Iodixanol fortification in freezing extender protects sperm DNA damage and improves antioxidant capacity

BACKGROUND: One of the most essential ingredients of artificial insemination (AI) programs is semen processing which needs extender with additives to protect spermatozoa against cold stress during cryopreservation. The selection of cryoprotectant and composition of extenders are of great importance for sperm survival during and after cryopreservation. The addition of small quantities of iodixanol in the freezing extender can protect spermatozoa by altering the glass transition temperature of the mixture and changing the structure of the growing ice crystals. OBJECTIVE: To reveal the effect of iodixanol fortification in semen extender on post thawed sperm qualities, DNA intactness and antioxidant status. MATERIALS AND METHODS: The ejaculates were collected from Barbari goats using artificial vagina method and samples with >80% initial progressive sperm motility were extended with tris-citric acid-fructose diluent. Iodixanol was added to the sperm preparation medium at different concentration (Control, 0 μM; 100 μM; 200 μM; 300 μM and 400 μM). Sperm concentrations were adjusted 400 million per mL and diluted semen was kept for equilibration at 5°C for 4 h before being cryopreserved in liquid nitrogen. Semen samples were evaluated for sperm quality at the pre-freeze and post‐thaw stages. RESULTS: Semen samples fortified with 400 μM iodixanol had improved cryopreservation, with significantly higher motiliy, live sperm count, acrosome integrity and hypo osmotic swelling (HOS) positive spermatozoa compared to the control. In addition, fortified semen had significantly lower sperm MDA and protein carbonyl contents after cryopreservation and greater sperm DNA integrity (fewer TUNEL+ve sperm) and lower mitochondrial membrane potential. Finally, semen fortification resulted in a small improvement in post‐cryopreservation kidding rate. CONCLUSION: Iodixanol at 400 μM significantly improves post‐thaw sperm qualities and fertility in Barbari goat and its value as a freezing extender seems to relate to an enhanced antioxidant capacity.