Expression of heat shock protein 27 with the transition from proliferation to differentiation of acinar precursor cell in regenerating submandibular gland of rats

Microanatomical, histochemical and morphometric features of the major and selected minor salivary glands in laboratory Wistar rat

The major and minor salivary glands are responsible for saliva production, a fluid drained in the oral cavity that will be involved in several functions at this level. The present study aimed to compare the microanatomy of the major (parotid, mandibular, sublingual) and minor salivary glands (von Ebner's and Weber's) of the Wistar rat, from a histological, histochemical and morphometrically point of view. Predominantly serous glands (parotid, mandibular and von Ebner's) showed differences in the secretion composition on both PAS and alcian blue reactions. The same observations were identified also for the mostly mucous salivary glands (sublingual and Weber). In terms of surface dimensions, the measurements suggested that the mucous acini have a greater surface compared with the serous ones, and, at the same time, a better-represented polymorphism. In conclusion, the major and minor salivary glands in Wistar rats, a commonly used species in experimental procedures, showed similarities with other species including humans, but some structural traits are breed-specific, this finding is very important for an extensive understanding of the morphophysiology of the salivary glands.

Salivary Glands after Prolonged Aluminum Exposure: Proteomic Approach Underlying Biochemical and Morphological Impairments in Rats

Aluminum (Al) is one of the most abundant elements on Earth, and its high extraction rate and industrial use make human exposure very common. As Al may be a human toxicant, it is important to investigate the effects of Al exposure, mainly at low doses and for prolonged periods, by simulating human exposure. This work aimed to study the effects of low-dose exposure to chloride aluminum (AlCl₃) on the oxidative biochemistry, proteomic profile, and morphology of the major salivary glands. Wistar male rats were exposed to 8.3 mg/kg/day of AlCl₃ via intragastric gavage for 60 days. Then, the parotid and submandibular glands were subjected to biochemical assays, proteomic evaluation, and histological analysis. Al caused oxidative imbalance in both salivary glands. Dysregulation of protein expression, mainly of those related to cytoarchitecture, energy metabolism and glandular function, was detected in both salivary glands. Al also promoted histological alterations, such as acinar atrophy and an increase in parenchymal tissue. Prolonged exposure to Al, even at low doses, was able to modulate molecular alterations associated with morphological impairments in the salivary glands of rats. From this perspective, prolonged Al exposure may be a risk to exposed populations and their oral health.

Wound healing after applying a gelatin-based hydrogel sheet to resected rat submandibular gland

The present study was done to develop a useful experimental model for analysis of the effects of physiologically active substances on atrophy and regeneration of salivary gland acinar cells. Resection wounds (diameter, 3 mm) were made in the submandibular glands of 8-week-old Wistar rats (n = 24) for histochemical examination on Days 3, 5, 7, 10, 14, and 21 after implantation of a gelatin-based hydrogel sheet. The results showed that the sheet had nearly disappeared by Day 10. Regions around the resection wounds were classified as normal, atrophic, or necrotic. In atrophic regions, acinar cells atrophied after resection, and few acinar cells were observed on Day 7. On Days 5-7, striated and granular ducts resembled duct-like structures. On Day 10, newly formed acinar cells were confirmed by increased periodic acid-Schiff staining, and a greater number of mature cells was present thereafter. In necrotic regions, acinar and ductal cells were destroyed, and scattered enucleated acinar cells and duct-like structures were present, on Day 3; newly formed acinar cells were observed on Day 10. Thus, the experimental model demonstrated atrophy and regeneration of the submandibular gland and enabled analysis of the effects of sustained release of physiologically active substances contained within an implanted sheet.

Treatment of human neuroblastoma cell line SH-SY5Y with HSP27 siRNA tagged-exosomes decreased differentiation rate into mature neurons

Heat shock proteins (HSPs) participate in the regulation of different cell activities in response to stimuli. By applying different strategies, the modulation of heat shock proteins is at the center of attention. Conventional delivery approaches are not fully encouraged due to cytotoxicity and immunogenicity issues. Exosomes are touted as bio-shuttles for delivery of distinct biomolecules inside the cells. Here, we aimed to HSP27 small interfering RNA (siRNA)-tagged exosomes for the inhibition of Hsp27 in human neuroblastoma cell line SH-SY5Y and explored differentiation into neuron-like cells. Exosomes were isolated, characterized by scanning electron microscope (SEM) and CD63 then enriched with siRNA against Hsp27. Neuroblastoma cells were incubated with exosomes carrying siRNA for 48 hr. Exosome uptake was monitored by immunofluorescence assay. The cell viability and proliferation were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and bromodeoxyuridine/5-bromo-2'-deoxyuridine incorporation assays. The ability of cells to form colonies was evaluated by clonogenic assay. The cell potential to express NeuN, a mature neuron factor, was studied by flow cytometry analysis. SEM showed the nano-sized particles and a high level of CD63 after enrichment. Immunofluorescence imaging revealed an appropriate transfection rate in cell exposed to Hsp27 siRNA tagged exosomes. The cell viability and proliferation were reduced compared to cells received nude exosomes ( p < 0.05). Clonogenic activity of cells was diminished by the inhibition of Hsp27. Flow cytometry analysis revealed that the inhibition of Hsp27 prohibited NeuN content, showing the maturation of SH-SY5Y cells to mature cells compared to control. These data confirmed that exosomes could be used as appropriate bio-shuttles for the inhibition of Hsp27-aborted cell differentiation toward mature neuron.

