Introduction: Delivery of vascular endothelial growth factor (VEGF) protein or gene transfer has been shown to accelerate re-endothelialization and attenuate neointimal hyperplasia in various arterial injury models, including balloon injury, stent implantation, and vein grafts. In addition to stimulating re-endothelialization, we hypothesize that VEGF has further vascular protective functions to prevent neointimal hyperplasia by directly inhibiting mitogen-induced proliferation of vascular smooth muscle cells (VSMCs) via the mitogen-activated protein kinase pathway.
Materials and methods: Human aortic VSMCs were seeded and serum starved for 24 h. The cells were then stimulated with a mitogen, recombinant human platelet derived growth factor at 20 ng/mL together with 0, 10, 20, 30, 40, 50 ng/mL recombinant human VEGF. A proliferation assay was used to quantitate bromodeoxyuridine uptake into newly synthesized DNA. Western immunoassay was used to quantify extracellular signal-regulated kinase (ERK) 2 protein and phosphorylation of retinoblastoma and ERK 1/2 protein.
Results: VEGF inhibited bromodeoxyuridine incorporation into mitogen-induced VSMC in a dose-dependent manner, reaching statistical significance at concentrations of 30 (P < 0.05), 40 (P < 0.05), and 50 ng/mL (P < 0.01). Densitometry of western immunoblots revealed an inhibition of phosphorylation of retinoblastoma at VEGF concentrations of 40 and 50 ng/mL and ERK 1/2 phosphorylation at concentrations of 30, 40 and 50 ng/mL.
Conclusion: In addition to stimulating re-endothelialization, VEGF appears to have a vascular protective function by directly inhibiting VSMC proliferation. This effect occurs in the absence of endothelial cells and via the mitogen-activated protein kinase pathway. VEGF may serve as an important modulator of mitogen-induced VSMC proliferation after vascular injury.