COL6A2 and autosomal dominant polycystic kidney disease: Compared to other renal cell types, ADPKD fibroblast cluster was the major source of 13 collagen subtypes, including COL1A1, COL1A2, COL3A1, COL4A1, COL4A2, COL5A1, COL5A2, COL6A2, COL6A3, COL12A1, COL14A1, COL15A1, and COL16A1 (Fig 1A).