Project Summary Saliva is an important defense mechanism for protecting oral health. Salivary gland (SG) hypofunction results in uncontrolled and severe oral diseases that lead to severely compromised quality of life. SGs are highly differentiated and have little regenerative capacity once they are destroyed by therapy or disease (e.g. radiation therapy or autoimmune Sjgren?s syndrome). Therefore, the development of strategies for preserving or regenerating the secretory function of SGs is essential for successful management of these patients. The extracellular matrix (ECM) is a major component of the unique microenvironment or ?niche? that directs and maintains the differentiated functions of cells in vivo Presently, there are two main obstacles to stem cell-based regenerative therapies: 1) the limited availability of multi-potent stem cells and 2) the difficulty of selectively controlling the differentiation multi-potent stem cells into the desired cell lineage. Our research group has developed a novel ECM- based cell culture system for expanding multipotent mesenchymal stem cells (MSCs) from bone marrow and 3D silk fibroin scaffolds (SFS) for establishing the SG niche ex vivo. Therefore, we propose to test the hypothesis that salivary gland specific ECM (SG-ECM), established on a natural 3D SFS, is a biomimetic niche capable of directing MSC proliferation and differentiation into functional SG progenitor cells. In Specific Aim 1, we will optimize scaffold characteristics for the production of SG- ECM on the SFS by primary SG epithelial cells. In Specific Aim 2, we will determine whether the optimal SG-ECM coated SFS directs MSC differentiation into the SG cell lineage. In Specific Aim 3, the efficacy of the cells, produced in Specific Aim 2, will be evaluated in an in vivo model of SG damage due to irradiation. The novelty of this proposal includes (1) testing our novel cell culture technology to obtain sufficient numbers of multipotent MSCs from human bone marrow to repair or regenerate SG function; (2) testing a natural 3D scaffold material and optimizing its properties for supporting SG regeneration and tissue engineering; (3) examining the role of SG-derived ECM coated scaffolds in directing MSC differentiation to the SG cell lineage and functional SG units, and (4) assembling a multidisciplinary team to study stem-cell based SG therapy. The success of this study may lead to new therapeutic strategies for clinical management of SG dysfunction.