Background—In murine embryonic stem cells, the onset of vascular endothelial growth factor receptor 2 (VEGFR-2) expression identifies endothelial precursors. Undifferentiated human embryonic stem cells express VEGFR-2, and VEGFR-2 expression persists on differentiation. The objective of our study was to identify a single population of endothelial precursors with common identifying features from both human and murine embryonic stem cells.

Methods and Results—We report that expression of the VEGF coreceptor neuropilin-1 (NRP-1) coincides with expression of Brachyury and VEGFR-2 and identifies endothelial precursors in murine and human embryonic stem cells before CD31 or CD34 expression. When sorted and differentiated, VEGFR-2⁺NRP-1⁺ cells form endothelial-like colonies that express CD31 and CD34 7-fold more efficiently than NRP-1 cells. Finally, antagonism of both the VEGF and Semaphorin binding functions of NRP-1 impairs the differentiation of vascular precursors to endothelial cells.

Conclusions—The onset of NRP-1 expression identifies endothelial precursors in murine and human stem cells. The findings define the origin of a single population of endothelial precursors from human and murine stem cells to endothelial cells. Additionally, the function of both the VEGF and Semaphorin binding activities of NRP-1 has important roles in the differentiation of stem cells to endothelial cells, providing novel insights into the role of NRP-1 in a model of vasculogenesis.