Collagen Turnover-Stimulated Gene Delivery to Enhance Chronic Wound Repair 

Biomaterial scaffolds are commonly employed to guide tissue regeneration. Ideal scaffolds act as analogs of the extracellular matrix, providing a cell-responsive structural support for cellular attachment and phenotypic commitment. For this purpose, the stable incorporation and controllable delivery of bioactive cues is required. In particular, the use of gene-containing biomaterials has been shown to address key obstacles in repair by enabling in situproduction of growth factors and other therapeutic molecules to modulate cell behavior. However, significant concerns with off-target delivery/safety and limited gene delivery efficacy have restricted clinical success. To address these issues, we have developed an innovative strategy for improving spatiotemporal control over gene expression by developing collagen-mimetic peptides (CMPs) to engineer DNA polyplex-modified collagens with tailorable release profiles and improved gene transfer. The unique collagen-like properties of CMPs permits their use as both adjustable tethers, via CMP-collagen hybridization, and as endocytic ligands.

For instance, variation of CMP-display on polyplex permitted tailoring of polyplex retention vs. release over a month, while non-modified polyplexes were retained for under 20 days. In cell culture studies, bound CMP-modified polyplexes also exhibited improved stability in the presence of serum-supplemented media over a 14-day period and different intracellular trafficking resulting in improved gene delivery efficiency. MMP-stimulated cells exhibited substantially higher levels of expression suggesting collagen remodeling mediates transfection. Additional experiments in a murine model demonstrated CMP-display enabled up to a 10-fold increase in transgene expression duration with average expression levels up to 2-orders of magnitude greater than when non-modified polyplex were delivered. Furthermore, DNA polyplex-modified collagens encoding for platelet-derived growth factor -BB (PDGF-BB) exhibited the capacity to express enhanced levels of PDGF-BB and to subsequently encourage fibroblast proliferation/chemotaxis and wound closure when applied to an in vitro wound model. This work is the first to investigate the potential of exploiting the natural process of collagen remodeling to achieve enhanced gene delivery efficacy utilizing CMPs. These results suggest that this versatile approach has the potential to better integrate gene delivery with natural tissue repair while also improving polyplex safety and activity.