Morphology and characterization of human endothelial progenitor cells (EPCs) from peripheral blood. (A) Peripheral blood mononuclear cells (MNCs) were plated on a fibronectin-coated culture dish on the first day. (B) Four days after plating, adherent early EPCs with a spindle shape were shown. (C) Three weeks after plating, ECFCs with a cobblestone-like morphology were selected, reseeded, and grown to confluence. (D-I) ECFC characterization was performed by immunohistochemical staining. Most of the EPC expressed endothelial and hematopoietic stem cell markers, VE-cadherin, PECAM-1 (CD31), CD34, KDR, AC133, and eNOS, which are considered critical markers of EPCs. Cells were counterstained with 4',6-diamidino-2-phenylindole (DAPI) for the nuclei (blue).