Figure 1.

(a) The cell-stretching device consists of a rectangular acrylic dish with a stretchable silastic membrane fitted to the bottom and attached to removable clamps. The embryonic mesenchymal cells are cultured on the membrane coated with 0.1% poly-L-lysine to maintain the cells’ round shape and thereby prevent spread-induced SM differentiation or on 0.01% poly-L-lysine or collagen I to allow spread-induced SM differentiation. The membrane is longitudinally stretched up to several lengths by placing the clamps into different slots (labeled 1 to 6). (b) Diagram of the organ culture system used in this study is shown. Mouse and human embryonic lung explants are cultured embedded in a thin collagen gel layered on a transwell device. Dextran, a volume expander polysaccharide, is microinjected into the airways to increase the intraluminal pressure by attracting liquid. Alternatively, dextran is dissolved in the culture medium to obtain the opposite effect.