Osteoblasts extracellular matrix induces vessel like structures through glycosylated collagen I.

Extracellular matrix (ECM) plays a fundamental role in angiogenesis affecting endothelial cells
proliferation, migration and differentiation. Vessels-like network formation in vitro is a reliable
test to study the inductive effects of ECM on angiogenesis. Here we utilized matrix deposed by
osteoblasts as substrate where the molecular and structural complexity of the endogenous ECM is
preserved, to test if it induces vessel-like network formation by endothelial cells in vitro. ECM is
more similar to the physiological substrate in vivo than other substrates previously utilized for
these studies in vitro. Osteogenic ECM, prepared in vitro from mature osteoblasts at the phase of
maximal deposition and glycosylation of collagen I, induces EAhy926, HUVEC, and HDMEC
endothelial cells to form vessels-like structures and promotes the activation of metalloproteinase-
2 (MMP-2); the functionality of the p-38/MAPK signaling pathway is required. Osteogenic ECM
also induces a transient increase of CXCL12 and a decrease of the receptor CXCR4. The induction of
vessel-like networks is dependent from proper glycosylation of collagens and does not occur on
osteogenic ECMs if deglycosylated by -galactosidase or on less glycosylated ECMs derived from
preosteoblasts and normal fibroblasts, while is sustained on ECM from osteogenesis imperfecta
fibroblasts only when their mutation is associated with over-glycosylation of collagen type I. These
data support that post-translational glycosylation has a role in the induction in endothelial cells in
vitro of molecules conductive to self-organization in vessels-like structures.