Neutrophils are a major source of the epithelial barrier disrupting cytokine Oncostatin M in mucosal airways disease

Abstract

Background

We have previously shown that Oncostatin M (OSM) is elevated in nasal polyps of chronic rhinosinusitis (CRS) patients, as well as in bronchoalveolar lavage (BAL) fluids after segmental allergen challenge in allergic asthmatics. We also showed in vitro that physiological levels of OSM impair barrier function in differentiated airway epithelium.

Objective

We sought to determine which hematopoietic or resident cell type(s) were the source of the OSM expressed in mucosal airways disease.

Methods

Paraffin-embedded NP sections were stained with fluorescence-labeled specific antibodies against OSM, GM-CSF and hematopoietic cell specific markers. Live cells were isolated from NP and matched blood samples for flow cytometric analysis. Neutrophils were isolated from whole blood, cultured with the known OSM inducers GM-CSF and FSTL1, and levels of OSM were measured in the supernatants. Bronchial biopsy sections from controls, moderate asthmatics and severe asthmatics were stained for OSM and neutrophil elastase.

Results

OSM staining was observed in NP, showed co-localization with neutrophil elastase (n=10), and did not co-localize with markers for eosinophils, macrophages, T cells or B cells (n=3–5). Flow cytometric analysis of NP (n=9) showed that 5.1±2% of CD45 ⁺ cells were OSM ⁺, and of the OSM ⁺ cells, 56±7% were CD16 ⁺Siglec8 ⁻, indicating neutrophil lineage. Only.6±.4% of CD45 ⁺ events from matched blood samples (n=5) were OSM ⁺, suggesting that elevated OSM in CRS was locally stimulated and produced. A majority of OSM ⁺ neutrophils expressed Arginase 1 (72.5±12%), suggesting a N2 phenotype. GM-CSF was elevated in nasal polyp tissue compared to control, and was sufficient to induce OSM production (p<.001) in peripheral blood neutrophils in vitro. OSM ⁺ neutrophils were also observed at elevated levels in biopsies from patients with severe asthma. Additionally, OSM protein was elevated in induced sputum from asthmatic patients compared to controls (p<.05).

Conclusions

Neutrophils are a major source of OSM producing cells in CRS and severe asthma.