Role of cellular tone and microenvironmental conditions on cytoskeleton stiffness assessed by tensegrity model

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Abstract
We have tried to understand the role of cellular tone (or internal tension mediated by actin filaments) and interactions with the microenvironment on cellular stiffness. For this purpose, we compared the apparent elasticity modulus of a 30-element tensegrity structure with cytoskeleton stiffness measured in subconfluent and confluent adherent cells by magnetocytometry, assessing the effect of changing cellular tone by treatment with cytochalasin D. Intracellular and extracellular mechanical interactions were analyzed on the basis of the non-dimensional relationships between the apparent elasticity modulus of the tensegrity structure normalized by Young's modulus of the elastic element versus: (i) element size, (ii) internal tension, and (iii) number of spatially fixed nodes, for small deformation conditions. Theoretical results and rigidity measurements in adherent cells consistently showed that higher cellular tone and stronger interdependencies with cellular environment tend to increase cytoskeleton stiffness. Visualization of the actin lattice before and after depolymerization by cytochalasin D tended to confirm the geometrical and mechanical assumptions supported by analysis of the present model.