TGFB1 and renal fibrosis: In an in vitro renal fibrosis model, rat renal fibroblasts (NRK-49F cells) were treated with TGF-β1 (0, 1, 2, and 5 ng/mL) for 48 h, and α-smooth muscle actin (α-SMA), a key indicator of myofibroblast activation, was subsequently assessed [35].