PROJECT SUMMARY/ABSTRACT Cystic fibrosis (CF) is an autosomal recessive single-gene disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most common mutation, termed ∆F508, occurs in ~85% of CF patients. Because the CFTR gene encodes for an anion transport protein, CFTR mutations alter electrolyte and water transport, resulting in dense, pathologic, mucous and other secretions. The most harmful effects of CFTR dysfunction occur in the respiratory system, with recurrent infections and inflammation of the upper and lower airways. Despite substantial progress with medical therapies, there remains a tremendous unmet need for improved, durable therapies for CF. For the past 3 years, our collaborative group of complementary scientists and physicians has determined to develop a novel, stem cell-based treatment strategy for patients suffering from CF. For several critical reasons, we directed our efforts to cell-based therapy of CF upper airway disease using ex vivo-expanded, primary human airway basal stem cells, termed ABCs. The first major milestone was to utilize CRISPR/Cas9 genome editing technology to efficiently correct the ∆F508 mutation in ABCs cultured from CF patients undergoing sinus surgery. This gene correction approach has led to significant restoration of chloride anion transport from 0-3% to 30-40% in ABCs. This encouraging, and newly published, development now provides a pre-clinical roadmap for re-introducing CFTR gene-corrected ABCs into in vivo contexts as a stem cell replacement therapy. In this proposal, we will rigorously determine the most efficient, biomaterial platform for ex vivo-to-in vivo transplant and engraftment of human ABCs, and assess the behavior of gene-corrected ABCs in the lab and live animal model using a microsurgical model system of upper airway transplantation that we have developed. The experiments outlined are essential pre-clinical steps in order to translate this approach to CF patients to generate an innovative and possibly transformative therapy for patients with CF, and the first stem cell-based therapy for human airway disease.