Sperm DNA: organization, protection and vulnerability: from basic science to clinical applications--a position report

Immunoregulation and male reproductive function: Impacts and mechanistic insights into inflammation

This paper investigates the complex relationship between the immune system and male reproductive processes, emphasizing how chronic inflammation can adversely affect male reproductive health. The immune system plays a dual role; it protects and regulates reproductive organs and spermatogenesis while maintaining reproductive health through immune privilege in the testes and the activities of various immune cells and cytokines. However, when chronic inflammation persists or intensifies, it can disrupt this balance, leading to immune attacks on reproductive tissues and resulting in infertility.This study provides a detailed analysis of how chronic inflammation can impair sperm production, sperm quality, and the secretion of gonadal hormones both directly and indirectly. It also delves into the critical roles of testicular immune privilege, various immune cells, and cytokines in sustaining reproductive health and examines the impacts of infections, autoimmune diseases, and environmental factors on male fertility.

Comparison of Embryological Results of Microinjection in Two Groups of Men with and without Requesting Sperm DNA Fragmentation Index Measurement

Introduction

The sperm DNA fragmentation index (DFI) is considered a valuable measure to assess male fertility, but the predictive value of DFI for the outcomes in assisted reproductive technology (ART) is still controversial. Therefore, this study is aimed at investigating the effect of requesting a DFI test or performing ART without DFI on the results observed in the embryology laboratory (number of embryos, fertilization rate, and embryo quality) after intracytoplasmic sperm injection (ICSI).

Methods

This retrospective study was conducted on infertile men who underwent ICSI and were referred to the Avicenna Infertility and Recurrent Abortion Treatment Center in Tehran from 2019 to 2022. The samples were categorized into two groups: a case group with DFI measurement and a control group without DFI measurement. We conducted a comparative analysis of the embryology results between the two groups, focusing on parameters such as fertilization rate, number of embryos, and embryo quality. t-tests and Mann-Whitney U tests were used to conduct single variable analysis. Potential confounding effects were adjusted to use the multivariate linear and logistic regression.

Results

Data analysis showed no significant statistical difference between the case group and the control group in terms of the number of embryos (95% confidence interval for the regression coefficient (β) = -0.257-0.123), and embryo quality (95% confidence interval for β = -0.199-0.114). There was no significant statistical difference between the two groups due to the fertilization rate (95% confidence interval for β = -3.42-3.42), except for the variables of woman's age and sperm count after ICSI, as determined by adjusted linear regression.

Conclusions

Although DFI measurement is used to assess male infertility, its importance as a predictor for the embryology outcomes after ICSI requires further evaluation and the determination of a cut-off point for predicting results. This study was based on retrospectively collected DFI data, and prospective studies confirming the superiority of ICSI outcomes are necessary.

Human Papillomavirus and Male Infertility: What Do We Know?

In recent years, increasing attention has been paid to understanding the causes of infertility, which is being recognized as a growing health problem affecting large numbers of couples worldwide. Male infertility is a contributing factor in approximately 30-40% of cases, and one of its etiological causes is sexually transmitted infections (STIs). Among sexually transmitted pathogens, human papillomavirus (HPV) can contribute in various ways to the failure of spontaneous and assisted reproduction, acting in the different phases of conception, especially in the early ones. In particular, HPV infection can affect sperm DNA integrity, sperm motility, count, viability, and morphology and can induce the production of anti-sperm antibodies (ASAs). In this narrative review, we aimed to provide an overview of existing research on the potential adverse effects of HPV infection on male reproductive health. Furthermore, we analyzed how limiting the spread of the infection, particularly with gender-neutral vaccination, could be a possible therapeutic tool to counteract male and female fertility problems.

Environmental and Genetic Traffic in the Journey from Sperm to Offspring

Recent advancements in the understanding of how sperm develop into offspring have shown complex interactions between environmental influences and genetic factors. The past decade, marked by a research surge, has not only highlighted the profound impact of paternal contributions on fertility and reproductive outcomes but also revolutionized our comprehension by unveiling how parental factors sculpt traits in successive generations through mechanisms that extend beyond traditional inheritance patterns. Studies have shown that offspring are more susceptible to environmental factors, especially during critical phases of growth. While these factors are broadly detrimental to health, their effects are especially acute during these periods. Moving beyond the immutable nature of the genome, the epigenetic profile of cells emerges as a dynamic architecture. This flexibility renders it susceptible to environmental disruptions. The primary objective of this review is to shed light on the diverse processes through which environmental agents affect male reproductive capacity. Additionally, it explores the consequences of paternal environmental interactions, demonstrating how interactions can reverberate in the offspring. It encompasses direct genetic changes as well as a broad spectrum of epigenetic adaptations. By consolidating current empirically supported research, it offers an exhaustive perspective on the interwoven trajectories of the environment, genetics, and epigenetics in the elaborate transition from sperm to offspring.

Progress on the roles of zinc in sperm cryopreservation

One of the effective methods for the long-term preservation of mammalian genetic resources is the cryopreservation of semen. However, a number of parameters, including diluents, the rate of freezing and thawing, cryoprotectants, etc., can easily alter the survival of frozen-thawed sperm. Numerous studies have documented the addition of a variety of zinc compounds, to the diluents used to cryopreserve sperm. The primary objective of this review is to briefly describe that adding zinc to diluents as an antioxidant significantly enhances frozen-thawed sperm quality. Second, a summary of the present understanding of zinc's molecular mechanism on semen cryopreservation is provided. Thirdly, this study addresses that nanoparticles of zinc can offer suggestions for raising cryopreservation effectiveness.

The Sperm DNA Fragmentation Assay with SDF Level Less Than 15% Provides a Useful Prediction for Clinical Pregnancy and Live Birth for Women Aged under 40 Years

This retrospective cohort study was conducted on 1148 males who presented along with their partners for infertility management at the PIVET Medical Centre between 2013 and 2022 and had a sperm DNA fragmentation (SDF) assay performed by Halosperm, thereafter participating in 1600 assisted reproductive technology (ART) cycles utilising one of three modalities, namely, IVF-Only, ICSI-Only or IVF-ICSI Split cycles. The outcomes from the ART cycles were then analysed as two groups based on SDF levels <15% and ≥15%. The study showed the unadjusted fertilization rates were not different between the groups, neither across the four female age ranges. However, when the fertilization rates were adjusted for the mature oocytes (metaphase-II oocytes), there was a highly significant difference in fertilization rates in favour of the group with SDF levels < 15% where the women were in the younger age grouping of <35 years (78.4% vs. 73.0%; p < 0.0001). Overall, there was no difference in the rates of blastocyst development nor clinical pregnancy rates between the two SDF groups, but there was a significantly higher pregnancy rate for the younger women (<35 years) with the group of SDF level < 15% (44.1% vs. 37.4%; p = 0.04). Similarly, there was no difference in the miscarriage rates overall with respect to SDF groups, and no clear picture could be deciphered among the women's age groups. With respect to cumulative live births, this reflected the pregnancy rates with no overall difference between the two SDF groups, but there was a significantly higher cumulative live birth rate for women <35 years where the SDF level was <15% (38.6% vs. 28.6%; p < 0.01). Among the three modalities, the highest cumulative live birth rate occurred within the group with SDF level < 15%, being highest with the IVF mode, particularly for women aged <40 years (43.0% vs. 37.7% for IVF-ICSI Split and 27.9% for ICSI; p = 0.0002), noting that the IVF case numbers were disproportionately low.

Condensation and protamination of sperm chromatin affect ICSI outcomes when gametes from healthy individuals are used

STUDY QUESTION

Do defects in sperm chromatin protamination and condensation have an impact on ICSI outcomes?

SUMMARY ANSWER

Sperm protamination is related to fertilization rates in healthy donors, and the in vitro capacity of sperm to condense their chromatin is linked to blastocyst rates, both associations being more apparent in women <33 years of age.

WHAT IS KNOWN ALREADY

Previous data on how sperm chromatin damage affects ICSI outcomes are inconsistent. Revealing which sperm factors influence embryo development is necessary to understand the male contribution to ICSI success and to develop novel sperm selection techniques or male-based treatments. Sperm chromatin is mainly condensed in protamines, which are cross-linked through disulphide bridges. This study aimed to determine whether sperm protamination and the integrity of disulphide bonds (condensation) are related to embryo development after ICSI.

STUDY DESIGN, SIZE, DURATION

The design was a retrospective study with a blind analysis of sperm chromatin. Gametes were divided into two groups: double donation (DD) cohort and single donation (SD) cohort. Samples from 45 semen donors used in 55 ICSI cycles with oocyte donors (age range 19-33 years), generating 491 embryos, were included in the DD cohort. The SD cohort consisted of samples from 34 semen donors used in 41 ICSI cycles with oocytes from healthy females (single-parent families or lesbian couples, age range 20-44 years), generating a total of 378 embryos.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Donor sperm samples from DD and SD cohorts were used for standard ICSI, and embryo development was observed by time-lapse imaging. The incidence of thiol reduction (dibromobimane, DBB) and the degree of chromatin protamination (chromomycin A3, CMA3, indicating non-protaminated regions) in sperm were determined by flow cytometry at 0 and 4 h post-thawing.

