Background: DNA fragmentation index (DFI) enhances routine semen analysis by providing valuable insights into male reproductive potential. Utilizing Halosperm test, a sperm chromatin dispersion (SCD) assay based on induced condensation. The purpose of this study was to assess sperm DNA damage both before and after freezing. By following the specified kit instructions, an attempt was made to validate the SCD test protocol, with a particular emphasis on the implications of sperm freezing on its DNA integrity.
Methods: In total, 380 fresh human semen samples from normozoospermic patients were frozen at -20°C for 10 days, using SCD cryopreservation reagent. Routine semen analysis and DNA fragmentation index (DFI) were determined for each sample before freezing and after thawing. Semen morphology and sperm DFI were compared before and after freezing/thawing process.
Results: There was a significant decrease in sperm normal morphology after thawing (9.31±2.42% vs. 7.1±1.53%, p<0.05, respectively). The sperm head, midpiece, and tail defect rate increased after freezing at -20°C. Moreover, DFI was significantly higher after thawing compared to before freezing (20.71±1.61% before freezing vs. 29.1±0.21% after thawing with p<0.001).
Conclusion: Cryoconservation of semen samples at -20°C for 10 days using SCD cryopreservation reagent seems to damage sperm morphology, resulting in a reduction in sperm DNA integrity. The measurement of DFI on a fresh sample remains the most reliable technique for obtaining accurate results.