Studying lung microvascular endothelial dysfunction upon cigarette smoke exposure using an alveolus-on-chip

Lung microvascular endothelial cells are hypothesized to contribute to alveolar repair and regeneration. We recently demonstrated loss of these cells in unaffected tissue regions from patients with emphysema and confirmed their support function for alveolar epithelial cells in vitro. Here, we modelled the cellular cross-talk between these compartments in response to whole cigarette smoke (WCS) using a novel alveolus-on-chip, to identify potential therapeutic targets. Primary endothelial cells, pericytes and alveolar epithelial type-2 cells (AEC2) were isolated from human lung tissue. First, endothelial cells were seeded in a fibrin-collagen hydrogel in an open-top alveolus-on-chip to form vascular networks, alone, or in co-culture with pericytes. AEC2 were next seeded as a monolayer on top of the hydrogel. After confluence was reached, chip cultures were exposed to WCS, after which chips were processed for various analyses. Endothelial cells alone were able to form networks with vessel diameters of 5-10 μm, while in presence of pericytes, networks with a 1-3 μm vessel diameter were observed. Upon whole CS exposure, AEC2 monolayer integrity was maintained while the vascular network disintegrated. Interestingly, when vascular networks were exposed in absence of the AEC2 layer, disintegration was not observed, suggesting that an AEC2-derived component(s) promotes this disintegration. In conclusion, lung microvascular endothelial cells are negatively affected by CS exposure via alveolar epithelial cross-talk. Further studies will focus on identification of this AEC2-derived factor(s) to investigate if it could provide a therapeutic target for prevention of emphysema progression.