Cellular traction forces increase during consecutive mechanical stretching following traction force attenuation

Abstract

Adherent cells generate traction forces, which are generated by and transmitted along the actin cytoskeleton to the underlying external substrate via focal adhesions. These cell generated forces are fundamental for maintaining cell shape and driving cell migration as well as triggering signaling pathways to promote processes such as differentiation and proliferation. Here we investigate how mechanical stretch affects traction forces. Following moderate mechanical stretching and release, traction forces are increased and then return to basal levels. However, when cells are stretched with relatively large strains, >10%, traction forces fail to return to basal levels and are attenuated. In this study, we investigate whether cells experiencing attenuated traction forces, following a large strain, can still respond to subsequent mechanical stretching. Traction forces were measured in cells following a consecutive 12% increase in mechanical stretch. We show that, even after traction force attenuation occurs, cells are able to respond to consecutive mechanical stretching by increasing traction force. Visualization of stress fibers, with GFP-actin, indicates that the attenuation of traction force is accompanied by a decrease in stress fiber integrity during mechanical stretching. The ability of cells to increase traction force during a second round of stretching, following attenuation, maybe generated by intact stress fibers that escape damage.

Mechanical Response of an Epithelial Island Subject to Uniaxial Stretch on a Hybrid Silicone Substrate

“…Traction forces exerted by uniaxially stretched human alveolar single epithelial cells was greater than the baseline but it significantly weakened to a level lower than the baseline upon release 12 . Human umbilical vein endothelial cells also displayed traction forces that increased by 5-20% upon uniaxial stretch 29 . Under equibiaxial sustained stretch, an acute cell stiffening and enhancement of traction force was observed in smooth muscle cells before their gradual reduction 20 .…”