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The role of fluctuations and stress on the effective viscosity of cell aggregates

Marmottant, P., Mgharbel, A., Kafer, J., Audren, B., Rieu, J.-P., Vial, J.-C., Van Der Sanden, B., Maree, A.F.M., Graner, F. and Delanoe 2009. The role of fluctuations and stress on the effective viscosity of cell aggregates. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 106 (41) , pp. 17271-17275. 10.1073/pnas.0902085106

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Abstract

Cell aggregates are a tool for in vitro studies of morphogenesis, cancer invasion, and tissue engineering. They respond to mechanical forces as a complex rather than simple liquid. To change an aggregate's shape, cells have to overcome energy barriers. If cell shape fluctuations are active enough, the aggregate spontaneously relaxes stresses (“fluctuation-induced flow”). If not, changing the aggregate's shape requires a sufficiently large applied stress (“stress-induced flow”). To capture this distinction, we develop a mechanical model of aggregates based on their cellular structure. At stress lower than a characteristic stress τ*, the aggregate as a whole flows with an apparent viscosity η*, and at higher stress it is a shear-thinning fluid. An increasing cell–cell tension results in a higher η* (and thus a slower stress relaxation time tc). Our constitutive equation fits experiments of aggregate shape relaxation after compression or decompression in which irreversibility can be measured; we find tc of the order of 5 h for F9 cell lines. Predictions also match numerical simulations of cell geometry and fluctuations. We discuss the deviations from liquid behavior, the possible overestimation of surface tension in parallel-plate compression measurements, and the role of measurement duration.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
ISSN: 1111-0105
Last Modified: 18 Feb 2019 08:30
URI: https://orca.cardiff.ac.uk/id/eprint/119512

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