Intercellular adhesion stiffness moderates cell decoupling on stiff substrates
Author:
Abstract:
The interplay between cell-cell and cell-substrate interactions is complex yet necessary for the formation and well-functioning of tissues. The same mechanosensing mechanisms used by the cell to sense its extracellular matrix, also play a role in intercellular interactions. We used the discrete element method to develop a computational model of a deformable cell that includes subcellular components responsible for mechanosensing. We modeled a cell pair in 3D on a patterned substrate, a simple laboratory setup to study intercellular interactions. We explicitly modeled focal adhesions between the cells and the substrate, and adherens junctions between cells. These mechanosensing adhesions matured; their disassembly rate was dictated by the force they carry. We also modeled stress fibers which bind the discrete adhesions and contract. The mechanosensing fibers strengthened upon stalling and exerted higher forces. Traction exerted on the substrate was used to generate maps displaying the magnitude of the tractions along the cell-substrate interface. Simulated traction maps are compared to experimental maps obtained via traction force microscopy. The model recreates the dependence on substrate stiffness of the tractions’ spatial distribution across the cell-substrate interface, the contractile moment of the cell pair, the intercellular force, and the number of focal adhesions. It also recreates the phenomenon of cell decoupling, in which cells exert forces separately when substrate stiffness increases. More importantly, the model provides viable molecular explanations for decoupling. It shows that the implemented mechanosensing mechanisms are responsible for competition between different fiber-adhesion configurations present in the cell pair. The point at which an increasing substrate stiffness becomes as high as that of the cell-cell interface is the tipping point at which configurations that favor cell-substrate adhesion dominate over those favoring cell-cell adhesion. This competition is responsible for decoupling. Additionally, we learn that extent of decoupling is modulated by adherens junction maturation.