Expression of endothelial cell antigens by CFU-ECs and ECFCs. (A) Immunophenotyping of CFU-EC and ECFC colonies by confocal microscopy. CFU-ECs and ECFCs express CD31, CD105, CD144, CD146, KDR, VWF, and UEA-I. Shown are isotype and antigen staining (green) representing 5 independent experiments using cells from different donors. Nuclei are stained with Hoechst 33342 (blue) and scale bar represents 200 μm. (B) CFU-ECs and ECFCs incorporate Ac-LDL. Shown is a confocal photomicrograph of cells that have taken up Ac-LDL (green) following a 4-hour incubation, representing 5 independent experiments using cells from different donors. Nuclei are stained with Hoechst 33342 (blue) and scale bar represents 200 μm.