Myoepithelial Cells (MEC) of the Salivary Glands in Health and Tumours

Histomorphogenesis of sublingual salivary gland of Indian sheep

The primordial anlage of sublingual gland was first noticed as a solid epithelial bud from oral epithelium at the 24th day of foetal development. The terminal buds were arranged in the form of clusters with undifferentiated epithelial cells and terminated in a bulb-like structure in the 30-day-old sheep foetus. On the 37th day, lumenization and branching of the main cord was noticed. The primary septa were observed from the 55th day onwards which resulted in the formation of lobulation on the 60th day. The capsule formation was initiated by aggregation of mesenchymal tissue on the 63rd day. On the 100th day, terminal tubules differentiated to form secretory end pieces. Tubular portions formed intercalated and striated ducts. Predominantly mucous type of acinar cells was seen from the 110th day onwards with myoepithelial cells. The number of lobules increased with increase in parenchyma from 130th day onwards. Micrometrical studies revealed that the mean diameter of acini, intercalated, striated and large ducts was increased with advancement of age and significant differences were observed between groups. Localization of acidic and neutral mucopolysaccharides were observed in mucous and goblet cells. Fine lipid droplets were observed in intralobular and interlobular connective tissue however, phospholipids were observed in cell membrane of acini and ducts. The current investigation provides microstructural standards for the organogenesis of the sublingual gland of miniature sheep and can lay the foundation for further studies in the morphological investigation of salivary gland development.

Immunoexpression of Autophagy-Related Proteins in Salivary Gland Tumors: An Exploratory Study

BACKGROUND

Autophagy is a cellular survival mechanism involved in several human diseases, but its participation in the development of salivary gland tumors is not fully understood. This study investigated the immunoexpression of autophagy-related proteins (autophagy-related 7 [Atg7], microtubule-associated protein 1 light chain 3A [LC3A], microtubule-associated protein 1 light chain 3B [LC3B], protein p62 [p62], and phosphorylated mammalian target of rapamycin [p-mTOR]) in pleomorphic adenoma (PA), polymorphous adenocarcinoma (PAC), mucoepidermoid carcinoma (MEC), and adenoid cystic carcinoma (ACC) of salivary glands.

METHODS

Twenty PAs, 20 PACs, 20 MECs, and 14 ACCs were selected. The percentages of cytoplasmic and nuclear positivity for autophagy-related proteins in neoplastic cells were assessed and correlated with histopathological parameters.

RESULTS

Cytoplasmic immunoexpression of Atg7 was observed in all groups, with high median percentages of positivity. Regarding LC3A and LC3B, cytoplasmic immunoexpression was found in most PACs (95%) and in all cases of PA, MEC and ACC, with the highest percentages of positivity in PACs and PAs (p < 0.005). ACCs exhibited lower cytoplasmic immunoexpression of p-mTOR (p < 0.005) and lower nuclear expression of p62 (p < 0.05) when compared to PAs, PACs and MECs. Low nuclear immunoexpression of Atg7, LC3A and p-mTOR and absence of nuclear staining for LC3B were observed in all groups. Regarding histopathological parameters of PAs, MECs and ACCs, there were no significant differences in the expression of autophagy-related proteins. In all groups, positive correlations were observed between the immunoexpression of some autophagy-related proteins (p < 0.05).

CONCLUSIONS

The results suggest the participation of autophagy in the pathogenesis of PA, PAC, MEC, and ACC of salivary glands. Upregulation of autophagy and reduced nuclear translocation of p62 may contribute to the aggressive biological behavior of salivary gland ACC.

Organoid Models for Salivary Gland Biology and Regenerative Medicine

The salivary gland is composed of an elegant epithelial network that secrets saliva and maintains oral homeostasis. While cell lines and animal models furthered our understanding of salivary gland biology, they cannot replicate key aspects of the human salivary gland tissue, particularly the complex architecture and microenvironmental features that dictate salivary gland function. Organoid cultures provide an alternative system to recapitulate salivary gland tissue in vitro, and salivary gland organoids have been generated from pluripotent stem cells and adult stem/progenitor cells. In this review, we describe salivary gland organoids, the advances and limitations, and the promising potential for regenerative medicine.

