Endothelial cells from hESC-derived CD34⁺ progenitor cells are functional in vitro and in vivo. (A,C) Immunostaining for EC markers (CD31, VWF, KDR, ANG2, and VE-cadherin) in hESC- and hiPSC-derived ECs. hESC-derived ECs showed typical endothelial cell morphology (A and Ci), and expressed multiple EC markers (A and Cii-iv). (B) and (D) In vitro functional assay for hESC- and hiPSC-derived ECs. hESC- and hiPSC-derived ECs formed vascular tube-like structures on Matrigel (B and Di), and took up Dil-labeled acetylated-LDL (B,Dii). (E) Matrigel plug assay for hESC-derived CD34⁺ cells. Antibody for VWF was used to observe both mouse and human blood vessels. Species-specific CD31 antibodies were used to discriminate mouse and human blood vessels. Mouse and human specific CD31 antibodies are indicated as blue and red colors, respectively. Scale bar is 20 μm.