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

A 2-step remote TUNEL approach for sperm DNA fragmentation assessment. Analysis in donors and patients

OBJECTIVES

Infertility is a disease of the male or female reproductive systems. Male reproductive workup is based on routine semen analysis, although of limited value. The 2021 WHO Manual incorporated Sperm DNA Fragmentation (SDF) assessment, and highlighted the need for individual laboratories to define suitable thresholds. This study aimed to present an alternative to address this issue, determine an SDF cut-off value with fertile donors, and characterize SDF in a patient cohort and their relationship with semen parameters.

STUDY DESIGN

A service unit was established to remotely perform TUNEL assay in a 2 step-process. Semen samples were received at andrology laboratories, subjected to routine semen analysis (WHO, 2010), partially processed and transported to the service unit for SDF evaluation. Using this setting, studies were done in fertile donors (n = 15) to define the cut-off value, and in men undergoing infertility workup (n = 318).

RESULTS

A cut-off value of 9.17 % was determined with the fertile donor cohort. With this cut-off, a 64.46 % abnormal SDF incidence was determined in the patient cohort. SDF negatively correlated with sperm number, vitality and motility, and positively with abnormal morphology and male age (P < 0.05). TUNEL-positive cases depicted lower sperm quality and higher male age (P < 0.05). A similar abnormal SDF incidence was determined among patients with semen abnormalities. Asthenozoospermic and ≥40 years patient samples depicted higher (P < 0.05) SDF than those of the general population. SDF incidence was also high in normozoospermic patients.

CONCLUSIONS

Using a 2-step remote approach with a standardized procedure and an SDF cut-off value established with fertile donors, high SDF incidence in semen samples depicting normal and abnormal quality were identified in men consulting for infertility, highlighting the relevance of its evaluation as part of the male fertility workup.

Analysis of research trends (2014-2023) on oxidative stress and male fertility based on bibliometrics and knowledge graphs

Background

Oxidative stress (OS) is considered one of the major factors affecting male fertility, and research in this field has seen constant growth year by year. Currently, around 700 relevant papers are published each year, with a trend of further growth. Therefore, this study systematically summarizes the literature published in the last decade from a bibliometric perspective, revealing the dynamic development of the field, identifying research hotspots, analyzing future trends, and providing reference for further research.

Methods

Relevant literature on oxidative stress and male fertility was retrieved from the Web of Science Core Collection (WoSCC) database, covering the timespan from 2014 to 2023 and including two types, articles and reviews. CiteSpace and VOSviewer were used for bibliometric analysis, including cluster analysis, co-occurrence analysis, co-citation analysis, and burst analysis of countries/regions, institutions, journals, authors, references, and keywords.

Results

This paper studied a total of 5,301 papers involving 107 countries/regions, with China having the highest number of publications (898 papers) and the United States having the highest centrality (0.62). Burst analysis of journal citations revealed the emergence of many new journals (e.g., Antioxidants-Basel, Front Endocrinol) after 2021, indicating continuous expansion and development in this field. Cluster analysis of co-cited references and co-occurring keywords divided the research into areas such as oxidative stress and male infertility, oxidative stress level detection, and antioxidants. The keywords associated with research hotspots shifted from oxidative stress detection, sperm DNA damage, apoptosis, and redox potential to DNA methylation, embryonic development, infection, polyunsaturated fatty acids, and antioxidants.

Conclusion

Bibliometric methods provide an intuitive reflection of the development process in the field of oxidative stress and male fertility, as well as the analysis of research hotspots in different periods. Research on oxidative stress and embryonic development, as well as antioxidant health management, may become hotspots in future research.

Age, sexual abstinence duration, sperm morphology, and motility are predictors of sperm DNA fragmentation

Purpose

Sperm DNA fragmentation (SDF) has recently received attention as a cause of male infertility. However, SDF cannot be fully assessed using conventional semen parameter evaluations alone. Therefore, the authors aimed to elucidate the relationship between SDF and sperm parameters via computer-assisted sperm analysis (CASA) to improve treatment strategies in reproductive medicine.

