Adult Rat Odontoblasts Lack Noxious Thermal Sensitivity

Abstract

Dentin hypersensitivity is a common symptom treated in the dental clinic, yet the underlying cellular and molecular mechanisms are not clear. We hypothesized that odontoblasts detect noxious thermal stimuli by expressing temperature-sensing molecules, and investigated whether temperature-activated TRP channels (thermo-TRP channels), which are known to initiate temperature signaling, mediate temperature sensing in odontoblasts. mRNA expression of dentin sialophosphoprotein and collagenase type 1, odontoblast-specific proteins, was shown in acutely isolated adult rat odontoblasts by single-cell RT-PCR, while TRPV1, TRPV2, TRPM8, and TRPA1 were not detected. Application of noxious temperatures of 42 degrees C and 12 degrees C, as well as capsaicin, menthol, and icilin, agonists of thermo-TRP channels, failed to increase intracellular calcium concentration. Immunohistochemical study also revealed no expression of TRPV1. Thus, it is unlikely that odontoblasts serve as thermal sensors in teeth via thermo-TRP channels.

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…Similarly, in human odontoblasts differentiated in vitro from the pulp of extracted molar teeth, expression of TRPV1, TRPA1, and TRPM8 was described (El Karim et al, 2011). By contrast, odontoblasts isolated short term from adult rat incisors showed no evidence of TRPV1, TRPV2, TRPA1, and/ or TRPM8 expression (Yeon et al, 2009). To resolve these discrepant results, one might argue that either the actual odontoblasts are different from those obtained via in vitro differentiation or that the procedure of short-term isolation itself eliminates the odontoblasts that express TRPV1 or TRPV2.…”

Single-cell RT-PCR and immunocytochemical detection of mechanosensitive transient receptor potential channels in acutely isolated rat odontoblasts

“…15 Briefly, upper and lower incisors were extracted within 5-10 min of sacrifice of the animal and were kept in cold (3-5 8C) Extracellular saline (ECS). After the surrounding soft tissues were all removed, the teeth were sectioned transversely with 500 mm thickness with a diamond disc for plaster.…”

“…2,15 Briefly, the targeted cell was aspirated into a patch pipette with tip diameter of about 20 mm and put into reaction tube containing reverse transcription agents. Reverse transcription was for 1 h at 37 8C.…”

“…15 The cells showing these morphological characteristics were collected for scRT-PCR analysis for mRNA expression of stretch-activated TRP channel subfamilies and sialophosphoprotein (DSPP). 16 Most of the cells collected based on the visual inspection were positive for DSPP, and a small fraction of cells that lacks DSPP expression were not considered as odontoblasts.…”

TRP Channels in Dental Pain

“…Son et al used odontoblasts obtained by in vitro differentiation of pulpal cells of neonatal rats and found that odontoblasts expressed TRPV1, TRPV2, TRPV3, TRPV4, and TRPM3 by patch clamp recording and RT-PCR analysis [17]. Yeon et al used acutely isolated odontoblasts from adult rat incisors and reported that they could not find any evidence for the expression of TRPV1, TRPV2 by single cell RT-PCR, immunohistochemistry and functional analysis using calcium imaging [36]. Possible explanations for this discrepancy include: (1) the differentiated pulp cells might not be identical to the actual odontoblasts, (2) acutely isolation procedures damage the odontoblasts with TRPV1 or TRPV2, and (3) developmental difference in TRP expression between adult and neonatal rats.…”