Quantitative analysis of receptor-mediated adhesion of mammalian cells

Cell-substratum adhesion is an essential component of a variety of physiologic processes. The success of biomedical devices such as vascular grafts depends upon their ability to support cell adhesion. Adhesion of mammalian cells to extracellular matrix (ECM) protein-coated surfaces is largely mediated by receptors such as integrins. In this study the strength of this interaction was measured through the use of a Radial Flow Detachment Assay (RFDA) in which a radial variation in surface shear stress was applied to adherent cells. Through the pattern of detachment observed, the shear stress (critical shear stress) necessary to remove 50% of the cells from the surface was determined and used as a measure of adhesion strength. Through the systematic variation of parameters such as surface ligand density, ligand type and attachment time, some of the determinants of adhesive strength were assessed. The critical shear stress was found to increase linearly with increasing ligand surface density and to increase in an inverse exponential manner with the time allowed for attachment. Previously, these behaviors had been predicted in theoretical modelling studies which examined the role of bond formation kinetics in determining adhesion strength. The shear stress for detachment of individual cells was found to be lognormally distributed within fibroblast populations. The RFDA was also used to show that maximal migration of vascular smooth muscle cells occurs at intermediate adhesion strengths and to determine the effect of a series of integrin point mutations on adhesion strength