Oral mucosal epithelial cells express the membrane anchored mucin MUC1.
OBJECTIVE
The presence of a stable salivary pellicle (SP) is essential to provide a wet surface for the oral mucosal epithelia. The oral mucosa is covered by the SP which is suggested to be a mixed film of both salivary and epithelial components. Our aim was to analyse the presence of membrane-anchored mucin MUC1 in the oral mucosal epithelia.
The presence of MUC1 was studied by immunohistochemical and immunoelectron microscopical methods in 19 buccal mucosal specimens. The localization and intensity of the epithelial expression were analyzed.


RESULTS
Strong staining of MUC1 was found in the epithelial cells of intermediate and superficial layers. Some basal cells were shown faint expression. In the intermediate and superficial layers, the MUC1 expression was seen mainly on the upper cell surface. Furthermore, the expression of MUC1 was noted in the cytoplasm near the nucleus and in the rough granules. By electron microscopy, extracellular domain of membrane-anchored molecules extruded about 15-30nm above the cell surface in the apical cells of the oral epithelium. Immunoelectron microscopic examination shows that MUC1 is mainly localized in the plasma membrane of epithelial cells and also in small vesicles (75-100nm) just below the plasma membrane.


CONCLUSIONS
The membrane-anchored MUC1 is expressed in the superficial layer of the oral mucosal epithelium, especially on the upper surface of epithelial cells. MUCI may be the anchoring protein of the salivary pellicle stabilization.
Research Group of Oral Health Sciences, Faculty of Medicine, University of Oulu and Oulu University Hospital, Aapistie 5, FI-90220 Oulu, Finland.
Helena
H
Ukkonen
Department of Oral Diagnostic Sciences, Institute of Dentistry, University of Eastern Finland, Kuopio campus, Yliopistonranta 1, FI-70210 Kuopio, Finland.
Paula
P
Pirhonen
Research Group of Oral Health Sciences, Faculty of Medicine, University of Oulu and Oulu University Hospital, Aapistie 5, FI-90220 Oulu, Finland.
Maria
M
Herrala
Department of Oral Diagnostic Sciences, Institute of Dentistry, University of Eastern Finland, Kuopio campus, Yliopistonranta 1, FI-70210 Kuopio, Finland; SIB Labs and Department of Applied Physics, University of Eastern Finland, Kuopio campus, Yliopistonranta 1, FI-70210 Kuopio, Finland.
Jopi J W
JJ
Mikkonen
Department of Oral Diagnostic Sciences, Institute of Dentistry, University of Eastern Finland, Kuopio campus, Yliopistonranta 1, FI-70210 Kuopio, Finland; Laser Biomedical Research Centre, Massachusetts Institute of Technology, Boston, USA.
Surya P
SP
Singh
Biocenter Oulu, University of Oulu, Departments of Pathology, University of Oulu and Oulu University Hospital, Aapistie 5, FI-90220 Oulu, Finland.
Raija
R
Sormunen
Research Group of Oral Health Sciences, Faculty of Medicine, University of Oulu and Oulu University Hospital, Aapistie 5, FI-90220 Oulu, Finland; Department of Oral Diagnostic Sciences, Institute of Dentistry, University of Eastern Finland, Kuopio campus, Yliopistonranta 1, FI-70210 Kuopio, Finland; Department of Oral and Maxillofacial Surgery, Institute of Dentistry, University of Turku, and Turku University Hospital, FI-20014 Turku, Finland. Electronic address: arja.kullaa@uef.fi.
Arja M
AM
Kullaa
D000328:Adult; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D044622:Dental Pellicle / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D008875:Middle Aged; D009061:Mouth Mucosa / Q000166:cytology / Q000378:metabolism*; D018396:Mucin-1 / Q000096:biosynthesis*
C060192:MUC1 protein, human; D018396:Mucin-1
Electron microscopy; Immunoelectron microscopy; MUC1; Mucins; Oral epithelium; Oral mucosa