Cryopreservation increases sperm DNA fragmentation in normozoospermic Libyan men: the role of oxidative stress and the protective effect of melatonin
Bibliographic record
Abstract
Cryopreservation of sperm is routinely used in assisted reproduction technology (ART) for male fertility preservation. However, this method has been associated with oxidative stress and DNA fragmentation that may impair sperm quality. Additionally, antioxidant interventions such as melatonin supplementation have not been thoroughly explored in this setting. Although Libya is reported to have one of the highest global prevalence rates of male infertility, Libya-specific data remain limited. This study aimed to determine the effect of a single freeze–thaw cycle on sperm DNA fragmentation and oxidative stress markers, and to evaluate whether melatonin has an impact on post-thaw oxidation profiles. This prospective cohort study was conducted at the Fertility and Reproductive Medicine Center, Beirut Hospital, Benghazi. Semen samples of 104 normozoospermic Libyans were evaluated before and after freezing. DNA fragmentation index (DFI) was measured by sperm chromatin dispersion (SCD) test, and reactive oxygen species (ROS) were quantified by using luminol-enhanced chemiluminescence. In a subset of ejaculates, aliquots were supplemented with 2 mM of melatonin prior to cryopreservation. Cryopreservation was associated with a statistically significant increase in DFI (46.3 ± 18.3% to 60.0 ± 23.0%; p < 0.001) and ROS levels (3.2 × 10³ to 14.7 × 10³ RLU/s; p < 0.001). Smokers presented significantly higher DFI at both pre-freeze and post-thaw evaluations (p < 0.001). We detected a positive correlation between ROS and post-thaw DFI (r = 0.68; p < 0.001). Melatonin-treated samples exhibited moderate but significant differences in ROS (12%, p = 0.045) and DFI (11%, p = 0.004) compared to untreated aliquots. These findings suggested that the freeze–thaw process may contribute to oxidative and genomic stress in spermatozoa, while melatonin supplementation appears to provide limited protection. Larger, multicenter studies incorporating ART endpoints are required to determine the potential translational relevance of these findings.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".