MUC5B
Mucin-5B precursor (MUC-5B) (Cervical mucin) (High molecular weight salivary mucin MG1) (Mucin-5 subtype B, tracheobronchial) (Sublingual gland mucin) [MUC5]
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The minor salivary glands are of great importance for maintenance of homeostasis in the oral cavity. These glands continuously secrete substances which lubricate and protect the oral tissues, contributing to comfort and health. The minor salivary glands contribute approximately 7-8 per cent of the total volume of saliva. Flow rate and composition seem to vary according to anatomical location. Current knowledge about the minor salivary glands is derived primarily from studies on adults. The overall aim of this thesis was to study age-related changes in minor gland saliva, from childhood to adulthood. By increasing the knowledge of minor gland secretion, we hopefully better understand how different mucosal locations are lubricated and protected in individuals of different ages and various health statuses. The project comprises four papers. In Paper I, the flow rate and numerical density of the labial and buccal minor glands of pre-school children, adolescents and adults were investigated. Saliva was collected on filter paper discs and the flow rate was measured by the Periotron-method. The numerical density was assessed by PAS-staining. The flow rate of the buccal glands was significantly lower in children than in adults and the number of labial glands was significantly higher in children than in the other age-groups. In Paper II, the composition of minor gland saliva of the three age groups (Paper I) was analysed (by ELISA-technique), with reference to the mucins MUC5B and MUC7, representing some of the major components of innate salivary immunity. Children did not differ from adolescents and adults with respect to MUC5B content in labial gland saliva, but had less MUC7 than the adults. In the buccal gland saliva, detectable amounts of the mucins were found in only a few of the participants. In Paper III, the content of the adaptive immune component (salivary IgA) in minor gland saliva of pre-school children, adolescents and adults was measured by the ELISA technique. The salivary IgA-concentration in whole saliva of the three age-groups was also estimated. The IgA-concentration was significantly lower in the labial glands and the whole saliva of the children than in the adults. In Paper IV, age-dependent differences of other innate components were studied in pre-school children, adolescents and adults, by analysing the amount of glycoprotein 340 (gp-340) in minor gland and whole saliva, using the ELISA technique. The content of sialic acid, a common terminal structure of glycoproteins, was analysed using the ELLA technique. With respect to minor gland saliva, no differences were disclosed among pre-school children, adolescents and adults. However, the gp-340 content of whole saliva was significantly higher in the children than in the adults. The above investigations of properties of minor salivary glands in children, adolescents and adults seems to be the first to present data on age-dependent variations in gland density and secretions from healthy individuals. The results show high gland density, mature innate immunity and an ongoing maturation of adaptive immunity in the saliva of children. The report provides a reference for further comparative studies on minor gland saliva of younger individuals in health and disease.
MeSH Terms
- Adolescent
- Adult
- Aging
- Child
- Child, Preschool
- Humans
- Immunoglobulin A
- Mucin-5B
- Mucins
- Salivary Glands, Minor
- Salivary Proteins and Peptides
- Secretory Rate
- Young Adult
The secretory cells of the human lacrimal gland show a PAS-positive reaction in cytochemical staining procedures, suggesting the production of mucous substances. Recently, these substances were differentiated according to modern molecular classifications. Expression studies detected mRNA for MUC1, MUC4, MUC5AC, MUC5B, MUC6, and MUC7, whereas MUC2 transcripts were absent in all samples investigated. Immunohistochemistry revealed membrane-bound MUC1 at the apical surface of acinar cells, MUC5AC associated with goblet cells of excretory ducts, MUC5B and MUC7 in the cytoplasm of acinar cells, and MUC7 also in epithelial cells of excretory ducts. MUC2 (RT-PCR negative) and MUC6 (RT-PCR positive) were not detectable by immunohistochemistry. MUC4 mRNA was present in all samples from patients treated for dry eye but only in 6 of 30 glands from individuals who did not receive treatment with artificial tears. Dot-blot analyses clearly revealed increased amounts of MUC4, MUC5AC and MUC5B in the glands of elderly women who received treatment for dry eye as compared to the remaining samples. These results confirm that the human lacrimal gland synthesizes a spectrum of mucins, some of which might be involved in the pathophysiology of dry eye syndrome.
MeSH Terms
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Aging
- Child
- Dry Eye Syndromes
- Female
- Humans
- Lacrimal Apparatus
- Male
- Middle Aged
- Mucins
- Tissue Distribution
The origin of gastric metaplasia of the duodenum (GMD) remains enigmatic. We studied expression of mucins and trefoil peptides in GMD to gain insight into its phenotype and origin. We examined duodenal tissue of 95 patients (0 to 83 years old, 26 with gastric Helicobacter pylori infection) for the presence of GMD. Expression was examined immunohistochemically of secretory mucins (MUC2, MUC5AC, MUC5B, and MUC6), trefoil peptides (TFF1, TFF2, and TFF3), and sucrase-isomaltase (SI). GMD, found in 37 patients, correlated positively to gastric H. pylori infection, age, and villus atrophy. MUC2 and TFF3, expressed in normal goblet cells, were absent from 100% and 87% of GMD, respectively. GMD ubiquitously expressed MUC5AC, whereas MUC5AC expression in adjacent goblet cells was closely correlated with the extent of GMD. TFF1, TFF2, and MUC6 were found in 84%, 92%, and 65% of GMD, respectively. MUC5B was absent from epithelium and GMD. SI, expressed by villus enterocytes, was absent from GMD. Brunner's glands ubiquitously expressed MUC5B, MUC6, and TFF2. GMD was characterized by the expression of gastric-type proteins MUC5AC, MUC6, TFF1, and TFF2 and the absence of intestinal markers MUC2, TFF3, and SI. In terms of the location of metaplastic cells, our results suggest that epithelial cells migrating toward villus tips switch to gastric-type secretory cells. Positive correlation with infection suggests an inductive role H. pylori in the development of GMD.
MeSH Terms
- Adolescent
- Adult
- Aged
- Aged, 80 and over
- Aging
- Brunner Glands
- Cell Differentiation
- Child
- Child, Preschool
- Duodenum
- Gastric Mucosa
- Goblet Cells
- Growth Substances
- Helicobacter Infections
- Helicobacter pylori
- Humans
- Infant
- Metaplasia
- Middle Aged
- Mucin 5AC
- Mucin-2
- Mucin-5B
- Mucin-6
- Mucins
- Muscle Proteins
- Neuropeptides
- Peptides
- Proteins
- Stomach Diseases
- Trefoil Factor-1
- Trefoil Factor-2
- Trefoil Factor-3
- Tumor Suppressor Proteins