Figure 4.

Durotaxis efficiency on different regions of the stiffness gradient. (A) FMI for cells moving parallel (bars) versus perpendicular (stippled bars) to the stiffness gradient on the soft, medium, or stiff regions. (B) The proportion of cells moving toward the stiff side of the gradient (forward, darker colored bars) compared to the number of cells moving toward the increasingly soft side (reverse, pastel). (C) Polar histograms indicate the angular displacement of cells within the three different stiffness regions. (D) Speed and persistence (directionality) of cells with respect to position on the gradient. Error bars represent mean ± SE, N = 3, n = 793. Boxplot center lines denote the median, and edges represent the 25th and 75th percentiles, with whiskers incorporating 99.3% of all data. For clarity, nonmigrating outliers were excluded from the graph as described in Materials and Methods, but they were not excluded from the statistical analysis. FMI was evaluated statistically using two-way ANOVA with Tukey’s post hoc test (^∗∗∗p ≤ 0.001). Angular displacement was evaluated statistically using a Rayleigh test (^∗p ≤ 0.05, ^∗∗∗p ≤ 0.001). Speed and persistence (straightness index) were evaluated by one-way ANOVA and Tukey’s post hoc test (^∗∗∗p ≤ 0.001). To see this figure in color, go online.