Abstract 802: The Fibroblast Growth Factor System Regulates Vascular Integrity in Mice
Background: The fibroblast growth factor (FGF) system plays important roles in a wide variety of physiologic and pathologic conditions; however, early embryonic lethality of mice lacking either Fgfr-1 or Fgfr-2 precludes further studies focusing on FGF functions in the post-developmental stage.
Methods: To address the FGF role in the adult vasculature, three approaches which differently disrupt FGF signaling were used:
conditional transgenic mice expressing dominant-negative form of FGFR1 (FGF-R1DN) in the endothelium under the control of tetracycline regulated Tie2 promoter,
Ad-FGF-R1DN transduction of normal mice arteries, and
systemic expression of soluble (s)FGFR-IgFc chimera proteins (FGF Traps).
For the FGF Trap approach, we used FGF-R1IIIc (FR1c) isoform which binds FGF1, 2, 4, 5, and 6, and FGF-R3IIIb (FR3b) isoform which almost exclusively binds FGF1 to elucidate specific contribution of different FGF ligands.
Results: Micro-CT and fluorescent stereo-microscope analyses demonstrated vascular leakage and significant retention of the contrast reagent throughout the ischemic region at the early stage of ischemic injury in FGF-R1DN mice. Introduction of FGF-R1DN adenovirus in normal rat femoral artery or Ad-FGF Trap in the systemic circulation induced rearrangement of endothelial cells and disruption of cell-cell junctions as demonstrated by immunostaining and scanning electron microscopy (SEM), leading to the loss of shear stress sensing. Increased permeability of the vasculature was observed in multiple organs including heart, skeletal muscle and lungs. In vitro studies demonstrated that inhibition of FGF signaling in bovine aortic endothelial cells leads to displacement of VE-cadherin and other adherence and tight junction proteins from cell junctions without altering total expression levels of these proteins. These resulted in increased permeability of the endothelial monolayer to 70 kD and 2 mD dextran, which was morphologically confirmed by SEM analysis.
Conclusion: The FGF system appears to control endothelial barrier function and vascular integrity by regulating junctional protein dynamics, which in turn plays an important role in the maintenance of endothelial stability and shear stress sensing