Immunohistochemical expression of podoplanin as a myoepithelial cell marker in pleomorphic adenoma

Purpose

Pleomorphic adenoma (PA) is the most common benign salivary gland tumor with salivary gland excision as the treatment of choice; however, recurrences after parotidectomy have been reported. The current study is aimed at evaluating podoplanin expression in PA as a myoepithelial (ME) cell marker and its role in estimating the prognosis and outcome of the tumors by correlating it with various clinical and histological parameters.

Materials and Methods

A total of 10 paraffin-embedded specimens of histologically diagnosed PA with clinical records of the patients were retrieved and the slides were then stained using hematoxylin and eosin staining and were then immunohistochemically stained with podoplanin.

Results

The study revealed the specificity of podoplanin as a differential marker for ME cells.

Conclusion

Although the study revealed the specificity of podoplanin as a differential marker for ME cells, additional markers to overcome the limitations of podoplanin which will predict the biologic behavior (biologic behavior of the tumor) the tumor with respect to parameters such as age, gender and site of the tumor are required. Furthermore, a larger sample size is required to validate the findings in our data.

[Expression of thymidylate synthase in salivary adenoid myoepithelial cells and its clinical significance]

OBJECTIVE

To evaluate the expression of thymidylate synthase (TS) in myoepithelial cells (MECs) of salivary adenoid tissues and explore its clinical significance.

METHODS

Immunohistochemical staining EnVision method was used to detect the expression of TS, P63, Calponin, CK5/6 and S-100 in 32 salivary gland specimens, including 10 non-neoplastic and salivary inflammation specimens, 11 mixed tumor specimens, 5 basal cell carcinoma specimens and 6 adenoid cyst carcinoma specimens. The specificity and sensitivity of TS as a specific molecular marker of salivary muscle epithelial cells were evaluated in comparison with P63, Calponin, CK5/6 and S-100.

RESULTS

The expression pattern of TS in all the salivary gland tissue specimens was identical with that of p63. TS and P63 both showed strong immunohistochemical expressions in MECs of salivary adenoid tissue specimens. Calponin, CK5/6, and S-100 showed cytoplasmic/membranous expressions in the MECs. In addition, TS exhibited weak or moderate cytoplasmic expression in a few salivary gland epithelial cells, cancer cells and scattered stromal cells, with negative expression in the cell nuclei. The expression of TS in the MECs of all the salivary adenoid specimens was highly consistent with those of P63, Calponin, CK5/6 and S-100 (P&gt;0.05) Except for CK5/6 expression in Salivary inflammation and Salivary gland specimens. Kappa&gt;0.75. The specificity and sensitivity of TS as a molecular marker of MECs were both 100%.

CONCLUSIONS

TS is a new specific marker of MECs for differential diagnosis of salivary gland tumors.

Lacrimal Gland Myoepithelial Cells Are Altered in a Mouse Model of Dry Eye Disease

The purpose of this study was to determine the pathogenic changes that occur in myoepithelial cells (MECs) from lacrimal glands of a mouse model of Sjögren syndrome. MECs were cultured from lacrimal glands of C57BL/6J [wild type (WT)] and thrombospondin 1 null (TSP1^-/-, alias Thbs1^-/-) mice and from mice expressing α-smooth muscle actin-green fluorescent protein that labels MECs. MECs were stimulated with cholinergic and α₁-adrenergic agonists, vasoactive intestinal peptide (VIP), and the purinergic agonists ATP and UTP. Then intracellular [Ca²⁺] was measured using fura-2, and contraction was observed using live cell imaging. Expression of purinergic receptors was determined by Western blot analysis, and mRNA expression was analyzed by microarray. The increase in intracellular [Ca²⁺]_I with VIP and UTP was significantly smaller in MECs from TSP1^-/- compared with WT mice. Cholinergic agonists, ATP, and UTP stimulated contraction in MECs, although contraction of MECs from TSP1^-/- mice was reduced compared with WT mice. The amount of purinergic receptors P2Y1, P2Y11, and P2Y13 was significantly decreased in MECs from TSP1^-/- compared with WT mice, whereas several extracellular matrix and inflammation genes were up-regulated in MECs from TSP1^-/- mice. We conclude that lacrimal gland MEC function is altered by inflammation because the functions regulated by cholinergic agonists, VIP, and purinergic receptors are decreased in TSP1^-/- compared with WT mice.

