Effect of Astragalus polysaccharides on the cryopreservation of goat semen

During cryopreservation, sperm encounters oxidative stress induced by excessive reactive oxygen species (ROS), destroying the sperm plasma membrane structure and reducing its physiological functions. The present study aimed to evaluate the effect of Astragalus polysaccharides (APS) on the cryopreservation of dairy goat semen. Semen was collected from six goats, and then qualified semen with movement >80% was selected after preliminary evaluation. The semen was divided into six aliquots, diluted with dairy goat semen extender (1:10) at 37 °C, containing 0 g/L (control), 0.1 g/L, 0.2 g/L, 0.3 g/L, 0.4 g/L and 0.5 g/L APS, cryopreserved, and stored in liquid nitrogen (-196 °C). Sperm quality was assessed after freeze-thawing. The highest sperm motility, motion performance, plasma membrane integrity, acrosome integrity, and antioxidant properties (total antioxidant capacity and levels of antioxidant enzymes) were recorded (P < 0.05) in the 0.2 g/L APS group after the semen was freeze-thawed. The control and the optimal group (0.2 g/L) were then selected to analyze the effects of APS on sperm energy metabolism (mitochondrial membrane potential [MMP] and adenosine triphosphate [ATP]), sperm apoptosis, and the expression of the AMPK signaling pathway. The results showed that treatment with 0.2 g/L APS increased sperm MMP and ATP content after freeze-thawing, reduced sperm apoptosis by regulating apoptosis-related proteins, and promoted AMPK phosphorylation by activating the AMPK signaling pathway. The cleavage rate of frozen goat sperm during in vitro fertilization (IVF) was also observed to increase. These findings suggest meaningful ways to improve cryopreservation of dairy goat semen and provide new insights into the mechanism by which APS protects sperm from oxidative damage via AMPK activation.