Lectins and heparin-binding features of human spermatozoa as analyzed by flow cytometry

Abstract

Sperm cell surface characteristics may serve as a useful diagnostic feature for the evaluation of seminal samples, but to date no useful analytical method(s) is available for their routine quantitative analysis. Fluorescein isothiocyanate-conjugated lectins, proteins with unique and specific saccharide-binding characteristics, and heparin are potentially useful markers for such an analytical procedure. A protocol is outlined whereby frozen semen is thawed and treated with either fluorescein isothiocyanate-conjugated soybean agglutinin SBA (Glycine max), peanut agglutinin PNA (Arachis hypogaea), and garden pea agglutinin PSA (Pisum sativum) lectins or fluorescein isothiocyanate-heparin to assess differences in spermatozoa-bound fluorochrome by flow cytometry. Use of propidium iodide to identify nuclei containing sperm cells within the ejaculate is essential to the method because of the large amount of debris associated with the samples. The precision of the assay is high, with the coefficient of variation for the individual probes being less than 20%. Analysis of a patient pool of 22 revealed that a range in binding properties is observed and a mode of grouping these samples into classes for later analysis is outlined. Semen parameters and fluorescein isothiocyanate-ligand binding values were different in a population of unproven fertility as compared with a comparable population of known fertility. A positive correlation (p less than 0.001) for garden pea agglutinin PSA binding and concentration of motile cells, percentage of motility, and number of motile cells was found. These data suggest the possible utility of flow cytometry for the assessment of human seminal samples.