Journal Article

S144 Failure to repair: an in vitro model of aspergillus fumigatus infection in airway epithelial injury

Gifford, HEC, Lim, D, Silva, J, Cook, PC, Scotton, C, Vere, G

2023

Overview

Question: How does the ubiquitous environmental mould, Aspergillus fumigatus, impact bronchial epithelial cells (BECs) during injury? This study aimed to assess an in vitro model of host-pathogen interaction with the underlying hypothesis that A.f. infection disrupts lung epithelial repair in disease.Background A.f. causes a broad spectrum of life-threatening invasive and allergic respiratory diseases in over 18 million individuals worldwide. The impact of A.f. infection during co-morbid acute and chronic respiratory diseases has been identified but the underlying mechanistic basis of this is unclear.MethodologyTo mimic lung barrier damage, we employed a scratch assay on CM-DiI labelled 16HBE14o- cell (BEC) monolayers on 0.4μm pore transwells cultured in MEMα containing 10% FBS. Scratch closure in the presence and absence of transgenic GFP+ A. fumigatus was measured using timelapse fluorescence microscopy. Epithelial migration velocity was calculated using non-linear regression with the Levenberg-Marquardt algorithm. To determine epithelial uptake of spores, BEC were isolated at different time points of the culture and spore uptake was measured via flow cytometry.ResultsWhile we found wound closure occurred within 12–18 hours (mean maximum closure 97.2%), this was prevented in the presence of live A.f. spores (MOI 10:1, mean maximum closure 54.9%). Spore inhibition of wound closure was associated with presence of mycelium growth. Furthermore, addition of spores to BEC cultures 24h prior to scratch wounding dramatically inhibited wound closure (mean maximum closure 3.9%). Despite this, epithelial velocity during wound repair between 3–7 hours post scratch was increased in the presence of spores (MOI 1:1000, 0.28 μm/h; 1:100, 0.47 μm/h; 1:10, 0.58 μm/h). Finally, flow cytometry analysis showed that spores were not internalised by epithelial cells (uptake 0.50–0.66 %), showing that the impact of A.f. epithelial cell wound closure and cell velocity was not due to epithelial cell uptake of spores.ConclusionsBEC wound repair accelerates and then fails during A.f. infection in a dose-dependent manner. Further research should explore the reproducibility of these preliminary findings and the mechanisms underlying wound repair failure. Potential candidates include A.f. secreted factors as mediators of altered BEC cytoskeletal function and epithelial migration.Please refer to page A288 for declarations of interest related to this abstract.

• Publisher: BMJ Publishing Group Ltd and British Thoracic Society,BMJ Publishing Group LTD
• Subject: Flow cytometry / Infections / Respiratory diseases / ‘Welcome to the jungle’ – Diving into the airway mycobiome