Localization and expression of TRPV 1 and TRPA 1 in the human oropharynx and larynx

Background Previous studies have found that TRPV 1 and TRPA 1 receptor agonists improve swallow response in patients with oropharyngeal dysphagia ( OD ), but little is known about the expression of these receptors in the human oropharynx. The aim of this study was to assess the expression and localization of TRPV 1 and TRPA 1 in human samples from the oropharynx of healthy patients, to provide the basis for new pharmacological treatments for OD . Methods Samples from oropharyngeal regions innervated by cranial nerves V, IX, and X (tongue, pharynx, and epiglottis) were obtained during ENT surgery and processed either for mRNA (21 patients) or for immunohistochemical assays (seven patients). The expression analysis was performed with RT ‐ qPCR using ACTB h as reference gene. Hemotoxylin and eosin staining was used to study the histology; the immunohistochemical assay used (i) neuron‐specific enolase to detect nerve fibers or (ii) fluorescent probes to locate TRPV 1 and TRPA 1. Results TRPV 1 was expressed in the three studied regions, with higher levels in CN V region (tongue) than in CN X region (epiglottis; p < 0.05), and was localized at epithelial cells and nociceptive fibers in all studied regions. TRPA 1 was also expressed in all studied regions, but was always localized below the basal lamina. No immunoreactivity for TRPA 1 was found on epithelial cells. Conclusions & Inferences TRPV 1 and TRPA 1 are widely expressed in the human oropharynx with two distinct patterns. Our study further confirms that TRPV 1/A1 receptors are promising therapeutic targets to develop active treatments for OD patients.