Cell dynamics of dividing cells in the olfactory epithelium of guinea pigs, using the immunohistochemical double staining method

It is thought that olfactory receptor cells regenerate after degeneration caused by various factors and that these cells undergo turnover under normal circumstances in the animal olfactory epithelium. Furthermore, the precursors of olfactory receptor cells were previously thought to be basal cells. Recently, however, it was reported that cells located just above the basal cells are the precursor cells on the basis of observation of dividing cells in the normal olfactory epithelium using methods such as bromodeoxyuridine (BrdU) uptake. In this study, the author observed the cell dynamics of dividing cells in the olfactory epithelium of guinea pigs by labeling the dividing cells with BrdU. Many of the BrdU-labeled cells migrated to the superficial layers of the olfactory epithelium, but a few of these cells remained just above the basal cells and did not express cytokeratin. Furthermore, the BrdU-labeled cells definitely matured to olfactory receptor cells. BrdU-labeled cells expressed a neural cell adhesion molecule (N-CAM) from 1 to 35 days after being labeled with BrdU. These cells also expressed protein gene product 9.5 (PGP 9.5), which is a kind of neuron-specific protein, from 5 to 35 days after being labeled with BrdU. From these results, it was concluded that the precursors of olfactory receptors cells were not basal cells. In other words, the lineage of olfactory receptor cells did not involve basal cells. Immature olfactory receptor cells expressed N-CAM, and PGP 9.5 as well as N-CAM were expressed with maturation.