Olfactory Sensory Neuron: Immunohistochemical Markers, Technique of Flat-Mounted Mucosa and Cell Count

A classification of olfactory sensory neuron (OSN) markers, a simple and robust technique of immunostaining on flat-mounted olfactory epithelium (OE) and a reliable quantification of the density of mature and immature OSNs are three crucial tools to study the pathophysiology of olfactory dysfunction. Using the rat model, we first categorized the main OSN markers by immunohistochemistry (IHC) on cross sections of OE. The OSN markers were divided into 3 groups: mature OSNs (OMP), immature OSNs (Tuj-1, DCX, OLIG2) and both (N-cadherin, LHX2, PGP9.5). The subcellular localization of each marker was also described. Tuj-1, OMP, DCX, PGP9.5 and N-cadherin were selected for immunostaining on flat-mounted OE because of their staining of OSN dendrites. We were able to successfully label OE with all the 5 markers using a simple technique for flat-mounted OE. In addition, this technique allowed the first mapping of the OE directly on the ethmoid turbinates. Finally, we quantified the mature (OMP+, Tuj-1-), immature (OMP-, Tuj-1+), transitory (OMP+, Tuj-1+) and total OSN density which were respectively 42080 ± 11820, 49384 ± 7134, 14448 ± 5865 and 105912 ± 13899 per mm 2 (mean ± SD). The transitory population was quantified for the first time.