Combination of Exogenous Spermidine and Phosphocreatine Efficiently Improved the Quality and Antioxidant Capacity of Cryopreserved Boar Sperm and Reduced Apoptosis-Like Changes

The low resistance of boar sperm to cryopreservation dictates that addition antioxidants and energetic substances to the diluent to improve sperm quality is necessary. This study evaluated the effect of spermidine and phosphocreatine in combination on the quality, antioxidant capacity, and antiapoptotic-like changes capacity of cryopreserved boar sperm based on previous reports. The results showed that the combined application of spermidine and phosphocreatine significantly enhanced the motility, average path velocity, straight-line velocity, curvilinear velocity, beat cross frequency, acrosome integrity, plasma membrane integrity, mitochondrial activity, and DNA integrity compared with the control group (p < 0.05). In addition, the combined application of spermidine and phosphocreatine significantly enhanced the total antioxidant capacity, superoxide dismutase activity, glutathione peroxidase activity, and catalase activity while significantly decreasing malondialdehyde content and hydrogen peroxide content (p < 0.05). Western Blot analysis further showed that spermidine and phosphocreatine significantly decreased the expression of CASP3 and BAX and significantly enhanced the expression of BCL2 (p < 0.05); therefore, the combination of spermidine and phosphocreatine has potentially positive implications for improving the quality of cryopreserved boar sperm.