Vascular, glial and neuronal effects of vascular endothelial growth factorin mesencephalic explant cultures

Vascular endothelial growth factor is a highly conserved, heparin-binding p rotein which mediates a number of critical developmental processes in both vertebrates and invertebrates, including angiogenesis, vasculogenesis and h ematopoiesis. We employed an organotypic rat explant model (produced from e mbryonic day 17 fetuses) to assess the effects of vascular endothelial grow th factor on brain microvasculature in general and the ventral midbrain spe cifically. Immunohistochemistry using antisera to rat endothelial cell anti gen and laminin demonstrated a robust, dose-dependent effect of vascular en dothelial growth factor, resulting in increased vessel neogenesis, branchin g and lumen size by three days in vitro. This effect was blocked by additio n of an anti-vascular endothelial growth factor antibody. At higher doses o f vascular endothelial growth factor, the effect was attenuated, though a s tatistically significant increase in both astrocyte, and neuronal density w as observed using antisera to glial and neuronal markers. Tyrosine hydroxyl ase-immunoreactive (i.e. dopaminergic) neurons, particularly, exhibited inc reased survival in response to vascular endothelial growth factor applicati on. Vascular endothelial growth factor had a mitogenic effect on endothelia l cells and astrocytes, but not dopaminergic neurons, as demonstrated by th e addition of [H-3]thymidine to the cultures 2 h after the cultures were es tablished. Similarly, results of a radioreceptor assay indicated that speci fic vascular endothelial growth factor binding sites were present on blood vessels and astrocytes, and were up-regulated by exposure to vascular endot helial growth factor. We conclude that, in explants of the ventral mesencephalon, exogenously app lied vascular endothelial growth factor is mitogenic for endothelial cells and astrocytes, and promotes growth/survival of neurons in general and dopa minergic neurons in particular. (C) 1999 IBRO. Published by Elsevier Scienc e Ltd.