Effects of cryopreservation on human sperm deoxyribonucleic acid integrity.

OBJECTIVE To evaluate the effect of cryopreservation on sperm motility and viability and to assess sperm DNA fragmentation and oxidation in men undergoing infertility investigation before and after cryopreservation in liquid nitrogen. DESIGN Analysis of cryopreservation effects on sperm DNA integrity. SETTING Laboratory of Histology-Embryology of medicine faculty, Sfax, Tunisia. PATIENT(S) Fifteen semen samples from men undergoing infertility investigation. INTERVENTION(S) Neat semen samples were cryopreserved in liquid nitrogen using a commercial freezing medium (SpermFreeze, Fertipro, Belgium) according to the manufacturer's instructions. Samples were thawed at room temperature. MAIN OUTCOME MEASURE(S) Sperm DNA fragmentation was assessed using terminal deoxynucleotidyl transferase (Tdt) mediated dUTP nick end labeling and sperm DNA oxidation was determined using a fluorescent assay (OxyDNA test) for the detection of 8-oxoguanine. Evaluation of DNA fragmentation and oxidation rates was carried out before and after cryopreservation using flow cytometry. RESULT(S) A significant decrease in sperm motility and viability was observed after cryostorage. In addition, sperm DNA fragmentation and DNA oxidative damage increased significantly after cryopreservation/thaw. CONCLUSION(S) Cryopreservation has deleterious effects on sperm DNA by inducing DNA fragmentation and oxidation but the mechanisms underlying such damages need to be elucidated by further investigations.