SPARC and autosomal dominant polycystic kidney disease: Several matricellular proteins, including osteopontin (SPP1), cellular communication network factors (CCN1 and CCN2), osteonectin (SPARC), fibulin-1 (FBLN1), FBLN5 and SERPINE1 exhibited higher expression in fibroblasts clusters from ADPKD kidneys compared to normal control kidneys (Fig 1D).