MAIN RESULTS AND THE ROLE OF CHANCE

Percentages ± standard deviation of CMA3 were 21.08 ± 9.09 and 35.01 ± 14.68 at 0 and 4 h post-thawing, respectively, in the DD cohort and 22.57 ± 9.48 and 35.79 ± 12.58, at 0 and 4 h post-thawing, respectively, in the SD cohort. Percentages of DBB+ were 16.57 ± 11.10 and 10.51 ± 8.40 at 0 and 4 h post-thawing (P < 0.0001), respectively, in the DD cohort and 17.98 ± 10.19 and 12.72 ± 8.76 at 0 and 4 h post-thawing (P < 0.0001), respectively, in the SD cohort. Female age correlated with fertilization rates, and the relation between sperm chromatin and embryo development was determined through multiple linear regression. While CMA3 was associated with fertilization rates, with no influence of female age, in the DD cohort (β1 = -1.036, P < 0.001 for CMA3; β2 = 0.667, P = 0.304 for female age), this was not observed in the SD cohort, where female age had a significant effect, masking the effects of CMA3 (β1 = -0.066, P = 0.804 for CMA3; β 2 = -1.451, P = 0.003 for female age). The in vitro capacity of sperm to condense their chromatin after 4 h of incubation was associated with blastocyst rates, independent of female age (DD cohort: β1 = -0.238, P = 0.008 for %DBB+ variation; β2 = 0.404, P = 0.638 for female age; SD cohort: β1 = -0.278, P = 0.010 for %DBB+ variation; β2 = -0.292, P = 0.594 for female age). The in vitro capacity of sperm to condense their chromatin was also related to the time required for the embryo to reach blastocyst stage in the DD cohort (P = 0.007). Finally, multiple logistic regression showed that both chromatin protamination and condensation, together with the age of the oocyte donors and the embryo recipients, had an impact on pregnancy achievement (P < 0.01) and on live birth rates (P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

The main limitation was the restrictive selection of couples, which led to a relatively small sample size and could influence the observed outcomes. For this reason, and to reduce Type I error, the level of significance was set at P ≤ 0.01. On the other hand, the use of cryopreserved samples could also be a limitation.

WIDER IMPLICATIONS OF THE FINDINGS

This research demonstrated that protamination and condensation of sperm chromatin are related to embryo development after ICSI, but female age could be a confounding factor when oocytes from older females are used.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the European Union's Horizon 2020 Research and Innovation scheme under the Marie Skłodowska-Curie grant agreement No 801342 (Tecniospring INDUSTRY; TECSPR-19-1-0003); La Marató de TV3 Foundation (214/857-202039); the Ministry of Science and Innovation, Spain (IJC2019-039615-I); the Catalan Agency for Management of University and Research Grants, Regional Government of Catalonia, Spain (2017-SGR-1229); and the Catalan Institution for Research and Advanced Studies, Spain (ICREA). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Correlation analysis of sperm DNA fragmentation index with semen parameters and the effect of sperm DFI on outcomes of ART

Routine semen analysis provides limited information about a man's male reproductive potential and can not always fully explain male infertility. Many male infertilities are caused by sperm DNA defects that routine semen quality analyses fail to detect. In this study, we analyzed the association of sperm DNA fragmentation index (DFI) with the semen routine, sperm morphology, in vitro fertilization embryo transfer (IVF-ET)/intracytoplasmic sperm injection (ICSI). Further, we explored the predictive value of sperm DFI in evaluating male fertility and the outcome of IVF-ET/ICSI. Data on sperm DFI, sperm routine, and sperm morphology were collected from 1462 males with infertility. According to DFI levels, there were 468 cases in group I (DFI ≤ 15%), 518 cases in group II (15% < DFI < 30%), and 476 cases in group III (DFI ≥ 30%). The correlations of sperm DFI with semen routine and malformation rate were analyzed. Seminal plasma malondialdehyde (MDA), and total antioxidant capacity (TAC) were assessed. Sperm DFI, semen routine, and sperm morphology were detected in male patients of 101 pairs of IVF-ET/ICSI infertile couples and subdivided into IVF-I group (DFI ≤ 15%), IVF-II group (15% < DFI < 30%), IVF-III group (DFI ≥ 30%), ICSI-I group (DFI ≤ 15%), ICSI-II group (15% < DFI < 30%) and ICSI-III group (DFI ≥ 30%) according to DFI value. The effect of sperm DFI on the outcome of IVF-ET/ICSI was analyzed. There were significant differences in sperm survival rate, sperm concentration, and PR% between groupIII and group II (P < 0.01). There were significant differences in sperm survival rate, sperm concentration and PR% between group III and group I (P < 0.01). There was no significant difference in semen volume, age, abstinence days, or percentage of normal sperm between the three groups (P > 0.05). DFI was positively correlated with MDA content ( P < 0.01) and negatively correlated with TAC (P < 0.01). Sperm DFI was negatively correlated with sperm survival rate, sperm concentration, and PR% (P < 0.01). There was no correlation with age, abstinence days, semen volume, or percentage of normal-form sperm (r = 0.16, 0.05, 0.04, -0.18, p > 0.05). Compared with IVF-I group, the sperm concentration and PR were decreased in IVF-III group. The sperm malformation rate was higher in IVF-III group than that in IVF-II group. Comparatively, the PR was decreased in ICSI-III group. The sperm malformation rate was higher in ICSI-III group than that of the ICSI-I group (P < 0.05). There were no statistically significant differences in fertilization rate, cleavage rate, embryo rate, and clinical pregnancy rate between IVF group or ICSI group, and between all subgroups (P > 0.05). Sperm DFI is negatively associated with sperm survival rate, sperm concentration, and PR%. Antioxidants can decrease the rate of DNA fragmentation. Sperm DFI has proven to be very valuable in the male fertility evaluation, but its significance as a predictor of pregnancy outcomes following assisted reproductive technology. (ART) requires further investigation.

Semen Thresholds of Normality Established by the WHO Do Not Reveal Genome Instability-A Potential Occult Male Factor

Semen parameters are unable to inform on the function or fertilizing capacity of the male gamete. Standardized methods are provided by the WHO but, the lower reference limits have reduced sensitivity to predict chances of conception. Subfertile men may be falsely classified as "normal" and a male factor contributing to genome instability may be overlooked. Semen parameters, sperm DNA fragmentation (SDF), sperm chromatin maturity and stability, and sperm aneuploidy were assessed in fertile (F), subfertile normozoospermic (SN) and subfertile non-normozoospermic males (SN-N). Standardized assays employing flow cytometry were used to detect genome instability. Sperm DNA fragmentation did not differ significantly whether the semen samples were from a fertile (F), subfertile normozoospermic (SN) or subfertile non-normozoospermic male (SN-N). Chromatin decondensation was significantly reduced and hyperstability significantly increased in the SN group as compared to the F group. The frequency of diploidy was significantly different in the three study groups with significance between F and SN and between F and SN-N groups. Subfertile men with normal semen parameters are often excluded from extensive genetic testing. Genome instability might be an independent attribute of semen quality detecting problems not seen with semen analysis alone.

Sperm DNA integrity does play a crucial role for embryo development after ICSI, notably when good-quality oocytes from young donors are used

Based on the inconsistent literature published thus far involving infertile patients, whether intracytoplasmic sperm injection (ICSI) allows overcoming total fertilization failure due to sperm DNA fragmentation is still unclear. Related to this, female factors, which may have a significant impact on assisted reproduction outcomes, can mask male infertility. In this scenario, evaluating ICSI outcomes following cycles using healthy donor gametes could shed light on this realm, as it would avoid the influence of (un)known confounding factors present in infertile individuals. The present work, therefore, aimed to address whether single- and double-stranded sperm DNA fragmentation leads to impaired ICSI outcomes in double gamete donation cycles. The study also compared these double-gamete donation cycles to cycles in which only sperm were donated and oocytes were obtained from infertile patients. Two cohorts were included: (a) the Donor-Donor (DD) cohort, which included 27 semen donor samples used in 49 ICSI cycles with young healthy oocyte donors; and (b) the Donor-Infertile (DI) cohort, which involved 34 semen donor samples used in 57 ICSI cycles with oocytes from patients. Single- and double-stranded sperm DNA breaks were determined with alkaline and neutral Comet assays, respectively; ICSI was conducted following standard protocols and embryos were monitored through time-lapse microscopy. In the DD cohort, the percentage of sperm with high overall DNA damage correlated with fertilization rates (Rs = - 0.666; P < 0.001) and with the percentage of blastocysts per injected oocyte (Rs = - 0.414; P = 0.040). In addition, sperm DNA damage delayed the first embryo division (Rs = 0.421; P = 0.036), and development from the 8-cell to the morula stage (Rs = 0.424; P = 0.034). In contrast, double-stranded DNA breaks had no effect in this cohort. As far as the DI cohort is concerned, while overall sperm DNA damage was not found to be correlated to fertilization or blastocyst rates, pronuclei formation following ICSI was delayed when the incidence of double-stranded DNA breaks was high (Rs = 0.485; P = 0.005). In conclusion, this study, which is the first involving double donation cycles (i.e., a donor-donor cohort), supports that sperm DNA damage has a detrimental impact on fertilization rates after ICSI, and delays embryo development. Moreover, the use of oocytes from infertile individuals is suggested to hide the male-factor effect.

