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Cytokeratins (CKs) are now considered to be reliable markers for following the development and differentiation of epithelial tissue. We have investigated the pathway of differentiation in human developing junctional epithelium using monoclonal antibodies and two-dimensional gel electrophoresis of microdissected tissue to identify CK 19, CK 16, CK 14, CK 13, CK 6, CK 5, CK 4 in the junctional epithelium (JE) over partially erupted human teeth. The CK profile was similar to that of developing oral epithelia, suggesting that the junctional epithelium in teeth during eruption is of odontogenic origin. The present study used in situ hybridization to determine the distribution of the mRNAs of CKs 19, 16, 13 and 4 in human developing junctional epithelium and to examine the correlation between mRNAs and their encoded proteins. CK 19 mRNA was abundant in the basal cell layers of the primary junctional epithelium (PJE) but less concentrated in the suprabasal layers. CK16, 13 and 4 mRNAs were abundant in the basal cell layers of the PJE. The parabasal cell layers reacted intensely to the cRNA probe complementary to CK16 mRNA, as were the reactions in the suprabasal cell layers of the PJE for the CK 13 and 4 probes. Our results demonstrate that the PJE express the genes encoding for CKs 16 and 4 that have been revealed previously only by electrophoresis. They therefore confirm that the PJE is a well-differentiated stratified epithelium with a complex unique phenotype that produces CKs specific for basal cells (CK 19), CKs associated with hyperproliferation (CK 16), and finally those associated with stratification (CKs 4 and 13). Only synthesis of CK 19 protein and mRNA are strictly parallel. CKs 4 and 13 mRNAs are present in basal and suprasal cells, while their encoded proteins were not, except for CK 13 in suprabasal cell layers of PJE, where the amount of its mRNAs was coincident with the expression of the protein. [ABSTRACT FROM AUTHOR]

The changes in cytokeratin expression by the developing oral mucosa of 10 to 23-week-old human fetuses were studied by indirect immunofluorescence using a panel of 15 monoclonal antibodies. The lining and masticatory mucosae were incompletely differentiated in 10-wk fetuses, since they expressed identical patterns of cytokeratins (CK 4, 5, 8, 13, 18, 19 and probably CK 14, 16, 17) very similar to that of adult alveolar mucosa, The main difference was the presence of cytokeratins 8, 18 and 19 in embryonic tissues. Cytokeratins 1, 2, 10 and 11 began to appear in gingival and hard palate epithelium from wk 11, predicting the differentiation of the masticatory mucosa by wk 16. The patterns of cytokeratin expression in the 23-wk fetus in the lining and masticatory mucosae appear to be different. In lining mucosa, the only difference from the 10th wk is is a decrease in cytokeratins 8, 18, and 19, whereas the pattern of cytokeratin expression in masticatory mucosa (CK 1, 2, 4, 5, 8, 10, 11, 13, 18, 19 and probably CK 14, 16 and 17) is now very near that of adult gingiva. This pattern appears, as in the adult, to be similar to that of the epidermis in the same period. [ABSTRACT FROM AUTHOR]

This study uses cytokeratins (CK) as markers to investigate the phenotype of the junctional epithelium (JE) in partially erupted human teeth. The gingival samples, which were clinically healthy, were carefully dissected from the teeth. Cryostat sections were cut for histological staining, immunofluorescence microscopy and gel electrophoresis. Cytokeratins were extracted after microdissection. The basal and suprabasal epithelial cell markers, cytokeratins 4, 5, 13, 14 and 19 were detected with specific monoclonal antibodies. They showed that the junctional epithelium in erupting teeth has a complex topography. The cytokeratin immunohistochemical profile distinguished between the primary junctional epithelium (CK 5, 14 and 19 in basal and suprabasal cells and CK 13 faintly stained throughout the suprabasal layers) and the adjacent epithelium that had the same cytokeratin profile as the sulcular epithelium (CK 5, 14 and 19 in basal cells and CK 4 and 13 intensively stained in the suprabasal cells). Extraction, two-dimensional electrophoresis and western blotting showed that this transitional JE during eruption also contained CK 6, 16 and perhaps CK 4. Thus, the JE in erupting teeth shows patterns of CK distribution that are very similar to that of developing oral epithelia. [ABSTRACT FROM AUTHOR]