Sperm decondensation and semen parameters: utilization of a simple staining technique for the evaluation of human sperm decondensation

Summary. The ability of spermatozoa to fertilize an oocyte depends on a sequence of events ending ultimately in the decondensation of the sperm chromatin on penetration of the oocyte. Knowledge of what percentage of sperm decondenses is useful, especially in patients where other functional tests and sperm quality fail to explain the reported poor in vitro fertilization (IVF) rates. The objective of this study was (1) to compare sperm decondensation induced by either SDS/EDTA or heparin with semen parameters (volume, concentration, motility and morphology), and (2) to evaluate the use of a simplified staining technique (Diff Quik^R DQ]) in comparison with the standard phase contrast method (Rose Bengal-RB]). Randomly selected semen samples from 31 men attending an assisted reproductive programme were analysed for basic semen parameters and decondensation with SDS/EDTA and heparin. Two staining methods for the evaluation of decondensation were compared (phase contrast microscopy after Rose Bengal RB] staining and light microscopy after Diff Quik^R (DQ) staining). Moderate and grossly swollen sperm heads were recorded. Semen samples included both fertile and unfertile semen parameters. Sperm decondensation results showed poor to moderate correlations with semen parameters. The SDS/EDTA (DQ) (moderate forms) showed a significant negative correlation (r = -0.46) with seminal volume and and a significant positive correlation (r = 0.41) with normal sperm morphology. The heparin (DQ) (moderate forms) decondensation showed a significant positive correlation with motility (r = 0.61) and sperm concentration (r = 0.43). The DQ method was preferred over the RB method due to its optical and storage advantage. Sperm decondensation by SDS/EDTA and heparin have limited use in the IVF laboratory as they correlate poorly with semen parameters. Future studies should investigate the use of an ooplasmic factor similar to nucleoplasmin in Xenopus laevis egg.