Effects of astragalus polysaccharides on the quality of frozen-thawed Tibetan boar spermatozoa and levels of genomic DNA methylation in the sperm

Abstract

Astragalus polysaccharides (APS) have strong antioxidant effects and may thus be useful for the preservation of
semen at low temperatures in vitro. However, the effects of APS on the quality of frozen-thawed Tibetan boar sperm
have yet to be clarified. Here, the effects of APS on the quality and levels of genomic DNA methylation in Tibetan boar
spermatozoa were assessed. Tibetan boar semen was cryopreserved in high-density tubules in freezing extender
supplemented with 0, 0.2, 0.4, 0.6, or 0.8 g·L-1 APS to determine the optimal concentration of APS. Sperm genomic DNA
methylation levels of the three groups (Fresh group represents fresh spermatozoa, No add group represents
unsupplemented frozen spermatozoa, and Optimum add group represents frozen spermatozoa supplemented with the
optimal concentration of APS) were detected using a fluorescence method. The results showed that sperm quality was
significantly higher in the group supplemented with 0.4 g·L-1 APS (increased sperm motility, acrosome integrity, and
plasma membrane integrity, simultaneously decreased abnormality and the ROS level) than in all other groups. p<0.05),
and the DNA methylation levels of frozen sperm in this group were significantly lower than that of the No add group
(p<0.05). The results indicated that semen freezing extender supplemented with 0.4 g·L-1 APS was suitable for Tibetan
boar semen.