Delivery of basic fibroblast growth factor using heparin-conjugated fibrin for therapeutic angiogenesis

Heparin-conjugated fibrin (HCF, a mixture of heparin-conjugated fibrinogen and thrombin) was developed as an injectable carrier for long-term delivery of fibroblast growth factor 2 (FGF2), and the therapeutic potential of the HCF system was investigated by evaluating neovascularization in a mouse hind limb ischemia model. HCF released FGF2 for a much longer period than normal fibrin containing free heparin in vitro. The FGF2 released from HCF was bioactive, as it stimulated growth of human dermal fibroblasts in a serum-depleted medium in vitro. In contrast, FGF2 released from normal fibrin did not induce significant cell growth, probably because of its short-term release. HCF alone, HCF loaded with FGF2, and normal fibrin containing free heparin and FGF2 were implanted into mouse ischemic hind limbs for 4 weeks. Histological analysis, Western blot analysis, and immunohistological analysis revealed that ischemic limbs treated with normal fibrin containing free heparin and FGF2, or treated with HCF only, showed severe muscle fibrosis, inflammation, and a low vasculature density. In contrast, mice treated with FGF2-loaded HCF showed significantly reduced muscle fibrosis and inflammation, and dramatically enhanced neovascularization. FGF2 delivery using HCF could be useful for therapeutic angiogenesis as HCF delivery enhances the therapeutic efficacy of FGF2.