3.1 Mimicking the alveolar-capillary barrier based on LOC
The schematic for this study is shown in Figure 1, which includes a diagram of lung injury, the LOC system, and major experimental methods. The LOC device featured an upper layer for culturing human umbilical vein endothelial cells (HUVECs), simulating blood vessels, and three independent lower chambers for culturing lung epithelial cells (Figure 2A-a, b, and Supplementary Figure 1). Elastic tubes interconnected multiple lung chips, facilitating communication between alveolar channels (Figure 2A-e). A gravity-driven flow strategy was employed using a programmable rocking device, ensuring stable fluid flow in the vascular channel by adjusting the angle and frequency (20° and 5 cycles per minute, respectively) (Figure 2A-c, d, and Videos 1-2).
HUVECs and lung epithelial cells, stained with live-cell dyes (red and green, respectively), were cultured on opposite sides of the membrane to establish the alveolar-capillary interface. On day 7, cell viability exceeded 90%, as shown by the live/dead staining assay (Supplementary Figure 1A). The resistance value reached a steady state from days 3 to 7, indicating the formation of a robust alveolar-capillary barrier (Supplementary Figure 1B). Immunofluorescence assays confirmed the expression of E-cadherin and CD31 in the epithelial cells and HUVECs, respectively (Supplementary Figure 1C).