Mechanosensitive Ion Channels in Odontoblasts
Odontoblasts are post-mitotic cells involved in the dentine formation throughout the life of the tooth and suspected to play a role in tooth pain transmission. They are organized as a single layer of specialized cells along the interface between dental pulp and calcified dentinal tubules into which run a cellular extension (odontoblast process) bathed in a liquid phase. Dense sensory unmyelinated nerve fibres surrounded the odontoblast bodies, coiled around the cell processes and give to this complex (nerve/odontoblast) a fundamental role as a barrier regulating molecules, fluid flow, ion transferts between dentine and pulp following external stimuli (mechanical thermal, electrical, osmotic shock…). Thus, this unique spatial situation of odontoblasts closely related with nerve endings and fluid movements suggest that odontoblasts could convert pain-evoking fluid displacement within dentinal tubules into electrical signals via at least mechanosensitive ion channels. Along this line, two kinds of mechanosensitive K+ channels have been identified in human odontoblasts: I- TREK-1 channels belonging to the two-pore-domain potassium channel family and expressed in the plasma membrane of coronal odontoblasts; II- high-conductance Ca2+ -activated potassium channels (KCa) activated by stretch of the membrane as well as osmotic shock. These findings strengthened by the recent evidence for excitable properties of odontoblasts, concentration of mechanosensitive channels in the borderline between cell extension and bodies and clustering of key molecules at the site of odontoblast-nerve contact strongly suggest that odontoblasts may operate as sensor cells.
KeywordsTeeth Odontoblast Mechanosensitive potassium channel TREK-1 channel KCa channel Voltage-gated sodium channel Tooth pain
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