Keynote Address: Deconstruction and Construction of a Salivary Gland

An artificial salivary gland that could directionally produce saliva could drastically improve the quality of life for millions of patients suffering from salivary gland hypofunction. Objective: To engineer an artificial salivary gland it will be necessary to understand how to produce a polarized cell monolayer to achieve directional secretion. Method: Using siRNAs and wild type and dominant negative adenoviral constructs to interfere with activity of the apicobasal polarity protein, PAR-1b/MARK2/ EMK1, we examined a role for PAR-1b in maintenance of polarity. Western analysis was used to examine protein levels of basement membrane proteins and apical proteins, while confocal imaging of whole mount tissues was used to examine protein localization at the apical and basal sides of cells. We used quantitative image analysis methods to assay for effects on branching morphogenesis. Results: Either overexpression of wild type PAR-1b or knockdown of Par-1b is required for optimal branching morphogenesis. We determined that PAR1b is required for deposition of basement membrane at the basal surfaces in developing submandibular gland via regulation of basement membrane expression levels and regulation of their deposition. Appropriately positioned basement membrane was required for establishment of the apical membrane. Conclusion: Par-1b is required for the establishment of basement membrane and of the apical membrane in early developing salivary glands. Future studies will examine the functional significance of Par-1b in establishment of functional monolayers of acinar cells in engineered organs.