Primary culture of adult mouse olfactory receptor neurons.

Olfactory receptor neurons (ORNs) are unique because they can be replaced by stem cells throughout life. Previous studies have demonstrated that adult mouse olfactory epithelium (OE) injured by exposure to ZnSO4 through nasal irrigation can stimulate stem cell mitotic activity in situ, which continues when placed in culture. We report on an improved ZnSO4 delivery method, mist inhalation, which produces more consistent and greater yields of OE cells. Cultures established following this method contained bipolar, nest, fusiform, and giant cells. The bipolar cells usually underwent asymmetric process development. Some bipolar cells reacted positively to neuron-specific antibodies and were immunonegative for keratin and glia-specific proteins, suggesting that they were ORNs. Those that were negative for the neuron-specific proteins may represent either neuron progenitors or olfactory ensheathing cells. The fusiform cells were relatively small and undifferentiated, exposure to brain-derived neurotrophic factor resulted in their decrease and an increase in bipolar cells. Therefore, they might be the stem cells. The nest cells had morphological characteristics of epithelia and bound keratin antibodies. The giant cells had the morphology of epithelial cells but were negative for keratin; they may represent a unique cell population induced by the ZnSO4. These results indicate that the major cell types of intact OE are present in our cultures, and each retains characteristics found in situ. The mist inhalation method provides an in vitro population of adult mitotically active neurons for study.