Figure 2. Self‐renewing human fetal lung bud tip progenitor organoids differentiate at air–liquid interface to alveolar type I‐ and type II‐like cells.

• A
  Immunofluorescent staining of fetal lung bud tip progenitor organoids grown in expansion medium co‐expressing stem cell markers Sox2 (green) and Sox9 (red). Phalloidin (white) was used to stain actin.
• B
  Immunofluorescent staining of rare HTII‐280 + type II pneumocytes (green) in a subpopulation of fetal lung bud tip progenitor organoids grown in expansion medium.
• C
  Schematic of the 2D air–liquid interface bronchioalveolar‐like model.
• D–I
  Differentiated lung bud tip organoids at air–liquid interface in co‐culture with donor‐specific human fetal lung fibroblasts. After 14 days of differentiation at air–liquid interface, cells express alveolar type I (HOPX, green, (D); HTI‐56, green, (E)), type II cells (HTII‐280, green, (F); LPCAT1, green, (G); SFTPC (SPC), green, (H)), and basal cell (TP63 (P63), green, (I)) markers in areas containing one cell layer. Dotted lines indicate the barrier between multilayered and single‐layered epithelium.

Data information: Nuclei are stained with Hoechst (blue in (A, B) or white in (D–I)). Scale bars indicate 50 μm.