Expression of PAR2 and NF-κB in human primary dental pulp odontoblasts during the progression of caries

Abstract

Increased proteinase-activated receptor-2 (PAR2) expression is observed in various diseases related to inflammation. However, the expression of PAR2 in odontoblasts in response to dental caries has not been investigated. Therefore, to explore the functions of odontoblasts during the progression of carious infection, we measured PAR2 and NF-κB expression using immunofluorescence techniques in the odontoblast layer and pulpocytes in the sub-odontoblast region of 44 teeth extracted from children undergoing dental treatment (eight sound samples, 13 early carious samples, 16 advanced carious samples, and eight exposed pulp samples). PAR2 and NF-κB were expressed at moderate levels in sound teeth with non-carious pulp, and the expression levels changed as caries progressed. PAR2 was significantly upregulated in the odontoblast layer during early-stage and advanced-stage caries, and reduced below healthy levels in teeth with exposed pulp. NF-κB was significantly upregulated in early-stage caries and significantly downregulated in advanced-stage and late-stage caries. Moreover, in the sub-odontoblast region, NF-κB expression increased with the progression of caries. Overall, this study suggests PAR2 may represent a crucial cell signalling receptor in the dentine-pulp complex during dental inflammation, and that NF-κB may be one of the key pathways that regulate inflammatory immune responses in the dental pulp.