VEGF-A-Cleavage by FSAP and Inhibition of Neo-Vascularization.

Alternative splicing leads to the secretion of multiple forms of vascular endothelial growth factor-A (VEGF-A) that differ in their activity profiles with respect to neovascularization. FSAP (factor VII activating protease) is the zymogen form of a plasma protease that is activated (FSAPa) upon tissue injury via the release of histones. The purpose of the study was to determine if FSAPa regulates VEGF-A activity in vitro and in vivo. FSAP bound to VEGF ₁₆₅ , but not VEGF ₁₂₁ , and VEGF ₁₆₅ was cleaved in its neuropilin/proteoglycan binding domain. VEGF ₁₆₅ cleavage did not alter its binding to VEGF receptors but diminished its binding to neuropilin. The stimulatory effects of VEGF ₁₆₅ on endothelial cell proliferation, migration, and signal transduction were not altered by FSAP. Similarly, proliferation of VEGF receptor-expressing BAF3 cells, in response to VEGF ₁₆₅ , was not modulated by FSAP. In the mouse matrigel model of angiogenesis, FSAP decreased the ability of VEGF ₁₆₅ , basic fibroblast growth factor (bFGF), and their combination, to induce neovascularization. Lack of endogenous FSAP in mice did not influence neovascularization. Thus, FSAP inhibited VEGF ₁₆₅ -mediated angiogenesis in the matrigel model in vivo, where VEGF's interaction with the matrix and its diffusion are important.