Reengineering salivary gland cells to enhance protein secretion for use in developing artificial salivary gland...

Salivary glands (SGs) are considered exocrine glands, which mainly secrete water into the oral cavity. Nevertheless, they also exhibit a smaller endocrine secretory pathway toward the bloodstream. The concept of an artificial SG device for exocrine fluid secretion into the oral region in xerostomic patients has been previously studied. The purpose of the current study was to examine the potential of such a device for enhancing bioactive protein secretion. We engineered a plasmid encoding a SG-specific signal peptide sequence adjacent to a normally nonsecreted encoded reporter gene creating a chimera protein, and examined if this construct can enhance secretion from salivary epithelial cells. An N-terminal encoding epidermal growth factor (EGF) sequence was synthesized and inserted into a pGL3 control vector 5' of a firefly luciferase gene, creating a pGL3-EGF signal peptide (pGL3-EGFSP) fused vector. This vector was cotransfected with a pRL-CMV vector containing a Renilla luciferase gene, in 293 cells (serving as controls), and human submandibular gland ductal epithelial (HSG), rat submandibular gland acinar epithelial (SMIE), and rat submandibular gland ductal epithelial (A5) salivary cell lines. The transfected 293, SMIE, and HSG cells showed 8-, 18-, and 40-fold higher luciferase activity, respectively. These observations lead to the concept of an envisioned secretory device, which can serve as a potential biological pump for bioactive proteins.