Figure 2. AFM scanning images of HPAEC monolayer (A, B, C) and a single (D, E, F) live cell in response to thrombin and S1P.

Monolayer pulmonary EC grown on collagen-coated plastic petri dish with (A) no stimulation, exhibiting a polygonal shape with a cobblestone appearance without any apparent intercellular gap; (B) thrombin (1 unit/mL, 30 min), illustrating that central filament bundles begin to appear and become aligned with the long axis of the cells and that intercellular gaps begin to appear locally due to cell lateral contraction; and (C) S1P (1 μM, 60 min), illustrating the formation of the cortical actin ring and recovery of the intercellular gap. A single pulmonary EC grown on a plastic petri dish with (D) no stimulation, illustrating that the cell is well spread on the substrate and that actin filaments are distributed along the edge of the cells, forming peripheral bundles; (E) thrombin (1 unit/mL, 10 min), illustrating the thrombin-induced cell retraction response; and (F) S1P (1 μM, 60 min), inducing the respreading of the cell periphery on the substrate and the formation of the cortical actin ring along the cell periphery. (G) Cross-section profiles of live cells showing the selection of 3 different regions of the cell labeled as the nucleus, cytoplasm and periphery.