Regulation of VEGF‐Induced Angiogenesis by MMPs

Aim:  We have recently reported that connective tissue growth factor (CTGF) inhibits the angiogenic activity of VEGF165, one of the vasucular endothelial growth factor (VEGF) isoforms, through the complex formation with VEGF165. In the present study, we examined the susceptibility of the VEGF165/CTGF complex to matrix metalloproteinases (MMPs), ADAMTS4 and serine proteinases, and evaluated the recovery of the angiogenic activity of VEGF165 after the treatment. Methods:  VEGF165/CTGF complex was digested with six different MMPs, ADAMTS4, elastase or plasmin. The reaction products were analyzed on silver-stained gels and by immunoblotting. Angiogenic activity of the complex treated with MMPs was assayed by in vitro tube formation assay and in vivo angiogenesis assay using a Matrigel injection model in mice. Results:  Among the MMPs, MMP-1, -3, -7, and -13 processed CTGF of the complex into the major NH2- and COOH-terminal fragments, whereas VEGF165 was completely resistant to the MMPs. The in vitro angiogenic activity of VEGF165 blocked in the VEGF165/CTGF complex was reactivated to original levels after CTGF digestion of the complex with MMPs. Recovery of activity was further confirmed by in vivo angiogenesis assay. Conclusions:  These results demonstrate that CTGF is a substrate of MMPs and that the angiogenic activity of VEGF165 suppressed by the complex formation with CTGF is recovered through the selective degradation of CTGF by MMPs. MMPs may play a novel role through CTGF degradation in VEGF-induced angiogenesis during formation of granulation and scar tissue in wound healing process.