UNPROTECTED FREEZING OF HUMAN SPERMATOZOA EXERTS A DETRIMENTAL EFFECTON THEIR OOCYTE ACTIVATING CAPACITY AND CHROMOSOME INTEGRITY

The influence of unprotected freezing of mammalian spermatozoa on thei r oocyte activating capacity and chromosome integrity is unknown. Howe ver, this type of sperm treatment has been used in assisted reproducti on by intracytoplasmic sperm injection in cattle and humans. The mouse oocyte injection test was used to analyse the influence of unprotecte d freezing of human spermatozoa on their reproductive characteristics. Mouse oocytes were microinjected with intact human spermatozoa or spe rmatozoa treated with two cycles of unprotected freeze-thawing. Oocyte s surviving the injection were either cultured without further treatme nt or exposed to ethanol solution to induce parthenogenetic activation . Both injected and activated oocytes were used for sperm chromosome a nalysis. The results revealed a significant reduction in oocyte activa ting capacity and a tenfold increase in the incidence of structural ch romosomal abnormalities in human spermatozoa treated by unprotected fr eezing. We conclude that unprotected freezing of human spermatozoa has a detrimental effect on their reproductive characteristics. Our data also provide a new perspective on the stability of mammalian spermatoz oa to physical factors and demonstrate the importance of detailed anal ysis of the stability of sperm structures for successful development o f new approaches in assisted reproduction.