Adhesive Interactions Figure 4. Dynamics of cell-cell interactions in a narrow wound. Time-lapse images of colliding cells. (A, B) Nontransformed IAR-2 cells extend lamellipodia (arrows) and establish a cell-cell contact that expands laterally. By 15–20 min, protrusion of lamellipodia at the site of the contact is inhibited (contact paralysis) (arrowhead) (see also Video S4). Protrusive activity at the free edges of contacting cells also decreases (asterisks). Kymographs were generated along straight lines in different regions. (B) Left: kymograph generated at the site of the cell-cell contact (red line in A) shows contact paralysis of protrusive activity by 15–20 min after the establishment of the contact. White line on kymograph indicates the time of the establishment of the contact. Right: quantification of the rates of lamellipodial protrusion and retraction at the sites of cell-cell contacts. Data are presented as means6SEM. Brackets indicate statistically significant differences between the mean rates of lamellipodial protrusion (*, p,0.001; **, p,0.005, n = 25 cells, t-test). (C, D) Transformed IAR-6-1 cells. During formation of the cell-cell contact, protrusive activity persists both at the site of the contact (arrowhead) and at the free edges, where new lamellipodia are formed (arrows) (see also Video S5). (D) Left: kymograph generated at the site of the contact (left) shows the disappearance of contact paralysis. White line on kymograph indicates the time of the establishment of the contact. Right: the rates of lamellipodial protrusion and retraction at the sites of cell-cell contacts did not change within the time of observation. Data are presented as means6SEM. (E). Measurement of overlapping areas of contacting cells (15 min after formation of cell-cell contact). In cultures of transformed IAR-6-1 cells, there is prominent overlapping of lamellae of contacting cells. Bar, 10 mm. doi:10.1371/journal.pone.0008027.g004 PLoS ONE | www.plosone.org 6 November 2009 | Volume 4 | Issue 11 | e8027