Mast cells constitute a significant proportion of cells infiltrating
nasal polyp tissue, and epithelial cells may release
stem cell factor (SCF), a
cytokine with chemotactic and survival activity for mast cells. We aimed to assess the expression of SCF in human
nasal polyp epithelial cells (NPECs) as related to patients' clinical phenotypes.
Nasal polyp tissues were obtained from 29 patients [including nine with
aspirin (ASA)-
hypersensitivity and 12 with
bronchial asthma] undergoing polypectomy for
nasal obstruction. Epithelial cells were obtained following 6-week culture of
nasal polyps explants. The SCF released into the culture supernatant was assessed by
enzyme-linked
immunosorbent assay (ELISA) and total SCF
mRNA in the
polyp tissue was determined by semiquantitative
reverse transcriptase polymerase chain reaction (RT-PCR). For the whole group of patients, the number of polypectomies correlated with expression of SCF
mRNA (r = 0.62; P < 0.005), SCF
protein in the NPECs supernatants (r = 0.39; P < 0.05) and with density of mast cells in epithelial layer (r = 0.37; P < 0.05) and stromal layer (r = 0.5; P < 0.01) of
nasal polyps. The SCF/
beta-actin mRNA ratios were significantly higher in ASA-hypersensitive (AH) asthmatics (median 0.97, range: 0.8-1.5) when compared with ASA-tolerant (AT) patients (median 0.5, range: 0.1-0.7; P < 0.001). The SCF
protein concentration in NPEC supernatants was also significantly higher in AH asthmatics (median 1.10 pg/microg
DNA, range: 0.4-1.9) when compared with AT patients (median 0.1 pg/microg
DNA, range: 0.02-1.2; P < 0.001). In the subpopulation of ASA-sensitive asthmatics the number of polypectomies correlated also with the density of mast cells and eosinophils in the
polyp tissue.