Measurement of mechanical tractions exerted by cells in three-dimensional matrices

Tracking the displacement of fluorescent beads surrounding a cell embedded in a hydrogel matrix allows quantitative measurement of the three-dimensional traction forces exerted by the cell. Quantitative measurements of cell-generated forces have heretofore required that cells be cultured on two-dimensional substrates. We describe a technique to quantitatively measure three-dimensional traction forces exerted by cells fully encapsulated in well-defined elastic hydrogel matrices. Using this approach we measured traction forces for several cell types in various contexts and revealed patterns of force generation attributable to morphologically distinct regions of cells as they extend into the surrounding matrix.