Osteoprotegerin, a new actor in vasculogenesis, stimulates endothelial colony-forming cells properties.
BACKGROUND
Osteoprotegerin (OPG), a soluble receptor of the tumour necrosis factor family, and its ligand, the receptor activator of nuclear factor-κB ligand (RANKL), are emerging as important regulators of vascular pathophysiology.


OBJECTIVE
We evaluated their effects on vasculogenesis induced by endothelial colony-forming cells (ECFC) and on neovessel formation in vivo.


METHODS
Effects of OPG and RANKL on in vitro angiogenesis were evaluated after ECFC incubation with OPG or RANKL (0-50 ng mL(-1)). Effects on microvessel formation were evaluated with an in vivo murin Matrigel plug assay. Vascularization was evaluated by measuring plug hemoglobin and vascular endothelial growth factor (VEGF)-R2 content 14 days after implantation.


RESULTS
We found that ECFC expressed OPG and RANK but not RANKL mRNA. Treatment of ECFC with VEGF or stromal cell-derived factor-1 (SDF-1) upregulated OPG mRNA expression. OPG stimulated ECFC migration (P < 0.05), chemotaxis (P < 0.05) and vascular cord formation on Matrigel(®) (P < 0.01). These effects were correlated with SDF-1 mRNA overexpression, which was 30-fold higher after 4 h of OPG stimulation (P < 0.01). OPG-mediated angiogenesis involved the MAPK signaling pathway as well as Akt or mTOR cascades. RANKL also showed pro-vasculogenic effects in vitro. OPG combined with FGF-2 promoted neovessel formation in vivo, whereas RANKL had no effect.


CONCLUSIONS
OPG induces ECFC activation and is a positive regulator of microvessel formation in vivo. Our results suggest that the OPG/RANK/RANKL axis may be involved in vasculogenesis and strongly support a modulatory role in tissue revascularization.
INSERM, U765, Paris, France.
Z
Z
Benslimane-Ahmim
D
D
Heymann
B
B
Dizier
A
A
Lokajczyk
R
R
Brion
I
I
Laurendeau
I
I
Bièche
D M
DM
Smadja
I
I
Galy-Fauroux
S
S
Colliec-Jouault
A M
AM
Fischer
C
C
Boisson-Vidal
D000818:Animals; D001808:Blood Vessels / Q000166:cytology*; D015153:Blotting, Western; D049109:Cell Proliferation; D002633:Chemotaxis; D016222:Fibroblast Growth Factor 2 / Q000502:physiology; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D018919:Neovascularization, Physiologic; D053244:Osteoprotegerin / Q000502:physiology*; D053245:RANK Ligand / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D053244:Osteoprotegerin; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D016222:Fibroblast Growth Factor 2