Long-lasting fibrin matrices ensure stable and functional angiogenesis by highly tunable, sustained delivery of recombinant VEGF 164

• Published in: Proceedings of the National Academy of Sciences - PNAS 2014-05, Vol.111 (19), p.6952-6957
• Main Authors: Sacchi, Veronica, Mittermayr, Rainer, Hartinger, Joachim, Martino, Mikaël M., Lorentz, Kristen M., Wolbank, Susanne, Hofmann, Anna, Largo, Remo A., Marschall, Jeffrey S., Groppa, Elena, Gianni-Barrera, Roberto, Ehrbar, Martin, Hubbell, Jeffrey A., Redl, Heinz, Banfi, Andrea
• Format: Article
• Language: English
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1404605111

Inducing the growth of new blood vessels by specific factors is an attractive strategy to restore blood flow in ischemic tissues. Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis, yet clinical trials of VEGF gene delivery failed. Major challenges include the need to control the tissue distribution of factor dose and the duration of expression. Here, we developed a highly tunable fibrin-based platform to precisely control the dose and duration of VEGF protein delivery in tissues. Optimized delivery of fibrin-bound VEGF ensured normal, stable, and functional angiogenesis and improved perfusion of ischemic tissues, without genetic modification and with limited duration of VEGF delivery. These findings suggest a strategy to improve both safety and efficacy of therapeutic angiogenesis. Clinical trials of therapeutic angiogenesis by vascular endothelial growth factor (VEGF) gene delivery failed to show efficacy. Major challenges include the need to precisely control in vivo distribution of growth factor dose and duration of expression. Recombinant VEGF protein delivery could overcome these issues, but rapid in vivo clearance prevents the stabilization of induced angiogenesis. Here, we developed an optimized fibrin platform for controlled delivery of recombinant VEGF, to robustly induce normal, stable, and functional angiogenesis. Murine VEGF 164 was fused to a sequence derived from α2-plasmin inhibitor (α 2 -PI 1–8 ) that is a substrate for the coagulation factor fXIIIa, to allow its covalent cross-linking into fibrin hydrogels and release only by enzymatic cleavage. An α 2 -PI 1–8 –fused variant of the fibrinolysis inhibitor aprotinin was used to control the hydrogel degradation rate, which determines both the duration and effective dose of factor release. An optimized aprotinin-α 2 -PI 1–8 concentration ensured ideal degradation over 4 wk. Under these conditions, fibrin-α 2 -PI 1–8 -VEGF 164 allowed exquisitely dose-dependent angiogenesis: concentrations ≥25 μg/mL caused widespread aberrant vascular structures, but a 500-fold concentration range (0.01–5.0 μg/mL) induced exclusively normal, mature, nonleaky, and perfused capillaries, which were stable after 3 mo. Optimized delivery of fibrin-α 2 -PI 1–8 -VEGF 164 was therapeutically effective both in ischemic hind limb and wound-healing models, significantly improving angiogenesis, tissue perfusion, and healing rate. In conclusion, this optimized platform ensured ( i ) controlle