PCNA and cyst: We further found that treatment with Pkd1-null cell EVs/exosomes not only increased cyst lining epithelial cell proliferation but also the surrounding interstitial cell proliferation in Pkd1RC/RC kidneys compared to PBS-treated Pkd1RC/RC kidneys, as analyzed by PCNA staining and qRT-PCR analysis (Fig. 4h–j) and Ki67 staining (Supplementary Fig. 7a), suggesting that Pkd1-null cell EVs/exosomes might affect the biology of neighboring cells, such as fibroblasts and macrophages.