Management of recurrent implantation failure: British Fertility Society policy and practice guideline

Recurrent implantation failure (RIF) is defined as the absence of a positive pregnancy test after three consecutive transfers of good quality embryos. There remains significant variation in clinical practice in the management of RIF. This British Fertility Society (BFS) Policy and Practice guideline analyses the evidence for investigations and therapies that are employed in RIF and provides recommendations for clinical practice and for further research. Evidence for investigations of sperm and egg quality, uterine and adnexal factors, immunological factors and thrombophilia, endocrine conditions and genetic factors and for associated therapies have been evaluated. This guideline has been devised to assist reproductive medicine specialists and patients in making shared decisions concerning management of RIF. Finally, suggestions for research towards improving understanding and management of RIF have also been provided.

Variability in Sperm DNA Fragmentation in Men with Mild/Unexplained Subfertility in a Prospective Longitudinal Intrauterine Insemination Trial

The biological variability of semen and sperm DNA fragmentation (SDF) parameters in a longitudinal intrauterine insemination (IUI) trial over multiple IUI cycles was investigated. A TUNEL assay was used for SDF testing, both before and after density gradient centrifugation. A significant age effect was observed: while semen parameters deteriorated with advancing age, on average, higher SDF values were observed for older males. There was quite some variability observed for both semen and SDF variables. Using fertile threshold values, three patient categories were distinguished: those with a high SDF in all samples, those with low SDF in all samples and those who fluctuated between high and low during the whole IUI trial. Density gradient centrifugation increases SDF. However, the three patient categories react differently after semen processing. A large percentage of those with high SDF retain their high SDF even after gradient centrifugation. The SDF fluctuaters react with a high SDF after gradient centrifugation. The low SDF category, on the contrary, distributes itself evenly between the three categories after gradient centrifugation. SDF testing after semen processing might be indispensable for therapeutic purposes, probably influencing medical decision-making. In order to isolate fluctuaters, a second SDF testing might be advocated in certain cases. SDF after semen processing is indispensable for therapeutic management.

Sperm as a Carrier of Genome Instability in Relation to Paternal Lifestyle and Nutritional Conditions

Endogenous and exogenous factors can severely affect the integrity of genetic information by inducing DNA damage and impairing genome stability. The extent to which men with and without subfertility are exposed to several adverse lifestyle factors and the impact on sperm DNA fragmentation (SDF), sperm chromatin maturity (condensation and decondensation), stability (hypo- and hypercondensation) and sperm aneuploidy are assessed in this study. Standardized assays employing flow cytometry were used to detect genome instability in 556 samples. Semen parameters deteriorated with age, BMI, increased physical activity and smoking. Age and BMI were associated with increased SDF. Increased BMI was associated with increased hypocondensed chromatin and decreased decondensed chromatin. Increase in age also caused an increase in sex chromosome aneuploidy in sperms. Surprisingly, alcohol abuse reduced chromatin hypercondensation and drug abuse reduced SDF. Although genome instability was more pronounced in the subfertile population as compared to the fertile group, the proportion of men with at least one lifestyle risk factor was the same in both the fertile and subfertile groups. While one in three benefited from nutritional supplementation, one in five showed an increase in SDF after supplementation. Whilst the message of ‘no smoking, no alcohol, no drugs, but a healthy diet’ should be offered as good health advice, we are a long way from concluding that nutritional supplementation would be beneficial for male fertility.

Impact of oxidative stress SNPs on sperm DNA damage and male infertility in a south-east Iranian population

AIM

We examined four single nucleotide polymorphisms in four antioxidant genes (PON1 , CAT , GPx1 and SOD2 ) in 100 infertility cases and 100 controls from an Iranian population-based case-control study to confirm the assumption that polymorphisms in oxidative stress genes increase the risk of sperm DNA damage and idiopathic male infertility.

METHODS

Restriction fragment length polymorphism and tetra-primer amplification refractory mutation system PCR were used to identify genotypes. Sperm DNA damage was assessed using the Sperm Chromatin Dispersion test (Halo Sperm), and the total antioxidant capacity of seminal fluid was determined using the FRAP assay.

KEY RESULTS

Our findings demonstrated that alleles Arg-PON1 (rs662) and Ala-MnSOD (rs4880) variant genotypes were considerably linked with a higher risk of male infertility.

CONCLUSIONS

Linear regression analysis revealed that those with the PON1 Gln192Arg or SOD2 Val16Ala variants have significantly higher levels of sperm DNA fragmentation and lower levels of the total antioxidant capacity in seminal fluid.

IMPLICATIONS

These findings suggest that genetic differences in antioxidant genes may be linked to oxidative stress, sperm DNA damage, and idiopathic male infertility.

Sperm DNA damage compromises embryo development, but not oocyte fertilisation in pigs

Background

The assessment of sperm DNA integrity has been proposed as a complementary test to conventional mammalian semen analysis. In this sense, single-strand (SSB) and double-strand (DSB) DNA breaks, the two types of sperm DNA fragmentation (SDF), have been reported to have different aetiologies and to be associated to different fertility outcomes in bovine and humans. Considering that no studies in porcine have addressed how SDF may affect sperm quality and fertility outcomes, the present work aimed to determine the impact of global DNA damage, SSB and DSB on sperm quality and in vitro fertilising ability. To this end, 24 ejaculates (one per boar) were split into three aliquots: the first was used to assess sperm quality parameters through a computer-assisted sperm analysis (CASA) system and flow cytometry; the second was used to perform in vitro fertilisation, and the third, to evaluate sperm DNA integrity using alkaline and neutral Comet assays.

Results

The results showed that global DNA damage negatively correlates (P < 0.05) with normal sperm morphology (R = − 0.460) and progressive motility (R = − 0.419), and positively with the percentage of non-viable sperm (R = 0.507). Multiple regression analyses showed that non-viable sperm were related to SSB (β = − 0.754). In addition, while fertilisation did not seem to be affected by sperm DNA integrity, global DNA damage, DSB and SSB were found to be correlated to embryo development outcomes. Specifically, whereas global DNA damage and DSB negatively affected (P < 0.05) the later preimplantation embryo stages (percentage of early blastocyst/blastocyst D6: for global DNA damage, R = − 0.458, and for DSB, R = − 0.551; and percentage of hatching/hatched blastocyst D6: for global DNA damage, R = − 0.505, and for DSB, R = − 0.447), global DNA damage and SSB had a negative impact (P < 0.05) on the developmental competency of fertilised embryos (R = − 0.532 and R = − 0.515, respectively). Remarkably, multiple regression analyses supported the associations found in correlation analyses. Finally, the present work also found that the inclusion of Comet assays to the conventional sperm quality tests improves the prediction of blastocyst formation (AUC = 0.9021, P < 0.05), but not fertilisation rates (P > 0.05).

Conclusion

Considering all these findings, this work sets a useful model to study how SDF negatively influences fertility.

Carryover effects of feeding bulls with an omega-3-enriched-diet-From spermatozoa to developed embryos

The impact of omega-3 nutritional manipulation on semen cryosurvival and quality post thawing is controversial. Our aim was to examine how feeding bulls with omega-3 supplementation from different sources affects the spermatozoa quality parameters. Fifteen Israeli Holstein bulls were fed for 13 weeks with a standard ration top-dressed with encapsulated-fat supplementation: fish or flaxseed oil or saturated fatty acids (control). Ejaculates were collected before, during, and after the feeding trial. Frozen-thawed samples were evaluated by a flow cytometer for spermatozoa viability, mitochondrial membrane potential, the level of reactive oxygen species (ROS), acrosome membrane integrity, DNA fragmentation, phosphatidylserine translocation, and membrane fluidity. Both fish and flaxseed oil treatment resulted in lower ROS levels vs. control groups, during and after the feeding trial. Fewer spermatozoa with damaged acrosomes were observed in the fish oil group after the feeding trial. The spermatozoa membrane fluidity was altered in both the fish and flaxseed oil groups throughout the feeding trial, but only in the flaxseed oil group after the feeding trial. The proportion of spermatozoa with fragmented DNA was lower in the flaxseed oil group after the feeding trial. The spermatozoa fertilization competence did not differ between groups however, blastocyst formation rate was higher in the fish and flaxseed oil groups relative to the control. This was associated with differential gene expression in the blastocysts. Overall, the omega-3-enriched food improved the spermatozoa characteristics; this was further expressed in the developing blastocysts, suggesting a carryover effect from the spermatozoa to the embryos.

