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.
