Exogenous clustered neuropilin 1 enhances vasculogenesis and angiogenesis

Neuropilin 1 (NP-1) is a receptor for vascular endothelial growth factor (V EGF) 165 (VEGF(165)) and acts as a coreceptor that enhances VEGF(165) funct ion through tyrosine kinase VEGF receptor 2 (VEGFR-2). Transgenic overexpre ssion of np-1 results in an excess of capillaries and blood vessels and a m alformed heart. Thus, NP-1 may have a key role in vascular development. How ever, how NP-1 regulates vascular development is not well understood. This study demonstrates how NP-1 can regulate vasculogenesis and angiogenesis in vitro and in vivo. In homozygous np-1 mutant (np-1(-/-)) murine embryos, v ascular sprouting was impaired in the central nervous system and pericardiu m. Para-aortic splanchnopleural mesoderm (P-Sp) explants from np-1(-/-) mic e also had vascular defects in vitro. A monomer of soluble NP-1 (NP-1 tagge d with Flag epitope) inhibited vascular development in cultured wild-type P -Sp explants by sequestering VEGF(165). In contrast, a dimer of soluble NP- 1 (NP-1 fused with the Fc part of human IgG) enhanced vascular development in cultured wildtype P-Sp explants. Moreover, the NP-1-Fc rescued the defec tive vascular development in cultured np-1(-/-) P-Sp explants. A low dose o f VEGF alone did not promote phosphorylation of VEGFR-2 on endothelial cell s from np-1(-/-) embryos, but simultaneous addition of a low dose of VEGF a nd NP-1-Fc phosphorylated VEGFR-2 significantly. Moreover, NP-1-Fc rescued the defective vascularity of np-1(-/-) embryos in vivo. These results sugge st that a dimer form of soluble NP-1 delivers VEGF(165) to VEGFR-2-positive endothelial cells and promotes angiogenesis. (Blood. 2001; 97:1671-1678) ( C) 2001 by The American Society of Hematology.