Characterization of the Elasticity of Valve Interstitial Cells on Soft Substrates Using Atomic Force Microscopy

Mechanical stimuli, including the elasticity of the extracellular matrix (ECM), can have profound effects on the function of cells and their responsiveness to other microenvironmental cues, thereby regulating homeostasis and disease development. For example, the response of aortic valve interstitial cells (VICs) to growth factors [1] and VIC differentiation to pathological phenotypes [2] depend on ECM elasticity. The ability of cells to sense and respond to mechanical stimuli depends on several factors, including their inherent cellular-level mechanical properties. The mechanical properties of suspended VICs [3, 4] and VICs grown on stiff glass/polystyrene [5] have been reported. However, neither of these test conditions is physiological, as VICs adhere to ECM that is orders of magnitude more compliant than glass. Some other cell types adapt their stiffness to that of their substrate [6]; we hypothesized that adherent VICs would similarly change their elasticity in response to the elastic properties of their ECM.