Assessment of DNA integrity and morphology of ejaculated spermatozoa from fertile and infertile men before and after cryopreservation

Cryopreservation of human spermatozoa is extensively used in artificial ins emination and IVF programmes. Despite various advances in cryopreservation methodology, the recovery rate of functional post-thaw spermatozoa remains mediocre, with sperm motility being significantly decreased after freezing, This aim of this study was to investigate the effects of cryopreservation on both DNA integrity and morphology of spermatozoa from fertile and infert ile men. Semen samples were obtained from 17 fertile and 40 infertile men. All samples were prepared by discontinuous Percoll density centrifugation ( 95.0:47.5). Samples were divided into aliquots to allow direct comparison o f fresh and frozen spermatozoa from the same ejaculate. Aliquots for cryopr eservation were mixed with a commercial cryoprotectant and frozen by static phase vapour cooling before plunging into liquid nitrogen. Thawing was car ried out slowly at room temperature, Sperm DNA integrity was determined usi ng a modified alkaline single cell gel electrophoresis (comet) assay and sp erm morphology analysed using the Tygerberg criteria. DNA of semen and prep ared spermatozoa from fertile men was found to be unaffected by cryopreserv ation, In marked contrast, spermatozoa from infertile men were significantl y damaged by freeze-thawing. Cryopreservation had a detrimental effect on m orphology of semen and prepared samples from fertile and infertile men.