Sperm DNA integrity and male infertility: a narrative review and guide for the reproductive physicians

The Effect of Endurance Exercise on Semen Quality in Male Athletes: A Systematic Review

BACKGROUND

Endurance exercise has the potential to affect reproductive function, with amenorrhea in female athletes. However, most studies focus on women. Evidence on the association between endurance exercise and male fertility is limited.

OBJECTIVE

To synthesise existing literature on exercise-induced alterations in semen parameters and to assess the clinical impact on male fertility.

METHODS

Studies reporting on the association between semen parameters and endurance exercise in healthy men were eligible. Men attending fertility clinics were excluded. We searched MEDLINE (PubMed), Embase, SPORTDiscus, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov and International Clinical Trials Registry Platform (ICTRP) from their inception to May 28th 2022. JBI Critical Appraisal Tool was used to assess the potential risk of bias.

RESULTS

Thirteen studies met inclusion criteria, reporting on 280 subjects. Eight articles reported on endurance runners, three on cyclists and four on triathletes. Four studies did not find any statistically significant sperm alterations. Five reported significant changes in semen parameters, but these were not clinically relevant, as semen parameters remained well above World Health Organisation (WHO) thresholds. Four articles reported a decrease in semen quality with potential clinical consequences as they found a reduced number of sperm cells exhibiting normal morphology in cyclists and triathletes and a greater amount of DNA fragmentation in triathletes.

CONCLUSION

Endurance exercise can have a negative effect on semen quality, although rarely with a clinically relevant impact on male fertility. Evidence is however limited, with poor quality of the included studies.

REGISTRATION

PROSPERO International prospective register of systematic reviews (CRD42022336753).

The Global Andrology Forum (GAF): Structure, Roles, Functioning and Outcomes: An Online Model for Collaborative Research

PURPOSE

There are no published examples of a global online research collaborative in andrology. We describe the development, profile and member characteristics of the first consortium of this type, the Global Andrology Forum (GAF).

MATERIALS AND METHODS

An online survey sent to all GAF members collected demographic information (sex, age, experience, academic title, degrees, country, specialty, profession). It also tapped data on members' characteristics e.g., skills in research, software and statistics; preferred activities; time commitments; expected roles; and interest in participating in research, in GAF's scientific activities and collaborative online research. The findings were analyzed and tabulated. We outline members' demographic and professional characteristics and scientific achievements to date. A narrative approach outlined GAF's structure and functioning.

RESULTS

A total of 418 out of 540 members completed the survey and were included in the analysis (77.4% response rate). The sample comprised mainly urologists (34.2%) and a third of the respondents had practiced for >15 years (33.3%). Up to 86.1% of the members expressed interest in being actively engaged in writing scientific articles. A third of the sample (37.1%) could dedicate 4 to 6 hours/week. Few respondents reported skills in statistics and artwork (2.6% and 1.9% respectively). Members were assigned to specific roles based on their expertise and experiences. Collaborative working ensured the timely completion of projects while maintaining quality. For outcomes, GAF published 29 original articles within one year of its creation, with authors from 48 countries spanning topics that included varicocele, sperm DNA damage, oxidative stress, semen analysis and male infertility, oocyte/embryo, and laboratory issues of assisted reproductive technique (ART) and male infertility evaluation.

CONCLUSIONS

GAF is a successful global online andrology research model. A healthy number of scientific articles have been published. Given such effectiveness, adopting the GAF model could be useful for other disciplines that wish to create and coordinate successful international online research groups.

Low Birth Weight is Associated with Sperm DNA Fragmentation and Assisted Reproductive Technology Outcomes in Primary Infertile Men: Results of a Cross-Sectional Study

PURPOSE

To assess the relationship between clinical and semen characteristics and assisted reproductive technology (ART) outcomes with different birth weight (BW) categories in a cohort of infertile men.

MATERIALS AND METHODS

Data from 1,063 infertile men were analyzed. Patients with BW ≤2,500, 2,500-4,000, and ≥4,000 g were considered as having low BW (LBW), normal BW (NBW), and high BW (HBW), respectively. Testicular volume (TV) was assessed with a Prader orchidometer. Serum hormones were measured in all cases. Semen analyses were categorized based on 2021 World Health Organization reference criteria. Sperm DNA fragmentation (SDF) was tested in every patient and considered pathological for SDF >30%. ART outcomes were available for 282 (26.5%) patients. Descriptive statistics and logistic regression analyses detailed the association between semen parameters and clinical characteristics and the defined BW categories.

