Connexin Expression in Human Minor Salivary Glands: An Immunohistochemical Microscopy Study.

Connexins (Cxs) are transmembrane proteins involved in the formation of hemichannels and gap junctions (GJs). GJs are involved in various physiological functions, including secretion in glandular tissue. It has been demonstrated that Cx26, Cx32, and Cx43 are mainly expressed in glands, but no data are available in human salivary glands to date. The aim of our study was to investigate the presence and the localization of Cxs in human minor labial salivary glands. Immunofluorescence and immunoelectron microscopy were employed to evaluate the Cx26, Cx32, and Cx43 protein in human labial salivary gland biopsies (hLSGBs). RT-PCR was also used to detect their mRNA expression. Cx expression was found at both the mRNA and protein levels in all hLSGBs analysed. Cxs were observed at the level of the duct and acinar cells, as well as in myoepithelial cells. The localization of the three Cx types was very similar, suggesting colocalization of these Cxs in the same connexons. These results demonstrated the presence of Cxs in human salivary glands for the first time. Moreover, the few samples with primary Sjögren's Syndrome analysed only by immunofluorescence showed an alteration of the Cx expression, indicating that these proteins could be involved in salivary gland dysfunctions.

Inhibition of Alk signaling promotes the induction of human salivary-gland-derived organoids.

Hyposalivation and xerostomia are the cause of several morbidities, such as dental caries, painful mucositis, oral fungal infections, sialadenitis and dysphagia. For these reasons, preservation of normal saliva secretion is critical for the maintenance of functionally normal oral homeostasis and for keeping good health. Several strategies for restoring salivary gland function have been reported, from different points of view, based on the use of salivary-gland-derived epithelial stem/progenitor cells and tissue engineering approaches to induce organoids that mimic in vivo salivary glands. In this study, we clarified that inhibition of activin receptor-like kinase (Alk) signaling was essential for the induction of human salivary-gland-derived organoids, and demonstrated the usefulness of such organoids as an inflammatory disease model. In inflammatory conditions like sialadenitis, in general, pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α, also known as TNF) are upregulated, but their function is still unclear. In our established human salivary-gland-derived organoid culture system, we successfully induced organoid swelling by stimulation with carbachol, a non-selective cholinergic agonist, and forskolin, an activator of cystic fibrosis transmembrane conductance regulator (CFTR). Furthermore, we found that this organoid swelling was inhibited by TNF-α. From these results, we could clarify the inhibitory function of TNF-α on saliva secretion in vitro Thus, our established human salivary-gland-derived organoids would be useful for in vitro analyses of the morphological and functional changes involved in salivary gland dysfunctions in several research fields, such as pathobiology, inflammation and regenerative medicine.This article has an associated First Person interview with the first author of the paper.

Salivary functions in mastication, taste and textural perception, swallowing and initial digestion.

Saliva exerts multiple functions in relation to the initial digestive processes taking place in the upper parts of the gastrointestinal tract. Ingestion of food and beverages, in turn, is a strong stimulus for secretion of saliva with a differential composition depending on the neuronal stimulation pattern. This review paper provides insight into the mechanisms by which saliva acts in relation to taste, mastication, bolus formation, enzymatic digestion and swallowing. Also, the protective functions of saliva including maintenance of dental and mucosal integrity will be discussed as they indirectly influence the digestive process. The final part of this study focuses on the implications of xerostomia and salivary gland dysfunction on gastrointestinal functions.

Overview of Human Salivary Glands: Highlights of Morphology and Developing Processes.

Salivary glands are essential organs that produce and secrete saliva to the oral cavity. During gland morphogenesis, many developmental processes involve a series of coordinated movements and reciprocal interactions between the epithelium and mesenchyme that generate the ductal system and the secretory units. Recent studies have shown new findings about salivary gland development, particularly regarding lumen formation and expansion, with the involvement of apoptosis and cell polarization, respectively. Moreover, it has been observed that human minor salivary glands start forming earlier than previously published and that distinct apoptotic mediators can trigger duct lumen opening in humans. This review summarizes updated morphological and cellular features of human salivary glands and also explores new aspects of the human developmental process. Anat Rec, 300:1180-1188, 2017. © 2017 Wiley Periodicals, Inc.

Clarification of the terminology of the major human salivary glands: acinus and alveolus are not synonymous.