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.

Direct but Not Indirect Methods Correlate the Percentages of Sperm With Altered Chromatin to the Intensity of Chromatin Damage

Although sperm chromatin damage, understood as damage to DNA or affectations in sperm protamination, has been proposed as a biomarker for sperm quality in both humans and livestock, the low incidence found in some animals raises concerns about its potential value. In this context, as separate methods measure different facets of chromatin damage, their comparison is of vital importance. This work aims at analyzing eight techniques assessing chromatin damage in pig sperm. With this purpose, cryopreserved sperm samples from 16 boars were evaluated through the following assays: TUNEL, TUNEL with decondensation, SCSA, alkaline and neutral sperm chromatin dispersion (SCD) tests, alkaline and neutral Comet assays, and chromomycin A3 test (CMA3). In all cases, the extent of chromatin damage and the percentage of sperm with fragmented DNA were determined. The degree of chromatin damage and the percentage of sperm with fragmented DNA were significantly correlated (p < 0.05) in direct methods (TUNEL, TUNEL with decondensation, and alkaline and neutral Comet) and CMA3, but not in the indirect ones (SCD and SCSA). Percentages of sperm with fragmented DNA determined by alkaline Comet were significantly (p < 0.05) correlated with TUNEL following decondensation and CMA3; those determined by neutral Comet were correlated with the percentage of High DNA Stainability (SCSA); those determined by SCSA were correlated with neutral and alkaline SCD; and those determined by neutral SCD were correlated with alkaline SCD. While, in pigs, percentages of sperm with fragmented DNA are directly related to the extent of chromatin damage when direct methods are used, this is not the case for indirect techniques. Thus, the results obtained herein differ from those reported for humans in which TUNEL, SCSA, alkaline SCD, and alkaline Comet were found to be correlated. These findings may shed some light on the interpretation of these tests and provide some clues for the standardization of chromatin damage methods.

The TUNEL assay underestimates the incidence of DNA damage in pig sperm due to chromatin condensation

Inconsistencies in the relationship between sperm DNA fragmentation and reproductive outcomes as well as the low incidence in farm animals raise concerns on its actual value as a sperm quality parameter. Previous studies suggested that the different sensitivity of techniques evaluating DNA fragmentation could explain variations in the correlation with reproductive outcomes. While the TUNEL assay is one of the most standardized methods to detect DNA damage and cell death, the steric impediment for the terminal nucleotidyl transferase enzyme to access the highly condensed sperm nucleus may decrease the ability of this test to detect internal DNA breaks. In the present study, we sought to determine whether increasing chromatin decondensation makes the TUNEL assay more sensitive to detect DNA damage in pig sperm. We compared three chromatin decondensation treatments (2 mM DTT for 45 min; 5 mM DTT for 8 min and further 45 min; and 5 mM DTT+ 1 M NaCl for 8 min) through the Chromomycin A3 test (CMA3). While incubation with DTT increased the percentages of sperm with decondensed chromatin, regardless of concentration and time of incubation (P < 0.05), the extent of that decondensation was higher when 5 mM DTT was combined with 1 M NaCl. In addition, the TUNEL assay detected a higher number of DNA breaks in sperm with decondensed chromatin (1.89% ± 1.63% vs 8.74% ± 6.05%; P = 0.003). This study shows, for the first time, that previous chromatin decondensation increases the sensitivity of the TUNEL assay to detect DNA damage in pig sperm. These findings also support that larger chromatin decondensation is needed in order for DNA damage to be evaluated properly in species containing protamine P1 only.

Application of the comet assay for the evaluation of DNA damage in mature sperm

DNA integrity is considered an important parameter of semen quality and is of significant value as a predictor of male fertility. Currently, there are several methods that can assess sperm DNA integrity. One such assay is the comet assay, or single-cell gel electrophoresis, which is a simple, sensitive, reliable, quick and low-cost technique that is used for measuring DNA strand breaks and repair at the level of individual cells. Although the comet assay is usually performed with somatic cells from different organs, the assay has the ability to detect genotoxicity in germ cells at different stages of spermatogenesis. Since the ability of sperm to remove DNA damage differs between the stages, interpretation of the results is dependent on the cells used. In this paper we give an overview on the use and applications of the comet assay on mature sperm and its ability to detect sperm DNA damage in both animals and humans. Overall, it can be concluded that the presence in sperm of significantly damaged DNA, assessed by the comet assay, is related to male infertility and seems to reduce live births. Although there is some evidence that sperm DNA damage also has a long-term impact on offspring's health, this aspect of DNA damage in sperm is understudied and deserves further attention. In summary, the comet assay can be applied as a useful tool to study effects of genotoxic exposures on sperm DNA integrity in animals and humans.

Complete Chromatin Decondensation of Pig Sperm Is Required to Analyze Sperm DNA Breaks With the Comet Assay

Sperm quality is usually evaluated prior to artificial insemination in farm animals. In addition to conventional semen analysis, other biomarkers, such as mitochondrial activity, integrity and lipid disorder of plasma membrane, generation of reactive oxygen species (ROS) and sperm DNA integrity, have been found to be related to fertility rates in different species. While mounting evidence indicates that the Comet assay is a sensitive method for the detection of DNA breaks, complete sperm chromatin decondensation is required in order to properly analyze the presence of single- and double-strand DNA breaks. In this sense, a previous study showed that longer lysis treatment with proteinase K is needed to achieve complete chromatin decondensation. The current work sought to determine which specific lysis treatment leads to complete chromatin decondensation in pig sperm, as this is needed for the measurement of DNA damage in this species. With this purpose, incubation with a lysis solution containing proteinase K for 0, 30, and 180 min was added to the conventional protocol. The impact of the DNA damage induced by hydrogen peroxide (H₂O₂; 0.01 and 0.1%) and DNAse I (1U and 4U) was also evaluated. Complete chromatin decondensation was only achieved when a long additional lysis treatment (180 min) was included. Furthermore, olive tail moment (OTM) and percentage of tail DNA (TD) indicated that a higher amount of DNA breaks was detected when hydrogen peroxide and DNAse I treatments were applied (P < 0.05). The comparison of treated and control sperm allowed defining the thresholds for OTM; these thresholds revealed that the percentage of sperm with fragmented DNA determined by the alkaline Comet does not depend on chromatin decondensation (P > 0.05). In conclusion, complete chromatin decondensation prior to alkaline and neutral Comet assays is needed to analyze DNA breaks in pig sperm.

De novo cytogenetic alterations in spermatozoa of subfertile males might be due to genome instability associated with idiopathic male infertility: Experimental evidences and Review of the literature

Male infertility is caused by many factors including genetics. Although part of genetic damages are inherited and could be traced in blood leukocytes, but those de novo alterations induced in spermatogenesis are not part of diagnostic work up. De novo alterations might be the cause of many idiopathic conditions of male infertility. The aim of this study was to evaluate DNA damage, sex chromosomal aneuploidy and DAZ microdeletion in sperms of subfertile males in comparison with normal healthy individuals. Whole blood and semen samples were obtained from 75 subfertile and 45 normal men. Semen samples from karyotypically normal subfertile and normal individuals were used for DNA fragmentation, sex chromosome aneuploidy and DAZ microdeletion analysis. Sperm DNA damage was assessed by alkaline comet assay, chromosome aneuploidy and DAZ microdeletion was assessed using a combined primed in situ labeling and fluorescent in situ hybridization (PRINS-FISH) method. A significantly high percentage of DNA fragmentation was observed in subfertile patients compared to control. Similar observation was observed for sex chromosome aneuploidy and DAZ microdeletion (p < 0.01). A relatively small interindividual difference was seen in all three assays performed. However DAZ microdeletion was observed as mosaic form in Y bearing sperms. Results indicate that subfertile males experience higher genome instability in spermatogenesis expressed as DNA damage and consequently sperm chromosomal 220 AIMS Genetics Volume 3, Issue 4, 219-238. aneuploidy or microdeletions. Occurrence of de novo genetic alterations caused by environmental chemico-physical genotoxic agents during spermatogenesis might be one of the causes of idiopathic male infertility.

