Epithelial-to-mesenchymal transition (EMT) is an active process in the large airways of patients with asthma-COPD overlap (ACO) and partially masked by inhaled corticosteroid treatment: a bronchoscopy endobronchial biopsy study

Surajit Dey¹Wenying Lu¹Prabuddha Sanjeewa Pathinayake²Maddison Waters³Greg Haug³Josie Larby³Heinrich C Weber¹Peter A B Wark⁴Mathew Suji Eapen¹Sukhwinder Singh Sohal^1*

• ¹University of Tasmania, Hobart, Australia
• ²The University of Newcastle, Callaghan, New South Wales, Australia
• ³Launceston General Hospital (LGH), Launceston, Tasmania, Australia
• ⁴Monash University, Melbourne, Victoria, Australia

Asthma and chronic obstructive pulmonary disease (COPD) overlap (ACO) is a term used to describe a patient with coexisting clinical features of asthma and COPD. We have previously reported that epithelial to mesenchymal transition (EMT) is active in the lungs of patients with COPD however, EMT in ACO remains an unexplored area. We hypothesize that EMT is an active process in ACO. In this cross-sectional study, large airway endobronchial biopsy (EBB) tissues from patients with asthma (14), COPD (22, current (CS) and ex-smokers (ES), and ACO (12) were immunohistochemically stained with EMT markers (E and N-cadherin, vimentin, S100A4, and Collagen IV) and compared with 12 current smokers with normal lung function (NLFS) and 10 non-smoking healthy control (HC) subjects. In addition, air-liquid interface (ALI) cell cultures were performed and cells from patients with ACO and HC were treated with TGF-β, IL-13 and cigarette smoke extract. Later cells from ALI cultures were lysed for Immunoblotting. Immunostained tissues were enumerated for percent expression of E and N-Cadherin in the epithelium, vimentin and S100A4 positive cells both in the epithelium and reticular basement membrane (RBM). Additionally, the degree of RBM fragmentation was evaluated, a key tissue structural marker of EMT. Compared to healthy controls and asthmatics, ACO had the greatest fragmentation of RBM (P < 0.01). ACO also had substantially decreased percentage expression of E-cadherin (P <0.01), increase percentage of N-cadherin expression, and higher vimentin and S100A4 positive basal cells, in comparison to healthy controls. In the RBM of ACO, S100A4 positive cells (P <0.05) and Vimentin-positive cells were markedly higher in comparison to HC. This data is suggestive of active EMT in ACO. Additionally, 50% of the patients with ACO were on 800 mcg/day inhaled corticosteroid (ICS) treatment which may have abrogated some EMT activity, however, it suggests protective effects of ICS. Studies with larger cohorts are needed to further confirm ICS effect.