In a recent study published in Scientific Reports, researchers developed a rapid diagnostic method for double-strand breaks (DSBs), Sperm deoxyribonucleic acid (DNA) Fragmentation (SDF) Releasing Assay (SDFR). They also explored the association between sperm DNA double-stranded breaks (DSBs) and reproductive outcomes.
Study: Innovative technology for evaluation of sperm DNA double-strand breaks diagnoses male factor infertility and prevents reproductive failures. Image Credit: Shidlovski/Shutterstock.com
Background
Millions of couples worldwide are affected by infertility, with male factors accounting for a considerable number of instances. In rare circumstances, sperm examinations such as volume, concentration, motility, and morphology may fail to detect abnormalities.
Sperm DNA DSBs are a diagnostic feature in instances of idiopathic infertility and are associated with reproductive failures.
The neutral comet test, which correlates with DSBs in clinical settings, has been used to examine DSBs; however, due to its technique sensitivity and absence of a consistent grading system, its clinical applicability is restricted. Further research is required to increase its clinical use.
About the study
In the present prospective cohort study, researchers designed a novel technology to evaluate DSBs, the R11 rapid assay, based on unique molecular features. They validated its specificity, sensitivity, and reliability and used it to assess the link between DSBs and reproductive outcomes.
The study included 640 infertile males aged 20 to 60 years who sought assisted reproductive therapy at Lee Women's Hospital in Taiwan between May 2020 and December 2021. Individuals with retrograde ejaculation or azoospermia were excluded.
The participants masturbated to provide sperm samples, which were examined for sperm concentration, progressive motility, and total motility.
Sperm Chromatin Dispersion experiments utilizing bright-field microscopes were used to determine the total DNA fragmentation index (DFI). A medium to large halo denoted intact sperm DNA, whereas a small to negligible halo denoted fragmented DNA.
Sperm DNA was described to have DSBs in the neutral comet assay if the DNA tail was 40 m or longer and had ≥20% fraction of the deoxyribonucleic acid tail over the entire signal.
The samples were treated at 37 °C with 5.0 U/ml, 10 U/ml, 20 U/ml, and 40 U/ml of deoxyribonuclease I (DNase I) and 5.0 U/ml, 15 U/ml, 25 U/ml, and 50 U/mL of Alu I endonucleases, which are routinely used to model DSBs.
To produce oxidative stress and cause DNA strand breakage, the sperm samples were treated with 0.030%, 0.150%, and 0.300% hydrogen peroxide (H2O2).
Further, the researchers conducted a retrospective investigation of 140 couples with at least two embryos under preimplantation genetic testing for aneuploidy (PGT-A). Based on the worldwide genetic testing community consensus, embryonic aneuploidy was determined based on mosaicism levels exceeding 80%; biopsied blastocyst counts ascertained the aneuploidy rates.
Results
The modified PA network enabled the trapping of DSBs, which distributed a halo on an immunological slide; undamaged chromatin, on the other hand, did not form a halo. A significant association was found between reproducible SDFR and the neutral comet assay readings.
SDFR responded to dose/time-dependent simulated DSBs with great specificity and sensitivity. DSB predicted embryonic aneuploidy, although basic semen characteristics did not.
The DSB DFI did not change significantly between the R11 test (mean, 11) and the comet assay (mean, 10). The Bland-Atman plot analysis revealed that the two tests were in good agreement.
R11 DFI rose when treatment duration and dosages were increased using dose- and time-dependent Alu I and DNase I treatment. However, after H2O2 treatment, the R11 DNA fragmentation index remained unaltered, demonstrating that R11 could selectively identify sperm DSBs.
R11 DFI had significant negative relationships with normal morphology and total motility and showed substantial associations with progressive motility. The DFI values for R11 were significantly positively linked with the male's age.
Among the sperm characteristics, sperm concentration, normal morphology, total motility, R10 (total DNA fragmentation index), and R11 (double-stranded break DNA fragmentation index), R11 [area under the receiver-operating characteristic curve (AUC), 0.7] was shown to predict aneuploidy prevalence (a 50% or higher aneuploidy rate).
Given that maternal age (AUC of 0.7) and paternal age (AUC of 0.7) were likewise linked to embryonic aneuploidy, the researchers performed adjusted modeling excluding females above 38 years, accounting for confounding variables.
Compared to the other semen quality indicators, R11 exhibited the highest AUC in aneuploidy prediction (0.7). The R11 cutoff was higher than 8.0%, and the specificity and sensitivity were at their greatest.
Conclusions
Overall, the study findings highlighted the design of the R11 sperm DSB assay, which employs polyacrylamide to capture DSBs, providing a faster technique compared to neutral comet assays.
R11 reduces the subjectivity of DNA fragmentation index interpretation by providing consistent binary halo categorizations for double-stranded breaks and undamaged DNA.
Image-based data may be combined with an artificial intelligence-integrated automated system, making DSB assessments more efficient, uniform, and controllable in the laboratory.
R11 was significantly linked with morphology and total and progressive motility in 640 males. The researchers established the predictive ability of the R11 assay in detecting embryonic aneuploidy in the preimplantation stage, establishing it as a valuable tool to assess paternal risk determinants and minimize the effects of DSBs.
More clinical trials with larger sample sizes are required to determine the link between R11 and ART failures.
DDT exposure found to alter sperm epigenome in humans