Premium
Evaluation of VEGF‐mediated signaling in primary human cells reveals a paracrine action for VEGF in osteoblast‐mediated crosstalk to endothelial cells
Author(s) -
Clarkin Claire E.,
Emery Roger J.,
Pitsillides Andrew A.,
WheelerJones Caroline P.D.
Publication year - 2008
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.21234
Subject(s) - paracrine signalling , autocrine signalling , osteoblast , vascular endothelial growth factor , microbiology and biotechnology , angiogenesis , prostanoid , endocrinology , vascular endothelial growth factor a , medicine , chemistry , biology , cell culture , cancer research , prostaglandin , biochemistry , receptor , vegf receptors , in vitro , genetics
Communication between endothelial and bone cells is crucial for controlling vascular supply during bone growth, remodeling, and repair but the molecular mechanisms coordinating this intercellular crosstalk remain ill‐defined. We have used primary human and rat long bone‐derived osteoblast‐like cells (HOB and LOB) and human umbilical vein endothelial cells (HUVEC) to interrogate the potential autocrine/paracrine role of vascular endothelial cell growth factor (VEGF) in osteoblast:endothelial cell (OB:EC) communication and examined whether prostaglandins (PG), known modulators of both OB and EC behavior, modify VEGF production. We found that the stable metabolite of PGI 2 , 6‐keto‐PGF 1α and PGE 2 , induced a concentration‐dependent increase in VEGF release by HOBs but not ECs. In ECs, VEGF promoted early ERK1/2 activation, late cyclooxygenase‐2 (COX‐2) protein induction, and release of 6‐keto‐PGF 1α . In marked contrast, no significant modulation of these events was observed in HOBs exposed to VEGF, but LOBs clearly exhibited COX‐dependent prostanoid release (10‐fold less than EC) following VEGF treatment. A low level of osteoblast‐like cell responsiveness to exogenous VEGF was supported by VEGFR2/Flk‐1 immunolabelling and by blockade of VEGF‐mediated prostanoid generation by a VEGFR tyrosine kinase inhibitor (TKI). HOB alkaline phosphatase (ALP) activity was increased following long‐term non‐contact co‐culture with ECs and exposure of ECs to VEGF in this system further increased OB‐like cell differentiation and markedly enhanced prostanoid release. Our studies confirm a paracrine EC‐mediated effect of VEGF on OB‐like cell behavior and are the first supporting a model in which prostanoids may facilitate this unidirectional VEGF‐driven OB:EC communication. These findings may offer novel regimes for modulating pathological bone remodeling anomalies through the control of the closely coupled vascular supply. J. Cell. Physiol. 214: 537–544, 2008. © 2007 Wiley‐Liss, Inc.