Discrepancies in the terminology of the major human salivary glands often appear in anatomical textbooks and tend to adversely affect student's learning experience in Microscopic Anatomy. The main culprit is the inconsistent description of the morphology of these glands secretory end pieces where "acinus" and "alveolus" are used interchangeably. The correct terminology originated from Malpighi (1687), repeated by Kölliker (1854), but over the years has been misinterpreted by prominent authors as a result of the nature of specimen preparation. This commentary is based on etymology, current standard light microscopy, research studies and consultation with experts. The overall objective of this publication is to recommend that textbooks should endeavour to modify the relevant descriptions about this terminology in their future editions. The most appropriate terminology for the major human salivary glands would be: (1) the parotid gland, entirely serous, should be called compound acinar glands; (2) the submandibular glands are mixed glands; their serous components are compound acinar while some of the mucinous areas are tubular with serous, crescents or demilunes, as acinar end pieces hence they should be named compound tubuloacinar glands; (3) the sublingual glands, mainly mucous glands with tubular shape, with small acinar end pieces that are serous crescents thence they should be called compound tubuloacinar glands.

Comparação microscópica de glândulas sublinguais de cadáveres humanos e de pacientes desdentados portadores de tumefações do soalho da boca relacionadas às glândulas sublinguais: estudo morfológico e morfométrico / Microscopic comparative study of human cadaver sublingual glands and mouth floor enlargements related to the sublingual glands in edentulous patients: morphological and morphometric analysis

O soalho da boca de alguns pacientes desdentados parciais ou totais pode apresentar tumefações do soalho da boca relacionadas às glândulas sublinguais que dificultam a adaptação de próteses totais ou parciais, às vezes requerendo tratamento cirúrgico. Erroneamente, estas tumefações têm sido atribuídas à hiperplasia glandular. Alterações decorrentes do envelhecimento têm sido aventadas como possível causa, mas a etiopatogenia continua incerta. Na busca de explicar a causa das tumefações do soalho da boca de desdentados, foi elaborada a presente pesquisa. Foram comparadas microscopicamente as glândulas sublinguais de cadáveres humanos com glândulas removidas em tratamento cirúrgico pré-protético das tumefações do soalho da boca de desdentados. Estudo morfológico e morfométrico foram realizados em indivíduos de idades cronológicas semelhantes. Os resultados foram analisados com nível de significância de 5%. No estudo morfológico foram analisados: atrofia acinar (p=0,758), autólise acinar (p=0,014), infiltrado mononuclear focal (p=1,000) e difuso (p=0,142), substituição do parênquima por tecido fibroso (p=0,547), substituição do parênquima por tecido adiposo (p=0,547), extravasamento de muco focal (p=0,192) e difuso (p=0,758) e oncocitose (p=0,883). As variáveis ductos e/ou estruturas ductiformes (p=1,000) e vasos sangüíneos congestos (p=0,043) foram classificadas em ausentes e presentes. Morfometricamente foi determinada a densidade de volume de ácinos (p=0,752), ductos (p=0,444), estroma (p=0,209) e tecido adiposo (p=0,794). A análise dos resultados mostrou diferença estatisticamente significante para os aspectos microscópicos autólise (p=0,014) e vasos sanguíneos congestos (p=0,043). As características microscópicas das glândulas sublinguais nas tumefações do soalho da boca de desdentados retratam o processo normal de envelhecimento das glândulas salivares. Concluiu-se que nas tumefações do soalho da boca de pacientes desdentados as glândulas sublinguais não...

Mouth floor enlargements related to sublingual glands in edentulous or partially edentulous patients may be present, impairing denture fitting. Sometimes surgical treatment is needed. Erroneously, these enlargements have been attributed to glandular hyperplasia. Changes due to aging process have been suggested as a possible cause but the etiopathogenesis continues uncertain. The aim of the study was to explain the cause of mouth floor enlargements in edentulous patients. Human sublingual glands from necropsies and glands removed in pre-prosthetic surgical treatment of mouth floor enlargements in edentulous patients were microscopically compared. Morphological and morphometric studies were performed in individuals of similar chronological ages. Results were analyzed with significance set for p0,05. The morphological study analyzed: acinar atrophy (p=0,758), acinar autolysis (p=0,014), focal (p=1,000) and diffuse mononuclear infiltrate (p=0,142), replacement of parenchyma by fibrous tissue (p=0,547), replacement of parenchyma by adipose tissue (p=0,547), focal (p=0,192) and diffuse mucus overflow (p=0,758) and oncocytosis (p=0,883). The variables ducts and/or duct-like structures (p=1,000) and congested blood vessels (p=0,043) were classified in absent and present. The volumes densities of acini (p=0,752), ducts (p=0,444), stroma (p=0,209) and adipose tissue (p=0,794) were determined by the morphometric study. The results showed statically significant difference to the microscopic aspects: autolysis (p=0,014) and congested blood vessels (p=0,043). The microscopic aspects of the sublingual glands in mouth floor enlargements in edentulous patients revealed the normal aging process of the salivary glands. Concluding, the sublingual glands in mouth floor enlargements in edentulous patients are not pathological glands.