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Dear Sir,
We read with interest the paper by Hayashi et al. [1] reporting the expression of AQP2 and AQP3 in cyst-lining epithelial cells from ADPKD kidneys. The authors suggest that about 30% of the cysts in ADPKD are derived from collecting-duct cells and that these cells remain well differentiated in terms of AQP expression. However, these conclusions are limited by the small number of ADPKD kidneys (n = 2) studied and by the fact that both AQP2 and AQP3 are located in the same cells - the principal cells of the collecting duct.
Recently, we have investigated the expression of AQP1 (also called CHIP28), the constitutively active water channel, and that of AQP2 (or AQP-CD) in a large series of early- and end-stage ADPKD kidneys (n = 21), using Western blot analysis and immunohistochemistry [2]. Early-stage ADPKD kidneys contained morphologically normal tubules as well as cysts, while end-stage kidneys contained...