Olfactory epithelium consisting of supporting cells and horizontal basal cells in the posterior nasal cavity of mice

The olfactory epithelium of mice generally consists of olfactory cells, pro genitors of olfactory cells (globose bas;al cells), supporting cells, and h orizontal basal cells. However, in the dorsal fossa (the roof) of the poste rior nasal cavity of mice, we found seven epithelial patches consisting of only non-neuronal cell types, i.e., supporting cells and horizontal basal c ells, among the normal olfactory epithelium. The supporting cells occupied three or four layers in the apical to middle regions; in the basal region, horizontal basal cells were localized in a single row adjacent to the basem ent membrane. Bowman's gland ducts were also present in the epithelium. Neu ronal cells (olfactory cells and globose basal cells) were totally absent. The ultrastructure of the supporting cells, horizontal basal cells, and Bow man's glands was essentially similar to that in the normal olfactory epithe lium. In the early postnatal period (P1-P7), cell types in the epithelium w ere the same as those in the normal olfactory epithelium. From P10 to P21, olfactory cells and globose basal cells had disappeared from the olfactory epithelium. At this period, the number of TUNEL-positive cells was signific antly higher than that in the surrounding olfactory epithelium; ultrastruct urally, many apoptotic figures were observed. This suggests that the epithe lium consisting of supporting cells and horizontal basal cells is generated by the apoptotic death of olfactory cells and globose basal cells during p ostnatal development.