Methods

This retrospective observational study analyzed the relationship between sperm parameters assessed by CASA and SDF values determined by the TUNEL assay in 359 patients who visited the Mie University Hospital for infertility treatment. The methodology involved semen analyses covering concentration, motility, and morphology, followed by SDF quantification using the flow cytometry.

Results

Statistical analysis revealed significant correlations between SDF and various factors, including age, sexual abstinence period, and specific CASA-measured parameters. Notably, lower sperm motility rates and abnormal head dimensions were associated with higher SDF values, indicating that these parameters were predictive of SDF.

Conclusions

This study highlights the importance of sperm motility and head morphology as indicators of SDF, suggesting their usefulness in assessing male fertility. These findings demonstrate the efficacy of detailed sperm analysis, potentially increasing the success rate of assisted reproductive technologies by improving sperm selection criteria.

Sperm-oviduct interaction: Differential gene expression of growth factors induced by sperm DNA fragmentation

The present study investigated the effects of DNA fragmentation of spermatozoa on the growth factors expression by a human oviduct epithelial cell line (OE-E6/E7). Two separate groups were examined in this study. The cell line was cultured in the presence of spermatozoa with normal DNA fragmentation index (DFI) or abnormal DFI. Total RNA from the cell line in each group was isolated, and relative expression of objective genes was analysed using PCR array. Also, the concentration of VEGF, BMP-2, BMP-7 and MSTN in the supernatant of cell culture was analysed by the ELISA method. The PCR array analysis revealed that most of the growth factors had been upregulated in the abnormal group. However, the differences between groups were statistically significant (p < 0.05) for five genes, including VEGF-A, BMP-2, BMP-6, BMP-7 and OSM. Furthermore, MSTN was the only gene that down-regulated significantly under the influence of the spermatozoa with abnormal DFI. Moreover, the results of ELISA analysis were in agreement with the data of the PCR array. It has been concluded that DNA fragmentation in human spermatozoa can probably change regular events throughout the oviducts. Consequently, the genes of interest may change sperm function and probably its fate in the female reproductive tract.

Effect of varicocele on sperm DNA damage: A systematic review and meta-analysis

The updated meta-analysis was conducted to further verify the effect of varicocele on sperm DNA damage, supplying clinicians and researchers with high-grade evidence. The sperm DNA damage was evaluated by DNA fragmentation index (DFI), associated with the male fertility capability tightly. PubMed, Web of Science and Cochrane Library were searched extensively for eligible studies with the search terms: varicocele, sperm DNA and sperm DNA damage. Finally, a total of 12 studies were included in our meta-analysis with a total of 845 patients diagnosed with varicocele and 2,377 healthy controls. A statistical difference of DFI between varicocele patients and healthy controls was found after pooling the data ((Standardised mean difference) SMD: 1.40, 95%CI: 0.83-1.98, p < .0001), using the random effect model. We conducted subgroup analysis according to study region (Brazil and Other countries), detection methods of DFI (TUNEL, Comet, and SCSA), sample size (<50 and >50) and age (<30 and >30 years), based on substantial heterogeneity among eligible studies. The stability of pooled results was verified by sensitivity analysis. All these statistical analyses were conducted using Stata version 16.0. In conclusion, patients diagnosed with clinical varicocele had higher DFI than healthy controls, which means varicocele could impair sperm DNA, consequently the fertility potential of affected men.

Reproductive Outcomes of Different Sperm Selection Techniques for ICSI Patients with Abnormal Sperm DNA Fragmentation: a Randomized Controlled Trial

The aim of the study is to compare the reproductive outcomes of different sperm selection techniques: density gradient centrifugation (DGC), testicular sperm (Testi), physiological ICSI (PICSI), and magnetic-activated cell sorting (MACS) in abnormal sperm DNA fragmentation (SDF) ICSI patients. A randomized controlled trial included 302 patients with abnormal SDF undergoing ICSI where they were randomized into 4 groups: a control group of DGC (n= 72), Testi (n=73), PICSI (n=78), and MACS (n=79). Results showed no significant differences in the male age, female age, or SDF between the four groups. Testi group had significantly lower cleavage and blastulation rates compared to PICSI, DGC, or MACS groups (p =0.001). For the high-quality blastocysts, DGC and MACS groups had significantly higher rate than the Testi group (p =0.014). The highest pregnancy rate was scored for the PICSI group (69.6%), while the lowest pregnancy rate was scored for the DGC group (51.4%) with (p =0.025). The PICSI group showed a significantly higher implantation rate compared to the other groups (p =0.003). Regarding the ongoing pregnancy rate, the significant difference was observed between the PICSI (62.8%) and MACS (62%) vs. DGC (45.8%). Besides, no significant differences were found in the miscarriage rates between the four groups. In conclusion, PICSI and MACS along with DGC showed significant improvement in embryological and clinical outcome over testicular sperm or sperm processed by DGC alone in patients with abnormal SDFRegistration number: NCT04482517.

