Mechanical behavior of multi-cellular spheroids under osmotic compression

TL;DR

This study investigates the mechanical properties of multicellular spheroids under osmotic compression, modeling their behavior with an active poroelastic framework to understand stress, strain, and fluid dynamics relevant to tumor environments.

Contribution

It introduces an active poroelastic model to describe spheroid mechanics under osmotic shocks, linking cellular permeability and compressibility to emergent material properties.

Findings

Effective rheology characterized at minutes to hours timescale

Bulk modulus and hydraulic diffusion are influenced by preexisting active stress

Cells behave as impermeable, incompressible inclusions within a permeable matrix

Abstract

The internal and external mechanical environment plays an important role in tumorogenesis. As a proxy of an avascular early state tumor, we use multicellular spheroids, a composite material made of cells, extracellular matrix and permeating fluid. We characterize its effective rheology at the timescale of minutes to hours by compressing the aggregates with osmotic shocks and modeling the experimental results with an active poroelastic material that reproduces the stress and strain distributions in the aggregate. The model also predicts how the emergent bulk modulus of the aggregate as well as the hydraulic diffusion of the percolating interstitial fluid are modified by the preexisting active stress within the aggregate. We further show that the value of these two phenomenological parameters can be rationalized by considering that, in our experimental context, the cells are effectively impermeable and incompressible inclusions nested in a compressible and permeable matrix.