Rheological behavior of living cells is timescale-dependent

Abstract

The dynamic mechanical behavior of living cells has been proposed to result from timescale-invariant processes governed by the soft glass rheology theory derived from soft matter physics. But this theory is based on experimental measurements over timescales that are shorter than those most relevant for cell growth and function. Here we report results measured over a wider range of timescales which demonstrate that rheological behaviors of living cells are not timescale-invariant. These findings demonstrate that although soft glass rheology 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.

FIGURE 1

The magnitude of the dynamic modulus (|G*|) versus frequency (f) relationship measured in cultured HASM cells at the baseline (solid symbols) and after cell stretching by an ∼12% uniform substrate strain (open symbols) using oscillatory magnetic cytometry. Cells displayed two power-law regimes at 10⁰–10³ Hz and at 10⁻³–10⁻¹ Hz, separated by a plateau (10⁻¹–10⁰ Hz). Each regime was fitted by a function ∼f^α (solid lines). Data are means ±SE of median values of |G*| obtained from 180 to 500 magnetic beads distributed in 3–5 different wells for each condition (circles and triangles indicate data from two protocols).