Smoking-associated squamous metaplasia in olfactory mucosa of patients with chronic rhinosinusitis

Abstract

Few studies have examined the induction of squamous metaplasia in human olfactory nasal tissue caused by tobacco use and the implications it may have for olfaction, particularly when there are pre-existing insults, such as chronic rhinosinusitis (CRS). Quantitative histopathological analyses were performed on Alcian blue- and H&E-stained sections of nasal biopsies taken from the upper aspect of the middle turbinate of CRS patients. Chronic rhinosinusitis patients who were current smokers had a predominance of squamous metaplasia in the olfactory sensory epithelium, whereas CRS patients who were nonsmokers and were not exposed to secondhand cigarette smoke had a prevalence of goblet cell hyperplasia. In spite of this difference, the groups did not differ significantly in olfactory threshold sensitivity. The impact of primary cigarette smoke on olfaction and a possible role of squamous metaplasia in preserving olfactory neurogenesis are discussed.

Figure 1

The percent distribution of four different OM morphologies. The percent distribution of OM morphology (i.e., normal pseudostratified, goblet cell hyperplasia, squamous metaplasia and erosion) for A. individual CRS nonsmokers, B. individual CRS smokers in relation to age. The number of pack years is also included for CRS smokers.. C. The average percent distribution of the four OM morphologies for each group. Error bars = SEM.

Figure 2

Olfactory mucosal histopathology of CRS smokers with different pack year histories. Sections were stained with Alcian blue, hematoxylin, and eosin and two olfactory mucosal regions from the same biopsy section were imaged with a 40× objective. A. <1 pack year with normal olfactory epithelium and goblet cell hyperplasia, B. 1 pack year, C. 7 pack years, D. 9 pack years, and E. 15 pack years. Asterisks = goblet cells, MG = mucus gland, BV = blood vessel, and arrowhead = basement membrane. Scale bar = 50µm.

Figure 3

Olfactory neurogenesis persisted in the squamous OM. Sections were labeled with antibody to olfactory marker protein (OMP) and imaged with a 40× objective. A. <1 pack year: the presence of OMP-immunoreactive (OMP-ir, green) olfactory sensory neurons (OSNs, arrows) in the olfactory epithelium, B. 1 pack year: layers of OMP-ir OSNs are present, and C. 9 pack years: the presence of abnormally-shaped OMP-ir OSNs (asterisk) near the apical squamous layer. DAPI = blue. Scale bar = 20µm.