Introduction & Aims: Patients with respiratory diseases, such as chronic obstructive pulmonary disease (COPD), are highly susceptible to viral infection. Therapy with glucocorticosteroids (GCS) provides some anti-inflammatory benefit, however, GCS suppress immune responses required to combat infection, enhancing viral growth and adversely impacting lung health. Precision-cut lung slices (PCLS) provide a unique platform for integrated assessment of inflammatory and immune responses. The aim of this study was to establish an ex vivo mouse elastase-induced model of COPD and to model infection using the viral mimetic poly I:C (pI:C).
Methods: PCLS prepared from C57Bl/6 mice were incubated with elastase for 16 hr, and a further 24 hr without elastase. PCLS were then stimulated with pI:C (10 µg/ml) for 24 hrs before supernatant and PCLS were collected for analysis of COPD phenotype (mean linear intercept (MLI) and alveolar cell destruction) and elastase- and pI:C-induced effects on viability (LDH, MTT assays) and inflammatory mediators (mRNA, protein).
Results: PCLS viability was maintained following elastase treatment. Indicative of the induction of a COPD phenotype, MLI (mean free distance in the air spaces) was increased (p<0.01) and gene expression of alveolar type II cell markers, Aqp5, Rage and Sftpc was decreased (p<0.05) in the elastase-treated PCLS. Inflammatory gene expression (Il-6, Kc, Tnfα; p<0.05) and mediators (IL-6, KC, MCP-1, RANTES; p<0.01) were also significantly increased following elastase. pI:C-induced production of MCP-1, IL-6, KC and RANTES was further enhanced in elastase-treated PCLS, without affecting viability.
Conclusion: We have successfully established an elastase-induced COPD phenotype in mouse PCLS with enhanced inflammation in response to pI:C. Future studies will extend this pathogen-free mouse model to compare responses to viral infection in elastase-treated human PCLS and PCLS from COPD patients, to provide insights into immune responses to viral infection in disease context and opportunities for relatively high throughput screening of novel therapies.