Effect of matrix-bound SDF-1α on cell spreading and protrusion formation. Cell morphology was observed 16 h after plating by staining the actin cytoskeleton with rhodamine phalloidin (red) and the nuclei with DAPI (blue). MDA-MB-231 cells were grown on films with No SDF, sSDF, and bSDF: (A) Upper row: fluorescence images, scale bar: 50 μm; lower row: confocal fluorescence images, scale bar: 20 μm,; the yellow arrow indicates lamellipodia and the white arrow indicates filopodia. (A’) Quantitative analysis of the cell spreading area and circularity. At least 50 cells were analyzed for each experimental condition in each independent experiment. Experiments were performed at least in duplicate (ie at least two independent experiments). * p < 0.05 in comparison to control (Anova one way on ranks). (B) Representative images of MDA-MB-231 cells exhibiting four major phenotypes depending on their protrusions, whether they had Lamellipodia (L+ or L-) and/or Filopodia (F+ or F-) : L+/F+, L+/F-; L-/F+ and L-/F-. Scale bar: 20 μm; (B’) Quantitative analysis of the % of each L/F phenotype in the presence of sSDF and bSDF in comparison to the absence of SDF (No SDF). At least 50 cells were analyzed for each experimental condition. Experiments were performed in duplicate.