Identification and culture of functional salivary gland ductal epithelial cells.

Sialadenitis is a prevalent salivary gland disease resulting in decreased salivary flow rate. To date, little is known about the exact changes and mechanism of ductal cells in sialadenitis. This study aims to establish an efficient method to identify and isolate ductal cells, thereby facilitating further research on this specific cell type. Immunofluorescence for cytokeratin 13 and cytokeratin 19 was conducted in salivary glands to confirm their specificity as ductal cell markers. The dissected ducts were assessed through PCR and Western blot of cytokeratin 19 and digested by dispase and collagenase. The functionality of the isolated ductal cells was determined by measuring intracellular calcium. Cytokeratin 19 and cytokeratin 13 were expressed in all segments of human ducts. Cytokeratin 19 was limited to ducts excluding granular convoluted tubules in rat and mouse. The purities of the obtained ductal cells were approximately 98% in humans and 93% in rats. Furthermore, intracellular free calcium increased with time and concentration of carbachol treatment. Cytokeratin 19 serves as a dependable marker for identifying ductal cells in salivary glands, except for granular convoluted tubules. Moreover, we have successfully developed an efficient method for isolating ductal cells from salivary glands.

The intact parasympathetic nerve promotes submandibular gland regeneration through ductal cell proliferation.

OBJECTIVES: Salivary gland regeneration is closely related to the parasympathetic nerve; however, the mechanism behind this relationship is still unclear. The aim of this study was to evaluate the relationship between the parasympathetic nerve and morphological differences during salivary gland regeneration. MATERIALS AND METHODS: We used a duct ligation/deligation-induced submandibular gland regeneration model of Sprague-Dawley (SD) rats. The regenerated submandibular gland with or without chorda lingual (CL) innervation was detected by haematoxylin-eosin staining, real-time PCR (RT-PCR), immunohistochemistry and Western blotting. We counted the number of Ki67-positive cells to reveal the proliferation process that occurs during gland regeneration. Finally, we examined the expression of the following markers: aquaporin 5, cytokeratin 7, neural cell adhesion molecule (NCAM) and polysialyltransferases. RESULTS: Intact parasympathetic innervation promoted submandibular gland regeneration. The process of gland regeneration was significantly repressed by cutting off the CL nerve. During gland regeneration, Ki67-positive cells were mainly found in the ductal structures. Moreover, the expression of NCAM and polysialyltransferases-1 (PST) expression in the innervation group was significantly increased during early regeneration and decreased in the late stages. In the denervated submandibular glands, the expression of NCAM decreased during regeneration. CONCLUSIONS: Our findings revealed that the regeneration of submandibular glands with intact parasympathetic innervation was associated with duct cell proliferation and the increased expression of PST and NCAM.

MMP-9 Inhibition Suppresses Interferon-γ-Induced CXCL10 Production in Human Salivary Gland Ductal Cells.

Gene expression profiling of lip salivary gland (LSG) has shown that C-X-C motif chemokine 10 (CXCL10) and matrix metalloproteinase 9 (MMP9) expression is upregulated in primary Sjögren's syndrome (pSS) patients. Although CXCL10 and MMP-9 are both associated with pSS pathogenesis, the potential relationship between these two factors has not been investigated. In this study, we used LSG sections from pSS patients and human salivary gland cell lines to investigate the relationship between CXCL10 and MMP-9. Immunofluorescence analyses revealed that CXCL10 and MMP-9 were co-expressed in the LSG of pSS patients, particularly in expanded ductal cells. Furthermore, RT-qPCR analyses on human salivary gland ductal NS-SV-DC cells confirmed that CXCL10 expression was induced by interferon (IFN)-γ, whereas that of MMP9 was stimulated by IFN-α, tumor necrosis factor-α, and interleukin-1ß. Remarkably, MMP-9 inhibition in IFN-γ-stimulated NS-SV-DC cells significantly decreased CXCL10 mRNA and secreted protein levels. Further analyses established that MMP-9 inhibition in IFN-γ-stimulated NS-SV-DC cells decreased STAT1 phosphorylation and hence suppressed IFN-γ signaling. Collectively, these results suggest that in addition to its reported role in the destruction of acinar structures, MMP-9 is involved in the IFN-γ-induced production of CXCL10 in pSS lesions. We believe that our findings open the door to the development of novel treatments for pSS, based on the modulation of MMP-9 activity.

Sox9 regulates the luminal stem/progenitor cell properties of salivary glands.