Immunohistochemical evaluation of salivary gland tumors differentiation and proliferation by using calponin and telomerase

Background

Salivary gland tumors are a heterogeneous group of lesions with diverse histological features. Hence they are considered as a diagnostic challenge for the pathologist. Myoepithelial cells are considered as a key in the morphogenetic process, with diverse differentiation in various salivary gland tumors. Calponin is an actin filament- associated protein that represents a sensitive marker of myoepithelial cells. Telomerase is a ribonucleoprotein that adds telomere repeats at the end of chromosomes in order to prevent replicative senescence. It has a key role in cellular immortality and tumorgenesis of various tumors. This study evaluates the immunohistochemical expression of calponin and telomerase in various salivary gland tumors.

Methods

This retrospective study involved 30 formalin fixed paraffin embedded blocks of salivary gland tumors. The immunohistochemical staining and evaluation of subcellular localization, pattern, intensity, and distribution for calponin and immune scoring for telomerase were done. The statistical analyses of data were conducted by Chi-square and ANOVA-test, a P-value of <0.05 was considered significant.

Results

Calponin showed expression at the periphery of acini and intercalated ducts in the normal salivary gland. It revealed cytoplasmic expression in 83.3% of benign tumors. The pleomorphic adenoma showed a diffuse pattern of staining (85.7%), strong intensity (64.3%), and mixed distributions (57.1%). The diffuse pattern of calponin was seen in all cases of mucoepidermoid, polymorphous low-grade adenocarcinoma and epithelial-myoepithelial carcinoma (100%). Telomerase revealed negative expression in the normal salivary gland. Pleomorphic adenoma illustrated high telomerase expression in score 2 and score 3 (93.3%). Telomerase immune scoring is significantly related to the benign tumors as P value was 0.03. Both polymorphous low grade and epithelial-myoepithelial carcinoma were detected only in score 3. Finally, the mean level of telomerase activity was slightly higher in malignant tumors than benign ones with non-significant relation as P value was 0.6.

Conclusions

Calponin showed high diffuse staining with altered distribution in salivary gland tumors, which might give an additional role for this marker in the identification of luminal immuno-modified neoplastic cells. Telomerase is considered as a useful marker in identifying proliferation capacity of salivary gland tumors and is remarkably more detected in malignant salivary gland tumors.

Reduced myofilament component in primary Sjögren's syndrome salivary gland myoepithelial cells

Primary Sjögren's syndrome (pSS) is a solitary poorly understood autoimmune inflammatory disease by involvement of the salivary and lacrimal glands resulting in dry mouth and dry eyes. Myoepithelial cells (MECs) are cells knowing for its hybrid epithelial and mesenchymal phenotype that are important components of the salivary gland (SGs) structure aiding the expulsion of saliva from acinar lobules. In this study we investigate possible alteration in the myofilament component of MECs in SGs specimens obtained from pSS patients in comparison with healthy subjects, to evaluate MECs hypothetical involvement in the pathogenesis of pSS. The expression of alpha-smooth muscle actin (α-SMA) and p63, as MECs markers, was evaluated in bioptic specimens from pSS and healthy labial SGs through immunohistochemistry and immunofluorescence analyses; the distribution of MECs markers was quantified using Aperio ScanScope and ImageScope software to provide quantitative assessments of staining levels. Our observations demonstrated that p63 nuclear labeling in pSS MECs is preserved whereas α-SMA cytoplasmic staining is strongly and significantly reduced when compared with healthy SGs; the digital images analysis quantification of the expression of labeled α-SMA and p63 protein in the healthy and pSS MECs salivary tissues, led to results suggesting a loss of mechanical support for acini and ducts in pSS, correlated, probably, with the reduction of salivary flow that features one important aspect of pSS disease.