Clinical implications of sperm DNA damage in IVF and ICSI: updated systematic review and meta-analysis

The clinical effect of sperm DNA damage in assisted reproduction has been a controversial topic during recent decades, leading to a variety of clinical practice recommendations. While the latest European Society of Human Reproduction and Embryology (ESHRE) position report concluded that DNA damage negatively affects assisted reproduction outcomes, the Practice Committee of the American Society for Reproductive Medicine (ASRM) does not recommend the routine testing of DNA damage for in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Herein, our aim was to perform a systematic review and meta-analysis of studies investigating whether sperm DNA damage affects clinical outcomes in IVF and ICSI, in order to contribute objectively to a consistent clinical recommendation. A comprehensive systematic search was conducted according to PRISMA guidelines from the earliest available online indexing year until March 2020, using the MEDLINE-PubMed and EMBASE databases. We included studies analysing IVF and/or ICSI treatments performed in infertile couples in which sperm DNA damage was well defined and assessed. Studies also had to include information about pregnancy, implantation or live birth rates as primary outcomes. The NHLBI-NIH quality assessment tool was used to assess the quality of each study. Meta-analyses were conducted using the Mantel-Haenszel method with random-effects models to evaluate the Risk Ratio (RR) between high-DNA-damage and control groups, taking into account the 95% confidence intervals. Heterogeneity among studies was evaluated using the I² statistic. We also conducted sensitivity analyses and post-hoc subgroup analyses according to different DNA fragmentation assessment techniques. We identified 78 articles that met our inclusion and quality criteria and were included in the qualitative analysis, representing a total of 25639 IVF/ICSI cycles. Of these, 32 articles had sufficient data to be included in the meta-analysis, comprising 12380 IVF/ICSI cycles. Meta-analysis revealed that, considering IVF and ICSI results together, implantation rate (RR = 0.74; 95% CI = 0.61-0.91; I²  = 69) and pregnancy rate (RR = 0.83; 0.73-0.94; I²  = 58) are negatively influenced by sperm DNA damage, although after adjustment for publication bias the relationship for pregnancy rate was no longer significant. The results showed a non-significant but detrimental tendency (RR = 0.78; 0.58-1.06; I²  = 72) on live birth rate. Meta-analysis also showed that IVF outcomes are negatively influenced by sperm DNA damage, with a statistically significant impact on implantation (RR = 0.68; 0.52-0.89; I²  = 50) and pregnancy rates (RR = 0.72; 0.55-0.95; I²  = 72), although the latter was no longer significant after correction for publication bias. While it did not quite meet our threshold for significance, a negative trend was also observed for live birth rate (RR = 0.48; 0.22-1.02; I²  = 79). In the case of ICSI, non-significant trends were observed for implantation (RR = 0.79; 0.60-1.04; I²  = 72) or pregnancy rates (RR = 0.89; 0.78-1.02; I²  = 44), and live birth rate (RR = 0.92; 0.67-1.27; I²  = 70). The current review provides the largest evidence to date supporting a negative association between sperm DNA damage and conventional IVF treatments, significantly reducing implantation and pregnancy rates. The routine use of sperm DNA testing is therefore justified, since it may help improve the outcomes of IVF treatments and/or allow a given couple to be advised on the most suitable treatment. Further well-designed controlled studies on a larger number of patients are required to allow us to reach more precise conclusions, especially in the case of ICSI treatments.

Sperm DNA fragmentation on the day of fertilisation is not associated with assisted reproductive technique outcome independently of gamete quality

The evaluation of sperm DNA fragmentation has been postulated as a predictive molecular parameter of the semen fertilising potential, as well as the ability to give rise to a healthy embryo and an ongoing pregnancy. However, there are controversial results due to oocyte quality, the use of different measurement techniques and interpretation criteria. Our objective is to investigate if sperm DNA fragmentation on the day of fertilisation influences in vitro fertilisation (IVF) outcome in a prospective double-blind study. Three groups of patients were defined: (i) 68 couples undergoing intracytoplasmic sperm injection (ICSI) due to severe male factor with normal ovarian response (NOR); (ii) 113 couples undergoing conventional in vitro fertilisation (IVF) in our oocyte donation programme due to ovarian failure; and (iii) 150 low ovarian response (LOR) patients undergoing ICSI or IVF. TUNEL assay was performed from an aliquot of each capacitated semen sample to detect DNA fragmentation. There was no relationship between blood serum β-hCG positive test, clinical pregnancy and first trimester miscarriage with DFI levels in NOR (p = 0.41, p = 0.36, p = 0.40), recipient (p = 0.49, p = 0.99 and p = 0.38) and LOR (p = 0.52, p = 0.20, p = 0.64) groups of patients, respectively. Therefore, ART outcomes are not affected by sperm DNA fragmentation independently of gamete quality.

Male aging as a causative factor of detrimental changes in human conventional semen parameters and sperm DNA integrity

The effect of male aging on fertility potential is controversial and difficult to predict. The aim of our study was to determine the associations between age, basic semen parameters, and sperm DNA fragmentation (SDF). Comparison of four age-dependent groups (men ≤29 years, 30-35 years, 36-40 years, and >40 years) revealed a significant fall in the basic semen characteristics and sperm genomic integrity with age. Receiver operating characteristic (ROC) analysis confirmed that men >29 years had lower semen quality. In the group of men >29 years, the prevalence of men with abnormal semen parameters was higher, and these men had over a threefold higher odds ratio (OR) for abnormal semen parameters. Next, ROC analysis revealed that a threshold of 18% SDF was optimal for discriminating between men with normal and abnormal standard semen parameters. The prevalence of men with >18% SDF was higher in the group of men >29 years than in men ≤29 years. Older men had an almost twofold higher risk for >18% SDF than younger men. Our results suggest that age >29 years may be a causative factor of detrimental changes in semen quality, which may raise the risk for disorders of male fertility potential.

Antioxidant pretreatment for male partner before ART for male factor subfertility: a randomized controlled trial

STUDY QUESTION

Does oral antioxidant pretreatment for the male partner improve clinical pregnancy rate in couples undergoing ART for male factor subfertility?

SUMMARY ANSWER

There was no significant difference in clinical pregnancy rate following oral antioxidant pretreatment for male partner in couples undergoing ART for male factor subfertility compared to no pretreatment.

WHAT IS KNOWN ALREADY

Damage to sperm mediated by reactive oxygen species (ROS) contributes significantly to male factor infertility. The ROS-related injury reduces fertilization potential and adversely affects the sperm DNA integrity. Antioxidants act as free radical scavengers to protect spermatozoa against ROS induced damage. During ART, use of sperms which have been exposed to ROS-mediated damage may affect the treatment outcome. Pretreatment with antioxidants may reduce the ROS-mediated sperm DNA damage. Currently, antioxidants are commonly prescribed to men who require ART for male factor subfertility but there is ambiguity regarding their role.

STUDY DESIGN SIZE DURATION

This was an open label, randomized controlled trial conducted at a tertiary level infertility clinic between February 2013 and October 2019. The trial included 200 subfertile couples who were undergoing ART treatment for male factor subfertility.

PARTICIPANTS/MATERIALS SETTING METHODS

Couples were randomized into treatment arm (n = 100) and control arm (n = 100). In the treatment arm, the male partner received oral antioxidants (Vitamin C, Vitamin E and Zinc) for 3 months just prior to the ART cycle. In the control arm, no antioxidant was given to the male partner. The primary outcome was clinical pregnancy rate, while live birth rate (LBR), miscarriage rate and changes in semen parameters were the secondary outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

Out of 200 women randomized, 135 underwent embryo transfer as per protocol. Following intention to treat analysis, no significant difference was noted in clinical pregnancy (36/100, 36% vs 26/100, 26%; odds ratio (OR) 1.60, 95% CI 0.87 to 2.93) and LBR (25/100, 25% vs 22/100, 22%; OR 1.18, 95% CI 0.61 to 2.27) between antioxidant and no pretreatment arms. The clinical pregnancy rate per embryo transfer was significantly higher following antioxidant pretreatment (35/64, 54.7% vs 26/71, 36.6%; OR 2.09, 95% CI 1.05 to 4.16) compared to no pretreatment. There was no significant difference in LBR per embryo transfer (25/64, 39.1%, vs 22/71, 31.0%; OR 1.43, 95% CI 0.70 to 2.91) after antioxidant pretreatment versus no pretreatment. The semen parameters of sperm concentration (median, interquartile range, IQR) (18.2, 8.6 to 37.5 vs 20.5, 8.0 to 52.5, million/ml; P = 0.97), motility (median, IQR) (34, 20 to 45 vs 31, 18 to 45%; P = 0.38) and morphology (mean ± SD) (2.0 ± 1.4 vs 2.2 ± 1.5%; P = 0.69) did not show any significant improvement after intake of antioxidant compared to no treatment, respectively.

LIMITATIONS REASONS FOR CAUTION

The objective assessment of sperm DNA damage was not carried out before and after the antioxidant pretreatment. Since the clinicians were aware of the group allotment, performance bias cannot be ruled out.

WIDER IMPLICATIONS OF THE FINDINGS

The current study did not show any significant difference in clinical pregnancy and LBR following antioxidant pretreatment for the male partner in couples undergoing ART for male subfertility. The findings need further validation in a larger placebo-controlled randomized trial.

STUDY FUNDING/COMPETING INTERESTS

This trial has been funded by Fluid Research grant of Christian Medical College, Vellore (internal funding). The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

CTRI/2013/02/003431.

