TGFB1 and renal fibrosis: Several pro-sclerotic factors contribute to develop renal fibrosis; the most potent is TGF-β1, which is increased in the diabetic kidney [6,7] Consistent with these reports, we found that the expression of TGF-β1 in diabetic rats was significantly higher in glomeruli and proximal tubules than in nondiabetic groups at week 3 after STZ injection.