Tissue engineering a salivary biological system

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The importance of this work is for the half-million of new head/neck cancer patients yearly with radiotherapy sequelae and also for 250 million Sjögren's syndrome patients worldwide. These patients experience considerable morbidity and discomfort such as dry mouth, tooth decay, oral infection and reduced food intake. There is currently no available adequate treatment when salivary cells are replaced by fibrotic tissue. Current knowledge on human salivary gland (SG) at the tissue-, cellular- and molecular-level comes from animal models, cell lines and patient biopsies, which despite their importance can only provide indirect evidence on how human SG can function and repair in real-time during health and disease. The challenge in building SG tissues is to expand fluid-secreting cells and to supply them with a supporting scaffold. The principal goal of our 5-year research is to engineer a healthy physiological salivary system to study human SG function ex vivo. We propose 3 specific aims. The expected outcome is to offer ex vivo models of engineered human salivary tissue at selected cellular organizational levels that will also benefit research in physiology, radiation biology, stem cell, drug screening, cell/ tissue engineering, and biomaterials. Our long-term goal is to engineer/ assemble a SG for patients with severe dry mouth.***Aim 1: Expansion of human salivary organoids. We recently show that recycled tissue digests can be used as “native scaffolds”. Interestingly, we also uncover that gentler enzymatic digestion result in 3D-salivary organoids that preserve their function, proliferation and basement membrane. We hypothesize that, by keeping an optimal 3D-configuration and matrix protein around organoids, acinar cells will expand efficiently. We will test this hypothesis with different enzymatic types, combinations and concentrations to optimize cell proliferation and organoid size, and then seed them on native scaffolds attached to microscope slides, or in human-made 3D-gels, for time-lapse studies.***Aim 2: Ex vivo SG tissue model. We recently establish a human SG 3D-organotypic slice culture model (50-100 um thick) with an intact native extracellular matrix (ECM) that maintains acini function for 14 days. We will use this tissue model to test if transplanted subpopulations of salivary cells can integrate/ assemble into an intact native tissue. Confocal microscopy will track cell migration and engraftment while drug-stimulated assays will measure fluid and protein secretion.***Aim 3: Bioprinting a 3D salivary construct. We recently uncover translucent “egg yolk plasma” (EYP) as an inexpensive gel, yet effective in recapitulating in-vivo conditions. We will test the hypothesis that fine tuning EYP physical properties (stiffness, gelation) allows to 3D print rapidly and position selectively SG cells. Time-lapse microscopy will evaluate human SG cells expansion.**