Abstract
BackgroundRecent studies have suggested that eosinophils may have a direct effect on airway smooth muscle cells (ASMC), causing their proliferation in patients with asthma, but the precise mechanism of the interaction between these cells remains unknown. We propose that changes in Wnt signaling activity and extracellular matrix (ECM) production may help explain these findings. Therefore, the aim of this study was to investigate the effect of eosinophils from asthmatic and non-asthmatic subjects on Wnt-5a, transforming growth factor β1 (TGF-β1), and ECM protein (fibronectin and collagen) gene expression and ASMC proliferation.MethodsA total of 18 subjects were involved in the study: 8 steroid-free asthma patients and 10 healthy subjects. Peripheral blood eosinophils were isolated using centrifugation and magnetic separation. An individual co-culture of eosinophils with human ASMC was prepared for each study subject. Adhesion of eosinophils to ASMC (evaluated by assaying eosinophil peroxidase activity) was determined following various incubation periods (30, 45, 60, 120, and 240 min). The expression of Wnt-5a, TGF-β1, and ECM protein genes in ASMC was measured using quantitative real-time polymerase chain reaction (PCR) after 24 h of co-culture. Proliferation of ASMC was measured using the Alamar blue method after 48 h and 72 h of co-culture with eosinophils.ResultsEosinophils from asthmatic subjects demonstrated increased adhesion to ASMC compared with eosinophils from healthy subjects (p < 0.05) in vitro. The expression of Wnt-5a, TGF-β1, collagen, and fibronectin genes in ASMC was significantly higher after 24 h of co-culture with eosinophils from asthmatic subjects, while co-culture of ASMC with eosinophils from healthy subjects increased only TGF-β1 and fibronectin gene expression. ASMC proliferation was augmented after co-culture with eosinophils from asthma patients compared with co-culture with eosinophils from healthy subjects (p < 0.05).ConclusionsEosinophils enhance Wnt-5a, TGF-β1, fibronectin, and collagen gene expression in ASMC and promote proliferation of these cells in asthma.Trial registrationClinicalTrials.gov Identifier: NCT02648074.
Highlights
Recent studies have suggested that eosinophils may have a direct effect on airway smooth muscle cells (ASMC), causing their proliferation in patients with asthma, but the precise mechanism of the interaction between these cells remains unknown
Eosinophil adhesion to airway smooth muscle cells Adhesion was expressed as eosinophil peroxidase (EPO) substrate oxidation in co-cultures of eosinophils and ASMC relative to EPO substrate oxidation in control ASMC; the control value is set as 100 %, and eosinophil expression is the difference from the control value
Adhesion of eosinophils from asthma patients was significantly greater than adhesion of eosinophils from healthy subjects at all time points: 30 min (97.5 ± 15.2 % vs 25.3 ± 4.1 %; p < 0.05), 45 min (78.2 ± 13.6 % vs 24.8 ± 6.9 %; p < 0.05), 60 min (112.9 ± 19.2 % vs 41.1 ± 7.7 %; p < 0.05), 120 min
Summary
Recent studies have suggested that eosinophils may have a direct effect on airway smooth muscle cells (ASMC), causing their proliferation in patients with asthma, but the precise mechanism of the interaction between these cells remains unknown. Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play critical roles. It is characterized by chronic inflammation, which is associated with airway hyperresponsiveness that leads to recurrent episodes of coughing, wheezing, breathlessness, and chest tightness [1]. Airway remodeling encompasses cellular and structural changes in the airway [4] These changes include subepithelial fibrosis, smooth muscle hypertrophy/hyperplasia [5, 6], epithelial cell mucus metaplasia, greater extracellular matrix (ECM) production [7], and angiogenesis [8, 9]. Increased airway smooth muscle mass is a pathological feature in individuals with asthma [10]
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