Phenotypic and functional analysis of BOECs. (A) Cobblestone-like morphology of BOECs under bright field microscopy. (Scale bar, 100 μm.) (B) BOECs store VWF (shown in red) and P-selectin (shown in green) in WPB. Yellow indicates the costorage of VWF and P-selectin in WPB (elongated organelles). Image was taken by Leica SL confocal laser scanning microscopy with a 63×/1.40 NA oil objective. (Scale bar, 10 μm.) (C) BOECs formed capillary-like structures in Matrigel. (Scale bar, 200 μm). (D-M) FACS analysis of BOECs derived from a single healthy donor. The representative data demonstrate that BOECs were negative for leukocyte cell makers CD14 (D, isotype; E, CD14) and CD45 (F, isotype; G, CD45) but positive for endothelial cell markers CD31 (endothelial cell marker CD31; H, isotype; I, CD31) and EPCR (J, isotype; M, EPCR). In addition, BOECs completely lost expression of the stem cell maker CD133 (J, isotype; K, CD133), although the majority of cells still express the progenitor cell marker CD34 (J, isotype; L, CD34). Shown are representative data from at least 4 independent experiments using BOECs derived from a single healthy donor. Cells derived from other healthy donors and the patients showed similar results.