Integration of growth factor gene delivery with collagen-triggered wound repair cascades using collagen-mimetic peptides.

Growth factors (GFs) play vital roles in wound repair. Many GF therapies have reached clinical trials, but success has been hindered by safety concerns and a lack of efficacy. Previously, we presented an approach to produce protein factors in wound beds through localized gene delivery mediated by biomimetic peptides. Modification of polyethylenimine (PEI) DNA polyplexes with collagen-mimetic peptides (CMPs) enabled tailoring of polyplex release/retention and improved gene transfer activity in a cell-responsive manner. In this work, CMP-mediated delivery from collagen was shown to improve expression of platelet-derived growth factor-BB (PDGF-BB) and promote a diverse range of cellular processes associated with wound healing, including proliferation, extracellular matrix production, and chemotaxis. Collagens were pre-exposed to physiologically-simulating conditions (complete media, 37°C) for days to weeks prior to cell seeding to simulate the environment within typical wound dressings. In cell proliferation studies, significant increases in cell counts were demonstrated in collagen gels containing CMP-modified polyplex versus unmodified polyplex, and these effects became most pronounced following prolonged preincubation periods of greater than a week. Collagen containing CMP-modified polyplexes also induced a twofold increase in gel contraction as well as enhanced directionality and migratory activity in response to cell-secreted PDGF-BB gradients. While these PDGF-BB-triggered behaviors were observed in collagens containing unmodified polyplexes, the responses withstood much longer preincubation periods in CMP-modified polyplex samples (10 days vs. <5 days). Furthermore, enhanced closure rates in an in vitro wound model suggested that CMP-based PDGF-BB delivery may have utility in actual wound repair and other regenerative medicine applications.