Pre-freezing sperm preparation does not impair thawed spermatozoa binding to the zona pellucida

The present study was conducted to assess the fertilizing potential of froz en-thawed spermatozoa, which were cryopreserved after separation on a Perco ll gradient, or washed out of seminal plasma. For this purpose, binding to the zona pellucida and other characteristics of the treated sperm cells wer e compared with those of cryopreserved spermatozoa from the same original s ample which were not manipulated before freezing. Semen specimens were obta ined from 80 candidates for sperm donation. Percoll-treated sperm samples c ompared with the sibling, unprocessed controls had significantly higher val ues of sperm motility characteristics and per cent of cells with normal mor phology after freezing and thawing. Sperm binding ability to the zona pellu cida was not statistically different (109 +/- 8.1% and 94 +/- 6.7% in unpro cessed and Percoll-treated samples respectively), Sperm specimens processed by washing had significantly higher values for motility characteristics th an untreated sibling samples, but no differences were found between the tre ated and untreated samples for morphology and binding to the zona pellucida (hemizona index of 75 +/- 7.0% and 76 +/- 6.7% in unprocessed and washed s amples respectively). These findings suggest that, judged by the binding as say, the aforementioned pre-freezing separation processes have no adverse e ffect upon the fertilizing potential of the thawed sperm cells. These proce dures make it possible to optimize the progressive motile sperm cell concen tration of the frozen specimen, which facilitates the storage of samples wi th good quality, even when the features of the original semen are sub-optim al.