The effect of cholesterol loaded cyclodextrins on post-thawing quality of buffalo semen in relation to sperm DNA damage and ultrastructure.

The cryopreservation of germ cells is a major tool for the propagation of animals with desired genetic traits. Although cryopreservation of spermatozoa in some animals is effective, its effectiveness is variable. For example, cryopreservation efficiency of buffalo bull spermatozoa remains very poor. In this study, we evaluated sperm DNA damage and ultrastructure in buffalo bull spermatozoa vitrified in the presence or absence of cholesterol-loaded cyclodextrins (CLC). Our results showed that cryopreserved buffalo spermatozoa had elevated levels of deteriorated plasma and mitochondrial membranes, which are the likely causes of DNA damage after vitrification. Accordingly, the levels of the activity of Alanine Aminotransferase (ALT), Alkaline phosphatase (ALP) and Aspartate Aminotransferase (AST) were also elevated following exposure of buffalo bull spermatozoa to a cycle of freezing-thawing. Importantly, supplementation of Tris-Egg Yolk-Glucose (TEYG) extender with (CLC) improved the quality of buffalo spermatozoa following cryopreservation. This protective effect of CLC is likely due to decreasing mitochondrial and plasma membrane deterioration with subsequent inhibition of DNA damage. These results suggest that cholesterol loss is the likely reason for poor semen quality in buffaloes following cryopreservation, and provide evidence that manipulating lipid content during cryopreservation is a promising strategy to improve the quality of buffalo semen.