Intracellular stress tomography reveals stress focusing and structural anisotropy in cytoskeleton of living cells

TLDR

The study introduces a synchronous detection approach to map mechanical stress transmission within the cytoplasm of adherent cells. Using fluorescent protein‑labeled mitochondria or cytoskeletal components as fiducial markers, the authors measured displacements and computed stresses in the cytoskeleton of living cells plated on extracellular matrix in response to a small, localized oscillatory load applied to apical transmembrane receptors. Induced displacements, stresses, and phase lags were concentrated at sites remote from the load and modulated by cytoskeletal prestress, with anisotropy revealed by directional phase differences; stresses at the apical surface also displaced focal adhesion sites at the base, demonstrating that mechanical forces propagate across discrete cytoskeletal elements over long distances in living adherent cells.

Abstract

We describe a novel synchronous detection approach to map the transmission of mechanical stresses within the cytoplasm of an adherent cell. Using fluorescent protein-labeled mitochondria or cytoskeletal components as fiducial markers, we measured displacements and computed stresses in the cytoskeleton of a living cell plated on extracellular matrix molecules that arise in response to a small, external localized oscillatory load applied to transmembrane receptors on the apical cell surface. Induced synchronous displacements, stresses, and phase lags were found to be concentrated at sites quite remote from the localized load and were modulated by the preexisting tensile stress (prestress) in the cytoskeleton. Stresses applied at the apical surface also resulted in displacements of focal adhesion sites at the cell base. Cytoskeletal anisotropy was revealed by differential phase lags in X vs. Y directions. Displacements and stresses in the cytoskeleton of a cell plated on poly-l-lysine decayed quickly and were not concentrated at remote sites. These data indicate that mechanical forces are transferred across discrete cytoskeletal elements over long distances through the cytoplasm in the living adherent cell.