Expression and localization of aqua-glyceroporins AQP3 and AQP9 in rat oral epithelia.

Aquaporins (AQPs) are a family of small integral membrane proteins made up of 6 hydrophobic, a-helical, membrane-spanning domains surrounding a highly selective aqueous pore. AQP3, AQP7, and AQP9, termed aqua-glyceroporins, are known to be involved in the transport of water, glycerol, and other small molecules. In this study, we investigated the expression and localization of aqua-glyceroporins in rat oral stratified squamous epithelia of the palate, the buccal mucosa, the inferior aspect of the tongue, and the oral floor by using RT-PCR, immunofluorescence, and immunogold electron microscopy. AQP3 and AQP9 mRNAs were expressed in whole oral epithelium. Immunostaining for AQP3 was recognized in each type of epithelium. The results suggest that AQP3 synthesis begins predominantly in the cytoplasm of the basal cells. During the process of epithelial cell differentiation, AQP3 protein appears to accumulate and be transported to the plasma membrane, from where it is incorporated into the cornified or surface layers. The intracellular localization of AQP3 appears to correlate with the differentiation of keratinocytes, suggesting that it acts as an enhancer of the physiological permeability barrier together with membrane coating granules. The distribution pattern of AQP9 was limited to the marginal areas of the basal and suprabasal layers, which was different from that of AQP3. This difference in distribution between AQP3 and AQP9 suggests that AQP9 in rat oral epithelia acts as a channel by facilitating glycerol uptake from the blood through the endothelial cells of the capillary vessels to the oral stratified squamous epithelium. AQP3 and AQP9 facilitate both transcellular osmotic water flow and glycerol transport as pore-like passive transporters in the keratinocytes of oral epithelia, and may play a key role in not only hydration and the permeability barrier, but also cell proliferation, differentiation, migration, development, and wound healing by generating ATP.

Effect of stretching stress on gene transcription related to early-phase differentiation in rat periodontal ligament cells.

Mechanical stress such as occlusal and orthodontic loading has been suggested to induce a homeostatic and regenerative response in periodontal ligament (PDL), but the underlying mechanism remains to be clarified. The purpose of this study was to investigate expression of mRNAs encoding proteins involved in osteogenesis and homeostasis by PDL cells following application of tensile stress and characterize the relationship between such expression and the regenerative and homeostatic functions of the PDL. PDL cells were obtained from rats and stretched by 9% or 18% at a frequency of 6 cycles/min for 12 hr to 5 days in a FX-4000T™ culture system. After stretching, expression of mRNAs encoding collagen type I (Col-I), alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), bone morphogenetic protein-4 (BMP-4), heat shock protein 70 (HSP70) and basic fibroblast growth factor (bFGF) was investigated. The highest levels of Col-I, ALP and BMP-2 mRNA expression occurred at 12 hr, while those of BMP-4 and HSP70 occurred at 1 day and 5 days, respectively. Expression levels of Col-I, ALP, BMP-2, BMP-4 and HSP70 increased magnitude-dependently with stretching force in the stretching groups. In contrast, expression of bFGF mRNA showed statistically significant reduction in both stretching groups, with the largest reduction seen in the 9% stretching group (p<0.01). These results suggest that stretching of PDL cells provokes significant increases in expression of factors promoting osteogenic differentiation and HSP70, which protects PDL cells undergoing mechanical stress and contributes to maintenance of PDL homeostasis. However, expression of bFGF was restrained. Reduced expression of bFGF mRNA suggested that there was an optimum magnitude of stretching force for increasing expression.

Cell proliferation, apoptosis and apoptosis-related factors in odontogenic keratocysts and in dentigerous cysts.

BACKGROUND: The purpose of this study was to elucidate why odontogenic keratocysts (OKC) can form cystic lesions but not tumor masses, notwithstanding their prominent proliferative activity. METHODS: We investigated cellular proliferation, cell death, and expression of apoptosis-related proteins in the lining cells of OKCs and of dentigerous cysts (DGCs). RESULTS: TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were observed in the surface layers of OKCs and of DGCs. However, no TUNEL-positive cells were seen in the basal or intermediate layers of both cysts. Ki67-positive ratio in the intermediate layer was the highest in OKCs. The p53-positive ratio of the intermediate layer was highest in OKCs. Bcl-2-positive cells were discernible exclusively in the basal layer of OKCs. CONCLUSIONS: These results suggest that cellular proliferation and death is regulated in association with apoptosis-related proteins in the lining epithelia of OKCs, and subsequently those cysts are seen as cystic lesions but not as tumor masses.

Biological characteristics of the junctional epithelium.

This review summarizes the biological properties of the junctional epithelium, focusing on its developmental aspects, wide intercellular spaces and desmosomes, dense granules, permeability barrier, phagocytotic activity, adhesive structures and nerve terminals. It also discusses the morphology and functions of long junctional epithelium and peri-implant epithelium. Junctional epithelium is derived from the reduced enamel epithelium during tooth development. Apoptosis occurs in the border between oral and reduced enamel epithelia during tooth eruption. Junctional epithelium expresses a cytokeratin-19 immunoreaction, suggesting that this protein is a consistent differentiation marker. Wide intercellular spaces, which contain neutrophils and nerve endings, are formed as there are fewer desmosomes than in the oral epithelium. Dense, membrane-bound granules in the epithelium might correspond with membrane-coating granules, as revealed by their shape, components and freeze-fracture images. Junctional epithelium with high permeability contains exogenously expressed alpha-defensins, while stratified epithelia contain endogenously expressed beta-defensins. The phagocytotic activity in this epithelium remains unclear. Integrin-alpha6beta4 and laminin-5 form a complex in the tooth surface internal basal lamina. Long junctional epithelium created experimentally attaches to the cementum surface by hemidesmosomes and basal lamina. The peri-implant epithelium differs in proliferation and in adhesive structure from the normal junctional epithelium. In conclusion, wide intercellular spaces and poorly developed desmosomes are closely correlated with a permeable nature. There is still uncertainty over the phagocytotic activity of the epithelium. Integrin-alpha6beta4 and laminin-5 form a significant complex in the internal basal lamina. Junctional epithelium receives a rich sensory nerve and has a high rate of cell turnover. Long junctional epithelium can be produced rapidly during wound healing, due to high proliferative activity. Peri-implant epithelium might be a poorly adhered and permeable epithelium.

Cytokeratins expression of constituting cells in ameloblastoma.

The purposes of this study were to investigate the distribution of cytokeratins in the different tissue types of ameloblastoma and to discuss the histogenesis of this tumor. CK19 and CK8, which are markers for odontogenic epithelium, reacted positively to the constituting cells in all types of ameloblastoma. This suggests that all types of ameloblastoma derive from odontogenic epithelium. However, the desmoplastic type diminished the odontogenic characteristics because the basal cells are negative to CK19. Immunoreactions of five kinds of cytokeratin revealed similar results in plexiform, follicular, acanthomatous, and granular cell types. The plexiform type is probably the original type of ameloblastoma; the other types have the characteristics of squamous epithelium, and the follicular, acanthomatous, and granular cell types can develop due to the differentiation of cells of the plexiform type into squamous epithelium.