AQP2 and cyst: These results convincingly identified the cells lining the kidney cysts in TSC as A-IC cells (Bissler et al., 2019b; Barone et al., 2021; Zahedi et al., 2022; Barone et al., 2023) and demonstrate that the loss of AQP-2 positive cells was due to the disappearance of principal cells and their replacement with A-intercalated cells in the cyst lining.