SMAD3 and chronic kidney disease: Furthermore, repletion of 25(OH)D3 significantly decreased the expression of pro-fibrotic genes (PAI-1, IL-1α, IL-1β, Agt, Ctgf, Akt1 and Smad3) while significantly increasing the expression of anti-fibrotic genes (Bmp7 and IL-13Rα2) of the gastrocnemius relative to repletion of 1,25(OH)2D3 in CKD mice.