Apparent apoptotic cell death in the olfactory epithelium of adult rodents: death occurs at different developmental stages.

In the olfactory epithelium of adult rodent, receptor neurons are generated continually. Despite the ongoing generation of new neurons, no corresponding increase occurs in the thickness of the mature olfactory epithelium. Thus, epithelial cell death must occur to offset the continual generation of new cells. In the present study, a sensitive method to label nicked DNA in dying cells was combined with immunocytochemistry to determine the identity of dying olfactory cells. In addition, the positions of putative apoptotic cells were mapped to provide additional information about the identity of dying cells. Double labeling experiments revealed that each of the olfactory cell types, i.e., basal cells (keratin-positive), immature neurons (GAP43-positive) and mature receptor neurons (olfactory marker protein (OMP)-positive), were positive for fragmented DNA, suggesting that they undergo apoptotic cell death. The results of the mapping study suggest that apoptotic cell death occurs primarily among GAP43-positive neurons.