Exocrine glands share a common morphology consisting of ductal, acinar, and basal/myoepithelial cells, but their functions and mechanisms of homeostasis differ among tissues. Salivary glands are an example of exocrine glands, and they have been reported to contain multipotent stem cells that differentiate into other tissues. In this study, we purified the salivary gland stem/progenitor cells of adult mouse salivary glands using the cell surface marker CD133 by flow cytometry. CD133+ cells possessed stem cell capacity, and the transplantation of CD133+ cells into the submandibular gland reconstituted gland structures, including functional acinar. CD133+ cells were sparsely distributed in the intercalated and exocrine ducts and expressed Sox9 at higher levels than CD133- cells. Moreover, we demonstrated that Sox9 was required for the stem cell properties CD133+ cells, including colony and sphere formation. Thus, the Sox9-related signaling may control the regeneration salivary glands.

Simultaneous Fluorescence and Phosphorescence Lifetime Imaging Microscopy in Living Cells.

In living cells, there are always a plethora of processes taking place at the same time. Their precise regulation is the basis of cellular functions, since small failures can lead to severe dysfunctions. For a comprehensive understanding of intracellular homeostasis, simultaneous multiparameter detection is a versatile tool for revealing the spatial and temporal interactions of intracellular parameters. Here, a recently developed time-correlated single-photon counting (TCSPC) board was evaluated for simultaneous fluorescence and phosphorescence lifetime imaging microscopy (FLIM/PLIM). Therefore, the metabolic activity in insect salivary glands was investigated by recording ns-decaying intrinsic cellular fluorescence, mainly related to oxidized flavin adenine dinucleotide (FAD) and the µs-decaying phosphorescence of the oxygen-sensitive ruthenium-complex Kr341. Due to dopamine stimulation, the metabolic activity of salivary glands increased, causing a higher pericellular oxygen consumption and a resulting increase in Kr341 phosphorescence decay time. Furthermore, FAD fluorescence decay time decreased, presumably due to protein binding, thus inducing a quenching of FAD fluorescence decay time. Through application of the metabolic drugs antimycin and FCCP, the recorded signals could be assigned to a mitochondrial origin. The dopamine-induced changes could be observed in sequential FLIM and PLIM recordings, as well as in simultaneous FLIM/PLIM recordings using an intermediate TCSPC timing resolution.

Stem Cell-Soluble Signals Enhance Multilumen Formation in SMG Cell Clusters.

Saliva plays a major role in maintaining oral health. Patients with salivary hypofunction exhibit difficulty in chewing and swallowing foods, tooth decay, periodontal disease, and microbial infections. At this time, treatments for hyposalivation are limited to medications (e.g., muscarinic receptor agonists: pilocarpine and cevimeline) that induce saliva secretion from residual acinar cells as well as artificial salivary substitutes. Therefore, advancement of restorative treatments is necessary to improve the quality of life in these patients. Our previous studies indicated that salivary cells are able to form polarized 3-dimensional structures when grown on growth factor-reduced Matrigel. This basement membrane is rich in laminin-III (L1), which plays a critical role in salivary gland formation. Mitotically inactive feeder layers have been used previously to support the growth of many different cell types, as they provide factors necessary for cell growth and organization. The goal of this study was to improve salivary gland cell differentiation in primary cultures by using a combination of L1 and a feeder layer of human hair follicle-derived mesenchymal stem cells (hHF-MSCs). Our results indicated that the direct contact of mouse submandibular (mSMG) cell clusters and hHF-MSCs was not required for mSMG cells to form acinar and ductal structures. However, the hHF-MSC conditioned medium enhanced cell organization and multilumen formation, indicating that soluble signals secreted by hHF-MSCs play a role in promoting these features.

Phenotype and cell proliferation activity of duct-like structures in human sublingual glands: a histological and immunohistochemical study.

