Incubation of hPCIS

hPCIS were incubated in 12-wells plates in 1.3 mL Williams Medium E (Gibco™, Life Technologies, Bleiswijk, The Netherlands, Cat. no. 32551) (supplemented with 25 mM Glucose (Merck, Darmstadt, Germany), 50 µg/mL Gentamycin (Merck, Darmstadt, Germany) and 2.5 µg/mL Amphotericin B (Merck, Darmstadt, Germany), or in organoid media prepared from supplemented Dulbecco’s Modified Eagle’s Medium/Nutrient Mixture F12 (DMEM/F12) medium (Gibco™, Life Technologies, Bleiswijk, The Netherlands, cat. no. 15290026) (Expansion medium, Emed, and Differentiation medium, Dmed, Table ​Table1),1), kindly provided by Utrecht University of Applied Science (Table ​(Table1).1). The supplements R-spondin-1 and Wnt3a-conditioned media were prepared as previously described (Bigaeva et al. 2019a). The slices were incubated for 24 h, 48 h, or 72 h at 37 °C, 80% O_2, and 5% CO₂ while shaking horizontally (90 rpm) and the medium was changed every 24 h.