Supporting cells as phagocytes in the olfactory epithelium after bulbectomy

Abstract

Macrophages are known to be phagocytes in the olfactory epithelium of adult rats. The participation of other cell types in phagocytosis in association with the cell death process was examined in the olfactory epithelium after unilateral bulbectomy of neonatal mice. The terminal deoxynucleotidyl transferase (TdT)-mediated biotinylated dUTP nick end-labeling (TUNEL) method revealed that the process of olfactory cell death consists of acute and chronic periods. The number of apoptotic cell profiles on the operated side peaked at 1 day, and the percentage of labeled cell profiles was 13.6%. The number of dying cells rapidly decreased at 3 days and decreased further at 5 days. Only 3% of the cells were labeled at 5 days. The percentage of dying cells increased again at the end of first postoperative week and remained two- to four-fold higher than control values for 2 months (4.7-5.3%). Electron micrographs of sections from early postbulbectomy stages (1-7 days) showed that as many as 30% of supporting cell profiles contained apoptotic bodies, cellular debris and phagosomes in the cytoplasm. The number of supporting cell profiles containing phagosomes declined to a plateau 2 weeks following bulbectomy and remained at 8-12% of the supporting cell population for 2 months. The results indicate that supporting cells in the olfactory epithelium play a significant role in phagocytosis in both acute and chronic of cell death after bulbectomy in newborn mice. However, supporting cells are not the exclusive phagocytic cell type in the bulbectomized epithelium; a small number of macrophages was also observed. Moreover, the phagocytosis by supporting cells was observed in unperturbed epithelium in the early stages during postnatal development.

Cell proliferation and apoptosis in the olfactory epithelium of the shark Scyliorhinus canicula

“…The TUNEL method has been used successfully in the OE of different vertebrates (e.g., Suzuki et al, 1996;Matz and Krone, 2007). The presence of apoptosis in the OE of vertebrates has been observed at all levels of the epithelium (Magrassi and Graziadei, 1995), despite low levels of apoptosis among SCs (Deckner et al, 1997;Fung et al, 1997).…”

Apoptotic cell removal in development and tissue homeostasis

“…However, in vitro, numerous cell types from different tissues can ingest cells undergoing programmed or other forms of cell death and there is significant evidence for similar removal in the embryo or adult (e.g. [67][68][69][70][71][72]). In general, the receptors and uptake mechanisms appear similar or identical to those for macrophages [14,73], although the so-called non-professional phagocytes could be less efficient in their rate or extent of uptake (but probably not of intracellular processing) [14,73,74].…”

Identification and molecular regulation of neural stem cells in the olfactory epithelium

“…This selfrenewing, non-neuronal cell type expresses enzymes involved in metabolizing foreign compounds (cytochrome p450, glutathione-S-transferase mu 2, and carbonyl reductase 2; [25]), suggesting a role for SUS cells in detoxifying many of the noxious substances present in the air, to which the OE is exposed. SUS cells also phagocytose dead ORNs [26], and much like the glia of the brain, probably provide structural support to ORNs.…”