FGF23 stimulates the proliferation of NRCF and induces the expression of the profibrotic markers collagen 1 (Col1), transforming growth factor beta 1 (Tgfb) and connective tissue growth factor (Ctgf). (A) The proliferation of NRCF increases in response to stimulation with FGF23, which was not inhibited in the presence of cyclosporine A (CsA), losartan (Los) or spironolactone (Spiro) as demonstrated by MTS-based proliferation assay. (B–D) The mRNA expression of Tgfb, Ctgf and Col1 in NRCF is increased upon FGF23 stimulation as measured by quantitative real-time PCR. Co-treatment with Los and Spiro inhibits the induction of fibrotic markers by FGF23, while CsA has lesser effects. TGFβ and angiotensin II (AngII) served as positive controls. Horizontal dotted lines represent the level of controls. All values are shown as mean ± SEM; * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001 versus control; §
p < 0.05 versus FGF23; n = 5–9 independent cell isolations.