Receptor-based differences in human aortic smooth muscle cell membrane stiffness

Cells respond to mechanical stimuli with diverse molecular responses. The n ature of the sensory mechanism involved in mechanotransduction is not known , but integrins may play an important role. The integrins are linked to bot h the cytoskeleton and extracellular matrix, suggesting that probing cells via integrins should yield different mechanical properties than probing cel ls via non-cytoskeleton-associated receptors. To test the hypothesis that t he mechanical properties of a cell are dependent on the receptor on which t he stress is applied, human aortic smooth muscle cells were plated, and mag netic beads, targeted either to the integrins via fibronectin or to the tra nsferrin receptor by use of an IgG antibody, were attached to the cell surf ace. The resistance of the cell to deformation ("stiffness") was estimated by oscillating the magnetic beads at 1 Hz by use of single-pole magnetic tw eezers at 2 different magnitudes. The ratio of bead displacements at differ ent magnitudes was used to explore the mechanical properties of the cells. Cells stressed via the integrins required approximate to 10-fold more force to obtain the same bead displacements as the cells stressed via the transf errin receptors. Cells stressed via integrins showed stiffening behavior as the force was increased. whereas this stiffening was significantly less fo r cells stressed via the transferrin receptor (P <0.001). Mechanical charac teristics of vascular smooth muscle cells depend on the receptor by which t he stress is applied, with integrin-based linkages demonstrating cell-stiff ening behavior.