Rheological behavior of living cells is timescale-dependent

The ability of mammalian cells to deform in response to mechanical forces is essential for behaviors that are critical for life, and thus many investigators seek to identify general principles that govern cell rheology.  It has been proposed recently that cell deformability results from timescale-invariant processes governed by soft glass rheology (SGR) theory derived from soft matter physics.  This claim is based on rheological measurements of cells over a range of timescales that are shorter than those most relevant for physiological cellular processes such as cell growth and movement.  Here we report results measured over longer timescales which demonstrate that rheological behaviors of living cells are timescale-dependent.  These findings demonstrate that although SGR appears to accurately predict certain cell mechanical behaviors, it is not a unified model of cell rheology under biologically relevant conditions and thus, alternative mechanisms need to be considered.

This study will appear as a "Biophysical Letter" in the October 2007 issue of the Biophysical Journal.