Vitamin D3 inhibited transforming growth factor-β1- (TGF-β1-) induced mesothelial cell (MC) cytoskeleton redistribution in vitro. MCs were cultured with TGF-β1 with or without addition of 1α,25(OH)2D3 (vit. D). MC cytoskeletons were stained with anti-F-actin antibodies. In normal culture medium, the actin cytoskeleton (green) was in the cortical band and TGF-β1 promoted cytoskeleton redistribution (fibroblast-like cytoskeleton). Vitamin D inhibited TGF-β1-induced cytoskeleton redistribution. Nuclei were stained with DAPI (blue). Magnification ×400.