Eur. Phys. J. E (2013) 36: 84
https://doi.org/10.1140/epje/i2013-13084-1

Regular Article

Multicellular aggregates: a model system for tissue rheology

¹ Institut Lumière Matière, UMR5306 Université de Lyon 1-CNRS, Université de Lyon, 69622, Villeurbanne cedex, France
² Laboratoire Matière et Systèmes Complexes, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7057, Université Paris 7 - Denis Diderot, 10 rue Alice Domon et Léonie Duquet, F-75205, Paris Cedex 13, France

^* e-mail: helene.ayari@univ-lyon1.fr

Received: 15 November 2012
Accepted: 21 June 2013
Published online: 12 August 2013

Abstract

Morphogenetic processes involve cell flows. The mechanical response of a tissue to active forces is linked to its effective viscosity. In order to decouple this mechanical response from the complex genetic changes occurring in a developing organism, we perform rheometry experiments on multicellular aggregates, which are good models for tissues. We observe a cell softening behavior when submitting to stresses. As our technique is very sensitive, we were able to get access to the measurement of a yield point above which a creep regime is observed obtained for strains above 12%. To explain our rheological curves we propose a model for the cytoskeleton that we represent as a dynamic network of parallel springs, which will break under stress and reattach at null strain. Such a simple model is able to reproduce most of the important behavior of cells under strain. We highlight here the importance of considering cells as complex fluids whose properties will vary with time according to the history of applied stress.