Establishment of mouse gingival junctional epithelial cell line using a bioengineered tooth system.

Junctional epithelium (JE), one of the constituents of periodontal tissue, has several unique features to prevent bacterial infection. However, the molecular mechanisms of these cells remain to be completely elucidated because there has been no JE cell line to date. We have succeeded in isolating JE cells expressing green fluorescent protein (GFP) by using a bioengineered tooth technique in mice. The gene expressions of GFP-positive JE cells, isolated from around the erupted bioengineered teeth using flow cytometry, were analyzed by RNA sequencing. GFP-positive cells derived from the bioengineered tooth germs showed similar gene expression patterns to primary JE cells. The isolated GFP-positive JE cells were immortalized by transducing the simian virus 40 large T antigen using lentiviral vectors. The established GFP-positive JE cells maintained proliferative activity for more than 20 passages, and did not show cellular senescence as demonstrated by ß-galactosidase assay. These cells also expressed similar gene expression patterns to primary JE cells. The established cell lines may prove useful for future investigation of JE characteristics in vitro.

Visualization of junctional epithelial cell replacement by oral gingival epithelial cells over a life time and after gingivectomy.

Junctional epithelium (JE), which is derived from odontogenic epithelial cells immediately after eruption, is believed to be gradually replaced by oral gingival epithelium (OGE) over a lifetime. However, the detailed process of replacement remains unclear. The aim of the present study was to clarify the process of JE replacement by OGE cells using a green fluorescent protein (GFP)-positive tooth germ transplantation method. GFP-positive JE was partly replaced by OGE cells and completely replaced on day 200 after transplantation, whereas there was no difference in the expression of integrin ß4 (Itgb4) and laminin 5 (Lama5) between JE before and after replacement by OGE cells. Next, GFP-positive JE was partially resected. On day 14 after resection, the regenerated JE consisted of GFP-negative cells and also expressed both Itgb4 and Lama5. In addition, the gene expression profile of JE derived from odontogenic epithelium before gingivectomy was partly different from that of JE derived from OGE after gingivectomy. These results suggest that JE derived from the odontogenic epithelium is gradually replaced by OGE cells over time and JE derived from the odontogenic epithelium might have specific characteristics different to those of JE derived from OGE.

The junctional epithelium originates from the odontogenic epithelium of an erupted tooth.

The junctional epithelium (JE) is an epithelial component that is directly attached to the tooth surface and has a protective function against periodontal diseases. In this study, we determined the origin of the JE using a bioengineered tooth technique. We transplanted the bioengineered tooth germ into the alveolar bone with an epithelial component that expressed green fluorescence protein. The reduced enamel epithelium from the bioengineered tooth fused with the oral epithelium, and the JE was apparently formed around the bioengineered tooth 50 days after transplantation. Importantly, the JE exhibited green fluorescence for at least 140 days after transplantation, suggesting that the JE was not replaced by oral epithelium. Therefore, our results demonstrated that the origin of the JE was the odontogenic epithelium, and odontogenic epithelium-derived JE was maintained for a relatively long period.