Retention of membrane charge attributes by cryopreserved-thawed sperm and zeta selection

Abstract

Purpose Mature sperm can be selected based on their negative zeta electrokinetic potential. The zeta selection of cryopreserved sperm is unknown. The objective was to study the effect of zeta processing on the morphology and kinematic parameters of cryopreserved-thawed sperm. Methods Colloid-washed sperm (N=9 cases) were cryopreserved for 24 h, thawed and diluted in serum-free medium in positive-charged tubes. After centrifugation, the tubes were decanted, serum-supplemented medium was added and the resuspended sperm were analyzed. Untreated sperm and fresh sperm served as the controls. Results There were improvements in strict normal morphology in fresh (11.8±0.3 versus control 8.8±0.3 %, mean ±SEM) and thawed (8.7±0.2 versus control 5.4±0.2%) sperm after zeta processing. Percent sperm necrosis was reduced after zeta processing (66.0±0.6 versus unprocessed 74.6±0.3%). Progression decreased by 50% but not total motility after zeta processing of thawed sperm. Conclusions The results suggested that the cryopreservation process did not impact the sperm membrane net zeta potential and higher percentages of sperm with normal strict morphology, acrosome integrity and reduced necrosis were recovered. The zeta method was simple and improved the selection of quality sperm after cryopreservation but more studies would be needed before routine clinical application.

Effects of cryopreservation on sperm parameters and ultrastructural morphology of human spermatozoa

“…Thus, it is critical to select the most viable spermatozoa, and exclude the damaged cells following cryopreservation. Kam et al stressed the usage of zeta method in order to improve the selection of quality sperm after cryopreservation; however the technique is currently experimental [39]. In this study TEM, SEM and light microscopic examinations have shown that the rate of sperm cells having normal morphology decreased significantly.…”

Effect of sperm storage and selection techniques on sperm parameters

“…Even though progressive motility declines after zeta selection on a cryopreserved sample, the selected sperm are more likely to have an intact acrosome and normal morphology. In one study, the markers of apoptosis and sperm necrosis were significantly reduced in a zeta selected sample [Kam et al 2007]. However, the recovery rate was only 8 to 10% of the original concentration used for cryopreservation.…”

“…However, the recovery rate was only 8 to 10% of the original concentration used for cryopreservation. An adequate sperm concentration could not be obtained when sperm selection using zeta potential was used before cryopreservation [Kam et al 2007]. Because the recovery rate is low after zeta selection, it should not be used prior to cryopreservation.…”

Optimization of microelectrophoresis to select highly negatively charged sperm

“…Sperm membrane charge has been exploited by two other methods of sperm selection, Zeta test [22,23] and electrophoretic sperm separation [24,25]. Use of NCS selected by Zeta method resulted in an improvement in fertilization, implantation, and pregnancy rates [31,36], suggesting that selection of sperm with a high negative charge could aid in the isolation of mature and healthy sperm for ART.…”

“…Such sperm have higher net negative charge when compared with abnormal and immature sperm [18]. Selection of mature sperm based on differences in sperm membrane charge has been employed by two methods, the Zeta test [22,23] and electrophoretic sperm separation [24,25]. Sperm with high negative membrane charge have been shown to be morphologically normal, contain high protamine content [26] and have low levels of DNA damage [24,[26][27][28][29].…”