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

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.

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.

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.

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.