Skin-targeted Cell Therapy for Recessive Dystrophic Epidermolysis Bullosa

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DESCRIPTION (provided by applicant): Recessive dystrophic epidermolysis bullosa (RDEB) is caused by loss-of-function mutations in the collagen type VII (C7) gene (COL7A1), and results in a potentially fatal and terribly debilitating disorder. Individuals with severe generalied RDEB develop blisters and erosions involving large portions of the body surface area, mutilating scarring, joint contractures, and strictures of the esophagus, with opportunistic infections and aggressive squamous cell carcinoma as principal causes of early death. We have shown that hematopoietic stem cell transplantation (HSCT) can increase C7 protein in skin and mucous membranes, and ameliorate many of the disease manifestations. Unfortunately not all mucocutaneous lesions heal, and the toxicities associated with HSCT are significant. Our overarching goal is to solve these problems by establishing a reliable method for delivering C7-expressing cells that home to the dermal-epidermal junction and secrete C7 protein. In order to accomplish this goal and to overcome the limitations of allogeneic HSCT, we will: 1) identify the optimal cellular vector and homing signal for targeting injured skin in RDEB, using human mesenchymal stromal/stem cells and induced pluripotent stem cells (iPSCs), 2) define the efficacy of systemic RDEB gene therapy by C7 gene augmentation, and 3) use nucleases for gene editing of individual mutations, as well as whole regions of the C7 gene. We propose to define the conditions conducive to wound healing in this severe blistering genodermatosis, but the impact of these studies may not be limited to RDEB. The function of C7 depends on extracellular polymerization, which makes RDEB an ideal model for understanding the mechanisms of cross- correction of structural protein deficiency in the extracellular matrix. In addition, wound healing integrates skin extracellular matrix and skin cells into a dynamic system, which in RDEB results in the depletion of skin stem cell niches and, in turn, provides a unique model of skin tissue repair with donor regenerative cells. By using powerful tools for studying and manipulating the information basis of biological systems-engineered restriction enzymes (nucleases), skin- targeting, and induced cell lineage conversion (iPSCs)-we will focus on developing personalized cell therapy for individuals with RDEB with the idea that our findings may have broad implications for understanding other connective tissue extracellular matrix diseases. Our proposal is equally motivated by wanting a better understanding of the biological mechanisms in injured skin and by needing to improve the lives of people with RDEB through maximizing the benefits and reducing the risks of potential novel therapies.