Extended Data Fig. 6: The membrane area over which ECM resists cell contraction is lower for polarized contraction than for isotropic contraction.
To investigate the effect of stress field directionality on cell activation, we simulated isotropic and anisotropic contraction of a circular cell within a three-dimensional collagen matrix. (A) In isotropic contraction, cells contract with the same initial contractility \({\rho }_{0}\) in all directions, while in polarized contraction, cells contract with the initial contractility \({\rho }_{0}\) only in the direction of polarity. Therefore, the contact area at the cell-matrix interface resisting cell contraction is higher for isotropic contraction than for anisotropic contraction. (B) The model predicts that both the magnitude and the anisotropy of the tensile stress field generated in the cell cytoskeleton promote actomyosin contractility. (C) Without accounting for the effect of tension anisotropy (fa = 0), the theoretical model predicts that isotropic contraction would lead to a greater actomyosin contractility, higher tension in the cytoskeleton, and higher force transmission within the matrix, analogous to predictions from pre-stressed/pre-strained cell models and other thermoelastic-based classical cell models that do not account for tension anisotropy. (D) However, when tension anisotropy is taken into account in our model, the model predicts that anisotropic contraction, despite applying traction over a smaller fraction of the cell membrane, results in greater actomyosin contractility and tension in the cytoskeleton, and higher force transmission within the matrix.
