Protective effects of coenzyme Q10-supplemented cryopreservation medium on oxidative stress in frozen canine sperm.

This study evaluated the protective effects of coenzyme Q₁₀ (CoQ₁₀) in the cryopreservation medium against oxidative stress in canine sperm. Semen was collected from five adult dogs, and only ejaculates with motility > 70% and concentration ≥ 200 million/mL were included. After extraction and centrifugation, the samples were diluted with a Tris-citric acid-fructose-egg yolk-gentamicin extender, mixed with a glycerol solution, and supplemented with 0, 0.5, 1, 1.5, or 2 µM coenzyme Q10; then, the two-step freezing process was performed using the same extender. Samples were equilibrated at 5 °C, frozen in nitrogen vapor, and stored in liquid nitrogen for two months. Fresh and post-thaw semen was assessed for sperm concentration, motility, viability, membrane integrity, DNA damage, and oxidative stress markers, including total antioxidant capacity (TAC), total oxidant status (TOS), malondialdehyde (MDA), and antioxidant enzyme activities (SOD, GPx, CAT). Cryopreservation significantly decreased TAC and increased TOS and MDA (p < 0.05). Supplementation with 1.5 µM CoQ₁₀ significantly preserved TAC and antioxidant enzyme activities, reducing oxidative markers, and reducing the reduction of motility, viability, membrane integrity, and DNA integrity compared with frozen controls (p < 0.05), while 0.5 µM was less effective and 2 µM showed only minor additional benefit. These findings indicate that 1.5 µM CoQ₁₀ optimally mitigates oxidative stress and preserves post-thaw sperm quality, highlighting its potential to improve fertility preservation outcomes in dogs.