Fig. 5.

Igfbp2⁺ AT1 cells are terminal differentiated AT1 cells and can differentiated from Hopx⁺ AT1 cells. (A–C) Lungs of PNX-treated Igfbp2-CreER; Rosa26-Zsgreen mice (A) were analyzed with antibodies against GFP, Hopx, and Prospc (B). (C) Organoids were grown from either Hopx⁺ AT1 cells or GFP⁺ lineage-labeled AT2 cells. (D and E) At post plating day 14, organoids growth Hopx⁺ AT1 cells (D) from were analyzed with antibodies against Igfbp2 and Hopx (E). (F–H) At post plating day 9, some flatten cells at the luminal side of organoids formed from GFP⁺ AT2 cells (F) expressed both Hopx and Pdpn (G). Hopx⁺ cells were then isolated from these day 9 organoids and cultured in a 3D organoid culture system. At post plating day 14, some Hopx⁺ AT1 cells expressed Igfbp2 (H). (I–K) Lineage-labeled Igfbp2⁺ AT1 cells were plated for the alveolar organoid culture (I). No RFP⁺ organoids formed by day 14 of culture (J and K). (Scale bars: B, E, G, and H, 25 μm; D, F, J, and K, 1 mm.)