Quantitative estimation of the degree of cell spreading on different surfaces and cell monolayers using a fluorescent plate scanner.

A simple, rapid, and quantitative method for estimation of the degree of spreading of fluorescently labeled cells adherent to an artificial or biological surface has been designed, based on the principle that the medium between adherent cells and the surface of adhesion absorbs fluorescent light emitted by the adherent cells. Using the Beer-Lambert equation for extinction coefficient of monochromatic light, we have calculated the factor by which fluorescence signal actually emitted from cells adherent to the bottom of the microtiter well would differ from the fluorescence of these cells detected by a bottom-scanning plate reader. The physical nature of cell-cell ligand-receptor bridges depends on many parameters, such as the type of the receptor(s), the intensity and direction of a stress force, blockade of the receptors with monoclonal antibodies (MAb), and transfer of adhesion mediation to different ligand-receptor pairs. When employed in various adhesion models, this new technique has demonstrated quantitative changes of cellular spreading of human neutrophils adherent to different extracellular matrix protein-coated surfaces and to endothelial cells after neutrophil/endothelial cell activation or in the presence of MAb directed against neutrophil integrins. These measurements of spreading of adherent cells appear more sensitive than visual observation of cellular morphology on biological surfaces or cells.