Angioblast differentiation is influenced by the local environment: FGF-2 induces angioblasts and patterns vessel formation in the quail embryo

The embryonic vasculature forms by the segregation, migration, and assembly of angioblasts from mesoderm, a process termed vasculogenesis. The initial role of fibroblast growth factor 2 (FGF-2) in vascular development appears to be in the induction of endothelial precursors, angioblasts. Quail somit es transplanted into chick embryos will give rise to angioblasts of quail o rigin, The number of angioblasts present within the chimera is dependent on the host environment. Angioblast induction can be demonstrated in vitro by the addition of FGF-2 to cultures of dissociated semitic mesoderm, as asse ssed by QH-1 epitope expression. Manipulation of FGF-2 concentration in the quail/chick chimeras by FGF-2 peptide or neutralizing antibody injections increases or decreases angioblast induction in the predicted manner. To bet ter control growth factor release in vivo we have implanted beads that rele ase FGF-2 into the embryonic environment. FGF-2 beads implanted into the so mite induce angioblast differentiation in the epithelial somite; whereas, b eads lateral to the semitic mesoderm induce the formation of ectopic vessel s. These studies suggest that FGF-2 is important for both the induction of angioblasts and the assembly of angioblasts into the initial vasculature pa ttern. Dev Dyn 2000;218:371-382. (C) 2000 Wiley-Liss, Inc.