Figure 7. Alveolar cell fate is maintained by active breathing movements.

a-d. Unilateral lung ligation reprograms AT1 cells into AT2 cells. A gross morphological image of a mouse lung 28 days after sham surgery or unilateral lung ligation (a). The left main bronchus was ligated without affecting the left pulmonary artery or vein. Unilateral lung ligation and lineage-tracing were performed on Hopx^CreERT2; R26R^EYFP mice, and the mice were analyzed at 28 days later (b). Both the right (control) and left (ligated) lungs were analyzed. AT1 lineage cells express AT2 marker Sftpc in the ligated lung (c). White arrowheads indicate AT1 cells and yellow arrowheads indicate AT2^rep cells. Quantification of EYFP⁺ Sftpc⁺ AT2^rep cells from n = 5 mice from 3 independent experiments (d).

e-f. scRNA-seq analysis of wildtype alveolar epithelial cells and lineage-traced cells from Hopx^CreERT2; R26R^EYFP mice after unilateral lung ligation. AT2^rep cells co-cluster with wildtype AT2 cells (e). Correlation analysis shows high similarity between AT2^rep and wildtype AT2 cells (f).

g-h. YAP does not localize to the AT2^rep nucleus and F-actin does not contact AT2^rep nucleus. Representative images (g) and quantification (h) of perinuclear actin for control AT1 and AT2^rep cells (n = 5 mice). Control lung and ligated left lung were adhered to the same glass slide. Actin intensity for AT2^rep cells was standardized to that of control AT1 cells on the same glass slide.

i. Model of AT1 and AT2 cell regulation by biophysical forces.

Each dot represents an individual mouse, and error bars indicate mean with s.d. Scale bars: c, 25 μm; g, 2.5 μm. See also Figure S7.