TRIAL REGISTRATION DATE

26 February 2013.

DATE OF FIRST PATIENT’S ENROLMENT

11 February 2013.

Analysis of age-associated alternation of SCSA sperm DNA fragmentation index and semen characteristics of 1790 subfertile males in China

BACKGROUND

It has been identified that incidence of infertility was about 20% among couples worldwide, about 50% caused by male elements. However, conventional semen laboratory detections could not handle clinical needs, which led to more comprehensive parameters for male fertility evaluation. We aimed to investigate the clinical relationship of age-linked changes and the sperm chromatin structure assay (SCSA) sperm DNA fragmentation index (DFI), and routine semen characteristics among subfertile Chinese males.

METHODS

1790 clinical semen specimens were enrolled from February 2018 to October 2019. Clinical and laboratory data including routine semen analyses, sperm DFI, and sperm morphology were collected and showed age-related alterations in semen parameters.

RESULTS

Our results, displayed an increase in sperm DFI with age, were demonstrated in three age-groups, particularly within the ≥35-year cohort. There were positive and inverse correlations of sperm DFI with abnormal semen characteristics and with normal morphological parameters, respectively. Furthermore, age, sperm morphology, concentration, and progressive motility, immotile sperm percentage, semen volume, sperm survival, and high acridine orange DNA stainability (indicating immature forms) were found to be independent risk factors affecting sperm DNA integrity. Likewise, men aged ≥35 years had a higher sperm DFI than did normozoospermic men in the overall cohort. Routine semen characteristics, sperm DFI, and morphology tended to alter with age.

CONCLUSIONS

The SCSA sperm DFI showed the greatest clinical application in the assessment of male fertility in this study, which should help infertility clinics decide on reproductive options for the treatment of older infertile couples.

Torpor expression is associated with differential spermatogenesis in hibernating eastern chipmunks

Hibernators suppress physiological processes when expressing torpor, yet little is known about the effects of torpor on male reproductive physiology. Studies of hibernating mammals suggest that deep torpor negatively impacts spermatogenesis and that transitions between torpor and euthermic arousals increase cellular oxidative stress, with potentially damaging effects on sperm. Here, we hypothesize that variation in torpor expression affects the reproductive readiness of hibernators by impacting their sperm production. To test this, we examined the relationship between torpor expression and spermatogenesis in captive eastern chipmunks (Tamias striatus). We determined torpor depth with temperature data loggers and assessed its relationship with spermatogenesis by examining spermatogenic progression, cell division, sperm counts, sperm maturity, and DNA damage. We show that deep hibernators (high levels of torpor) largely halted spermatogenesis in late hibernation in comparison with shallow hibernators (low levels of torpor), where ongoing spermatogenesis was observed. Despite these differences in spermatogenic state during hibernation, spermatogenic progression, sperm numbers, and maturity did not differ in spring, potentially reflecting similar degrees of reproductive readiness. Interestingly, shallow hibernators exhibited higher rates of DNA damage in spermatogenic cells during hibernation, with this trend reversing in spring. Our results thus indicate that once heterothermy is terminated, deep hibernators resume spermatogenesis but are characterized by higher rates of DNA damage in spermatogenic cells at the seasonal stage when spring mating commences. Therefore, our study confirmed posthibernation recovery of sperm production but also a potential impact of deep torpor expression during winter on DNA damage in spring.

Critical evaluation of two models of flow cytometers for the assessment of sperm DNA fragmentation: an appeal for performance verification

Lack of standardized, reproducible protocols and reference values is among the challenges faced when using new or upgraded versions of instruments in reproductive laboratories and flow cytometry. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay combined with flow cytometry routinely used for diagnostic measurement of sperm DNA fragmentation (SDF) is a unique example. Any change in the setting of the standard instrument, including upgrades of hardware or software, can lead to different results and may affect clinicians’ decision for treatment. Therefore, we compared TUNEL results of SDF obtained from a standard (C6) flow cytometer with a newer version of the same instrument (C6 Plus) and examined the cutoff, sensitivity, and specificity without calibration (adjustment) and after adjustment. Identical sperm preparation and matched acquisition settings were used to examine the performance of two flow cytometers. The strength of agreement of the results between the two observers was also assessed. After adjustment of the settings, overall concordance became high and the two cytometers showed 100% positive and negative predictive value with 100% area under the curve. The overall correlation coefficient observed between C6 and C6 Plus was highly significant (P < 0.0001; r = 0.992; 95% confidence interval [CI]: 0.982–0.997). After adjustment, the two cytometers showed very high precision of 98% and accuracy of >99%. The interobserver agreement on C6 flow cytometer for the two observers was 0.801 ± 0.062 and 0.746 ± 0.044 for C6 Plus. We demonstrated a strong agreement between the samples tested on the two flow cytometers after calibration and established the robustness of both instruments.

The Relationship between Sperm Oxidative Stress Alterations and IVF/ICSI Outcomes: A Systematic Review from Nonhuman Mammals

Achieving high embryo quality following IVF and ICSI procedures is a key factor in increasing fertility outcomes in human infertile couples. While the male factor is known to underlie infertility in about 50% of cases, studies performed in human infertile couples have not been able to define the precise effect of sperm affectations upon embryo development. This lack of consistency is, in most cases, due to the heterogeneity of the results caused by the multiple male and female factors that mask the concrete effect of a given sperm parameter. These biases can be reduced with the use of animal gametes, being a good approach for basic researchers to design more homogeneous studies analyzing the specific consequences of a certain affectation. Herein, we conducted a systematic review (March 2020) that assessed the relationship between sperm oxidative stress alterations and IVF/ICSI outcomes in nonhumans mammals. The review was conducted according to PRISMA guidelines and using the MEDLINE-PubMed and EMBASE databases. Thirty articles were included: 11 performed IVF, 17 conducted ICSI, and two carried out both fertilization methods. Most articles were conducted in mouse (43%), cattle (30%) and pig models (10%). After IVF treatments, 80% of studies observed a negative effect of sperm oxidative stress on fertilization rates, and 100% of studies observed a negative effect on blastocyst rates. After ICSI treatments, a positive relationship of sperm oxidative stress with fertilization rates (75% of studies) and with blastocyst rates (83% of studies) was found. In conclusion, the present systematic review shows that sperm oxidative stress is associated with a significant reduction in fertilization rates and in vitro embryo development.

Proteomic Analysis in Seminal Plasma of Fertile Donors and Infertile Patients with Sperm DNA Fragmentation

Seminal plasma proteomics studies could represent a new approach for the determination of molecular elements driving male infertility, resulting in a better male infertility characterization. The aim of this study is to investigate proteomic differences in seminal plasma samples from fertile and infertile individuals. For that, semen samples were selected according to semen analysis, clinical pathology, and values of sperm DNA fragmentation (alkaline and neutral Comet assay and Sperm Chromatin Dispersion test). A total of 24 seminal plasma samples classified in four groups were processed: fertile donors (FD), recurrent miscarriage patients (RM), asthenoteratozoospermic patients (ATZ), and asthenoteratozoospermic patients with varicocele (ATZ-VAR). Results obtained by 2D-differential gel electrophoresis (2D-DIGE) revealed 26 spots significantly increased in fertile donors when compared to patient groups. Also, eight spots in the ATZ group and two in the ATZ-VAR group were decreased compared to the other groups. Twenty-eight proteins were identified by mass spectrometry (MS), most of them involved in metabolic and cellular processes and with a catalytic or binding function. Protein-protein interactions through Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) tool suggest that a large part of them were associated with each other. Furthermore, most of them were associated with ubiquitin C, indicating that it could play an important regulation role, resulting in a potential male infertility biomarker.

A randomised trial comparing conventional semen parameters, sperm DNA fragmentation levels and satisfaction levels between semen collection at home and at the clinic

The aim of the randomised trial was to compare conventional semen parameters, sperm DNA fragmentation levels and satisfaction levels between semen samples collected at home and at the clinic. We recruited 110 men with a history of infertility for at least 1 year from the outpatient andrology clinic. Each man collected two semen samples, one at home and one at the clinic. Men were randomly assigned into the home first (n = 55) or clinic first (n = 55) groups. The primary outcome was sperm concentration. There was no significant difference in sperm concentration, sperm DNA fragmentation levels or other conventional semen parameters between home first and clinic first samples (p > .05), while satisfaction levels were significantly higher for home first samples (p < .01). Consistent results were obtained when comparing home-collected and clinic-collected samples within individuals. Men can be offered the option to collect semen samples at home for examination or assisted reproduction without compromising semen quality, especially for those with difficulty in producing semen samples at the clinic.

Increasing associations between defects in phospholipase C zeta and conditions of male infertility: not just ICSI failure?