BRCA1/2 Mutations in Salivary Pleomorphic Adenoma and Carcinoma-ex-Pleomorphic Adenoma

Objectives:

It is hypothesized that carcinoma-ex-pleomorphic adenoma (Ca-ex-PA) is malignant from the beginning or is a malignant transformation of a recurrent or a long-standing pleomorphic adenoma (PA). The accumulation of genetic instabilities is suggested to be the main reason for malignant transformation in PA. The aim of this study was to determine the prevalence of BRCA1/2 mutations in PA and Ca-ex-PA.

Materials and Methods:

A total of ninety salivary gland tumors (45 Ca ex-PA and 45 PA) were selected. Immunohistochemistry was performed for all samples. Analyses were conducted through SPSS software version 22.0 (SPSS, Inc., Chicago, IL, USA). Chi-square test was used to examine the differences between the variables. Significant level was set at 0.05.

Results:

In general, 93.3% of PA samples showed positive staining for BRCA1 (in myoepithelial cells); however, BRCA2 positivity was found in 60% of samples (in myoepithelial cells). Among 45 samples of Ca-ex-PA, 93.3% of showed positivity for BRCA1 and 80% of samples showed positivity for BRCA2. Chi-square test found differences between PAs and Ca-ex-PAs regarding BRCA1/2 mutations in ductal cells and myoepithelial cells (P = 0.007, 0.000), respectively.

Conclusions:

The present study found a trend toward the presence of BRCA1/2 mutations in PA and Ca-ex-PA samples. Patients with BRCA1/2 mutation carriers are excellent cases for therapies, such as the poly (ADP) ribose polymerase inhibitor.

Tuning Hydrogel Properties to Promote the Assembly of Salivary Gland Spheroids in 3D

Current treatments for chronic xerostomia, or "dry mouth", do not offer long-term therapeutic benefits for head and neck cancer survivors previously treated with curative radiation. Towards the goal of creating tissue-engineered constructs for the restoration of salivary gland functions, we developed new hyaluronic acid (HA)-based hydrogels using thiolated HA (HA-SH) and acrylated HA (HA-AES) with a significant molecular weight mismatch. Four hydrogel formulations with varying HA concentration, (1-2.4 wt%) and thiol/acrylate ratios (2/1 to 36/1) and elastic moduli (G': 35 to 1897 Pa, 2 h post-mixing) were investigated. In our system, thiol/acrylate reaction was initiated rapidly upon mixing of HA-SH/HA-AES to establish thioether crosslinks with neighboring ester groups, and spontaneous sulfhydryl oxidation occurred slowly over several days to install a secondary network. The concurrent reactions cooperatively create a cell-permissive network to allow for cell expansion and aggregation. Multicellular spheroids formed readily from a robust ductal epithelial cell line (Madin-Darby Canine Kidney, MDCK cells) in all hydrogel formulations investigated. Primary salivary human stem/progenitor cells (hS/PCs), on the other hand, are sensitive to the synthetic extracellular environment, and organized acini-like structures with an average diameter of 50 µm were obtained only in gels with G' ≤ 216 Pa and a thiol/acrylate ratio ≥18. The spheroid size and size distribution were dependent on the HA content in the hydrogel. Cells in hS/PC spheroids formed tight junctions (occludin), remained viable and proliferative, secreted structural proteins (collagen IV and laminin) found in the basement membrane and maintained key stem/progenitor markers. We conclude that incorporation of time-dependent, dynamic features into a covalently crosslinked HA network produces an adaptable hydrogel framework that promotes hS/PC assembly and supports early aspects of salivary morphogenesis, key to reconstitution of a fully functional implantable salivary gland.

