The Use of Cholesterol/Randomly Methylated β-Cyclodextrin (RAMEB) Inclusion Complexes to Improve Human Spermatozoa Cryosurvival

Сryoprotective properties of cholesterol/randomly methylated beta-cyclodextrin (RAMEB) inclusion complexes with respect to human spermatozoa have been investigated. The influence of different concentrations of RAMEB and cholesterol/RAMEB inclusion complexes on sperm membranes has been explored. It was shown that obvious cytotoxicity of RAMEB against spermatozoa is due to the interaction between cyclodextrins and lipid components of the membrane, in particular cholesterol extraction. Cholesterol/RAMEB inclusion complexes are significantly less cytotoxic. The dependence of cholesterol concentration in sperm membranes on the concentration of cholesterol/RAMEB inclusion complexes in the sample was established. It was demonstrated that incubation of spermatozoa with 2 mg/ml of cholesterol inclusion complexes before cryopreservation caused a statistically significant increase in survival rate (by 13.8%) and in the proportion of progressively motile spermatozoa (by 14.8%) post-thaw. X-ray diffraction revealed that the concentrations of RAMEB or cholesterol/RAMEB inclusion complexes (2, 4 and 8 mg/mL) do not affect the average size of ice crystals formed in the sample during cryopreservation in the samples. The mechanism of the cryoprotective effect of cholesterol/RAMEB inclusion complexes is proposed.