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

Abstract

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˚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.