Polarity, protrusion-retraction dynamics and their interplay during keratinocyte cell migration

Keratinocyte migration on a two-dimensional substrate can be split into fou r distinct phases: cell extension, attachment, contraction, and detachment. It is, preceded by polarization of the cell which leads to a functional as ymmetry observable by the formation of a leading lamella. In this work vari ation of fibronectin coating concentrations and competitive inhibition with RGD peptides are used to investigate the dependency of polarization, migra tion, lamella dynamics, and ruffling on substrate adhesiveness. Looking at migrating human epidermal keratinocytes with a well-defined polarity we fin d that a fibronectin-coating concentration of 10 mug/cm(2) stimulates migra tion and ruffling speed twofold, whereas protrusion speed increases only by 20% (compared to 2.5 mug/cm(2) fibronectin). Nonpolar cells show a constan t migration and ruffling speed independent of the amount of fibronectin. In contrast protrusion speeds of polar and nonpolar cells are equal. Treatmen t of cells on 10 mug/cm(2) fibronectin with 1 mg(ml GRGDS reduces the chara cteristic migration, protrusion, and ruffling speed of polar cells which co rresponds to lowering the effective coating concentration to under 5 mug/cm (2). The probability of being polarized (quantified by a polarity index) in creases with increasing fibronectin concentration. However, addition of sol uble RGD on 10 mug/cm(2) fibronectin does not simply reduce the polarity in dex like one would expect from the corresponding changes in the other motil ity parameters, but it remains unchanged. (C) 2001 Academic Press.