Genetics: Discontinuous Percoll gradients enrich X-bearing human spermatozoa: a study using double-label fluorescence int-situ hybridization

The aim of this study was to evaluate the efficacy of enrichingX-bearing human spermatozoa using 12-step (25–80%) discontinuousPercoll gradients. X- and Y-bearing spermatozoa were simultaneouslyidentified in neat semen (controls) and in 80% Percoll fractionsfrom the same samples using double-label fluorescence in-situhybridization and chromosome-specific DNA probes. Hybridizationand labelling efficiencies of 95–99% were obtained inall samples. The mean ratio of X- to Y-bearing spermatozoa inthe controls was 49.0: 48.2, whereas there was a significantenrichment (P < 0.0001) of X-bearing spermatozoa in the Percollfractions (mean X:Y ratio was 55.1:41.1 or 1.35). The ratiovaried from 1.1–1.5 in individual Percoll samples. Therewere no significant differences in the proportions of aneuploidspermatozoa (XX, YY, XY) between the control and Percoll fractions.We conclude that 12-step discontinuous Percoll gradients enrichX-bearing spermatozoa, but the degree of enrichment is insufficientfor use in preconceptional sex selection.