Characterization of the strain-rate–dependent mechanical response of single cell–cell junctions

Abstract

Cell–cell adhesions are often subjected to mechanical strains of different rates and magnitudes in normal tissue function. However, the rate-dependent mechanical behavior of individual cell–cell adhesions has not been fully characterized due to the lack of proper experimental techniques and therefore remains elusive. This is particularly true under large strain conditions, which may potentially lead to cell–cell adhesion dissociation and ultimately tissue fracture. In this study, we designed and fabricated a single-cell adhesion micro tensile tester (SCAµTT) using two-photon polymerization and performed displacement-controlled tensile tests of individual pairs of adherent epithelial cells with a mature cell–cell adhesion. Straining the cytoskeleton–cell adhesion complex system reveals a passive shear-thinning viscoelastic behavior and a rate-dependent active stress-relaxation mechanism mediated by cytoskeleton growth. Under low strain rates, stress relaxation mediated by the cytoskeleton can effectively relax junctional stress buildup and prevent adhesion bond rupture. Cadherin bond dissociation also exhibits rate-dependent strengthening, in which increased strain rate results in elevated stress levels at which cadherin bonds fail. This bond dissociation becomes a synchronized catastrophic event that leads to junction fracture at high strain rates. Even at high strain rates, a single cell–cell junction displays a remarkable tensile strength to sustain a strain as much as 200% before complete junction rupture. Collectively, the platform and the biophysical understandings in this study are expected to build a foundation for the mechanistic investigation of the adaptive viscoelasticity of the cell–cell junction.

Brick Strex: a robust device built of LEGO bricks for mechanical manipulation of cells

“…Along these lines, our western blot analyses suggest for increased -catenin membrane-association and/or suppression of beta-catenin signaling in response to lateral compression. Recent advances on cell–cell junction mechanics have indicated that mechanical forces sensed at the junctions lead to distinct mechanical responses at the junctions 29 . Thus, it can be hypothesized that the compression-induced membrane tethering of β-catenin is related in enforcement of the intercellular junctions upon increased mechanical loading.…”

“…Still, many of the developed devices need special techniques and are most often limited by the small number of cells. In these approaches, single cell or even subcellular mechanical manipulation is conducted via micromanipulation or by atomic force microscopy 27 – 29 . However, different and more robust approaches have been developed for larger cell populations.…”

Brick Strex – A Robust Device Built of LEGO® Bricks for Mechanical Manipulation of Cells

“…in the epithelium 71 . Finally, during the recent years it has become evident that in addition to cell membrane associated adhesion sites, forces can be sensed also deeper in the cells 39,[72][73][74] . Mechanical forces rising from the ECM can be transmitted into the cells and they have been shown to directly affect even cell nuclei and chromatin 75 .…”

“…Along these lines, our western blot analyses suggest for increased catenin membrane-association in response to lateral compression. Recent advances on cell-cell junction mechanics have indicated that mechanical forces sensed at the junctions lead to distinct mechanical responses at the junctions 39 . Thus, it can be hypothesized that the compression-induced membrane tethering of β-catenin is related in enforcement of the intercellular junctions upon increased mechanical loading.…”

“…However, many of the developed devices need special techniques and are most often limited by the small number of cells. In these approaches, single cell or even subcellular mechanical manipulation is conducted via micromanipulation or by atomic force microscopy [37][38][39] . However, different and more robust approaches have been developed for larger cell populations.…”