Theory of dynamical response of live cells to mechanical stresses

Abstract

Recent research at the interface of physics and biology has shown that cellular processes such as proliferation, differentiation and tissue development, are controlled by the mechanical properties of cells and their environment. This talk reviews current experiments on cell mechanics in the context of theoretical models in which cells are treated in terms of active force dipoles.  The theory includes non-equilibrium cell activity (related to the fact that the cell is “alive”), local mechanical equilibrium, and random forces to determine cell response to static and dynamic stress, as well as the curvature of the substrate. To understand how substrate rigidity determines the polarization of cells, we have generalized the treatment of elastic inclusions in solids to ”living” inclusions whose active polarizability, analogous to that of non-living matter, results in feedback in response to matrix stresses. We use this to explain recent observations of the non-monotonic dependence of stem cell polarization on matrix rigidity. Similar considerations are used to study the ordering of dipoles and are applied to the dependence of muscle striation on substrate properties. These findings provide a mechanical correlate for the existence of an optimal substrate elasticity for cell differentiation and function.

*Theoretical collaborations: Y. Biton, B. Friedrich, R. De, A. Zemel and experimental interactions: A. Bershadsky, A. Brown, D. Discher, B. Hoffmann, R. Kemkemer, R. Merkel, F. Rehdfeldt.

Brief Bio

Safran has been a professor in the Department of Materials and Interfaces of the Weizmann Institute since 1990.  He also served as Vice President of the Weizmann Institute and Dean of its Graduate School.  From 1980-1990 he was at the Exxon Corporate Research Labs where he worked on the theory of soft matter with a focus on the structure and phase behavior of oil-water-surfactant dispersions.  His recent research interests have extended soft matter concepts to treat biological membranes and cells.  Safran is the author of a graduate text on Statistical Thermodynamics of Surfaces, Interfaces and Membranes and a recipient of the Beller Lectureship Award of the American Physical Society and the Lectureship Award of the Japanese Chemical Society.

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