Temperature-induced sperm nuclear vacuolisation is dependent on sperm preparation

The influence of temperature during incubation on the degree of sperm nuclear vacuolisation was assessed by two different experiments. In a first experiment, motile spermatozoa from 24 patients were prepared by the swim-up technique and incubated either at room temperature or at 37 °C for up to 4 h. The presence of sperm nuclear vacuoles was determined by contrast-enhanced high magnification microscopy. No statistically significant difference was found in the degree of sperm nuclear vacuoles in both groups (RT: 45.6 ± 17.6%; 37 °C: 48.4 ± 17.0%) following 4 h of incubation. In a second experiment, spermatozoa from six patients were either prepared by swim-up or washed and incubated at 37 °C. After 4 h of incubation, a significant increase in sperm nuclear vacuolisation was found in washed sperm (from 51.5 ± 15.4% to 68.6 ± 9.0%; P < 0.05) but not in swim-up sperm (from 51.5 ± 15.4% to 48.2 ± 17.1%; n.s.). Our data show that the mode of sperm preparation does influence sperm nuclear vacuolisation at 37 °C (Experiment II). However, sperm nuclear vacuolisation is unaffected by temperature in motile sperm after preparation and isolation by swim-up.