AQP2 and cyst: Overall, OoC models representing the proximal tubule are mostly employed for drug efficacy and toxicity testing, for example for cisplatin (Jang et al., 2013) and antisense oligonucleotides (Nieskens et al., 2021), whereas OoC models mimicking distal segments are typically used to study basic cell biological aspects, such as the effects of shear stress on aquaporin-2 localization (Jang et al., 2011) or cyst formation (Verschuren et al., 2020).