Modeling Salivary Gland Fibrosis Using a Bioorthogonally Integrated Hydrogel Platform

Non-technical description We take saliva for granted; without it, we will not be able to digest food, maintain dental hygiene or speak normally. This is what many survivors of head and neck cancers and patients with Sjögren’s syndrome, a particular type of autoimmune disease, experience every day: persistent dry mouth. Scientists know that dry mouth is often associated with over-accumulation of interstitial fibrous proteins, a hallmark of tissue fibrosis. However, how the fibrotic environment causes permanent damage to the acinar cells, the saliva producing cells, is not understood. The goal of this project is to develop a lab-grown salivary gland tissue model using artificial matrices created employing highly efficient chemical reactions. Epithelial cells isolated from salivary gland and stromal cells isolated from the supporting connective tissue will be used to build the model. The model will be comprised of spherical epithelial entities held together through cell-cell recognition and individual stromal cells dispersed in the engineered matrix. The living tissue will be subjected to additional chemical transformations to alter its makeup and rigidity, which will convert the healthy stromal cells to abnormal cells with the ability to contract the tissue and deposit excessive fibrous proteins. We will analyze how these changes make epithelial cells cease to produce saliva. Using the engineered tissue model, we will evaluate the potential of therapeutic interventions to reverse fibrosis and restore the secretory function. Integrated with the research effort is an educational plan to engage and empower pre-service, early childhood teachers who will inspire the next generation of scientists. A series of hands-on exhibits, teaching modules, and makers lab activities will be created to prepare students for careers in materials science and biomedical engineering. Technical description Despite advances in treatment strategies, xerostomia (or dry mouth) remains a permanent and devastating disease that broadly affects patients with head and neck malignancies or the Sjögren’s syndrome. Although it is well accepted that the loss of secretory acini is the root cause of xerostomia, there is accumulating evidence underlying the importance of tissue fibrosis in contributing to and sustaining the disease. This application capitalizes on our recent innovations in bioorthogonal chemistry, materials synthesis, and tissue engineering to construct a physiologically relevant tissue model with integrated epithelial and mesenchymal cells, allowing in situ perturbation of the extracellular environment to simulate salivary gland fibrosis due to radiation injury or an aberrant immune system. The proposed model will be comprised of multicellular epithelial assemblies and individual mesenchymal stem cells in a customized synthetic matrix, whose composition and properties can be dynamically tuned to induce fibrogenesis. Using this model, we will investigate how the normal mesenchyme maintains tissue homeostasis, how the fibrotic microenvironment alters the phenotype and organization of the epithelial cells, and whether therapies targeting tissue fibrosis can lead to the restoration of the secretory function. The proposed research activity will not only contribute to the education of the next generation of scientists and engineers, but also empower early childhood teachers. Concerted efforts will be dedicated to the creation of discovery-based teaching methods, lab-based research modules and community-based design and innovation activities. The interdisciplinary nature of the proposed research and educational efforts will also equip graduate students with up-to-date information, experimental skills, and creative thinking that are all indispensable in maintaining the United States’ global competitiveness. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.