Evaluation of Turnover of Olfactory Epithelium

Abstract

Recently, a rapid immunohistochemical technique without the radioisotope have been developed in which a thymidine analogue, 5-brome-2′-deoxyuridine (BrdU), is incorporated into replicating DNA and subsequently localized using a specific monoclonal antibody. Cell dynamics of olfactory mucosa in mice were investigated by means of immunohistochemical technique. The labelled elements were concentrated at the basal layer of the epithelium, which were observed 1hr after the first injection, and the labelling index were 7.2±3.0%. At 14 days after administration of BrdU, the labelled elements were immigrated in the midlayer of the epithelium, where can be recognized as the compartment of nerve cells. After 30 days, the labelled cells disappeared from the epithelium. It indicates that the period of turnover in the olfactory epithelium of mice are within 30 days. Seven days after axotomy of the olfactory nerves, the labelling index significantly increased to 11.6±2.6%. Next, the localizations of N-CAM (neural cell adhesion molecule), MAP5 (microtubule associated protein 5), NSE (neuron-specific enolase) were studied in the mouse olfactory epithelium. N-CAM and MAP5 immuno-positive stainings were exclusively found in the basal layer of the epithelium and axons in the lamina propria. In contrast, mature neurons located in the upper layer were stained with anti-NSE antibody. It is indicated that the difference of immunostaining localizations reflects the maturity of the olfactory neurons.