For FACS analysis, differentiated cells were stained with combinations of APC-conjugated PDGFRα (FAB1264A; BD Biosciences) and PE-conjugated KDR (CD309; Miltenyi Biotec), APC-conjugated CD31 (17-0319-42; BD Biosciences) and PE-conjugated PDGFRβ (558821; BD Biosciences), or APC-conjugated PSA-NCAM (130-093-273; Miltenyi Biotec) and FITC-conjugated CD44 (338804; BD Biosciences), then subjected to analysis using FACS AriaII (Becton Dickinson). Negative controls used were non-staining cells or cells stained with APC-conjugated anti-rabbit IgG (711-136-152; Jackson ImmunoResearch) and PE-conjugated anti-mouse IgG (115-116-072; Jackson ImmunoResearch).