Effects of riboflavin on boar sperm motility, sperm quality, enzyme activity and antioxidant status during cryopreservation

Objectives: This study was conducted to evaluate the effect of adding riboflavin to boar sperm freezing extender on the challenge of cryopreservation. Methods: Different concentrations (0, 5, 10, 15, 20 or 25 mu M) of riboflavin were added to the freezing extender. Spermatozoa motility, membrane integrity, acrosomal integrity, mitochondrial membrane potential and enzyme activities were analysed once 10 min after thawing. Q-PCR was used to detect the m RNA expression of Caspase3, Bcl-2 and Bax. Results: The results showed that the addition of 10 mu M riboflavin to boar sperm freezing extender significantly increased the frozen-thawed sperm progressive motility compared with the control group (p < 0.05). Activities of superoxide dismutase, glutathione peroxidase and catalase improved after adding riboflavin to the extender (p < 0.05). During freezing-thawing, the boar sperm mitochondrial membrane potential, acrosomal integrity, plasma membrane and DNA at 10 mu M in the riboflavin group increased by 6.6%, 9.6%, 5.49% and 5.62% (p < 0.05), respectively, compared with the control group. The addition of 10 mu M riboflavin to the extender significantly decreased the malondialdehyde (p < 0.05) content, whereas it increased the ATP content (p < 0.05) of boar sperm during freezing-thawing. Furthermore, the expression of Caspase-3 and Bax (p < 0.05) were significantly lower, whereas the expression of BCL-2 (p < 0.05) was greater than the control group when adding 10 mu M riboflavin to the extender. Conclusions: Riboflavin showed cryoprotective capacity to the freezing extender used for boar sperm during the process of freezing-thawing, and the optimal concentration of riboflavin for the frozen extender was 10 mu M.