Expression of connexins and the effect of retinoic acid in oral keratinocytes.

Differential expression of members of the connexin (Cx) gap junction multigene family permits formation of gap junctions with the varied physiological properties required by different tissues. The aim of this study was to characterize connexin expression and the influence of all-trans-retinoic acid (RA) in mouse gingival epithelial cells (GE1). The cells were treated with RA, and expression of Cxs was analyzed by immunofluorescence, reverse transcriptase-polymerase chain reaction (RT-PCR), and real-time PCR. RT-PCR revealed that GE1 cells expressed mRNA for Cx26, Cx30.3, Cx31.1, Cx32, and Cx43. In addition, real-time PCR revealed that RA significantly decreased expression of Cx31.1 as compared with control. These results indicate that GE1 cells are useful in analyzing the expression of connexin molecules in oral keratinocytes from oral mucosal lesions.

Ductal adenocarcinoma of the pancreas with psammomatous calcification: report of a case with immunohistochemical study for bone morphogenetic protein.

We report a case of invasive ductal adenocarcinoma of the pancreas with psammomatous calcification. A 57-year-old man was admitted to our hospital complaining of abdominal pain and vomiting. Carcinoma of the head of the pancreas was diagnosed based on precise clinical examinations. A subtotal stomach-preserving pancreaticoduodenectomy was subsequently performed. Histological examination of the surgical specimen revealed a well-differentiated adenocarcinoma composed of irregular tubular structures involving the head of the pancreas. Conspicuously, numerous tiny psammomatous-type calcifications were observed, mainly within the neoplastic lumen, but also in association with carcinoma cells that had infiltrated the lymphatics and lymph nodes. In addition, expression of bone morphogenetic protein, cartilage and bone-inducing factor cloned from demineralized bone matrix and the transforming growth factor-ß subfamily was immunohistochemically examined for carcinoma cells. Reactivity for multiple kinds of bone morphogenetic protein (types 5, 6 and 7) was identified in the cytoplasm of carcinoma cells. Psammoma body formation is an unusual event in invasive ductal adenocarcinoma of the pancreas, with only one similar case previously reported in the English literature. We also discuss the formation of psammomatous calcifications by pancreatic cancer cells.

Establishment of human dental epithelial cell lines expressing ameloblastin and enamelin by transfection of hTERT and cdk4 cDNAs.

BACKGROUND: An in vitro cell culture system of dental epithelium is useful for the investigations of cellular differentiation and function of ameloblast in amelogenesis and of regenerative therapy in human tooth. However, there have been no immortalized human dental epithelial ameloblastic-lineage cell lines, which proliferate indefinitely and additionally produce enamel matrix proteins. METHODS: We transfected two retroviral constructs of human telomerase reverse transcriptase (hTERT) cDNA and mouse cyclin-dependent kinase 4 (cdk4) cDNA into the primary ameloblastoma cells and isolated immortalized human dental epithelial cell lines of HAM1, HAM2 and HAM3. The three cell lines were examined by electron microscopy, assay of senescence-associated ß-galactosidase activity, mRNA expression and immuno-reactivity of dental epithelial marker cell molecules and enamel matrix proteins. RESULTS: They showed undifferentiated phenotypes in monolayer culture and did not have any ß-galactosidase activity. The transcripts of dental epithelial cell markers of Msx2, Jagged1, Notch1, Sp3, Sp6, keratin 14 and keratin 18 were confirmed. In addition, mRNA and protein expression of ameloblastin and enamelin were also detected in three cell lines. All cells in the three cell lines were keratin 14- and 18-positive and some elongated cells were Jagged1-positive. Msx2-positive nuclei were noted in only HAM2 cells. CONCLUSION: We established three cell lines by transfection of hTERT and cdk4 cDNAs, which were characterized as dental epithelial progenitor cells containing ameloblast-lineage cell phenotype.

Localization of bromodeoxyuridine-incorporating, p63- and p75(NGFR)- expressing cells in the human gingival epithelium.

The objective of this study was to find the sites with proliferative activity in the human gingival epithelium, where stem cells are likely to exist. Gingival tissues were excised from 16 adult patients and immunohistochemically examined for the presence of bromodeoxyuridine (BrdU)-incorporating, p63- and low affinity nerve growth factor receptor (p75(NGFR))-expressing cells. BrdU-incorporating cells were rarely present in the junctional epithelium. The number of BrdU-incorporating cells in the sulcular and oral gingival epithelia was significantly higher than that found in the junctional epithelium (ANOVA, P < 0.01). A considerable number of p63-positive nuclei were detected in the basal layer to lower spinous layers in the sulcular and oral gingival epithelia, but only few p63-positive cells were present in the junctional epithelium. p75(NGFR)-positive cells were exclusively located in the basal layer in the sulcular and oral gingival epithelia, and in limited basal area in the junctional epithelium neighboring the sulcular epithelium. In the oral gingival epithelium, intense immunostaining of BrdU, p63 and p75(NGFR) was correspondingly observed on the base and side of the rete ridges. These areas probably exhibit high proliferative activity owing to the presence of stem cells.