Relationship between nuclear DNA fragmentation,mitochondrial DNA damage and standard sperm parameters in spermatozoa of fertile and sub‐fertile men before and after freeze‐thawing procedure

The aim of this study was to assess the stability of nuclear and mitochondrial DNA (n‐DNA and mt‐DNA) of spermatozoa under freeze‐thawing and to find out the correlation between them and their association with standard sperm parameters. Forty‐three semen samples were collected from fertile (G.1; n = 29) and sub‐fertile (G.2; n = 14). N‐DNA fragmentation was determined by TUNEL assay and mt‐DNA using caspase 3 staining. Each semen sample was frozen at ?196°C by the programmed freezer. Freeze‐thawing decrease vitality, total motility and membrane integrity from (43.02 ± 22.74%; 31.63 ± 18.15%; 51.5 ± 24.82%) to (22.71 ± 17.3%; 9.21 ± 6.61%; 34.64 ± 19.92% respectively p < .001]). G.1 native spermatozoa stained positive with TUNEL and caspase 3 were (14.85 ± 17.6% and 5.8 ± 11.59%) and increased after freeze‐thawing to 27.54 ± 19.74% (p = .004) and 7.3 ± 6.13% (p = .01) respectively. In G.2, TUNEL and caspase 3 were (19.84 ± 17.52% and 7.53 ± 8.56%) and increased to (29.48 ± 16.97% p = .03] and 10.21 ± 11.73%). In conclusion, freeze‐thawing process affects not only semen parameters but also n‐DNA and mt‐DNA. Therefore, n‐DNA and mt‐DNA could be used as sensitive parameters for assessment of the cryodamage of human spermatozoa.