Microvillar cells of the olfactory epithelium: morphology and regeneration following exposure to toxic compounds.
In recent years microvillar cells (MVC) have been identified in the olfactory epithelium of numerous species, including rodents, canines, and primates. However, there is no consensus on the morphologic or histochemical features of this cell, nor is the function of these cells currently known. Previous studies have examined MVC during development and in the mature olfactory epithelium, but not after toxic insult. A microvillar cell, defined by specific morphologic criteria, was studied in adult male Long-Evans rats exposed via inhalation to either 200 ppm methyl bromide for 4 h/day, 4 days/week for 2 weeks, or to 635 micrograms/m3 nickel for 6 h/day for 16 consecutive days, and sacrificed serially over several months. The pattern of recovery for MVC differed according to the severity and specificity of the insult to the olfactory epithelium. With methyl bromide, all cell types were completely depleted from olfactory epithelium immediately after injury, including MVC. MVC were slow to repopulate the epithelium, and appeared only when olfactory epithelium was complete in other respects. With nickel exposure, where the major effect was a gradual decrease in sustentacular cells with a thinning of the apical cytoplasm thickness, MVC showed a decline during exposure, but reappeared during recovery. In both cases, there was no difference in olfactory function, even when MVC were absent from the olfactory epithelium. A mature olfactory epithelium appears to be necessary to support the presence of this MVC, suggesting that it is not crucial to the regeneration processes or recovery of olfactory function, but perhaps plays some role, as yet undefined, in the unperturbed olfactory epithelium.
Miller
M L
ML
Department of Environmental Health, College of Medicine, University of Cincinnati, OH 45267-0056.
Andringa
A
A
Evans
J E
JE
Hastings
L
L
D000818:Animals; D001965:Bromides / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D008297:Male; D008854:Microscopy, Electron; D009296:Nasal Cavity / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D009297:Nasal Mucosa / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D051381:Rats; D012038:Regeneration
D001965:Bromides; D009532:Nickel