STRAIN-MEASUREMENTS IN CULTURED VASCULAR SMOOTH-MUSCLE CELLS SUBJECTED TO MECHANICAL DEFORMATION

Early work in the field of biomechanics employed rigorous application of the principles of mechanics to the study of the macroscopic structu ral response of tissues to applied loads. Interest in the functional r esponse of tissues to mechanical stimulation has lead researchers to s tudy the biochemical responses of cells to mechanical loading. Charact erization of the experimental system (i.e., specimen geometry and boun dary conditions) is no less important on the microscopic scale of the cell than it is for macroscopic tissue testing. We outline a method fo r appropriate characterization of cell deformation in a cell culture m odel; describe a system for applying a uniform, isotropic strain field to cells in culture; and demonstrate a dependence of cell deformation on morphology and distribution of adhesion sites. Cultured vascular s mooth-muscle cells were mechanically deformed by applying an isotropic strain to the compliant substrate to which they were adhered. The sta te of strain in the cells was determined by measurement of the displac ements of fluorescent microspheres attached to the cell surface. The m agnitude and orientation of principal strains were found to vary spati ally and temporally and to depend on cell morphology. These results sh ow that cell strain can be highly variable and emphasize the need to c haracterize both the loading conditions and the actual cellular deform ation in this type of experimental model.