Minor Salivary Gland Changes in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma - A Histopathological Study

INTRODUCTION

The most common etiology for Oral Squamous Cell Carcinoma (OSCC) is tobacco and tobacco related products which cause nuclear damage to the keratinocytes. The chemical carcinogens not only affect the lining of oral epithelium but also affect the lining epithelium of the excretory ducts of the salivary glands. Thus, there is a possibility of epithelial dysplasia of the salivary duct epithelium which may lead to potential malignant transformation.

AIM

The study was performed to see the changes in the minor salivary glands and excretory ducts in cases of oral epithelial dysplasia and OSCC.

MATERIALS AND METHODS

A total of 278 archival cases of mild, moderate and severe epithelial dysplasia, carcinoma in situ, OSCC including verrucous carcinoma were histopathologically evaluated to observe changes in the excretory ducts and the minor salivary glands.

RESULTS

In the study there were 56.5% males and 43.5% females. The age group that was most commonly affected in both the sexes was 50-60 yr old. Buccal mucosa was the most common site of involvement. Ductal changes observed in the excretory duct include simple hyperplasia, metaplastic changes such as mucous, oncocytic & squamous, and infiltration of inflammatory cells and malignant cells. Acinar changes observed were degeneration, squamous metaplasia, myoepithelial cell proliferation and inflammatory cell infiltration. Both the excretory ducts and ducts within the gland showed dysplasia.

CONCLUSION

According to observations in our study it is suggested that histopathological interpretation for oral mucosal lesions especially oral epithelial dysplasias and OSCC should also include changes related to salivary gland tissue to provide a better treatment plan and prevent recurrence of the malignant tumours.

Binge Drinking of Ethanol during Adolescence Induces Oxidative Damage and Morphological Changes in Salivary Glands of Female Rats

This study investigates morphological and biochemistry effects of binge ethanol consumption in parotid (PG) and submandibular (SG) salivary glands of rats from adolescence to adulthood. Female Wistar rats (n = 26) received ethanol at 3 g/kg/day (20% w/v) for 3 consecutive days/week from the 35th until the 62nd day of life. Animals were treated in two periods: 1 week (G1) and 4 weeks (G2), with a control (treated with distilled water) and an ethanol group to each period. In morphological analysis, morphometric and immunohistochemistry evaluation for smooth muscle actin (αSMA), cytokeratin-18 (CK-18), and vimentin (VIM) were made. Biochemical changes were analyzed by concentration of nitrites and levels of malondialdehyde (MDA). The difference between groups in each analysis was evaluated by Mann-Whitney U test or Student's t-test (p ≤ 0.05). PG showed, at one week of ethanol exposure, lower CK-18 and α-SMA expression, as well as MDA levels. After four weeks, lower CK-18 and higher MDA levels were observed in PG exposed to ethanol, in comparison to control group. SG showed lower α-SMA expression after 1 and 4 weeks of ethanol exposure as well as higher MDA levels after 1 week. Ethanol binge consumption during adolescence promotes tissue and biochemical changes with only one-week binge in acinar and myoepithelial PG cells.

Biomaterials-based strategies for salivary gland tissue regeneration

The salivary gland is a complex, secretory tissue that produces saliva and maintains oral homeostasis. Radiation induced salivary gland atrophy, manifested as "dry mouth" or xerostomia, poses a significant clinical challenge. Tissue engineering recently has emerged as an alternative, long-term treatment strategy for xerostomia. In this review, we summarize recent efforts towards the development of functional and implantable salivary glands utilizing designed polymeric substrates or synthetic matrices/scaffolds. Although the in vitro engineering of a complex implantable salivary gland is technically challenging, opportunities exist for multidisciplinary teams to assemble implantable and secretory tissue modules by combining stem/progenitor cells found in the adult glands with biomimetic and cell-instructive materials.