Addition of low concentration of cholesterol-loaded cyclodextrin (CLC) has a positive effect on cryopreserved canine spermatozoa evaluated by andrological and biophysical methods

Background This study was conducted to find the best concentration of cholesterol-loaded cyclodextrin (CLC) which has a positive impact on canine post thaw semen quality. Three different concentrations of CLC (0.83 mg/ml; 1.66 mg/ml; 3.32 mg/ml) and 2-hydroxylpropyl-beta-cyclodextrin (HBCD) (1.66 mg/ml) were used in addition to cryopreservation extender and compared with the control after thawing. Samples were assessed using computer-assisted semen analyzer (CASA), flow cytometry, fluorimeter by measuring the fluorescence anisotropy (ANISO) and determining the generalized membrane polarization (GP).Results An addition of 0.83 mg/ml CLC significantly increased the percentage of progressive motile (PROG) and rapid spermatozoa (RAP) (P < 0.05). 1.66 mg/ml HBCD decreased progressive motility of spermatozoa and population with rapid movement relative to the control (P < 0.05). Furthermore, the groups with an addition of 1.66 mg/ml and 3.32 mg/ml of CLC, as well as the group with only cyclodextrin, increased percentage of dead spermatozoa without lipid peroxidation and decreased percentage of viable spermatozoa without LPO which was lower in these groups than in the control (P < 0.05). Other sperm parameters assessed on flow cytometer were not significantly different. The addition of CLC at 0.83 mg/ml and 3.32 mg/ml concentrations and 1.66 mg/ml of HBCD caused an increase in ANISO measured at 23 oC (P < 0.05).Conclusions In conclusion, the results suggest that increasing cholesterol in the plasma membrane of canine spermatozoa can improve their freezability. However, only low concentrations of CLC may improve semen quality after thawing without adversely affecting other parameters.