Colocalization of PDGFR-β with CD31, VEGFR-2, and CD41 in hemangioprecursor cells. (A) Embryoid bodies cultured for 14 days in the absence (top panel) or presence (middle and bottom panels) of 30 ng/mL PDGF-BB were analyzed by immunofluorescent staining for CD31 (red) and α-SMA (green) in the 2 upper panels and for CD31 (red) and PDGFR-β (green) in the bottom panel. At this late time point, PDGFR-β expression was confined to perivascular α-SMA–positive cells. (B) Embryoid bodies cultured for 6 days in the absence (top panel) or presence of 30 ng/mL PDGF-BB were analyzed for expression of CD31 (red) and α-SMA (green), CD31 (red) and PDGFR-β (green), VEGFR-2 (red) and PDGFR-β (green), and for CD41 (red) and PDGFR-β (green), as indicated. At day 6 in the presence of PDGF-BB, colocalization was evident in clusters of immature hemangioprecursor cells. Merged images are shown to the right in each panel. Where indicated, cells were treated with Hoechst 33342 to visualize nuclei. Bars represent 20 μm.