Changes in Proteinase-Activated Receptor 2 Expression in the Human Tooth Pulp in Relation to Caries and Pain

Aims: To investigate the presence of proteinase-activated receptor 2 (PAR2) in the human tooth pulp and to determine whether there are any changes in receptor expression with caries and pain. Methods: Forty-four mandibular first permanent molars were collected from children (n = 36, mean age 9.96 years ± 2.11) requiring dental extractions under general anesthesia. Teeth were categorized as either intact (n = 22) or carious (n = 22). Carious teeth were further subdivided into asymptomatic (n = 10) and painful (n = 12). The coronal pulp was removed and processed for indirect immunofluorescence by using antibodies raised against PAR2 and double labeled with either a neuronal marker (protein gene product 9.5) or both a smooth muscle cell (SMA) and endothelial (UEIL) marker, in order to examine PAR2 presence in both neuronal and vascular tissue. In addition, hemotoxylin and eosin staining was performed to identify pulpal fibroblasts. Results: PAR2 expression was found to be present in pulpal nerve fibers, vascular tissue, and pulpal fibroblasts. PAR2 neuronal expression was not affected by the presence of caries (P > .05) but was significantly less in carious painful teeth than in carious asymptomatic teeth (P .05). No changes in vascular PAR2 expression were found (P > .05); however, the number of PAR2-labeled fibroblast-like cells per mm2 was significantly greater in carious teeth (P .05). Conclusion: These findings indicate that PAR2 receptors and changes in their level of expression may have relevance and clinical importance in nociception. Keywords: caries, human tooth pulp, immunohistochemistry, pain, proteinase-activated receptor 2