UNLABELLED: There are several age-related microscopic changes in the salivary glands, including the increase in the number of duct-like structures (DLS). However, the true origin and the phenotype of the DLS are not known. OBJECTIVE: To evaluate the phenotype and the cell proliferation index of the DLS of human sublingual glands. MATERIAL AND METHODS: Sixty sublingual glands obtained from human cadavers were divided into two groups - 0-30 and 61-90 years old. The phenotype was estimated by immunostaining for cytokeratin 19 (CK 19) and the S-100 protein as well as by the presence of mucin and glycogen. The cell proliferation index was determined by the Ki-67 antibody. The histochemical techniques used periodic acid-Schiff (PAS) and Alcian Blue. In each captured microscopic field, the DLS were counted to establish a percentage for the staining profile. The statistical analysis was accomplished using Student's t-test, the Mann-Whitney test and Pearson's correlation coefficient (p<0.05). RESULTS: Comparing both groups, only CK 19 showed a statistically significant difference (p=0.033), with the strongest expression in the elderly group. There was no significant difference between PAS and Alcian Blue (p=0.270). In both groups, the immunostaining for CK 19 was stronger than that for S-100 (p=0.004;p<0.001), but there was no correlation between the two immunomarkers (ρ=-0.163; p=0.315). There was no immunostaining for Ki-67. CONCLUSIONS: DLS demonstrate a ductal phenotypic profile and do not present cell proliferation activity. DLS may represent a regressive process arising from acini or represent the result of metaplasia.

Phenotype and cell proliferation activity of duct-like structures in human sublingual glands: a histological and immunohistochemical study

There are several age-related microscopic changes in the salivary glands, including the increase in the number of duct-like structures (DLS). However, the true origin and the phenotype of the DLS are not known. Objective To evaluate the phenotype and the cell proliferation index of the DLS of human sublingual glands. Material and Methods Sixty sublingual glands obtained from human cadavers were divided into two groups - 0-30 and 61-90 years old. The phenotype was estimated by immunostaining for cytokeratin 19 (CK 19) and the S-100 protein as well as by the presence of mucin and glycogen. The cell proliferation index was determined by the Ki-67 antibody. The histochemical techniques used periodic acid-Schiff (PAS) and Alcian Blue. In each captured microscopic field, the DLS were counted to establish a percentage for the staining profile. The statistical analysis was accomplished using Student's t-test, the Mann-Whitney test and Pearson's correlation coefficient (p<0.05). Results Comparing both groups, only CK 19 showed a statistically significant difference (p=0.033), with the strongest expression in the elderly group. There was no significant difference between PAS and Alcian Blue (p=0.270). In both groups, the immunostaining for CK 19 was stronger than that for S-100 (p=0.004;p<0.001), but there was no correlation between the two immunomarkers (ρ=-0.163; p=0.315). There was no immunostaining for Ki-67. Conclusions DLS demonstrate a ductal phenotypic profile and do not present cell proliferation activity. DLS may represent a regressive process arising from acini or represent the result of metaplasia. .

Localization of cystic fibrosis transmembrane conductance regulator signaling complexes in human salivary gland striated duct cells.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-dependent protein kinase (PKA)-regulated Cl(-) channel, crucial for epithelial cell regulation of salt and water transport. Previous studies showed that ezrin, an actin binding and A-kinase anchoring protein (AKAP), facilitates association of PKA with CFTR. We used immunohistochemistry and immunogold transmission electron microscopy to localize CFTR, ezrin, and PKA type II regulatory (RII) and catalytic (C) subunits in striated duct cells of human parotid and submandibular glands. Immunohistochemistry localized the four proteins mainly to the apical membrane and the apical cytoplasm of striated duct cells. In acinar cells, ezrin localized to the luminal membrane, and PKA RII subunits were present in secretory granules, as previously described. Immunogold labeling showed that CFTR and PKA RII and C subunits were localized to the luminal membrane and associated with apical granules and vesicles of striated duct cells. Ezrin was present along the luminal membrane, on microvilli and along the junctional complexes between cells. Double labeling showed specific protein associations with apical granules and vesicles and along the luminal membrane. Ezrin, CFTR, and PKA RII and C subunits are co-localized in striated duct cells, suggesting the presence of signaling complexes that serve to regulate CFTR activity.

Expression patterns of CD66a and CD117 in the mouse submandibular gland.

The epithelial tissue of the salivary gland consists of the acinar and ductal parts, the latter of which is further divided into the intercalated, striated and excretory duct segments and is the residential site for salivary stem/progenitor cells. In the present study, the expression patterns of two cell surface molecules, CD66a and CD117, were investigated in the adult mouse submandibular glands (SMG) by immunofluorescence microscopy. Combinations of the two molecules differentially marked several types of SMG epithelial cells, including acinar cells (CD66a-intense, CD117-negative), intercalated duct cells (CD66a-intense, CD117-positive), a subset of the striated and excretory duct cells (CD66a-weak, CD117-positive). Most of the CD117-positive ductal cells were negative for cytokeratin 5 and overlapped with the NKCC1-expressing cells. The CD117- and keratin 5-positive cells resided only in the excretory duct were suggested to correspond to the recently identified salivary stem cells. CD66a and CD117 may be useful markers to isolate several cell types consisting of SMG epithelium and to analyze their molecular and cellular nature. Our data also suggest that CD117-expressing epithelial cells of the gland include at least two distinct populations of the stem/progenitor cells.

