PKD1 and cystic kidney disease: In this work, we provide evidence that cystic epithelial cell-secreted extracellular vesicles/exosomes regulate the biology and function of adjacent cells, including renal epithelial cells, fibroblasts, and macrophages, and contribute to renal cyst formation; inhibition of exosome biogenesis/release delays cyst growth in Pkd1 mutant mouse kidneys.