Mechanical properties of stress fiber in adherent vascular cells characterized by in vitro micromanipulation

Intracellular tension transmission through basal actin stress fibers (SFs) running between separate focal adhesion sites has been proposed to play a role in sensing extracellular forces to adapt the adherent cell structure. However, quantitative descriptions of tension level in SFs are still poorly studied. Here, magnitude of preexisting tension in single SFs of endothelial cells was evaluated by in vitro tensile test. Single SFs were isolated from the cells with a combination of low ionic-strength solution and detergent extractions. A tensile test was conducted with a pair of micro-cantilevers driven by a piezo-electric actuator to measure the mechanical properties of the isolated single SF and the force required for stretching it up to its original length, yielding an estimate of the preexisting tension. The Young's modulus was estimated similar to 290 kPa assuming that the specimen was homogeneous. The magnitude of the preexisting tension, 4 nN on average, was comparable to previously reported data of the traction force generated by adherent cells at single adhesion sites to keep cell integrity. These data will contribute to quantitative understanding of intracellular stress transmission mechanism in adherent cells.