) and had initially higher TPMSC (median (25% −75%) = 34 (11–67) versus 9.5 (0–33) mln; p < .05). The stepwise discriminant analysis showed that male age (coefficient value = −0.157), total sperm motility (0.024) and postoperative increase in TPMSC (0.010) were the significant predictors of SP. The predictive ability, sensitivity and specificity of the discriminant function were 84%, 87%, 76% respectively. This algorithm can be recommended after varicocelectomy in decision-making on natural conception or the ART protocols usage.     

精子染色质结构分析的临床意义

目的探讨女方不明原因流产和不明原因不孕与其配偶精子染色质性状之间的关系;方法通过精子染色质结构分析(SCSA)对22例不明原因流产和36例不明原因不孕妇女配偶精子,以及20例正常对照者精子进行DNA完整性检测,并比较它们之间的差异;结果对照组与不明原因流产组以及不孕组之间精子DNA完整性存在差异,且差异具有统计学意义(P<0．05),而不明原因流产组与不孕组之间精子DNA完整性比较无明显差异(P>0．05);结论精子染色质结构分析有可能作为不明原因流产和不孕的辅助诊断方法在临床应用。     

Smoking influence on sperm vitality,DNA fragmentation,reactive oxygen species and zinc in oligoasthenoteratozoospermic men with varicocele

This study aimed to assess the influence of smoking duration and intensity on sperm vitality, sperm DNA fragmentation, reactive oxygen species (ROS) and zinc (Zn) levels in oligoasthenoteratozoospermic (OAT) men with varicocele (Vx). A total of 246 men were investigated who were divided into OAT nonsmokers, OAT smokers, OAT nonsmokers and OAT smokers with Vx. They were subjected to history taking, clinical examination and semen analysis. In their semen, sperm hypo‐osmotic swelling (HOS) test, sperm DNA fragmentation test, seminal ROS and seminal Zn were assessed. The results demonstrated significantly decreased HOS test, seminal Zn level and significantly increased sperm DNA fragmentation, seminal ROS levels in OAT smokers with Vx more than OAT smokers compared with OAT nonsmokers. Smoking intensity, smoking duration and Vx grade demonstrated significant negative correlations with sperm motility, HOS test percentage and significant positive correlations with sperm DNA fragmentation, seminal ROS level. It is concluded that smoking has a negative impact on sperm progressive motility, HOS test, seminal Zn and positive impact on sperm DNA fragmentation, semen ROS level that are exaggerated if Vx is associated being correlated with smoking intensity, smoking duration and Vx grade.