Expression and functional regulation of the nuclear receptors AHR, PXR, and CAR, and the transcription factor Nrf2 in rat parotid gland.

Nuclear receptors and transcription factors regulate the functions of many genes involved in cellular physiology and pathology (e.g. tumorigenesis and autoimmune diseases). The present study was performed to define the expression and the regulation of aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), constitutive androstane receptor (CAR), and nuclear factor E2-related factor 2 (Nrf2) in the rat parotid gland. Constitutive expression, as well as expression after stimulation with specific inducers for AhR [2,3,7,8-tetrachloro-dibenzylo-p-dioxin (TCDD)], Nrf2(oltipraz), PXR (dexamethasone), and CAR (phenobarbital), was evaluated using the quantitative PCR. Cellular localization of the nuclear receptors and the transcription factor was visualized by immunohistochemical staining. The study revealed constitutive expression of AhR as well as Nrf2, and their induction by TCDD andoltipraz, respectively. Immunohistochemical analysis revealed constitutive, predominantly cytoplasmic, expression of the AhR receptor, especially in interlobular striated duct cells, with nuclear shift upon exposure to TCDD. Inducible expression of Nfr2 was found mainly in the cytoplasm of intralobular striated duct cells. Constitutive expression of PXR and CAR was not found. Bearing in mind the involvement of AhR and Nrf2 in the regulation of many genes, it seems that these factors may play also a role in salivary gland physiology and pathology.

Capsaicin regulates the NF-κB pathway in salivary gland inflammation.

Salivary gland epithelial cells (SGEC) release several cytokines that play important roles in the inflammatory process. In this study, we examined whether capsaicin can modulate cytokine release in SGEC. After cells were stimulated with polyinosinic-polycytidylic acid [poly(I:C)] or lipopolysaccharide (LPS), mRNA transcript and protein levels were detected by reverse-transcriptase-polymerase chain-reaction (RT-PCR), real-time PCR, and enzyme-linked immunosorbent assay (ELISA). These findings demonstrated that the increases in TNFα and IL-6 mRNA transcripts were highest at 3 hrs and 1 hr after incubation with poly(I:C) and LPS, respectively. Pre-treatment of the cells with 10 µµ capsaicin, however, significantly inhibited mRNA transcripts and its protein levels. The simultaneous application of 10 µµ capsazepine with capsaicin did not block the inhibitory effect of capsaicin. Furthermore, the inhibitory effect of capsaicin was also shown in primary cultured cells from TRPV1(-/-) mice. We found that both poly(I:C) and LPS induced IκB-α degradation and phosphorylation, which resulted in NF-κB activation, and capsaicin inhibited this NF-κB pathway. These results demonstrate that SGEC release pro-inflammatory cytokines mediated by TLR, and capsaicin inhibits this process through the NF-κB pathway. This study suggests that capsaicin could potentially alleviate inflammation in salivary glands.

Acidosis-induced V-ATPase trafficking in salivary ducts is initiated by cAMP/PKA/CREB pathway via regulation of Rab11b expression.

Changes in systemic acid-base homeostasis cause a series of organ-specific cellular responses, among them changes of acid-base transporter activities, and recruitment or retrieval of these transporters from intracellular pools to the plasma membrane and vice versa. The purpose of this study was to investigate the impact of protein phosphorylation in the acidosis-induced translocation of vacuolar-type H(+)-ATPase (V-ATPase) in salivary ducts and to identify molecular targets. Therefore, the human submandibular gland cell line HSG was exposed to acidosis and V-ATPase trafficking was investigated in the presence or absence of inhibitors and activators of sAC/PKA and Src/ERK signaling pathways. Putative target genes have been identified by RT-PCR and immunoblotting, and validated by loss-of-function experiments. Acidosis caused activation of cAMP/PKA and Src signaling and inhibition of either pathway significantly impaired acidosis-induced V-ATPase redistribution and incorporation into the plasma membrane. Activation of ERK1/2 was Src-independent, whereas activation of PKA caused phosphorylation of cAMP response element-binding (CREB) and activation to regulate Rab11b transcription. Loss-of-function of CREB down-regulated Rab11b transcript and protein and significantly impaired acidosis-induced V-ATPase translocation in HSG cells. These data demonstrate that the cAMP/PKA/CREB signaling pathway initiates acidosis-induced V-ATPase trafficking in salivary ducts via regulation of Rab11b expression and provide first evidence for a molecular mechanism underlying cAMP/PKA-dependent transporter trafficking that could account for accumulation and activity of transporters in other cellular systems as well.

