The extracellular matrix (ECM) is highly cross-linked and insoluble, making studies of the ECM in its native state challenging. Traditional 2-dimensional in vitro cell culture models are not sufficient to reflect the native biology of the ECM that has a highly complex structure. The disadvantages of 2D culture systems are primarily that they do not accurately represent the 3D structures that are present in vivo. Alternatives to 2D culture systems include spheroid suspension cultures and 3D hydrogel cultures with numerous variations that aim to mimic specific niches to reflect the various in vivocell environments. More recently, decellularised lung matrices have been revealed to closely mimic the in vivolung environment and provide another, biologically relevant means of studying effects of ECM on cell phenotype. Tissue decellularisation is a novel technique that generates ECM scaffolds through the removal of cells from native tissue with preservation of much of the original ECM content and architecture, which holds much promise in the quest to understand the role of the ECM in disease.
To model the in vivo environment we used 3D cell cultures (primary human lung fibroblasts in collagen gel and decellularised human lung matrices). Multi Photon Second Harmonic imaging (SHG) microscopy was used to image these cultures. They were excited with 810 nm circular polarized light and emission collected at 405/10 nm at the same power and detector settings in both forward and backward detectors. 3 dimensional image stacks were collected and analysed.
In these 3D models we were able to induce collagen remodelling which mimics the invivo fibrosis seen in fibrotic lung diseases.