Investigating NF-κB signaling in lung fibroblasts in 2D and 3D culture systems

Background: Inflammatory respiratory diseases are amongst major global health challenges. Lung fibroblasts have been shown to play a key role in lung inflammatory responses. However, their exact role in initiation and maintenance of lung diseases has remained elusive partly due to the limited availability of physiologically relevant in vitro models. Therefore, developing new tools that enable investigating the molecular pathways (e.g. nuclear factor-kappa B (NF-kappa B) activation) that underpin inflammatory responses in fibroblasts could be a valuable resource for scientists working in this area of research. Results: In order to investigate NF-kappa B activation in response to pro-inflammatory stimuli in real-time, we first developed two detection systems based on nuclear localization of NF-kappa B by immunostaining and luciferase reporter assay system. Furthermore using electrospun porous scaffolds, with similar geometry to human lung extracellular matrix, we developed 3D cultures of lung fibroblasts allowing comparing NF-kappa B activation in response to pro-inflammatory stimuli (i.e. TNF-alpha) in 2D and 3D. Our data clearly show that the magnitude of NF-kappa B activation in 2D cultures is substantially higher than 3D cultures. However, unlike 2D cultures, cells in the 3D model remained responsive to TNF-alpha at higher concentrations. The more subdued and wider dynamic range of NF-kappa B responses in 3D culture system was associated with a different expression pattern for TNF receptor I in 3D versus 2D cultures collectively reflecting a more in vivo like TNF receptor I expression and NF-kappa B activation pattern in the 3D system. Conclusion: Our data suggest that lung fibroblasts are actively involved in the pathogenesis of lung inflammation by activation of NF-kappa B signaling pathway. The 3D culture detection system provides a sensitive and biologically relevant tool for investigating different pro-inflammatory events involving lung fibroblasts.