A mechanically homogeneous equivalent of real cells

Abstract text (incl. figure legends and references)

Biological cells are built up from many different constituents of
varying size and stiffness which all contribute to the global cell's
mechanical properties.
Despite this heterogeneity, in the analysis of experimental
measurements such as atomic force microscopy or high-throughput
microfluidic characterisation a strongly simplified homogeneous cell is
typically assumed and a single elastic modulus is assigned to the entire
cell.
This ad-hoc simplification has so far been used mostly without
proper justification.
Here, we use computer simulations to show that indeed a
heterogeneous cell can effectively be replaced by a homogeneous
equivalent cell with a volume averaged elastic modulus.
To study the validity of this approach, we investigate a
hyperelastic cell with an explicitly heterogeneous interior under
compression and in shear flow, mimicking atomic force and microfluidic
measurements, respectively.
We find that the homogeneous equivalent cell reproduces
quantitatively the behavior of its inhomogeneous counterpart, and that
this equality is largely independent of the stiffness or spatial
distribution of the heterogeneity.