Fig. 1.

Development of arrays of membranous lung microtissues. a The lung alveolar sac wall features large surface area and small tissue thickness, which is characterized by the high span length (S) to thickness (t) ratio. b Engineered lung microtissues were developed to model the membranous morphology of the alveolar sac wall. c Finite element (FE) models were developed to study the effects of microtissue geometry and size on the evolution of contractile stress during microtissue formation. First principal stress contour was plotted on deformed microtissue geometry with overlaid plot of stress vectors, where applicable. Scale bar is 500 µm. Representative 2D-projected fluorescent confocal images of an experimentally-created four-leaflet lung microtissue stained for nucleus (d) and F-actin (e). Note highlighted area shows highly aligned F-actin stress fibers running along the diagonal axis of the microtissue, matching with the direction of the principal stress in highlighted area in c. Scale bar in d is 500 µm. f 3D isometric view of the same microtissue stained for collagen type-I. g Merged fluorescent cross-sectional view (F-actin and collagen type-I) taken at a′–a′ plane of the four-leaflet microtissue showing S/t ratio of 28, corresponding well to alveolar sac geometry. SEM images of a four leaflet (h) and a three leaflet (i) human lung fibroblast-populated microtissue. j Arrays of square lung microtissues were integrated into a 12-well plate to enable parallel testing of multiple pharmacological conditions. Bright spots in each well correspond to individual microtissues. k Immunofluorescence imaging of the microtissue array allowed multi-parameter, phenotypic analysis of the drug efficacy. Scale bar is 3 mm