Linear correlation between active and resistive stresses informs on force generation and stress transmission in adherent cells

TL;DR

This study combines theoretical analysis and experiments to reveal a linear relationship between resistive and active stresses in adherent cells, highlighting localized adhesion points as key force transmission sites.

Contribution

It demonstrates a direct proportionality between active and resistive stresses in cells, linking mechanical behavior to adhesion at sub-400 nm scales.

Findings

Resistive and active stresses inside cells are proportional.

Force transmission occurs mainly through localized adhesion points.

A linear relationship exists between divergence of resistive stress and traction forces.

Abstract

Animal cells are active, contractile objects. While bioassays address the molecular characterization of cell contractility, the mechanical characterization of the active forces in cells remains challenging. Here by confronting theoretical analysis and experiments, we calculated both the resistive and the active components of the intracellular stresses that build up following cell adhesion. We obtained a linear relationship between the divergence of the resistive stress and the traction forces, which we show is the consequence of the cell adhering and applying forces on the surface only through very localized adhesion points (whose size is inferior to our best resolution, of 400 nm). This entails that there is no measurable forces outside of these active point sources, and also that the resistive and active stresses inside cells are proportional.