Figure 2: Organoids match the in vivo epithelium in structure and distribution of markers.

Confocal images of organoid sections show that epithelium contains both ciliated cells positive for detyrosinated tubulin (green (a)) and secretory cells positive for PAX8 (green (b)) confirming differentiation. Terminally differentiated ciliated cells are PAX8-negative (c). (d) Epithelial cells form tight junctions visible by labelling for occludin (green, left). Organoids also contain occasional domains of epithelial cells ubiquitously expressing CA125 (green, middle) as well as basolateral vimentin (green, right). (e) Electron transmission microscopy images of the fallopian tube epithelium (upper panel) and organoid monolayer after 2 months in vitro (middle panel), showing high levels of similarity. Monolayer of the columnar epithelium with two cell types (ciliated and secretory), with clear apicobasal polarization closing off the empty lumen. Higher magnifications of the middle panel (square) reveal completely formed junctional complexes, which ensure separation of the apical from basolateral side (arrow, lower panel, right). The apical surface is covered by abundant microvilli (*) and fully developed cilia (***). Ruffling of the apical membrane on the non-ciliated cells (left panel) is highly suggestive of active release and secretion into the lumen (double arrow).