Sensory Neuron Specific Receptor Expression in Human Dental Pulp

Objective: The mas-related gene (Mrg) family, also known as sensory neuron specific receptors (SNSRs), consists of a group of orphan G protein-coupled receptors, selectively expressed in nociceptive neurons.  In skin and other tissues, Mrg receptors have antinociceptive actions; however, it is not known whether they modulate pain sensation in dental pulp, a tissue with significant sensory innervation.  We have shown previously that MrgA and MrgX1 immunoreactivity is present in rat tooth pulp in a pattern that overlaps with, but is not identical to immunostaining with neurofilament antibodies. This study is designed to investigate the identity and cellular location of Mrg receptors in human pulp tissue.  Our working hypothesis is that Mrg receptors are present in human dental pulp and modulate nociceptive pathways.  The objectives are i) to identify the type/s of Mrg receptors expressed in human dental pulp and ii) to identify their cellular location in the pulp.

Method: Samples of human pulp tissue were removed intact from freshly extracted, healthy 3^rd molars of patients undergoing extractions as part of routine dental treatment, and used for preparation of mRNA and protein extracts for analysis by RT-PCR and Western blotting respectively.  Other samples were fixed in paraformaldehyde, and sectioned for analysis by immunostaining.  Sub cellular distribution of Mrg receptors will be determined using antibodies directed against neuronal and non-neuronal markers.

Result: We will present data indicating the type/s of Mrg receptors expressed in human dental pulp and the relationship of pulpal nociceptors with Mrg receptor expression.

Conclusion: The identification and distribution of Mrg receptors in human dental pulp provides new insights in the modulation and management of dental pain.  Characterization of novel antinociceptive molecules is important for developing new drugs targeting pain transduction mechanisms in the pulp.