Effect of culture conditions and media on the frequency of chromosomal abnormalities in human sperm chromosome complements

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Abstract
Human sperm chromosomes can be visualized after fusion with hamster eggs. Most laboratories use one of two methods of sperm treatment for capacitation: incubation in a modified Krebs‐Ringer medium (BWW) for 5–7 h at 37°C or storage in a TES‐Tris yolk buffer (TYB) for 24–72 h at 4°C. To determine whether data from the two methods were comparable, we performed a series of controlled experiments on one normal donor in which ejaculates were split and one aliquot of sperm was capacitated in BWW for 5–7 h at 37°C (fresh) and the second aliquot was capacitated in TYB for 48 h at 4°C (TYB). After capacitation, the technique used to obtain human sperm chromosome complements was identical for both aliquots. Both fresh and TYB sperm were further subdivided into two groups, which were subjected to either a short (1 h) or a long (3 h) gamete coincubation in BWW. This experiment was performed to determine if the longer incubation in BWW might induce chromosomal fragile sites and breaks because of nutritional depletion of the medium. A total of 458 human sperm chromosome complements was analysed. There was no significant difference in the frequency of sperm chromosomal abnormalities or in the sex ratio in the sperm coincubated with eggs for a short (1 h) or long (3 h) time in BWW. When sperm pretreatments were compared, there was a significant increase in the frequency of total sperm chromosomal abnormalities after TYB storage compared to fresh treatment. This difference was due to an increased frequency of structural chromosomal abnormalities in sperm stored in TYB, not in hyperhaploid or hypohaploid sperm. There was no difference in the sex ratio of fresh (47.2% X) or TYB sperm (47.2% X). Thus our results suggest that storing sperm at 4°C for 48 h in TYB does not alter the frequency of aneuploidy but significantly increases the frequency of structural chromosomal abnormalities.