RESULTS

Of all, LBW, NBW, and HBW categories were found in 79 (7.5%), 807 (76.0%), and 177 (16.5%) men, respectively. LBW men had smaller TV, presented higher follicle-stimulating hormone (FSH) but lower total testosterone levels compared to other groups (all p<0.01). Sperm progressive motility (p=0.01) and normal morphology (p<0.01) were lower and SDF values were higher (all p<0.01) in LBW compared to other groups. ART pregnancy outcomes were lower in LBW compared to both NBW and HBW categories (26.1% vs. 34.5% vs. 34.5%, p=0.01). At multivariable logistic regression analysis, LBW was associated with SDF >30% (odd ratio [OR] 3.7; p<0.001), after accounting for age, Charlson Comorbidity Index (CCI), FSH, and TV. Similarly, LBW (OR 2.2; p<0.001), SDF >30% (OR 2.9; p<0.001) and partner's age (OR 1.3; p=0.001) were associated with negative ART outcomes, after accounting for the same predictors.

CONCLUSIONS

LBW was associated with impaired clinical and semen characteristics in infertile men compared to both NBW and HBW. SDF and ART outcomes were significantly worse in the LBW group.

Management of Primary Infertility: A Comprehensive Approach With Magnetic-Activated Cell Sorting in an Asthenozoospermic Patient

This report presents the cases of a 34-year-old male and a 29-year-old female who visited a fertility clinic and were experiencing primary infertility for the past three years. No previous medical history was identified in the couple. After a failed attempt of intrauterine insemination, the male partner was diagnosed with asthenozoospermia. A second attempt of intracytoplasmic sperm injection (ICSI) was performed which failed again. Subsequently, magnetic-activated cell sorting (MACS) technique was used as the sperm selection technique. The male patient's sperms were selected through MACS before ICSI. After performing MACS, successful pregnancy was achieved, which resulted in the production of blastocysts and a positive beta-human chorionic gonadotropin test. This case report highlights the prospect of successful results, despite the presence of sperm DNA fragmentation, and a comprehensive strategy for managing infertility issues. Promoting knowledge of lifestyle factors and how they affect fertility remains an essential aspect of comprehensive infertility care.

Technical Aspects and Clinical Limitations of Sperm DNA Fragmentation Testing in Male Infertility: A Global Survey, Current Guidelines, and Expert Recommendations

PURPOSE

Sperm DNA fragmentation (SDF) is a functional sperm abnormality that can impact reproductive potential, for which four assays have been described in the recently published sixth edition of the WHO laboratory manual for the examination and processing of human semen. The purpose of this study was to examine the global practices related to the use of SDF assays and investigate the barriers and limitations that clinicians face in incorporating these tests into their practice.

MATERIALS AND METHODS

Clinicians managing male infertility were invited to complete an online survey on practices related to SDF diagnostic and treatment approaches. Their responses related to the technical aspects of SDF testing, current professional society guidelines, and the literature were used to generate expert recommendations via the Delphi method. Finally, challenges related to SDF that the clinicians encounter in their daily practice were captured.

RESULTS

The survey was completed by 436 reproductive clinicians. Overall, terminal deoxynucleotidyl transferase deoxyuridine triphosphate Nick-End Labeling (TUNEL) is the most commonly used assay chosen by 28.6%, followed by the sperm chromatin structure assay (24.1%), and the sperm chromatin dispersion (19.1%). The choice of the assay was largely influenced by availability (70% of respondents). A threshold of 30% was the most selected cut-off value for elevated SDF by 33.7% of clinicians. Of respondents, 53.6% recommend SDF testing after 3 to 5 days of abstinence. Although 75.3% believe SDF testing can provide an explanation for many unknown causes of infertility, the main limiting factors selected by respondents are a lack of professional society guideline recommendations (62.7%) and an absence of globally accepted references for SDF interpretation (50.3%).

CONCLUSIONS

This study represents the largest global survey on the technical aspects of SDF testing as well as the barriers encountered by clinicians. Unified global recommendations regarding clinician implementation and standard laboratory interpretation of SDF testing are crucial.

Outcomes comparison of testicular versus ejaculated sperm for intracytoplasmic sperm injection in infertile men with high DNA fragmentation: updated systematic review and meta-analysis

Background

The testicular sperm instead of ejaculated sperm for intracytoplasmic sperm injection (ICSI) in infertile men with high sperm DNA fragmentation (SDF) is a controversial topic. This updated systematic review and meta-analysis aims to evaluate whether couples with high level of SDF will benefit more from intracytoplasmic sperm injection with testicular sperm (Testi-ICSI) as compared to intracytoplasmic sperm injection with ejaculated sperm (Ejac-ICSI).

