Detrimental Effects of Cryopreservation on the Structural and Functional Integrity of the Sperm Membrane

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Abstract
Many centers have been disappointed with the pregnancy rate following the insemination of cryopreserved-thawed sperm, despite the maintenance of an adequate motile density. The possibility exists that damage to the sperm membrane might occur despite preservation of other semen parameters. Simple measurements of structural integrity (viability) and functional integrity (hypoosmotic swelling test) were performed on thawed specimens. In each instance, both the viability and HOS scores were less than the critical 50% level. Specimens from three different commercial centers had very poor HOS and viability scores from two of the centers, and, though the scores were generally ≥50% from the third center, this was achieved by eliminating 11 of 12 donors. Reducing the glycerol concentration from 12 to 7% and switching from Nunc vials to plastic embryo straws did not improve the poor sperm membrane tests. The possibility exists that if modification of the cryopreservation technique leads to improved HOS and viability scores, perhaps improved pregnancy results will be realized.