TGFβR Inhibition Represses TGF-β1 Initiated Keratin-7 Expression in Human Salivary Gland Progenitor Cells

Abstract

Towards the goal of engineering an implantable salivary gland for the treatment of xerostomia, we culture primary human salivary gland stem/progenitor cells (hS/PCs) in hyaluronic acid (HA)-based hydrogels containing a covalently conjugate integrin-binding peptide (RGDSP). We characterize how RGDSP affects hS/PC phenotype and discover the presence of cells expressing both amylase and keratin-7 (K7) in our 3D cultures. Typically, amylase is expressed by acinar cells, and K7 is found in ducts. After assaying an array of transforming growth factor-β (TGF-β) superfamily members, we find increased expression of TGF-β1 and growth/differentiation factor-15 (GDF-15) in RGDSP cultures. However, 2D model studies confirm that only TGF-β1 is required to induce K7 expression in hS/PCs. We then demonstrate that with pharmacological inhibition of TGF-β signaling, K7 expression is repressed while amylase expression is maintained in RGDSP cultures. Thus, TGF-β signaling regulates K7 expression in hS/PCs, and modulation of TGF-β signaling is essential for the regeneration of salivary gland function.