Extracellular matrix (ECM) scaffolds induce a type-2 immune response when implanted in vivo, which promotes wound healing and tissue regeneration. These materials are derived from native tissue treated with detergents to remove cells, creating a complex biologic scaffold. Interestingly, signals that can induce a tissue damage response, referred to as damage-associated molecular patterns (DAMPs), are present in ECM scaffolds. These DAMPs include low molecular weight hyaluronic acid created when ECM is fragmented, and ECM bound intracellular proteins, such as actin, that are indicative of cell damage. We theorize that ECM scaffold-mediated tissue regeneration is in part induced by DAMP signaling. Through engineered use of these DAMPs we hypothesize that we could induce such pro-regenerative responses. This will be accomplished through creation of a library of synthetic DAMP analogues used in a soluble form and derivatized to a resorbable gelatin-based scaffold. These engineered DAMPs (eDAMPs) as well as naturally occurring DAMPs will be screened in an in vitro assay of type-2 macrophage and T cell polarization through YFP-Arg1 and GFP-IL4 expression, respectively. Select compounds will be translated into murine skin and muscle injury models to evaluate their pro-regenerative capacity. Histologically, in the skin wound model, we will evaluate the rate of closure, extent of fibrotic collagen deposition, and regeneration of mature skin structures such as hair follicles and glands. In muscle wounds, quality of regeneration will be determined by the presence of actively developing muscle fibers by immunofluorescent staining of the different developmental myosins such as neonatal and embryonic myosin, and muscle structure including size of fibers and extent of fibrotic collagen deposition and ectopic adipogenesis. Additionally, the mechanism will be determined on the immunomodulatory level by evaluating cell recruitment, activation and polarization, and the molecular level by ligand-binding assays for DAMP receptors and signaling pathways. Results of this study will (1) provide insight into mechanisms of wound healing, (2) elucidate the molecular nature of pro-regenerative DAMP responses, and (3) create translational materials to improve human health in the field of tissue engineering and regenerative medicine.
The objective of the proposed research is to engineer damage-associated molecular patterns to promote tissue growth and regeneration. We are currently investigating chemical modifications of polymer scaffolds to decrease fibrosis in a pancreatic islet transplantation model. Translating these principles to pro-regenerative biomaterials, using known natural signals of tissue damage to induce wound healing responses, we will increase our understanding of the molecular motifs that promote such responses and utilize these motifs for materials design.
