Fig. 2.

Compression promotes formation of leader cells at the scratch-wound periphery. (A) Cell orientation at the wound periphery. For the calculated cell alignment correlation index, a value of 1 indicates that the cells align perpendicular to the cell-denuded areas, and a value of 0 indicates orientation parallel to the wound periphery. Random cell alignment would result in an index of 0.63 according to theory. Uncompressed (control) samples had randomly oriented cells, but compression resulted in directed elongation into the denuded region (n = 7). (B) The fraction of cells around the denuded periphery phenotypically identified as leader cells was dramatically higher in the compressed samples. Leader cells were defined as those cells at the wound margin that extend protrusions into the denuded area (n = 12; *P < 0.005 compared with control). (C) Average projected cell areas of the control and compressed 67NR cells at the leading edge of the “wound” and those in the internal monolayer, far from the edge (n = 8–9; NS, not significant; *P < 0.005 compared with the control in the same group). (D) Comparison of average cell lengths in control and compressed samples. Frontal length (filopodial protrusion length) was measured from the leading tip of the cell to its nucleus (*P < 0.005 compared with the control).