We also examined FSTL1 expression in kidneys from patients with immunoglobulin A nephropathy at grade III, or membranous nephropathy at grade II, which had developed renal fibrosis (data not shown), and found colocalization of FSTL1 with PDGFRβ (Figs. 1H and S4). Here, PDGFRB is linked to renal fibrosis.