COATs: Collagen-mimetic peptide and therapeutic gene-modified collagens for cell-mediated healing of diabetic foot ulcers

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PROJECT SUMMARY – Diabetic foot ulcers (DFU) are an enormously costly worldwide health concern. They cause nearly 80,000 lower leg amputations annually in the U.S. alone and are associated with significantly increased likelihood of death. Strategies to improve their healing have been a subject of intense study for decades, yet myriad cellular and pathophysiological abnormalities continue to severely limit efficacy of standard therapies. Promising therapeutic alternatives include the application of cellular scaffolds, topical growth factors (especially platelet-derived growth factor), or combination wound dressings. However, the incidence of complete closure remains strikingly low and growth factor delivery strategies largely fail owing to their instability in the inflammatory, MMP-rich environment of the chronic wound. New strategies that can normalize this proteolytic and inflammatory environment, by stimulating local production of therapeutic proteins by fibroblasts and macrophages, would thus offer a provocative approach to improve clinical outcomes. We have recently demonstrated that protease activity in the wound bed can be harnessed to stimulate localized growth factor gene delivery and provide tailorable expression of growth factors over multiweek timeframes. We introduce collagen mimetic peptide (CMP) and therapeutic gene-modified collagens (COATs) as a platform for (i) robust retention of growth factor-encoding polyplexes in collagen- containing wound dressings and (ii) localized, cell-initiated gene delivery during collagen remodeling. Because COATs integrate DNA polyplexes directly into collagen fibrils, our approaches have been shown to significantly improve in vivo wound repair at concentrations of growth factors orders of magnitude lower than those in currently employed topical therapies. These outcomes, coupled with recent advances in the translation of other gene therapies, suggests the high potential for clinical impact of the COATs platform. In the proposed R01 program, we will apply COATs in experimental DFUs and cell-based assays to understand three important aspects of orchestrating wound repair, in the following three Aims. In Aim 1, we will probe variations in CMP modifications that optimize the extended delivery of genes (initially for platelet-derived growth factor (PDGF)) in a murine diabetic wound environment. In Aim 2, we will complement these studies with cell-based investigations that elucidate the role of MMPs (soluble and membrane-bound) in regulating PDGF gene delivery by COATs and PDGF protein lifetime. In Aim 3, we will test how COATs-mediated, sequential delivery of genes for immunomodulatory cytokines (IL4 and IL10) modulates MMP activity in DFUs. These approaches will provide both mechanistic insights for resolving the chronicity of DFUs, and also a new platform that could be integrated into existing wound-care strategies to dramatically improve clinical outcomes.