Freezability of boar spermatozoa is improved by exposure to 2-hydroxypropyl-beta-cyclodextrin

The influence of 2-hydroxypropyl-beta-cyclodextrin (HBCD) exposure on post-thaw spermatozoa prior to freezing using acrosome integrity and the parameters of motility was studied. Acrosomal status was monitored by means of FITC-labelled peanut agglutinin, and the motility parameters were assessed using a computer-assisted sperm motility analysis (CASA) system. The spermatozoa were exposed to HBCD over a period of 3 h, during which the cells were slowly cooled from 25 to 5 degrees C, and then frozen into pellets. The percentage of frozen thawed spermatozoa with intact acrosomes in 40 mM HBCD group was approximately three-fold higher than that of the control. The motility and progressive motility values of the frozen-thawed spermatozoa were found to increase significantly with increased HBCD concentrations. On the other hand, further addition of cholesterol-3-sulfate to the BF5 extender containing 20 mM HBCD resulted in a drastic decrease in the percentage of spermatozoa with intact acrosomes, and decreased motility and progressive motility, suggesting that cholesterol-sulfate probably counter-acted the protective action of HBCD. In conclusion, the results of the present study indicate that HBCD protected boar spermatozoa against freeze-thaw damage, possibly by means of stimulating the efflux of membrane cholesterol.