Polymorphism and bistability in adherent cells

TL;DR

This paper models how contractile cells adopt various shapes on substrates, revealing bistability and shape transitions influenced by adhesion patterns, substrate stiffness, and contractility levels.

Contribution

It introduces a mechanical model capturing cell shape bistability and shape transitions based on adhesion geometry and contractility.

Findings

Cells exhibit convex and concave shapes depending on contractility.

Discontinuous transition to star-shaped cells occurs at high contractility.

Bistability and hysteresis are observed in cell shape transitions.

Abstract

The optimal shapes attained by contractile cells on adhesive substrates are determined by the interplay between intracellular forces and adhesion with the extracellular matrix. We model the cell as a contractile film bounded by an elastic cortex and connected to the substrate via elastic links. When the adhesion sites are continuously distributed, optimal cell shape is constrained by the adhesion geometry, with a spread area sensitively dependent on the substrate stiffness and contractile tension. For discrete adhesion sites, equilibrium cell shape is convex at weak contractility, while developing local concavities at intermediate values of contractility. Increasing contractility beyond a critical value, controlled by mechanical and geometrical properties of adhesion, cell boundary undergoes a discontinuous transition to a star-shaped configuration with cusps and protrusions, accompanied by a region of bistability and hysteresis.