Abstract P1129: Directing Revascularization In Vivo With Local Controlled Release Of An Optimized Angiogenic Growth Factor Cocktail

Abstract

Reduced vascular perfusion due to aging, ischemia, or injury impedes healing and tissue function in conditions like skin ulcers and myocardial infarction, motivating development of therapies to restore vasculature locally in target tissues. We hypothesize that specific combinations of signaling molecules stimulate angiogenesis and vascular remodeling in the local tissue environment to increase perfused vessel density. Using a vascular tissue engineering approach with a fractional factorial design of experiments (DOE), we evaluated in vivo angiogenesis of combinations of ten growth factors, cytokines and/or enzymes including VEGF, bFGF, Shh, PDGF, IGF-1, EGF, TGF-β1, Ang-1, MCP-1 and MMP-9 in a subcutaneous gel plug assay in the WT immune competent rat. Our initial assessment with Matrigel identified 5 factors that maximized CD31+ vessel lumen density and aSMA+ encoated vessels at 7 days, warranting further evaluation. We developed a fully defined biomaterial system with covalently bound heparin to alginate mixed with collagen type 1 as an injectable gel. This defined biomaterial prolonged protein release up to 14 days in vitro versus Matrigel and unmodified alginate (2-4 days). The defined biomaterial was used for a second round DOE to deliver high (2 μg) and low (0.5 μg) doses of VEGF, bFGF, Shh, PDGF, and/or IGF-1. The defined biomaterial alone enhanced average lumen diameter 15-fold and endothelial cell infiltration 12-fold versus Matrigel. Perfused lumen density increased 16-fold with high Shh; aSMA-positive lumen wall area increased 4-fold with high VEGF, PDGF, and IGF-1; perfused vessel size increased 3-fold with high VEGF, bFGF, and Shh; and endothelial cell recruitment increased 2-fold with high IGF-1 relative to unloaded controls after 7 days in vivo. Empirical testing of 2- to 5-factor combinations showed that cocktail potency required initiation of angiogenic sprouting by VEGF or bFGF and vascularization responses were strongest in the presence of Shh and IGF-1. In conclusion, we identified sets of highly potent cocktails and leveraged controlled release from a defined biomaterial as a tailored revascularization therapy for local angiogenesis, vascular remodeling, and tissue regeneration.