Induction of Sca-1 via activation of STAT3 system in the duct cells of the mouse submandibular gland by ligation of the main excretory duct.

To examine the very initial step that takes place immediately after tissue injury and is linked to tissue regeneration, we employed the submandibular gland (SMG), which was injured by ligation of its main excretory duct (MED). Ligation of the MED of the SMG in mice induced the expression of Sca-1, a protein marker of hematopoietic stem cells. In the normal gland, a low level of Sca-1 was expressed, which was localized predominantly in the excretory duct cells. At 1 day after ligation, Sca-1 expression increased prominently in almost all of cells in the duct system, but not in the acinar cells. The level of Sca-1 mRNA had begun to increase at 6 h after ligation and continuously rose thereafter until it reached a plateau, which occurred ∼12 h after ligation. STAT3 phosphorylated at its tyrosine-705 (p-STAT3) in the ligated gland increased immediately after ligation, and it was localized in the nuclei of all duct cells. The results of an EMSA revealed the specific binding of a nuclear extract to the sequence of the γ-interferon activation site (GAS) present in the Sca-1 promoter and confirmed that such binding increased after ligation. Thus the present study suggests that STAT3, having been phosphorylated following MED ligation, was transferred to the nucleus, where it bound to the GAS element in the promoter of Sca-1 gene, resulting in promotion of Sca-1 gene expression. Actual prevention of STAT3 phosphorylation reduced the ligation-induced Sca-1 elevation.

Salivary gland progenitor cell biology provides a rationale for therapeutic salivary gland regeneration.

An irreversible loss of salivary gland function often occurs in humans after removal of salivary tumors, after therapeutic radiation of head and neck tumors, as a result of Sjögren's syndrome and in genetic syndromes affecting gland development. The permanent loss of gland function impairs the oral health of these patients and broadly affects their quality of life. The regeneration of functional salivary gland tissue is thus an important therapeutic goal for the field of regenerative medicine and will likely involve stem/progenitor cell biology and/or tissue engineering approaches. Recent reports demonstrate how both innervation of the salivary gland epithelium and certain growth factors influence progenitor cell growth during mouse salivary gland development. These advances in our understanding suggest that developmental mechanisms of mouse salivary gland development may provide a paradigm for postnatal regeneration of both mice and human salivary glands. Herein, we will discuss the developmental mechanisms that influence progenitor cell biology and the implications for salivary gland regeneration.

Microchimerism in salivary glands after blood- and marrow-derived stem cell transplantation.

Blood- and marrow-derived stem cells (BMDSCs) provide disease-ameliorating effects for cardiovascular and autoimmune diseases. Microchimerism from donor BMDSCs has been reported in several recipient tissues. We hypothesized that this finding suggests a potential use of BMDSCs in the treatment of salivary dysfunctions. We investigated the presence of Y chromosome-positive cells in salivary gland biopsies of 5 females who had received a marrow or blood stem cell transplant from male donors. One to 16 years after transplantation, all recipients exhibited scattered Y chromosome-positive cells in the acini, ducts, and stroma of their salivary glands (mean of 1.01%). Potentially, these cells can be markers of transplantation tolerance, contribute to neoplastic epithelial tissues, or engraft at sites of injury. In addition, transplantation of BMDSCs could be used for treatment of Sjögren's syndrome and salivary glands damaged by therapeutic irradiation for cancers of the head and neck.

Lumen formation in salivary gland development.

During salivary gland morphogenesis, the developing ducts and acini must hollow out to form lumina which will eventually allow the free passage and modification of saliva on its journey from acini to oral cavity. The molecular mechanisms that participate in the creation of this tubular structure are of great research interest. Histological studies show that lumen formation begins during the mid stages of branching morphogenesis. At this stage, apoptotic cells are detectable in the developing salivary ducts at sites where lumina are forming, suggesting that programmed cell death is instrumental in clearing the luminal space. The formation of cell-cell junctions between the epithelial cells lining the space is also an integral part of lumen formation, since these junctions form a barrier around the lumen and allow the surfaces of the lumen-lining cells to become specialized. This chapter will discuss the mechanisms involved in salivary gland lumen formation during development, and draw on the most recent research in this interesting field.