Correlation between the DNA fragmentation index (DFI) and sperm morphology of infertile patients

Purpose

To evaluate the correlation between the DNA Fragmentation Index (DFI) and sperm morphology in patients undergoing ICSI, as a predictive parameter in reproductive outcomes.

Methods

A retrospective study was conducted on 125 infertile patients enrolled in a fertility clinic. Seminal characteristics were measured following the WHO guidelines (2010) for the examination of the seminal fluid. After collecting motile sperm population by pellet swim up, DFI was calculated and simultaneously associated with sperm morphology using in situ TUNEL assay and an image analyzer software in at least 250 spermatozoa for each patient.

Results

All subjects were divided into two groups according to a cutoff established, by choice, of the sperm DFI (15%): group A (< 15%) consisting of 65 patients and group B (≥ 15%) of 60 patients. Data were analyzed using non-parametric statistical methods. The results demonstrate that there is no statistical difference between the two groups in seminal characteristics. The collective data show a high significant correlation, suggesting that spermatozoa with abnormal morphology are the best candidates to contain DNA damage (p < 0.001). Also, when group A is compared with group B, an increased percentage of morphologically normal spermatozoa with fragmented DNA was observed in patients, with DFI values ≥ 15% (p < 0.001).

Conclusion

These results are aimed at providing an exact value of DFI in morphologically normal spermatozoa, which will be helpful to the embryologist in evaluating the risk of transferring, during the ICSI procedure, a spermatozoon whit normal morphology but fragmented DNA.

Association of XRCC1 and ERCC2 promoters' methylation with chromatin condensation and sperm DNA fragmentation in idiopathic oligoasthenoteratozoospermic men

The aim of the study was to investigate whether the promoter methylation of XRCC1 and ERCC2 genes is associated with sperm DNA fragmentation and chromatin condensation in idiopathic oligoasthenoteratozoospermic men. This study involved 77 infertile men with idiopathic oligoasthenoteratozoospermia and 51 normozoospermic controls. The methylight method, TUNEL assay and aniline blue staining were used for the evaluation of XRCC1 and ERCC2 genes' methylation, SDF and sperm chromatin condensation, respectively. SDF (p = .004) and XRCC1 methylation (p = .0056) were found to be significantly higher in men with idiopathic OAT than in the controls, while mature spermatozoa frequency was higher in controls as compared to infertile men (p < .0001). No significant association was found between SDF and methylation of XRCC1 and ERCC2 genes (p = .9277 and p = .8257, respectively). However, compared to the cut-off point obtained by receiver operating characteristic analysis, a significant association was found between SDF and XRCC1 methylation, positive and negative methylation groups, generated according to the cut-off value for XRCC1. XRCC1 methylation was found to have a significant effect on chromatin condensation (p = .0017). No significant difference was detected among ERCC2 methylation, male infertility and SDF. In conclusion, XRCC1 methylation may have a role in sperm chromatin condensation and idiopathic OAT.

The Effects of In Vitro Incubation of Asthenoteratozoospermic Semen after Density Gradient Centrifugation at Room Temperature and 37°C on Sperm Parameters, Chromatin Quality and DNA Fragmentation in a Short Time Period

Background:

Sperm quality is an important factor in assisted reproductive technology (ART) that affects the success rate of infertile couples treatment. In vitro incubation of sperm can influence its parameters and DNA integrity. The present study focused on the effect of different incubation temperatures sperm parameters on asthenoteratozoospermia semen prepared with density gradient centrifugation at different times.

