Changes on membrane integrity and ultrastructure of human sperm after freeze-drying

ObjectiveTo observe changes on membrane integrity and ultrastructure of human sperm after freeze-drying.MethodsSemen samples from both normospermic donors (group A, n=15) and infertile men with abnormal sperm parameters (group B, n=15) were enrolled into this study. These samples were freeze-dried by using a freeze-drying method. The membrane integrity in the head and tail regions of individual spermatozoon was examined by using the combined hypo-osmotic swelling-eosin Y exclusion test. Sperm ultrastructure in groups A (n=3) and B (n=3) was observed by scanning electron microscopy (SEM).ResultsAfter freeze-drying, all spermatozoa were types I (damaged both head and tail membranes) and III (damaged head membrane and intact tail membrane) membrane integrity in groups A and B. Type III of group B had lower value than that of group A (P<0.01). Under SEM, intact freeze-dried spermatozoa including abnormal morphology and normal-looking morphology were observed in both groups A and B. A few freeze-dried sperm heads had unsmooth or fuzzy surface. Isolated sperm heads, bent tails, broken sperm tails or fragmentary tails were more frequently seen in group B than those in group A.ConclusionFreeze-dried human spermatozoa could have intact structural components. However, freeze-drying resulted in severe damage on membrane integrity and ultrastructure of sperm. Samples from infertile men would have less resistance to freeze-drying.