Diabetic foot ulcers are a significant health problem that imposes high costs on both patients and society (Boulton, Vileikyte et al. 2005). A large proportion of foot ulcers remain unresponsive to available conventional treatment and their associated complications and costs have prompted extensive research that has led to promising breakthroughs. Recombinant growth factors, biodegradable matrices, and bioengineered skin equivalents have been developed to better promote healing (Edmonds, Bates et al. 2000). These therapies have shown promise, but still have limitations including high cost, immunogenicity, and the need for high, repeated doses of growth factor. Platelet Derived Growth Factor (PDGF) is a potent chemotactic, mitogen, and differentiation factor that promotes soft tissue formation and rhPDGF-BB is currently FDA approved to treat diabetic ulcers. Repeated application of high dose PDGF increases the cost and complexity of treatment. In general, biologic therapeutics are more expensive to develop and manufacture than synthetic therapeutics. Therefore, a synthetic alternative that also has a longer resident time could significantly reduce the cost and complexity of current therapies. The goal of this proposal is to generate a PDGF-BB mimetic that can be immobilized on a collagen scaffold used to promote soft tissue and wound healing. We plan to use phage display technology to identify peptides that mimic PDGF-like signaling of the PDGF B-receptor. These peptides will be linked to a previously identified high-affinity, collagen-binding peptide. The resulting hybrid molecule is expected to allow controlled, local delivery of a synthetic molecule from the surface of a collagen matrix. We expect that collagen binding peptides will significantly improve the retention of a bioactive PDGF mimetic in a wound. First, using phage display techniques, we will identify peptides that bind to the PDGF B-receptor. Secondly, to increase the affinity of the peptides for the B-receptors, focused libraries will be constructed based on the sequences of the initial B-receptor-binding peptides and screened again on the B-receptors. Next, synthetic peptides containing 2 copies of the B-receptor binding sequence will be chemically synthesized with a flexible linker and the resulting dimers will be tested for PDGF-BB-like activity with a fibroblast proliferation assay. Finally, we will synthesize combinations of Affinergy's existing collagen binding sequences and the newly identified PDGF-BB mimetic peptide and the hybrid molecule will be tested for binding to collagen and for its ability to induce fibroblast proliferation while bound to a collagen matrix. Project Narrative: Diabetic foot ulcers are a significant health problem that imposes high costs on both patients and society. A large proportion of foot ulcers remain unresponsive to conventional treatment and have prompted research that has led to promising breakthroughs, including recombinant growth factors, biodegradable matrices, and bioengineered skin equivalents. These therapies have shown promise, but still have limitations including high cost, immunogenicity, and the need for high doses of growth factor. In this project, we will develop a Platelet Derived Growth Factor (PDGF) peptide-based mimetic that can be immobilized on a collagen scaffold used to promote wound healing. We plan to use phage display technology to identify peptides that mimic PDGF's biologic activity. In general, biologic therapeutics are more expensive to develop and manufacture than synthetic therapeutics. Therefore, a synthetic alternative that also has a longer resident time could significantly reduce the cost and complexity of current therapies. ? ? ?
