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

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 tau*, the aggregate as a whole flows with an apparent viscosity eta*, and at higher stress it is a shear-thinning fluid. An increasing cell-cell tension results in a higher eta* (and thus a slower stress relaxation time t(c)). Our constitutive equation fits experiments of aggregate shape relaxation after compression or decompression in which irreversibility can be measured; we find t(c) 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.
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https://www.hal.inserm.fr/inserm-00524596
Contributor : Jean-Paul Issartel Connect in order to contact the contributor
Submitted on : Friday, October 8, 2010 - 11:46:16 AM
Last modification on : Thursday, June 2, 2022 - 3:52:02 PM
Long-term archiving on: : Friday, December 2, 2016 - 6:51:33 AM

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Philippe Marmottant, Abbas Mgharbel, Jos Käfer, Benjamin Audren, Jean-Paul Rieu, et al.. 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, National Academy of Sciences, 2009, 106 (41), pp.17271-5. ⟨10.1073/pnas.0902085106⟩. ⟨inserm-00524596⟩

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