Mural cell associated VEGF is required for organotypic vessel formation.
BACKGROUND
Blood vessels comprise endothelial cells, mural cells (pericytes/vascular smooth muscle cells) and basement membrane. During angiogenesis, mural cells are recruited to sprouting endothelial cells and define a stabilizing context, comprising cell-cell contacts, secreted growth factors and extracellular matrix components, that drives vessel maturation and resistance to anti-angiogenic therapeutics.


RESULTS
To better understand the basis for mural cell regulation of angiogenesis, we conducted high content imaging analysis on a microtiter plate format in vitro organotypic blood vessel system comprising primary human endothelial cells co-cultured with primary human mural cells. We show that endothelial cells co-cultured with mural cells undergo an extensive series of phenotypic changes reflective of several facets of blood vessel formation and maturation: Loss of cell proliferation, pathfinding-like cell migration, branching morphogenesis, basement membrane extracellular matrix protein deposition, lumen formation, anastamosis and development of a stabilized capillary-like network. This phenotypic sequence required endothelial-mural cell-cell contact, mural cell-derived VEGF and endothelial VEGFR2 signaling. Inhibiting formation of adherens junctions or basement membrane structures abrogated network formation. Notably, inhibition of mural cell VEGF expression could not be rescued by exogenous VEGF.


CONCLUSIONS
These results suggest a unique role for mural cell-associated VEGF in driving vessel formation and maturation.
Evensen
Lasse
L
Department of Biomedicine, University of Bergen, Bergen, Norway.
Micklem
David R
DR
Blois
Anna
A
Berge
Sissel Vik
SV
Aarsaether
Niels
N
Littlewood-Evans
Amanda
A
Wood
Jeanette
J
Lorens
James B
JB
D022005:Adherens Junctions / Q000378:metabolism; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D001485:Basement Membrane / Q000378:metabolism; D001808:Blood Vessels / Q000473:pathology*; D002196:Capillaries / Q000378:metabolism; D002450:Cell Communication; D049109:Cell Proliferation; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D018919:Neovascularization, Physiologic; D034622:RNA Interference; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D020533:Angiogenesis Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D042461:Vascular Endothelial Growth Factor A