PURPOSE

Oocyte activation is a fundamental event at mammalian fertilization. In mammals, this process is initiated by a series of characteristic calcium (Ca²⁺) oscillations, induced by a sperm-specific phospholipase C (PLC) termed PLCzeta (PLCζ). Dysfunction/reduction/deletion of PLCζ is associated with forms of male infertility where the sperm is unable to initiate Ca²⁺ oscillations and oocyte activation, specifically in cases of fertilization failure. This review article aims to systematically summarize recent advancements and controversies in the field to update expanding clinical associations between PLCζ and various male factor conditions. This article also discusses how such associations may potentially underlie defective embryogenesis and recurrent implantation failure following fertility treatments, alongside potential diagnostic and therapeutic PLCζ approaches, aiming to direct future research efforts to utilize such knowledge clinically.

METHODS

An extensive literature search was performed using literature databases (PubMed/MEDLINE/Web of Knowledge) focusing on phospholipase C zeta (PLCzeta; PLCζ), oocyte activation, and calcium oscillations, as well as specific male factor conditions.

RESULTS AND DISCUSSION

Defective PLCζ or PLCζ-induced Ca²⁺ release can be linked to multiple forms of male infertility including abnormal sperm parameters and morphology, sperm DNA fragmentation and oxidation, and abnormal embryogenesis/pregnancies. Such sperm exhibit absent/reduced levels, and abnormal localization patterns of PLCζ within the sperm head.

CONCLUSIONS

Defective PLCζ and abnormal patterns of Ca²⁺ release are increasingly suspected a significant causative factor underlying abnormalities or insufficiencies in Ca²⁺ oscillation-driven early embryogenic events. Such cases could potentially strongly benefit from relevant therapeutic and diagnostic applications of PLCζ, or even alternative mechanisms, following further focused research efforts.

Differential microRNAs expression in seminal plasma of normospermic patients with different sperm DNA fragmentation indexes

Sperm DNA fragmentation index (SDF), as an important supplement to routine semen parameters, has been proposed to discriminate between fertile and infertile men, and predicts the outcomes of natural conception and in vitro fertilization. Unfortunately there are uncertainty and contradictory evidences regarding the importance of SDF. An important reason is the fact that significant and fundamental research about SDF is rare. This study was designed to characterize the microRNA (miRNA) expression profile in seminal plasma of normospermic patients with different SDF and their implications in human fertility. Using next-generation sequencing (NGS), a total of 897 human miRNAs were detected from 10 seminal plasma samples, out of which 431 differentially expressed miRNAs in 5 pairs of seminal plasma samples (each pair of seminal plasma samples obtained from the same male), with 14 miRNAs were identified in all the pairs. According to the fold change and expression level, 7 miRNAs including miR-374b-5p, miR-429, hsa-miR-26b-5p, miR-21-5p, miR-4257, miR-135b-5p and miR-134-5p were selected for further excavation. MiR-374b-5p and miR-26b-5p were significantly different in 3 sets of individual seminal plasma samples with different SDF from total 90 infertile patients (30 patients each set). Our results demonstrate that the profile of miR-374b and miR-26b with significantly decreased expression could be used as a first indication of increased SDF. And miR-374b and miR-26b could serve as adjunct biomarkers for the diagnosis of idiopathic infertile males.

DNA fragmentation index (DFI) as a measure of sperm quality and fertility in mice

Although thousands of genetically modified mouse strains have been cryopreserved by sperm freezing, the likelihood of cryorecovery success cannot be accurately predicted using conventional sperm parameters. The objective of the present study was to assess the extent to which measurement of a sperm DNA fragmentation index (DFI) can predict sperm quality and fertility after cryopreservation. Using a modified TUNEL assay, we measured and correlated the DFI of frozen-thawed sperm from 83 unique mutant mouse strains with sperm count, motility and morphology. We observed a linear inverse correlation between sperm DFI and sperm morphology and motility. Further, sperm DFI was significantly higher from males with low sperm counts compared to males with normal sperm counts (P < 0.0001). Additionally, we found that viable embryos derived using sperm from males with high DFI (62.7 ± 7.2% for IVF and 73.3 ± 8.1% for ICSI) failed to litter after embryo transfer compared to embryos from males with low DFI (20.4 ± 7.9% for IVF and 28.1 ± 10.7 for ICSI). This study reveals that measurement of DFI provides a simple, informative and reliable measure of sperm quality and can accurately predict male mouse fertility.

Influence of the age of the individual on the stability of boar sperm genetic material

Routine evaluation of the sperm of livestock animals involves detection of morphological abnormalities. However, most sperm defects that reduce fertilizing capacity are a result of anomalies in spermatogenesis. The aim of the study was to evaluate the effect of a boar's age on the stability of the genetic material of its sperm. The age of the boar was found to have a significant effect on sperm DNA stability and chromatin structure. The highest percentage of spermatozoa with DNA fragmentation was found in the oldest group of boars (0,61%), while the highest proportion of spermatozoa with abnormal histone retention (8,01%) and protamination (9,78%) was found in the youngest group of boars. Aniline blue (AB), chromomycin A3 (CMA3) and acridine orange (AO) staining should be routinely used in individuals used for artificial insemination especially young animals at the start of their exploitation for breeding, as well as older individuals with an age-related decrease in the stability of genetic material. Earlier diagnosis based on additional tests would allow for stricter selection and elimination of males with fertility disorders from breeding, to be replaced by breeders of full value. It was also demonstrated that all three staining methods mentioned above can be used in classical morphological analysis, because they clearly distinguish the sperm head from the background of the slide. Chromomycin staining clearly reveals the midpiece and thus can be used as a specific staining method for its evaluation. Staining with aniline blue is a fast and simple test whose result can be analysed under a light microscope. This staining technique can be recommended for use at insemination stations.

Incidence of high sperm DNA fragmentation in a targeted population of subfertile men

Sperm DNA integrity is important for fertility, however the incidence of high levels of DNA fragmentation (DNA fragmentation index (DFI) >30%) is not well described. In 2011, our clinics implemented guidelines for sperm DNA fragmentation (SDF) testing based on risk factors using the sperm chromatin structure assay (SCSA). The aim of this retrospective study is to characterise SDF and associated factors (age, semen parameters, smoking status and BMI) for sub-fertile males (n = 1082) and sperm donors (n = 234). The average DFI was 12.1 ± 9.8%. The distribution of men with low, moderate and high SDF (<15, 15-30 and >30%) was 74.8%, 19.4% and 5.8%, respectively. Men with high DFI were older (45 ± 9.5 vs 38 ± 6.7) and had lower percentage of motile sperm (38.8 ± 16.1% vs 55.3 ± 15.8%) than men with normal DFI. Over 17% of the men in the quartile with the highest age and lowest motility had a high DFI (>30%), compared to a high DFI rate of 2-4% for the other 3 quartiles. Repeat testing following lifestyle interventions was available for 29 couples where the men had high initial DFI (35 ± 9.5%). Of these men, 71.4% had a decrease of DFI into the moderate or low range. This study shows that SDF testing can be targeted based on age and sperm motility, thereby reducing unnecessary testing. Furthermore, we provide evidence that lifestyle modifications can reduce DNA fragmentation in men with high DFI.

The functional anatomy of the human spermatozoon: relating ultrastructure and function

The Internet, magazine articles, and even biomedical journal articles, are full of cartoons of spermatozoa that bear minimal resemblance to real spermatozoa, especially human spermatozoa, and this had led to many misconceptions about what spermatozoa look like and how they are constituted. This review summarizes the historical and current state of knowledge of mammalian sperm ultrastructure, with particular emphasis on and relevance to human spermatozoa, combining information obtained from a variety of electron microscopic (EM) techniques. Available information on the composition and configuration of the various ultrastructural components of the spermatozoon has been related to their mechanistic purpose and roles in the primary aspects of sperm function and fertilization: motility, hyperactivation, capacitation, the acrosome reaction and sperm-oocyte fusion.

The effect of sperm DNA fragmentation index on assisted reproductive technology outcomes and its relationship with semen parameters and lifestyle

Background

The sperm DNA fragmentation index (DFI) is widely regarded as a key measure for assessing male fertility, but the predictive value of the DFI for outcomes of assisted reproductive technology (ART) remains under debate. In this study, we used a large sample to analyze the effect of sperm DFI on pregnancy outcomes following ART and its relationship with oocyte fertilization and embryo development in in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). We also explore the value of sperm DNA fragmentation (SDF) and its associated factors in assessing male fertility.

Methods

The relationship between the DFI measured with the sperm chromatin structure assay (SCSA) and pregnancy outcomes following ART were retrospectively analyzed in 2,622 ART treatment cycles, of which 1,185 were intrauterine insemination (IUI) cycles, 1,221 were IVF cycles and 216 were ICSI cycles. Rates of pregnancy, early abortion, oocyte fertilization and good quality embryos from IVF and ICSI cycles were compared between the groups of low DFI (DFI ≤15%), medium DFI (15%< DFI <30%) and high DFI (DFI ≥30%). Additionally, the relationships between sperm DFI and male lifestyle variables such as age, body mass index, smoking, and alcohol consumption, as well as routine semen parameters, were analyzed.

