Figure 1

Expression of VEGF receptors in the human Isl1⁺ progenitors. (A) Frozen sections from a human fetal heart at gestation week 9 were stained for DAPI (scale bar = 500 μm), Isl1, endothelial cell-specific markers: CD144, vWF, VEGF-A receptor 1 (Flt1) or 2 (KDR), or neurofilament (scale bars = 50 μm and 10 μm). Isl1⁺ cells are indicated by white asterisks (scale bar = 100 μm) and colocalization of Isl1 and EC markers are indicated by white arrows (scale bar = 10 μM). (B) Schematic diagram showing the Isl1 lineage-tracing construct in human ESCs. (C) Differentiation protocol used to derive the Isl1⁺ progenitors from human ESCs and to examine, which angiocrine factor (X) is responsible for endothelial differentiation of the progenitors. (D) FACS analyses showing expression of VEGFR1 or VEGFR2 in day-4 or day-7 human Isl1⁺ progenitors.