Expression of c-kit and Cytokeratin 5 in the Submandibular Gland after Release of Long-Term Ligation of the Main Excretory Duct in Mice

Long-term submandibular duct obstruction is thought to cause irreversible atrophy and dysfunction of the submandibular gland. As an atrophic gland may be induced clinically by chronic or recurrent infection, it is generally removed surgically. However, the regenerative capacity of atrophic submandibular glands after long-term obstruction is not completely understood. We studied the regenerative capacity of the mouse submandibular duct using an aneurysm clip ligation model. We documented changes in the size, histologic structure and gene expression of the submandibular gland after 2 months of ligation, and 1 week, 1 month and 2 months after clip removal. Two months of ligation caused atrophy, particularly in the acinar portion. In the 2 months after clip removal, we observed a steady and significant increase in the expression of the acinar cell precursor gene cytokeratin 5 (CK5), and a significant decrease in the expression of the stem cell marker c-kit. These findings suggest that the submandibular gland retains some capacity for regeneration even after long-term obstruction, and that CK5 could serve as a marker of this regenerative process.

Localization of hsp27 in the rat submandibular gland following the application of various surgical treatments

Salivary glands repair and regenerate following various types of injuries and surgical procedures. However, the tissue responses induced in the contralateral glands have yet to be elucidated in detail. Hsp27, a member of the heat-shock protein (Hsp) family, is strongly expressed in physiological environments, particularly during development. Hsp27 was previously shown to play a role in the regulation of acinar cell proliferation and differentiation in the rat submandibular gland. The present study performed the following surgical treatments on the right submandibular glands of adult rats: 1) duct ligation followed by unligation after one week; 2) partial sialoadenectomy; and 3) total sialoadenectomy. Immunohistochemistry for Hsp27 and Ki67 was performed in the experimental and normal contralateral glands, and localization was histologically and morphometrically analyzed. The results obtained revealed the localization of Hsp27 to the intercalated duct in the submandibular glands of non-treated rats. The expression of Hsp27 was strongly induced in both the uninjured contralateral control glands as well as treated glands of experimental rats regardless of the surgical procedure performed. The number of Hsp27-immunopositive cells increased rapidly following surgery, and subsequently returned to the same level as that in non-treated rats after 4 weeks. However, no marked changes were observed in the number of Ki67-immunopositive proliferating cells. Therefore, the change in the number of Hsp27-immunopositive cells may have contributed to compensatory hypertrophy. The results of the present study indicate that the expression of Hsp27 in the intercalated duct in the submandibular gland may play a role in the differentiation of acinar cells.

Hsp27 (HSPB1) differential expression in normal salivary glands and pleomorphic adenomas and association with an increased Bcl2/Bax ratio

Pleomorphic adenoma (PA) is the most common salivary gland neoplasm. The Hsp27 (HSPB1) is an antiapoptotic protein whose synthesis follows cytotoxic stresses and result in a transient increase in tolerance to subsequent cell injury. Although Hsp27 is expressed in a range of normal tissues and neoplasms, a wide variation in its expression exists among different cells and tissues types. In certain tumours of glandular origin (such as oesophageal adenocarcinomas), the level of Hsp27 is decreased. In the present study, Hsp27 protein levels were evaluated by enzyme-linked immunosorbent assay (ELISA) in a set of 18 fresh PA and 12 normal salivary gland samples. In addition, we tested if Hsp27 protein levels correlated with p53 expression and cell proliferation index, as well as with the transcriptional levels of Bcl-2-associated X protein (BAX), B cell lymphoma 2 (BCL2) and Caspase 3 in PA. We further tested the association between Hsp27 expression and PA tumour size. While all normal salivary gland samples expressed Hsp27 protein, only half of the PA samples expressed it, resulting in a reduced expression of Hsp27 in PA when compared with normal salivary glands (P = 0.003). The expression levels of this protein correlated positively with a higher messenger ribonucleic acid (mRNA) ratio of Bcl2/Bax (R = 0.631; P = 0.01). In conclusion, a decreased Hsp27 protein expression level in PA was found. In addition, Hsp27 levels correlated positively with the Bcl2/Bax mRNA ratio, suggesting an antiapoptotic effect.