Results

Clinical pregnancy rates following IUI among high, medium, and low sperm DFI groups were 12.5% (11/88), 14.3% (48/336), and 13.4% (102/761), respectively, with no statistical difference between the groups (P=0.88); however, early abortion rates among these groups were 27.3% (3/11), 14.6% (7/48), and 4.9% (5/102), respectively, and the difference was statistically significant (P=0.02). No significant differences in the rates of clinical pregnancy, early abortion, oocyte fertilization, or good quality embryos in IVF or ICSI cycles were detected among different DFI groups (P<0.05). Sperm DFI was negatively associated with sperm density, vitality and normal morphology; It was positively correlated with age, abstinence time and unhealthy lifestyles.

Conclusions

As an increasingly common technique for reproductive testing, sperm DFI has proven to be very valuable in male fertility evaluation, but its significance as a predictor of pregnancy outcomes following ART requires further investigation.

DNA fragmentation in concert with the simultaneous assessment of cell viability in a subfertile population: establishing thresholds of normality both before and after density gradient centrifugation

PURPOSE

TUNEL assay is the most common, direct test for sperm chromatin integrity assessment. But, lack of standardized protocols makes interlaboratory comparisons impossible. Consequently, clinical thresholds to predict the chance of a clinical pregnancy also vary with the technique adopted. This prospective study was undertaken to assess the incidence of sperm DNA fragmentation in a subfertile population and to establish threshold values of normality as compared to a fertile cohort, both before and after density gradient centrifugation in the total and vital fractions.

METHOD

Men presenting at a university hospital setup for infertility treatment. DNA damage via TUNEL assay was validated on fresh semen samples, as conventional semen parameters, to reduce variability of results.

RESULTS

Total DNA fragmentation in the neat semen was significantly higher in the subfertile group, but the vital fraction was not significantly different between the two cohorts. After gradient centrifugation, DNA fragmentation increased significantly in the total fraction of the subfertile group but decreased significantly in the vital fraction. In the fertile cohort, there was a non-significant increase in total fragmentation and in the vital fraction the trend was unclear.

CONCLUSIONS

Estimating total and vital sperm DNA fragmentation, after density gradient centrifugation, increased both the sensitivity and the specificity, thereby lowering the number of false negatives and false positives encountered. These findings provide opportunities to investigate the significance of the total and the vital fractions after different assisted reproductive technologies.

Chromatin condensation, fragmentation of DNA and differences in the epigenetic signature of infertile men

Epidemiological studies report an increase of pathologies of male reproductive tracts and suggest a link between this trend and the increased exposure of men to endocrine disruptors (EDs). The mechanisms by which EDs impact male fertility are far to be elucidated although DNA, chromatin and epigenome of spermatozoa appear to be relevant targets for these molecules. Indeed, many studies report associations between increased levels of sperm DNA fragmentation (sDF) or aberrant chromatin condensation or epigenetic modifications and poor semen quality and/or infertile phenotype. In this scenario, therapies able to reduce sperm damage to DNA, chromatin and epigenome are sought. Currently, antioxidants and FSH administration is proposed for treating high levels of sDF, but whether or not such therapies are really effective is still debated. Further studies are necessary to understand the link between endocrine disruptor exposure and damage to sperm function and/or structure and thus to define effective therapeutic strategies.

Vitamin B12 Prevents Cimetidine-Induced Androgenic Failure and Damage to Sperm Quality in Rats

Cimetidine, used as an anti-ulcer and adjuvant treatment in cancer therapy, causes disorders in the male reproductive tract, including steroidogenesis. However, its effect on sperm quality and male fertility has been poorly addressed. Since vitamin B₁₂ has demonstrated to recover spermatogonia number and sperm concentration in cimetidine-treated rats, we evaluated the impact of cimetidine on sperm quality and fertility potential and whether vitamin B₁₂ is able to prevent the harmful effect of this drug on steroidogenesis and sperm parameters. Adult male rats were treated for 52 consecutive days as follows: cimetidine group (100 mg/kg of cimetidine), cimetidine/vitamin B₁₂ group (100 mg/kg of cimetidine + 3 μg vitamin B₁₂), vitamin B₁₂ group (3 μg vitamin B₁₂) and control group (saline). Serum testosterone levels and immunofluorescence associated to western blot for detection of 17β-HSD6 were performed. Sperm morphology and motility, mitochondrial activity, acrosome integrity, DNA integrity by Comet assay, lipid peroxidation as well as fertility potential were analyzed in all groups. Apoptotic spermatids were also evaluated by caspase-3 immunohistochemistry. In the cimetidine-treated animals, reduced serum testosterone levels, weak 17β-HSD6 levels and impaired spermiogenesis were observed. Low sperm motility and mitochondrial activity were associated with high percentage of sperm tail abnormalities, and the percentage of spermatozoa with damaged acrosome and DNA fragmentation increased. MDA levels were normal in all groups, indicating that the cimetidine-induced changes are associated to androgenic failure. In conclusion, despite the fertility potential of rats was unaffected by the treatment, the sperm quality was significantly impaired. Therefore, considering a possible sperm-mediated transgenerational inheritance, the long term offspring health needs to be investigated. The administration of vitamin B₁₂ to male rats prevents the androgenic failure and counteracts the damage inflicted by cimetidine upon sperm quality, indicating that this vitamin may be used as a therapeutic agent to maintain the androgenic status and the sperm quality in patients exposed to androgen disrupters.

Is sperm DNA fragmentation a useful test that identifies a treatable cause of male infertility?

The present-day laboratory methods of sperm analysis are a poor predictor of reproductive outcome, and for many years it has been clear that newer and better tests are required. Although many such tests have been proposed, only those which determine sperm DNA quality are still being considered. Of these, several tests of sperm DNA fragmentation are available, although there is presently no consensus about the most appropriate test, the best test specimen (fresh or washed sperm) or what level of fragmentation is of clinical concern. Moreover, although several strategies have been proposed to reduce DNA fragmentation, there is no universal approach and few randomised trials have tested these in a clinical context. As such, most professional bodies do not presently support the use of sperm DNA fragmentation tests, and it is clear that large randomised trials are still required to further evaluate their clinical effectiveness.

Effects of different cryopreservation methods on DNA integrity and sperm chromatin quality in men

BACKGROUND

Cryopreserved human sperm are used in assisted reproductive technology. However, the effect of cryopreservation on sperm DNA integrity is unclear.

OBJECTIVES

The objectives of this study were to: (i) determine the impact of semen cryopreservation on human sperm DNA integrity and chromatin structure; (ii) test if parameters obtained from TUNEL and SCSA® correlate; and (iii) verify correlation between sperm motility, morphology and viability with TUNEL and SCSA® parameters.

MATERIALS AND METHODS

Men attending a fertility clinic were recruited and grouped according to their sperm parameters (n = 9/group): normozoospermia, oligoasthenoteratozoospermia and teratozoospermia. Each semen sample was processed as follow: (i) directly frozen at -80 °C; (ii) diluted in Sperm Maintenance Medium, cooled for 30 min at 4 °C and frozen at -80 °C; (iii) diluted in Sperm Maintenance Medium; or (iv) in SpermFreeze. Each mixture from method (iii) and (iv) was then suspended for 30 min in liquid nitrogen vapor and plunged into liquid nitrogen. After at least two months of storage, samples were thawed at room temperature and analyzed for motility and viability, TUNEL and SCSA® assays.

RESULTS

Progressive motility and viability decreased after freeze-thawing. TUNEL scores increased significantly in all samples after freezing-thawing while no significant change in the DNA fragmentation index (DFI) from SCSA® was observed. No change in the percentage high DNA stainability (HDS) was observed in normozoospermic samples; however it was significantly increased in all the methods in oligoasthenoteratozoospermic and in the methods (ii)-(iv) in teratozoospermic samples. The DFI and TUNEL scores correlated significantly with each other and inversely with sperm motility, viability and morphology.

DISCUSSION AND CONCLUSION

Cryopreservation seems to be deleterious for the integrity of human sperm DNA and compaction. However, the sperm DFI was not affected during cryopreservation under the various methods of storage tested. Clinicians and investigators should take this information into consideration when using cryopreserved sperm for assisted reproduction.

Recommendations regarding the genetic and immunological study of reproductive dysfunction

In this article several members of diverse scientific associations and reproduction experts from Spain have updated different genetic and immunological procedure recommendations in couples affected by reproductive dysfunction with the goal of providing a set of useful guidelines for the clinic. The laboratory test has been considered as highly recommendable for making clinical decisions when the result of the diagnostic test is relevant, moderately recommendable when the results are of limited evidence because they are inconsistent, and low when the benefit of the test is uncertain. It is expected that these recommendations will provide some useful guidelines for the diagnosis, prognosis and treatment of couples presenting reproductive dysfunction.