Influence of cryopreservation on the microelectrophoretic motility (EPM) of human spermatozoa

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

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.

A simple zeta method for sperm selection based on membrane charge

OBJECTIVE

The objectives were: [1] to develop a simple zeta potential method for sperm isolation; and [2] to analyze the sperm maturity, morphology, kinematic, and DNA parameters.

DESIGN

The phenomenon of sticky sperm adhering to slide surfaces was adapted for collecting charged sperm.

SETTING

Clinical and academic research environment.

PATIENT(S)

Discarded colloid-washed sperm from routine laboratory testing (n = 8).

INTERVENTION(S)

Sperm were centrifuged in serum-free medium and collected for analyses.

MAIN OUTCOME MEASURE(S)

Kinematic parameters, DNA integrity, and maturity.

RESULT(S)

The percentages of mature (73.0% +/- 0.5% vs. control 63.5% +/- 0.5% SEM) and DNA intact sperm (85.0% +/- 0.3% vs. 69.5% +/- 0.5%) increased in the male factor subgroup. Strict normal morphology (19.3% +/- 0.1% vs. 10.0% +/- 0.1%), hyperactivation (7.0% +/- 0.1% vs. 3.6% +/- 0.1%), and progressive motility (29.1% +/- 0.1% vs. 19.9% +/- 0.1%) increased by twofold.

CONCLUSION(S)

The zeta method improved sperm parameters associated with increased fertilization and pregnancy after assisted reproduction procedures. Manipulation from the attaching-detaching process stimulated sperm metabolism without causing premature acrosome reactions. Total motility was unchanged suggesting a lack of association between total motility and zeta potential.

In vitro evaluation of frozen-thawed stallion semen: a review

The article reviews methods used for in vitro evaluation of sperm, with particular emphasis on frozen-thawed stallion sperm. The techniques, limitations of the methods and correlations with fertility results are discussed. Very few studies have tried to find correlation between fertility of frozen stallion semen and laboratory tests. It is difficult and expensive to inseminate an adequate number of mares to achieve statistically significant differences. Significant, but low correlations have been demonstrated between the foaling rate and subjective motility of sperm incubated for 2 h and 4 h at 37 degrees C and hypoosmotic swelling test after 0 and 3 h of incubation. Significant correlations have been reported between the pregnancy rate and viability of propidium iodide-stained sperm assessed by flow cytometry as well as for glass wool and Sephadex filtration tests. No correlations have been detected between fertility and motility immediately after thawing. In spite of that, motility estimation by light microscope is the most commonly used method to evaluate frozen-thawed stallion sperm. Computer assisted automatic sperm analyzers have replaced light microscopy in research projects, but so far nobody has been able to demonstrate a correlation between fertility of frozen stallion semen and any of the motility parameters obtained by these instruments.