Abstract
VEGF is widely investigated for therapeutic angiogenesis, but while short-term delivery is desirable for safety, it is insufficient for new vessel persistence, jeopardizing efficacy. Here, we investigated whether and how VEGF dose regulates nascent vessel stabilization, to identify novel therapeutic targets. Monoclonal populations of transduced myoblasts were used to homogeneously express specific VEGF doses in SCID mouse muscles. VEGF was abrogated after 10 and 17 days by Aflibercept treatment. Vascular stabilization was fastest with low VEGF, but delayed or prevented by higher doses, without affecting pericyte coverage. Rather, VEGF dose-dependently inhibited endothelial Semaphorin3A expression, thereby impairing recruitment of Neuropilin-1-expressing monocytes (NEM), TGF-β1 production and endothelial SMAD2/3 activation. TGF-β1 further initiated a feedback loop stimulating endothelial Semaphorin3A expression, thereby amplifying the stabilizing signals. Blocking experiments showed that NEM recruitment required endogenous Semaphorin3A and that TGF-β1 was necessary to start the Semaphorin3A/NEM axis. Conversely, Semaphorin3A treatment promoted NEM recruitment and vessel stabilization despite high VEGF doses or transient adenoviral delivery. Therefore, VEGF inhibits the endothelial Semaphorin3A/NEM/TGF-β1 paracrine axis and Semaphorin3A treatment accelerates stabilization of VEGF-induced angiogenesis.
Highlights
Vascular endothelial growth factor-A (VEGF) is widely investigated for therapeutic angiogenesis, but while short-term delivery is desirable for safety, it is insufficient for new vessel persistence, jeopardizing efficacy
Vascular stabilization is progressively impaired by increasing VEGF doses As we previously found that the therapeutic window of VEGF overexpression is controlled by the dose of VEGF localized in the microenvironment around each expressing cell (Ozawa et al, 2004; von Degenfeld et al, 2006), to rigorously determine the role of VEGF dose on the vascular stabilization kinetics we took advantage of a unique and well-characterized platform, based on monoclonal populations of retrovirally transduced mouse myoblasts that express specific VEGF164 doses, thereby ensuring homogeneous microenvironmental levels (Ozawa et al, 2004; Misteli et al, 2010)
Neuropilin-1-expressing monocytes (NEM) recruitment during VEGF-induced angiogenesis requires Sema3A upregulation and inhibition of the endothelial Sema3A/NEM/transforming growth factor-b1 (TGF-b1) axis is a mechanism by which VEGF impairs vascular stabilization without affecting vascular maturation
Summary
VEGF is widely investigated for therapeutic angiogenesis, but while short-term delivery is desirable for safety, it is insufficient for new vessel persistence, jeopardizing efficacy. We investigated whether and how VEGF dose regulates nascent vessel stabilization, to identify novel therapeutic targets. Monoclonal populations of transduced myoblasts were used to homogeneously express specific VEGF doses in SCID mouse muscles. VEGF was abrogated after 10 and 17 days by Aflibercept treatment. VEGF dosedependently inhibited endothelial Semaphorin3A expression, thereby impairing recruitment of Neuropilin-1-expressing monocytes (NEM), TGF-b1 production and endothelial SMAD2/3 activation. TGF-b1 further initiated a feedback loop stimulating endothelial Semaphorin3A expression, thereby amplifying the stabilizing signals. Semaphorin3A treatment promoted NEM recruitment and vessel stabilization despite high VEGF doses or transient adenoviral delivery. VEGF inhibits the endothelial Semaphorin3A/NEM/ TGF-b1 paracrine axis and Semaphorin3A treatment accelerates stabilization of VEGF-induced angiogenesis
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