Methods

A systematic search was conducted according to PRISMA guidelines, using PubMed, Embase, Web of Science and the Cochrane Central Register of Controlled Trials (CENTRAL), encompassing studies from the earliest record until May 2022. We included studies analyzing comparative pregnancy outcomes of testicular versus ejaculated sperm for ICSI in infertile men with high DNA fragmentation. The risks of bias and certainty of evidence were assessed using the Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework, respectively.

Results

Eleven studies were included. Meta-analysis showed that SDF levels revealed a significant difference association [odds ratio (OR) =-25.81; 95% confidence interval (CI): -34.82, -16.81; I2=94%; P<0.00001] between testicular and ejaculated sperm. Compared with Ejac-ICSI, a non-significant tendency was observed for fertilization rates (FRs) in the Testi-ICSI group (OR =0.87; 95% CI: 0.67, 1.12; I2=81%; P=0.28). However, there was significant difference pointing to better outcomes for Testi-ICSI in clinical pregnancy rates (CPRs) (OR =2.36; 95% CI: 1.71, 3.24; I2=0%; P<0.00001), live birth rates (LBRs) (OR =3.10; 95% CI: 2.13, 4.51; I2=4%; P<0.00001) and miscarriage rates (MRs) (OR =0.28; 95% CI: 0.13, 0.60; I2=0%; P=0.001).

Conclusions

Results of this updated meta-analysis reveal that SDF rates are lower in testicular sperm than in ejaculated sperm and that Testi-ICSI is correlated with better clinical outcomes, including higher CPRs, higher LBRs, and lower MRs in infertile males with high SDF levels. Nevertheless, with the overall low to moderate quality of the studies, further well-designed controlled studies are required.

Development of a biomolecular approach to identify sperm functions and fertility using sperm RNAs

Infertility affects a significant percentage of couples worldwide, and male factors contribute significantly to this problem. Traditional assessments of male fertility rely primarily on parameters such as sperm motility, morphology, viability, and concentration. However, these metrics often do not provide a comprehensive understanding of sperm function, which is critical not only for fertilization but also for successful embryo development. Herein, we used porcine spermatozoa as a model to investigate the potential of sperm RNA markers in assessing various aspects of sperm function from motility to fertility. Using artificial insemination, we evaluated male fertility based on the litter size of sows inseminated with sperm from 20 boars. In addition, we measured parameters such as weaning rate, death births, live births, and mummy births. Sperm functional parameters, including motility and kinematics, were assessed before and after in vitro capacitation. Finally, correlations between various sperm functional parameters and sperm RNA markers were explored. Our results revealed interesting relationships between sperm functional parameters. While motility and kinematics were correlated, they were not correlated with sperm capacitation status. Surprisingly, no significant correlations were found between these parameters and male fertility. However, specific parameters of sperm capacitation status after in vitro capacitation were correlated with weaning rate and live births, highlighting their importance in predicting successful fertilization. Further analysis of sperm RNA markers identified genes related to male fertility, including IZUMO1, known for its role in sperm-egg fusion. These genes showed correlations with motility, capacitation, and fertilization parameters, shedding light on their potential roles in sperm function. In conclusion, our study demonstrates that sperm RNA markers hold promise for the diagnosis and prognosis of various aspects of sperm function, providing valuable insights into male infertility. These markers may serve as diagnostic tools to improve our understanding of male fertility problems, ultimately benefiting couples struggling with infertility.

Sperm DNA fragmentation in male infertility: From bench to bedside

Objectives

Sperm DNA fragmentation (SDF) is a molecular marker of sperm chromatin health. Elevated SDF is associated with male infertility, recurrent pregnancy loss, and failure of assisted reproductive technologies (ART). In 2021, the sixth edition of the World Health Organization (WHO) Manual for the Laboratory Examination and Processing of Human Semen has listed SDF as an extended test of semen that can be ordered under certain circumstances. However, the manual neither explained the indications for testing nor provided clear guidance on diagnostic thresholds.

Methods

This article summarizes the current body of knowledge regarding clinical applications of SDF, including the appropriate population to test, methods of testing, and management strategies.

Results

Several etiologic factors and pathophysiologic mechanisms for SDF have been described including poor lifestyle habits, noxious exposures, and varicocele. Four SDF assays are included in the WHO manual and may be utilized based on resources and expertise. Strategies to lower SDF levels in infertile men include addressing underlying causes, supplementation with antioxidants, shorter abstinence periods, and use of testicular sperm for intracytoplasmic sperm injection.