Lumen formation in three-dimensional cultures of salivary acinar cells.

OBJECTIVE: Development of an artificial salivary gland will benefit patients with xerostomia after radiation therapy for upper respiratory cancer. The goal is to devise a three-dimensional (3D) culture system in which salivary cells differentiate into polarized acini that express essential biomarkers and directionally secrete alpha-amylase. Differentiated acini-like structures in a 3D biomaterial-based scaffold will mimic salivary gland functions. STUDY DESIGN: Cells were seeded onto HA-based hydrogels containing PlnDIV peptide and allowed to differentiate into acini-like structures. Cell viability and phenotype were examined. SETTING: Laboratory-based tissue procurement study. SUBJECTS AND METHODS: Salivary gland tissue was obtained from patients undergoing surgery. Marker expression established the phenotype of salivary gland cells. Perlecan/HSPG2, an important component of the basement membrane, was highly expressed in salivary gland tissue. A culture system consisting of hyaluronic acid (HA) hydrogel and a coupled bioactive peptide derived from domain IV of perlecan (PlnDIV) was used. Prior studies demonstrated differentiation of acinar cells into lobular structures that mimicked intact glands when cultured on PlnDIV peptide-coated surfaces. RESULTS: Lobular acini-like structures formed on hydrogels and expressed tight junction components such as zona occludens 1. Acini-like structures were stained for the presence of alpha-amylase. Live/dead staining revealed the presence of apoptotic cells in the center of the acini-like structures, indicative of lumen formation. CONCLUSION: A novel system supporting acini-like assembly in a 3D culture system was established. Presence of biomarkers and secretion of salivary enzymes confirms functionality in vitro. Future experiments will test the 3D system in an animal model.

Trefoil factor family 3 expression in the oral cavity.

This study examined the expression, in oral keratinocytes and in the major and minor salivary glands, of Trefoil factor family 3 (TFF3) peptide. Trefoil factor family 3 messenger RNA (mRNA) and peptide were detected in cultures of normal oral keratinocytes by quantitative real-time polymerase chain reaction (PCR) and western blotting, respectively. Trefoil factor family 3 was found, by immunohistochemical analyses, to be expressed in the basal layers of the oral mucosal epithelium. In salivary glands, immunohistochemical staining showed that TFF3 peptide expression was strongest in the mucous acini of the submandibular and the small salivary glands. Serous cells in the same glands showed weak staining. In the parotid gland, many serous acini showed weak positive staining, while other areas did not. In all glands examined, the intercalated, striated, and collecting ducts were moderately TFF3-positive. Double immunostaining confirmed that mucous (MUC5B positive) cells were moderately or strongly positive for TFF3 and that some serous (MUC7 positive) cells showed restricted TFF3 expression, mostly in a granular pattern. The prevalence of the TFF3 peptide in the salivary secretions of healthy volunteers was detected by western blotting of saliva from minor salivary glands (four of five) and the parotid gland (one of five) and of mixed submandibular/sublingual saliva (five of five). In conclusion, the submandibular and small salivary glands appear to be the major producers of oral TFF3, but duct cells of all glands and keratinocytes of the oral mucosa may also contribute as sources of TFF3 in the oral cavity.

Distribution of tenascin-C, fibronectin and collagen types III and IV during regeneration of rat submandibular gland.

The aim of this study was to determine the localization of tenascin-C, fibronectin and collagen types III and IV during regeneration of the rat submandibular gland. After 7 days' obstruction, the regenerating glands were collected at days 0, 1, 3, 5, 7, 11 and 14 after duct release to study regeneration. Immunohistochemical staining revealed that tenascin-C was strongly expressed in the epithelial cells of duct-acinar structures at days 0-3, and down-regulated in its expression from day 5 to 11, though weak expression was detected in the intercalated duct and acinar cells of the normal gland. Strong labeling of fibronectin was detected around duct-acinar structures during days 0-3 of regeneration. Type IV collagen was expressed strongly in the thickened basement membrane of acinar cells and duct-acinar structures during days 0-3, but weakly around large ducts, though type III collagen was expressed at consistent levels. These findings suggest that tenascin-C and fibronectin affect only the duct-acinar structures, and type IV but not type III collagen is involved in the regeneration of acinar cells.