VEGF-A and FGF-2 synergistically promote neoangiogenesis through enhancement of endogenous PDGF-B–PDGFRβ signaling

Abstract

Combined stimulation with VEGF-A, FGF-2, or PDGF-BB has emerged as a potent strategy for therapeutic angiogenesis, although the mechanisms underlying the synergism of these factors are not well understood. In the present study, we investigated the mechanism of synergism between VEGF-A and FGF-2 by using Matrigel plug assay in vivo and embryonic stem cell (ESC)-derived VEGF receptor 2 (VEGFR2)-positive cells in vitro. Experiments in vitro revealed that, in addition to having direct mitogenic effects, these molecules enhance intercellular PDGF-B signaling in a cell-type specific manner: VEGF-A enhances endothelial PDGF-B expression, whereas FGF-2 enhances mural PDGF receptor β (PDGFRβ) expression. Co-stimulation with VEGF-A and FGF-2 caused significant mural cell recruitment in vitro and formation of functional neovasculature in vivo, compared with single-agent stimulation. These effects were abrogated not only by anti-PDGFRβ neutralizing antibody, but also by exogenous PDGF-BB, which could overwhelm the endogenous PDGF-BB distribution. These findings indicated the importance of preservation of the periendothelial PDGF-BB gradient. Thus, we demonstrated that the directional enhancement of endogenous PDGF-B–PDGFRβ signaling is indispensable for the synergistic effect of VEGF-A and FGF-2 on neoangiogenesis in adults. The findings provide insights into the mechanisms underlying the effects of co-stimulation by growth factors, which could lead to rational design of therapeutic angiogenic strategies.

Improvement of cancer-targeting therapy, using nanocarriers for intractable solid tumors by inhibition of TGF-β signaling

“…1 and 2). Because use of T␤R-I inhibitor induced the same alteration in neovasculature in the Matrigel plug assay (M.R.K., unpublished data), a model of adult neoangiogenesis (23), the effects of use of T␤R-I inhibitor on tumor vasculature observed in the present study may be common in adult neoangiogenesis. Although the roles of growth factors, including TGF-␤, may differ during development and in adults, these phenotypes are reminiscent of those of knockout mice deficient in certain components of TGF-␤ signaling, e.g., endoglin (28,29), ALK-1 (30,31), and ALK-5 (32), in which loss of pericyte-coverage and dilatation of the vasculature in yolk sac or embryos were observed.…”

“…We investigated the functional aspects of the effects of low-dose T␤R-I inhibitor, using i.v.-administered large-molecule dextran of 2 MDa with a hydrodynamic diameter of 50 nm (23,24), which is equivalent to the common sizes of nanocarriers (Fig. 1B).…”

Attenuation of flightless I improves wound healing and enhances angiogenesis in a murine model of type 1 diabetes

“…5b). The length of newly formed vessels was quantified and categorised into three groups as previously described [28]:…”

“…Matrigel plug assay Two plugs containing different ligands (FnAb or IgG antibodies were mixed by pipetting; 500 μl at 50 μg/ml) were injected into each mouse to avoid differences between the individual mice [28]. The plug on the left side of the abdomen contained Matrigel compound (354248, BD Biosciences) mixed with 50 μg/ml of FnAb and the plug on the right (control) contained an equivalent dose of rabbit IgG.…”

“…formalin and processed for histology. Quantification in Matrigel plug assay was as described previously [28] using Image ProPlus 5.1 (Media Cybernetics, Rockville, MD, USA). Matrigel plugs retrieved from Flii +/− , WT and Flii Tg/Tg mice were fixed in 4% (wt/vol.)…”