Junctional Epithelial Cells Attaching To Enamel Surface Maintain Proliferation Potential

Junctional epithelium is unique epithelial cell layer facing both to the gingival connective tissue and mature enamel surface via basal lamina, and has very limited free surface areas open toward the gingival sulcus. Ample evidence indicate that the cells comprising the junctional epithelium of functional teeth are highly mobile and are constantly replaced by the new ones arising from the proliferating cells of the basal layer facing the connective tissue but not from those facing the enamel surface. It is thus explained that the cells of junctional epithelium attaching to the enamel surface are non proliferating cells although these cells retain cytological features typical of basal epithelial cells.

Objectives: To survey and demonstrate the cells with proliferating potential in the junctional epithelium of rat molars in vivo.

Materials and Methods: Wistar rats at various developmental stages (3W and older) were fixed by perfusion with 4% PFA and paraffin-embedded after EDTA decalcification. Serial sections of molar regions were processed for double immunostaining for cell proliferation markers, PCNA and Ki67.

Results: CK14 immunostaining clearly demonstrated the entire epithelial elements of the dental and gingival epithelia and enabled easy distinction between the sulcular and junctional epithelia. The PCNA-positive cells in the gingival, sulcular, and junctional epithelia were mostly restricted to the basal layer facing the connective tissue. In the junctional epithelium, however, some cells attaching to the enamel surface were also strongly positive for both PCNA and Ki67.

Conclusion: These data provide first evidence indicating proliferation potential of the junctional epithelial cells attaching to the enamel surface, suggesting a new view of cell kinetics at the dento-gingival junction in young and adult rat molars. Cell proliferation assay of junctional epithelial cells using BrdU labeling is currently in progress. This work was supported in part by JSPS grants for scientific research (2122103).