Effect of cryopreservation on the nuclear chromatin decondensation ability of human spermatozoa

The possible effect of cryopreservation on human sperm chromatin decondensation ability has been investigated. Comparisons of the actions of the decondensation-inducing agent 1% (w/v) sodium dodecyl sulphate + 6 mM EDTA were made on 30 ejaculates between spermatozoa in seminal plasma, spermatozoa in semen diluted with cryoprotective medium (CPM) and spermatozoa frozen and thawed in the semen-CPM mixture. The results, analyzed as paired series, showed no significant differences between the spermatozoa under the three treatment conditions. Thus, spermatozoa cryopreserved by a method routinely used for semen storage for subsequent artificial insemination showed a nuclear stability equivalent to that of fresh semen. The CPM by itself had no effect upon chromatin instability. No correlation was found between the percentage recovery of post-thaw motility (an usual index for judging semen cryopreservation) and the tests of chromatin decondensation.