Neuronal and Vascular Vanilloid Receptor Expression in Human Tooth Pulp

The vanilloid receptor (TRPV1) acts as a physiological transducer for painful heat and may be important in development of inflammatory pain. Objectives: The aim of this study was to investigate the presence and distribution of TRPV1 in human dental pulp and to correlate its expression with inflammation and pain. Methods: Forty mandibular first permanent molars were collected from children requiring dental extractions under general anaesthetic. Teeth were categorised as intact or grossly carious. Grossly carious teeth were further categorised as carious asymptomatic (n=10) or carious painful (n=13) samples. Coronal pulps were removed and sections processed for indirect immunofluorescence using a TRPV1 antibody and either the general neuronal marker, protein gene product 9.5 or alpha smooth muscle actin and biotinylated Ulex europaeus agglutinin 1 lectin to label the pulp vasculature. Image analysis was used to quantify the percentage area of staining of TRPV1 in both neural and vascular tissue. Results: Examination revealed that TRPV1 was expressed within pulpal nerve fibres and was widely present within the pulp vasculature, including capillaries, arterioles and venules. TRPV1 was expressed in both vascular endothelium and smooth muscle. Expression of neuronal TRPV1 was found to be significantly greater in carious tooth pulp than in intact samples (p<0.05, independent sample t-test), but no significant differences were found between grossly carious asymptomatic and painful samples. However, a significant increase in vascular TRPV1 expression was observed in the mid-coronal pulp region in carious painful samples compared with carious asymptomatic samples (p<0.05, independent sample t-test). Conclusion: It appears that expression of neural TRPV1 is related to the development of inflammation but does not correlate with reported pain. However, vascular TRPV1 expression appears to be positively correlated with dental pain and this may provide new insights into symptomatic pulpitis. This study was supported by GlaxoSmithKline and the Medical Research Council.