It is becoming evident that physical forces in the microenvironment play a key role in regulating many important aspects of cell biology. However, although mechanical cues are known to have clear effects over the long-term (days), the short-term (seconds to minutes) cellular responses to mechanical stimuli are less well characterized. In our recent study, we exposed committed fibroblast cells to well controlled nanoscale forces while simultaneously imaging force transduction through the actin cytoskeleton. One of the earliest responses of a cell to physical force is rapid deformation of the cytoskeleton, taking place over the course of seconds. We were able to directly visualize deformation, force-propagation and strain dynamics in actin stress fibers in response to a relatively simple mechanical stimulus. Moreover, these dynamics were also dependent on myosin-driven contractility and the presence of an intact microtubule cytoskeleton. Interestingly, although stem cells are sensitive to mechanical cues, they do not display the same degree of stress fiber organization as observed in committed cells indicating the possibility of alternative sensing and mechanotransduction mechanisms.
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