Collective migration of MCF10A epithelial cell sheets on PAA gel substrates of various compliances. (A) Progression of wound healing on soft (3 kPa) and stiff (65 kPa) substrates. Red lines trace the wound edge; blue line on 12-h images reflects the wound edge at 0 h after wounding. (B) The distance advanced by cell sheets over 14 h of wound healing on various substrate stiffnesses. (C) Tracks of cell movements overlaid with images of H2B-mCherry–labeled nuclei in cell sheets at 12 h after wounding on soft (3 kPa) and stiff (65 kPa) substrates. (D and E) Mean speed (D) and mean wound-directed velocity (E) of individual cells within the collectively migrating cell sheet at 12 h after wounding, plotted as a function of cell distance from the wound edge. (F) Mean cell migration persistence for cells positioned at various distances from the wound edge after 5 h of migration starting at 8 h after wounding. N = number of experiments; n = total number of cells measured from N experiments. Error bars show 95% confidence interval of the mean (95% SEM); all nonoverlapping error bars are statistically significant with P < 0.05. Bars, 100 µm.