Hypertrophic scarring is a poorly understood condition which affects the lives of millions of people around the world annually. Despite its common occurrence following burn injury, trauma or surgery the present treatments are of limited efficacy. Research over the past decade in the Cowin laboratory has identified Flightless (Flii), a highly conserved cytoskeletal protein, as a negative regulator of wound healing. Wounding leads to an increased expression of Flii, while Flii has been shown to inhibit cellular migration and proliferation. Reducing Flii in vivo leads to improved wound healing. The aim of this study was to investigate the role of Flii in the fibroproliferative process underlying hypertrophic scarring. Chapter three shows for the first time that Flii expression in increased in human burn and hypertrophic scar tissue. Chapter four details the development of a novel murine model of hypertrophic scarring. Previous animal models have focused on reproducing the clinical characteristics of the human hypertrophic scar, which often required significant derangement of the animal immune response. The novel model used bleomycin to stimulate the fibroproliferative process that underlies hypertrophic scarring. Results in this chapter use histology and immunohistochemistry to verify the bleomycin model as a valid model of hypertrophic scarring. Chapter five uses the bleomycin mode to demonstrate that Flii is a key determinant of the extent of fibroproliferation that underlies hypertrophic scarring. Increasing Flii genetically in this animal model leads to increased dermal thickening and increases in key determinants of hypertrophic scarring, such as myofibroblasts, transforming growth factorβ-1 (TGFβ-1) and scar collagen composition. Decreasing Flii genetically causes a reduction in hypertrophic scarring using the same measures. Decreasing Flii using a monoclonal antibody therapy in the bleomycin model also led to a reduction in hypertrophic scarring, confirming Flii as a potential target for a novel therapy for hypertrophic scarring. Chapter six investigates potential mechanisms for the findings observed in previous chapters by using in vivo techniques. Focusing on the fibroblast, the key cell type in fibroproliferation, immunocytochemistry and cell migration assays, were used to show that decreasing Flii genetically or using a monoclonal antibody, reverses the fibroblast-myofibroblast phenotypic change that characterizes fibroproliferartive pathology. Flii appears to be a key determinant of the fibroproliferative process underlying hypertrophic scarring. This study uses human tissue, a novel small animal model and in vivo techniques to demonstrate this and identify Flii as a potential target for a novel therapy to reduce or prevent hypertrophic scarring.Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 201
