Fig 1: CDH1+ distal nephron dilates in PKHD1-/- kidney organoids cultured under flow.(A) Schematic of kidney organoid-on-a-chip (flow) culture and static culture. (B) Diagram of differentiation days and culture conditions for flow and static culture. (C) Representative phase-contrast images of PKHD1-/- and PKHD1+/- organoids cultured under flow on days 16 to 18, days 21 to 25, and day 32 of differentiation. Red arrows highlight dilated tubules. Scale bars, 100 µm (top). Representative phase-contrast images of PKHD1-/- and PKHD1+/- organoids cultured under flow on day 35 of differentiation. White arrows highlight dilated tubules. Dashed white lines highlight normal tubules. Scale bar, 50 µm (bottom). (D) Immunocytochemistry with sample clearing for proximal tubule (LTL and CFTR) and distal tubule (CDH1) in PKHD1-/- organoids with and without flow on day 35. Scale bar, 100 µm. (E) Bright-field images of patient-derived ARPKD organoids with and without forskolin treatment in 3D culture on day 66. Scale bar, 250 µm (top). Immunocytochemistry for proximal tubule (LTL), distal tubule (CDH1), and podocyte (PODXL) in PKHD1-/- organoids with and without forskolin treatment on day 35. Scale bar, 100 µm (bottom). (F) Tubular diameters in nephron segments [proximal tubule (LTL) and distal tubule (CDH1)] in PKHD1-/- organoids with and without flow (left) and with and without forskolin treatment (right). Values represent means ± SD. **P < 0.01, ****P < 0.0001.