Biological characteristics of the junctional epithelium

Abstract

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.

Influence of plasma and ultraviolet treatment of zirconia on initial attachment of human oral keratinocytes: Expressions of laminin γ2 and integrin β4

“…In this study, extensive distributions of laminin γ2 were also observed around the cells in the O2-plasma specimen after 24 h. Cells migrate after attachment and spreading, and turnover involving cell migration occurs in the junctional epithelium to maintain homeostasis of the periodontal tissues 23) . A previous study suggested that integrin β4 is expressed at the distal (back) regions of the cells to form basic points for attachment, while integrin α 3 is localized at the proximal (front) regions to promote cell migration 24) .…”

Comparative Temporospatial Expression Profiling of Murine Amelotin Protein during Amelogenesis

“…This is likely due to the lower sensitivity of the in situ hybridization protocol. Based on the observation that we did not find AMTN associated with hemi-desmosomes, which are known to be involved in cell to mineral attachment [Shimono et al, 2003], we experimentally queried whether AMTN could be directly involved in cell adhesion. The results from the in vitro cell adhesion experiments presented here do not support a direct role for AMTN in adhesion of a variety of cell types, including ameloblast-like cells.…”

“…At the maturation stage, ameloblasts reduce in size and diminish their secretory activity [for a review, see Zeichner-David et al, 1995;Thesleff and Aberg, 1997]. There is an overall loss of about 50% of the cells as they undergo apoptosis either during the transition stage immediately preceding the maturation stage, or during their transformation to create the reduced enamel epithelium, which is believed to subsequently fuse with the oral mucosa epithelium to form the initial junctional epithelium of the gingiva [Shimono et al, 2003;Nanci, 2007] Ameloblasts produce specific enamel matrix proteins depending on their differentiation stage. During the secretory stage, the majority ( 1 90%) of ameloblast proteins secreted are amelogenins (AMEL), which exist as a number of different splice variants.…”

Mobilization of TLR4 Into Lipid Rafts by Aggregatibacter Actinomycetemcomitans in Gingival Epithelial Cells

“…The gingival epithelium is the first line of defense against a microbial challenge and plays a crucial role as a mechanical barrier to bacterial invasion and in innate immune responses to infectious inflammation in periodontal tissue [1,2]. Therefore, an investigation of the interaction between the gingival epithelium and periodontopathic bacteria may provide insights into the pathogenesis of the initiation of periodontitis.…”