Cultivation and characterization of early and late EPCs. (A) Expression of indicated molecules in EPCs by flow cytometric analysis. (B) Late EPCs and matured ECs, but not early EPCs, formed tubules in vitro. Representative photos for in vitro angiogenesis are shown. (C) Both late EPCs and matured ECs formed vessel structures in 3D-angiogenesis assays. Bar = 200 um.