Methods:

Twenty-seven samples were collected and prepared. Then, the suspension was divided into two parts. One part was incubated at room temperature (RT), and another was incubated at 37°C. Immediately and after 2 hr (2H) and 4 hr (4H), spermatozoa were evaluated regarding motility, viability, morphology, sperm protamine deficiency, chromatin and DNA fragmentation. Statistical analysis was performed using paired t-test and repeated measures. The p<0.05 was considered statistically significant.

Results:

Our results showed that following 2 and 4 hr of incubation at RT, sperm progressive motility and viability decreased significantly. Sperm DNA fragmentation increased significantly following 2 and 4 hr of incubation at RT and 37°C. The Trend analysis confirmed that there were no significant differences between sperm parameters and DNA fragmentation after different times at RT and 37°C.

Conclusion:

Incubation of sperm at RT in comparison to 37°C didn’t preserve sperm parameters and DNA efficiently. Therefore, IVF, ICSI and IUI procedure should be performed in the soonest possible time after sperm preparation.

PICSI vs. MACS for abnormal sperm DNA fragmentation ICSI cases: a prospective randomized trial

PURPOSE

To know which sperm selection technique, physiological intracytoplasmic sperm injection (PICSI) or magnetic-activated cell sorting (MACS), is better for the selection of sperm with abnormal sperm DNA fragmentation (SDF) in patients undergoing intracytoplasmic sperm injection (ICSI).

METHODS

A prospective randomized trial included 413 ICSI cases with abnormal SDF (> 20.3%) by TUNEL assay. Patients with at least 1 million total progressive motile sperm count were randomized to PICSI or MACS groups on the day of ICSI. PICSI depends on the hyaluronan binding of better SDF sperm where individual sperm was selected, while MACS selects non-apoptotic sperm population using Annexin V magnetic beads. All pre-implantation embryogenic parameters were observed and the main outcome was the ongoing pregnancy rate.

RESULTS

There were no significant differences between patients allocated to PICSI and MACS in the studied parameters including pre-implantation embryological data, implantation, clinical pregnancy, and ongoing pregnancy rates. Meanwhile, sub-analysis according to the female age has shown that female patients with less than 30 years of age in the MACS group had significantly higher good-quality blastocyst, clinical pregnancy, and ongoing pregnancy rates than the PICSI group. However, the higher implantation (p = 0.051), clinical pregnancy (p = 0.078), and ongoing pregnancy (p = 0.097) rates observed in females between 30 and 35 years of age in the PICSI group did not reach significance level.

CONCLUSIONS

PICSI and MACS are efficient techniques for sperm selection in cases with abnormal sperm DNA fragmentation. However, MACS is preferred when the females are younger than 30 years, while PICSI is preferred in older females.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03398317 (retrospectively registered).

Tracking research trends and hotspots in sperm DNA fragmentation testing for the evaluation of male infertility: a scientometric analysis

BACKGROUND

This article describes the research trends in sperm DNA fragmentation (SDF) over the past 20 years (1999-2018) using a scientometric approach.

METHODS

A stepwise approach was adopted to retrieve scientometric data (articles per year, authors, affiliations, journals, countries) from Scopus and analyze the publication pattern of SDF with reference to key areas of research in the field of Andrology.

RESULTS

A total of 2121 articles were retrieved related to SDF. Our data revealed an increasing research trend in SDF (n = 33 to n = 173) over the past 20 years (R² = 0.894). Most productive country in publications was the USA (n = 450), while Agarwal A. (n = 129) being the most productive author. Most of the articles in SDF were primarily focused on lifestyle (n = 157), asthenozoospermia (n = 135) and varicocele (130). Mechanistic studies on SDF were published twice as much as prognostic/diagnostic studies, with significant emphasis on oxidative stress. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was the most widely used technique to evaluate SDF. Publications on SDF related to assisted reproductive techniques also showed a linear increasing trend (R² = 0.933).

CONCLUSIONS

Our analysis revealed an increasing trend in SDF publications predominantly investigating lifestyle, asthenozoospermia and varicocele conditions with TUNEL being the most widely used technique. A substantial increase in research is warranted to establish SDF as prognostic/diagnostic parameter to evaluate clinical scenarios and ART outcomes.