Immunofluorescence staining for endothelial markers. Morphology and immunofluorescence pattern is depicted for cells obtained from the standard protocol (A, B, E, F) or from the modified protocol (C, D, G, H) 28 days after isolation. Representative images of low colony-forming cells (upper row) and high colony-forming cells (lower row) in dependence of the culture protocol are presented for CD31 (B, C, F, G) and vWF (A). (A, D, E, H) staining. Scale bars (A–H): 75 μm. vWF, von Willebrand factor. Endothelial contacts are highlighted by arrows.