Conclusion

SDF testing can be implemented in the evaluation of infertile men and couples experiencing ART failure and appropriate management strategies can be offered to improve reproductive outcomes. There is vast potential for future research regarding the clinical utility of SDF in the evaluation and treatment of infertile couples.

Controversy and Consensus on the Management of Elevated Sperm DNA Fragmentation in Male Infertility: A Global Survey, Current Guidelines, and Expert Recommendations

PURPOSE

Sperm DNA fragmentation (SDF) has been associated with male infertility and poor outcomes of assisted reproductive technology (ART). The purpose of this study was to investigate global practices related to the management of elevated SDF in infertile men, summarize the relevant professional society recommendations, and provide expert recommendations for managing this condition.

MATERIALS AND METHODS

An online global survey on clinical practices related to SDF was disseminated to reproductive clinicians, according to the CHERRIES checklist criteria. Management protocols for various conditions associated with SDF were captured and compared to the relevant recommendations in professional society guidelines and the appropriate available evidence. Expert recommendations and consensus on the management of infertile men with elevated SDF were then formulated and adapted using the Delphi method.

RESULTS

A total of 436 experts from 55 different countries submitted responses. As an initial approach, 79.1% of reproductive experts recommend lifestyle modifications for infertile men with elevated SDF, and 76.9% prescribe empiric antioxidants. Regarding antioxidant duration, 39.3% recommend 4-6 months and 38.1% recommend 3 months. For men with unexplained or idiopathic infertility, and couples experiencing recurrent miscarriages associated with elevated SDF, most respondents refer to ART 6 months after failure of conservative and empiric medical management. Infertile men with clinical varicocele, normal conventional semen parameters, and elevated SDF are offered varicocele repair immediately after diagnosis by 31.4%, and after failure of antioxidants and conservative measures by 40.9%. Sperm selection techniques and testicular sperm extraction are also management options for couples undergoing ART. For most questions, heterogenous practices were demonstrated.

CONCLUSIONS

This paper presents the results of a large global survey on the management of infertile men with elevated SDF and reveals a lack of consensus among clinicians. Furthermore, it demonstrates the scarcity of professional society guidelines in this regard and attempts to highlight the relevant evidence. Expert recommendations are proposed to help guide clinicians.

Human Sperm as an In Vitro Model to Assess the Efficacy of Antioxidant Supplements during Sperm Handling: A Narrative Review

Spermatozoa are highly differentiated cells that produce reactive oxygen species (ROS) due to aerobic metabolism. Below a certain threshold, ROS are important in signal transduction pathways and cellular physiological processes, whereas ROS overproduction damages spermatozoa. Sperm manipulation and preparation protocols during assisted reproductive procedures-for example, cryopreservation-can result in excessive ROS production, exposing these cells to oxidative damage. Thus, antioxidants are a relevant topic in sperm quality. This narrative review focuses on human spermatozoa as an in vitro model to study which antioxidants can be used to supplement media. The review comprises a brief presentation of the human sperm structure, a general overview of the main items of reduction-oxidation homeostasis and the ambivalent relationship between spermatozoa and ROS. The main body of the paper deals with studies in which human sperm have been used as an in vitro model to test antioxidant compounds, including natural extracts. The presence and the synergic effects of different antioxidant molecules could potentially lead to more effective products in vitro and, in the future, in vivo.

Sperm DNA fragmentation testing in clinical management of reproductive medicine

Background

Approximately 8%-12% of couples worldwide face infertility, with infertility of individuals assigned male at birth (AMAB) contributing to at least 50% of cases. Conventional semen analysis commonly used to detect sperm abnormalities is insufficient, as 30% of AMAB patients experiencing infertility show normal results in this test. From a genetic perspective, the assessment of sperm DNA fragmentation (SDF) is important as a parameter of sperm quality.

Methods

In this narrative study, we review and discuss pathophysiological causes, DNA repair mechanisms, and management of high SDF. We then summarize literature exploring the association between SDF and reproductive outcomes.

Main Findings

Recent systematic reviews and meta-analyses have revealed a significant association between high SDF in AMAB individuals and adverse reproductive outcomes including embryo development, natural conception, intrauterine insemination, and in vitro fertilization. However, the association with live birth rates and pregnancy rates following intracytoplasmic injection remains inconclusive. The disparities among quantitative assays, inconsistent reference range values, absent high-quality prospective clinical trials, and clinical heterogeneity in AMAB patients with elevated SDF represent the main limitations affecting SDF testing.

Conclusion

The evaluation and management of SDF plays an important role in a subset of AMAB infertility, but widespread integration into clinical guidelines will require future high-quality clinical trials and assay standardization.