Treatment with a neutralizing anti-transforming growth factor-beta (TGF-beta) antibody can prevent the development of diabetic nephropathy in the db/db mouse, a model of type 2 diabetes, However, it is unknown whether anti-TGF-beta therapy can reverse the histological lesions of diabetic glomerulopathy once they are established. Diabetic db/db mice and their non-diabetic db/m littermates were allowed to grow until 16 weeks of age, by which time the db/db mice had developed glomerular basement membrane (GBM) thickening and mesangial matrix expansion. The mice were then treated with an irrelevant control IgG or a panselective, neutralizing anti-TGF-beta antibody for eight more weeks. Compared with control db/m mice, the dh/dh mice treated with IgG had developed increased GBM width (16.64 +/- 0.80 nm vs. 21.55 +/- 0.78 nm, P < 0.05) and increased mesangial matrix fraction (4.01 +/- 0.81% of total glomerular area vs. 9.55 +/- 1.041,), (P < 0.05). However, the db/db mice treated with anti-TGF-beta antibody showed amelioration of GBM thickening (18.40 +/- 0.72 nm, P < 0.05 vs. db/db-IgG) and mesangial matrix accumulation (6.32 +/- 1.79%, P < 0.05 vs. db/db-IgG). Our results demonstrate that inhibiting renal TGF-beta activity can partially reverse the GBM thickening and mesangial matrix expansion in this mouse model of type 2 diabetes. Anti-TGF-beta regimens would be useful in the treatment of diabetic nephropathy. (C) 2002 Elsevier Science (USA). All rights reserved.