Comparison of different hypo-osmotic swelling solutions to select viable immotile spermatozoa for potential use in intracytoplasmic sperm injection

The hypo-osmotic swelling test, originally developed as a diagnostic sperm test, is used to discriminate viable from non-viable spermatozoa for intracytoplasmic sperm injection (ICSI) in cases of complete asthenozoospermia. In the present study, three hypo-osmotic solutions were compared, i.e. (A) Jeyendran solution containing sodium citrate and fructose; (B) a mixture of 50% culture medium and 50% milli-Q water; and (C) milli-Q water. While both the percentage of swelling and vitality assessed by eosin Y remained unchanged after 5-30 min of sperm exposure to solutions A and B, incubation in water for only 5 min was in itself detrimental. Ten frozen-thawed donor samples and 10 asthenozoospermic patient samples were exposed to the three solutions for given periods of time. Percentages of swelling and the results of the eosin Y test were well correlated for solutions B and C, but only weakly correlated for solution A. Percentage viability was further assessed by eosin Y and motility of spermatozoa after 2 h and 24 h exposure to the three solutions was compared with unexposed control spermatozoa. While a significant decrease in both parameters was observed for all three solutions in comparison with the control, sperm quality was significantly higher after exposure to solution B than after exposure to solutions A and C. It may be concluded that solution B (composed of 50% culture medium and 50% water) is to be preferred for the selection of viable immotile spermatozoa for ICSI.