Growth factor regulation of the amylase promoter in a differentiating salivary acinar cell line

Abstract

Salivary glands contain two major epithelial cell types: acinar cells which produce the primary salivary secretion, including amylase, and ductal cells which reabsorb electrolytes but also secrete kallikrein. Here we investigated salivary acinar cell differentiation in vitro using the activity of the salivary amylase and tissue kallikrein promoters as markers of acinar cell and ductal cell differentiation, respectively. Each of the promoter sequences was cloned into a replication-deficient adenoviral vector containing the luciferase reporter gene. Previous studies showed that a human submandibular gland cell line (HSG) differentiated into acinar cells when cultured on a reconstituted basement membrane matrix (Matrigel). The luciferase activity of the amylase promoter vector (AdAMY-luc) was low in HSG cells cultured on plastic, where they grow as an epithelial monolayer. The promoter activity increased approximately tenfold when HSG cells were cultured on Matrigel and developed an acinar phenotype. Under the same conditions, the luciferase activity of the kallikrein promoter (AdKALL-luc) was not induced. Because HSG cells demonstrate acinar cell morphology, but not amylase gene expression, when cultured on laminin-1, certain soluble components of Matrigel were tested for their ability to induce the amylase promoter during in vitro differentiation of acinar cells. We find that epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), which are present in the basement membrane, and hepatocyte growth factor (HGF) increase activity of the amylase promoter. Other basement membrane-derived growth factors such as TGF-beta, basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PGDF), as well as tumor necrosis factor (TNF-alpha), keratinocyte growth factor (KGH), nerve growth factor (NGF) and interferon gamma (IFN-gamma) were inactive. This system will be further exploited to study the mechanisms by which extracellular matrix molecules and growth factors regulate salivary acinar cell differentiation.

Abnormal basement membrane type IV collagen α‐chain composition in labial salivary glands in Sjögren's syndrome

“…Not only was Ln-111 topologically restricted to the acinar compartment in healthy glands, it was also lacking in the acinar compartment in the labial salivary glands of patients with SS (7). This is in accordance with findings obtained using the in vitro HSG-Matrigel culture system, in which the laminin ␣1 chain has been shown to be essential to intercalated duct cell-to-acinar cell differentiation (9)(10)(11)(12)(13)(14). Type IV collagen ␣-chains do not seem to provide a similar differentiation signal.…”

“…These cells, when grown on growth and differentiation factor-depleted basement membranelike extracellular matrix, transdifferentiate into acinar cells, which start to express salivary amylase, cystatin C, and other acinar cell markers (9)(10)(11)(12)(13)(14)(15). At the same time, they aggregate to clusters, in which the central cells that are not in contact with basement membrane undergo apoptosis, so that an elementary acinar lumen is formed.…”

Growth Factors Polymerized Within Fibrin Hydrogel Promote Amylase Production in Parotid Cells

“…1E-H). Although Matrigel has been used previously to grow salivary cells, [22][23][24][31][32][33][34] it has been a challenge to maintain cell differentiation, determined by normal cellular function and maintenance of amylase expression, with time in culture. In this study, both single Par-C10 (Fig.…”

“…40 GFR-MG contains six growth factors, four of which have been demonstrated to induce no increase in the amylase promoter activity (i.e., bFGF at 0.1 ng/mL, PDGF at < 5 ng/ mL, NGF at < 0.2 ng/mL, and TGFb at 1.7 ng/mL). 31,34 Of the two remaining growth factors, one (EGF at < 0.5 ng/mL) was shown to increase the acinar cell-specific amylase promoter activity. 31,34 The other (IGF-1 at 5 ng/mL) was not tested in the cited studies (for reasons not stated by the researchers).…”

Parotid Secretory Granules: Crossroads of Secretory Pathways and Protein Storage

“…In general, these cell lines are not as highly differentiated as the native tissue, but they do provide insight into aspects of salivary physiology when used appropriately. As an example, the human submandibular gland (HSG) cell line is not highly differentiated under standard culture conditions, but the cells differentiate to a more acinar-like cell type when cultured on matrigel (Royce et al, 1993;Hoffman et al, 1998;Zheng et al, 1998;Jung et al, 2000). The differentiated cells grow in acinar-like structures and support the induction of the amylase promoter by growth factors, as measured by the expression of a reporter protein.…”