Immunohistochemical studies of the cellular changes in the peripheral olfactory system after zinc sulfate nasal irrigation.

The peripheral olfactory system has a remarkable capacity for repair. We have performed an immunohistochemical study of the cellular changes that occur after zinc sulfate irrigation of the nasal cavity. The rapid loss of epithelial cells was followed by the proliferation of basal cells and the restoration of the epithelium with olfactory tissue. Horizontal basal cell markers, anti-cytokeratin 5/6 (CK5/6), and the Bandeiraea simplicifolia (BS-1) lectin initially co-localized on day 1 after treatment but rapidly displayed a disparity in their staining profile, with CK5/6 immunoreactive cells having a profile more akin to cells expressing the sustentacular marker cytokeratin 18 (CK18). This suggests CK5/6 and BS-1 label a different subset of horizontal basal cells. Axonal degeneration and regeneration was studied with a panel of markers to olfactory receptor neurons, their terminals, and olfactory bulb dendrites. The glial cells of the peripheral olfactory system, olfactory ensheathing cells, remained in position, with little change in immunoreactivity to laminin, although an increase in the expression of glial fibrillary acidic protein was observed. The events and the extent of reconstitution of the olfactory system after degeneration serves as a foundation for future studies designed to understand the unique regenerative capacity of the olfactory system.