Dresden 2009 – scientific programme
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BP: Fachverband Biologische Physik
BP 4: Cell Mechanics
BP 4.1: Talk
Monday, March 23, 2009, 14:30–14:45, HÜL 186
Stem Cell Cytoskeleton Polarization Dictated by Matrix Elasticity - Modelling Cellular Biomechanics with Force Dipoles — •Florian Rehfeldt1, 2, Assaf Zemel3, Andre E.X. Brown1, Allison L. Zajac1, Samuel A. Safran4, and Dennis E. Discher1 — 1University of Pennsylvania, Philadelphia, USA — 2III. Physikalisches Institut, Georg-August-Universität, Göttingen, Germany — 3Hebrew University, Jerusalem, Israel — 4Weizmann Institute of Science, Rehovot, Israel
Biological cells are as responsive to their mechanical environment as they are to biochemical stimuli. As reported recently, human mesenchymal stem cells (hMSCs) plated on collagen-coated gels, differentiated towards the neurogenic, myogenic, and osteogenic lineage, depending on the Young’s elastic modulus E. We present experimental data and a physical model to explain the non-monotonic dependence of stress-fibre polarization on matrix elasticity. Cytoskeletal organization is analyzed with immunofluorescence images of NMM IIa and actin using an automated segmentation algorithm. The theory generalizes Eshelby’s treatment of elastic inclusions in solids to living inclusions (cells) that are capable of building up contractility. Their active polarizability, analogous to the electrical polarizability of non-living matter, results in the feedback of cellular forces that develop in response to matrix stresses. We demonstrate experimentally that matrix rigidity dictates cytoskeletal organization in two and three dimensional environments - a bio-mechanical process yielding different cell shapes that finally leads to lineage specific differentiation.