Negative regulation of NADPH oxidase 4 by hydrogen peroxide-inducible clone 5 (Hic-5) protein

Hydrogen peroxide-inducible clone 5 (Hic-5) is a focal adhesion adaptor protein induced by the profibrotic cytokine TGF-β1. We have demonstrated previously that TGF-β1 induces myofibroblast differentiation and lung fibrosis by activation of the reactive oxygen species-generating enzyme NADPH oxidase 4 (Nox4). Here we investigated a potential role for Hic-5 in regulating Nox4, myofibroblast differentiation, and senescence. In normal human diploid fibroblasts, TGF-β1 induces Hic-5 expression in a delayed manner relative to the induction of Nox4 and myofibroblast differentiation. Hic-5 silencing induced constitutive Nox4 expression and enhanced TGF-β1-inducible Nox4 levels. The induction of constitutive Nox4 protein in Hic-5-silenced cells was independent of transcription and translation and controlled by the ubiquitin-proteasomal system. Hic-5 associates with the ubiquitin ligase Cbl-c and the ubiquitin-binding protein heat shock protein 27 (HSP27). The interaction of these proteins is required for the ubiquitination of Nox4 and for maintaining low basal levels of this reactive oxygen species-generating enzyme. Our model suggests that TGF-β1-induced Hic-5 functions as a negative feedback mechanism to limit myofibroblast differentiation and senescence by promoting the ubiquitin-proteasomal system-mediated degradation of Nox4. Together, these studies indicate that endogenous Hic-5 suppresses senescence and profibrotic activities of myofibroblasts by down-regulating Nox4 protein expression. Additionally, these are the first studies, to our knowledge, to demonstrate posttranslational regulation of Nox4.

Anatomy and histology of rodent and human major salivary glands: -overview of the Japan salivary gland society-sponsored workshop-

MAJOR SALIVARY GLANDS OF BOTH HUMANS AND RODENTS CONSIST OF THREE PAIRS OF MACROSCOPIC GLANDS: parotid, submandibular, and sublingual. These glands secrete serous, mucous or mixed saliva via the proper main excretory ducts connecting the glandular bodies with the oral cavity. A series of discoveries about the salivary ducts in the 17th century by Niels Stensen (1638-1686), Thomas Wharton (1614-1673), and Caspar Bartholin (1655-1738) established the concept of exocrine secretion as well as salivary glands. Recent investigations have revealed the endocrine functions of parotin and a variety of cell growth factors produced by salivary glands.The present review aims to describe macroscopic findings on the major salivary glands of rodents and the microscopic differences between those of humans and rodents, which review should be of interest to those researchers studying salivary glands.

Localization of ATP-sensitive K+ channel subunits in rat submandibular gland

ATP-sensitive K(+) (K(ATP)) channel subunits were investigated in rat submandibular gland (SMG). RT-PCR detected the presence of mRNA transcripts of the Kir6.1, Kir6.2, SUR2A, and SUR2B in the SMG, whereas SUR1 mRNA was barely detected. Western blot analysis provided the evidence that these four K(ATP) channel subunits are expressed in rat SMG. Immunostaining detected that these four K(ATP) channel subunits are widely distributed, with different intensities, in myoepithelial cells, epithelial cells of intercalated ducts, granular convoluted tubules, striated ducts, and excretory ducts. Immunofluorescence double staining showed that Kir6.1 and Kir6.2 colocalized with SUR2A in the myoepithelial cells, granular convoluted tubules, striated ducts, and excretory ducts. Kir6.1 and Kir6.2 also colocalized with SUR2B, mainly in the duct system, e.g., the granular convoluted tubules, striated ducts, and excretory ducts. Taken together, these results indicate that the K(ATP) channels in SMG may consist of Kir6.1, Kir6.2, SUR2A, and SUR2B, with various combinations of colocalization with each other, and may play important roles in rat SMG during salivary secretion.

Proteomic analysis of human osteoprogenitor response to disordered nanotopography

Previous studies have shown that microgroove-initiated contact guidance can induce bone formation in osteoprogenitor cells (OPGs) and produce changes in the cell proteome. For proteomic analysis, differential in-gel electrophoresis (DIGE) can be used as a powerful diagnostic method to provide comparable data between the proteomic profiles of cells cultured in different conditions. This study focuses on the response of OPGs to a novel nanoscale pit topography with osteoinductive properties compared with planar controls. Disordered near-square nanopits with 120 nm diameter and 100 nm depth with an average 300 nm centre-to-centre spacing (300 nm spaced pits in square pattern, but with +/-50 nm disorder) were fabricated on 1x1 cm2 polycaprolactone sheets. Human OPGs were seeded onto the test materials. DIGE analysis revealed changes in the expression of a number of distinct proteins, including upregulation of actin isoforms, beta-galectin1, vimentin and procollagen-proline, 2-oxoglutarate 4-dioxygenase and prolyl 4-hydroxylase. Downregulation of enolase, caldesmon, zyxin, GRASP55, Hsp70 (BiP/GRP78), RNH1, cathepsin D and Hsp27 was also observed. The differences in cell morphology and mineralization are also reported using histochemical techniques.