Differential Sorting of Human Parathyroid Hormone After Transduction of Mouse and Rat Salivary Glands

Abstract

Gene transfer to salivary glands leads to abundant secretion of transgenic protein into either saliva or the bloodstream. This indicates significant clinical potential, depending on the route of sorting. The aim of this study was to probe the sorting characteristics of human parathyroid hormone (hPTH) in two animal models for salivary gland gene transfer. PTH is a key hormone regulating calcium levels in the blood. A recombinant serotype 5 adenoviral vector carrying the hPTH cDNA was administered to the submandibular glands of mice and rats. Two days after delivery, high levels of hPTH were found in the serum of mice, leading to elevated serum calcium levels. Only low amounts of hPTH were found in the saliva. Two days after vector infusion into rats, a massive secretion of hPTH was measured in saliva, with little secretion into serum. Confocal microscopy showed hPTH in the glands, localized basolaterally in mice and apically in rats. Submandibular gland transduction was effective and the produced hPTH was biologically active in vivo. Whereas hPTH sorted toward the basolateral side in mice, in rats hPTH was secreted mainly at the apical side. These results indicate that the interaction between hPTH and the cell sorting machinery is different between mouse and rat salivary glands. Detailed studies in these two species should result in a better understanding of cellular control of transgenic secretory protein sorting in this tissue.

Gene delivery in salivary glands: From the bench to the clinic

“…Over the last ~15 years we have studied the concept of employing salivary glands as a surrogate endocrine organ using several model human proteins, including α-1-antitrypsin (α1AT), erythropoietin (Epo), growth hormone (GH) and parathyroid hormone (PTH) [4,7,12, 23,24]. While results with α1AT and GH have been relatively straightforward, studies with Epo and PTH were not predictable, with differences in their secretory behavior occurring between certain species and gland types [e.g., 12,23–27].…”

Probing the Role of the Actin Cytoskeleton During Regulated Exocytosis by Intravital Microscopy

“…IVM relies on the use of fluorescently tagged proteins that can be either expressed in adult animals or introduced into mouse germ lines. In adult animals, genes can be delivered to selected organs using different approaches: One example being the administration of transgenes to the rat submandibular salivary glands through the salivary duct (Wharton’s duct) by using either non-viral or viral methods [13, 14]. Focusing specifically on non-viral delivery, we express fluorescently-tagged Lifeact in the acinar cells by mixing plasmid DNA with polyethyleneimine (PEI), a molecule extensively used for in vivo siRNA delivery [15].…”

Expression and Secretion of Human Proinsulin-B10 from Mouse Salivary Glands: Implications for the Treatment of Type I Diabetes Mellitus

“…SG cells can also secrete protein into the circulation via their basolateral membranes, which is thought to occur via the constitutive secretory pathway (CSP) [6], [7]. Although the route of secretion for transgenic proteins is not entirely predictable in vivo , we have shown that vectors targeted to the SG can lead to secretion of therapeutic levels of many transgenic proteins, such as growth hormone [8], parathyroid hormone [9], erythropoietin [10] and glucagon-like peptide-1 (GLP-1) [2] via the CSP as a potential treatment for endocrine disorders.…”