Heparin-fibroblast growth factor-fibrin complex: in vitro and in vivo applications to collagen-based materials

Biological molecules such as fibrin and growth factors could have interesting features to design bioactive biomaterials and particularly collagen-based materials used as connective tissue replacement. Different combinations of fibroblast growth factor (FGF) and heparin complexed to fibrin were analysed. In vitro, FGF bound to matrix was rapidly, but partially released, specifically with heparin. Heparin concentrations were progressively equilibrated between matrix and medium. DNA replication of fibroblasts grown either on or within fibrin matrices was increased in the presence of both FGF and high doses of heparin incorporated in fibrin. Subcutaneous implantations of collagen sponges impregnated with composite fibrin matrices showed qualitative and quantitative tissue ingrowth within the sponges. The uncross-linked collagen of fibrin-impregnated sponges swelled after implantation. The resulting fibroblast-infiltrated tissue resembled a normal dense connective tissue that was observed particularly in the presence of high doses of heparin and FGF incorporated in fibrin.

Extracellular matrix analogs as carriers for growth factors: in vitro fibroblast behavior

Repair of connective tissue involves interactions between growth factors (GFs) and extracellular matrix (ECM) molecules. On the other hand, biological biomaterials could be used to carry and deliver GFs to stimulate wound healing. In the present study, fibroblasts were cultivated in a serum-free culture medium onto collagen (type I), hyaluronic acid, chondroitin sulfate, fibronectin, or fibrin. FGF, EGF, or PDGF was incorporated within those substrates. Using immuno- and radiolabeling assays, the distribution of GFs within the ECM analogs was relatively uniform and GFs retained in substrates were dependent on the substrates. Fibroblast replication was determined by the incorporation of [3H]-thymidine and compared to control groups. On collagen or chondroitin sulfate, the incorporation of GFs did not significantly improve cell proliferation. On hyaluronic acid, the incorporation of FGF and PDGF enhanced cell replication at 48 h. The incorporation of PDGF in fibronectin enhanced cell replication. On fibrin, the incorporation of PDGF, EGF, and FGF significantly enhanced cell replication. However, cell replication on FGF-incorporated fibrin was higher by 48 h than that on fibrin in the presence of FGF-supplemented culture medium. Fibrin sustains the biological activity of GFs, FGF in particular, and can be a carrier for GF that stimulates cell replication.