Delayed wound healing by Rap1b-deficient lung endothelial cells. (A) Monolayer cultures of lung endothelial cells isolated from Rap1b^−/− and normal (WT) mice were wounded with a pipette tip and subjected to VEGF (A) or bFGF (B) stimulation (t = 0). Cells at the edge of the wound migrated into the wound, closing it over time. After 12 hours, the cells were photographed (t = 12 hours) and migrated distance was measured (C). Bar represents 100 μm. (C) The progress of wound closure, expressed as migrated distance, was significantly delayed in Rap1b^−/− cells (▧) compared with wild-type cells (■) in response to either VEGF or bFGF (n = 9, cells isolated from 4 sets of mice).