Diabetic nephropathy (DN) remains a major complication in both type 1 and type 2 diabetes. Systemic administration of antitransforming growth factor-beta (TGF-beta) antibody has shown some promise in mouse models of DN. However, chronic blockade of the multifunctional TGB-beta could be problematic. Several downstream effects of TGF-beta are mediated by connective tissue growth factor (CTGF), which is up-regulated in several renal cells and secreted in the urine in the diabetic state. Using murine models of DN (type 1 and type 2) and a CTGF antisense oligonucleotide (ASO) of novel chimeric chemistry, we evaluated the specific role of this target in DN. In the type 1 model of DN, C57BL6 mice were made diabetic using streptozotocin injections and hyperglycemic animals were treated with CTGF ASOs (20 mg/kg/2 qw) for 4 months. ASO, but not mismatch control oligonucleotide, -treated animals showed significant reduction in target CTGF expression in the kidney with a concomitant decrease in proteinuria and albuminuria. Treatment with the CTGF ASO for 8 wk reduced serum creatinine and attenuated urinary albuminuria and proteinuria in diabetic db/db mice, a model of type 2 DN. The ASO also reduced expression of genes involved in matrix expansion such as fibronectin and collagen (I and IV) and an inhibitor of matrix degradation, PAI-1, in the renal cortex, contributing to significant reversal of mesangial expansion in both models of DN. Pathway analyses demonstrated that diabetes-induced phosphorylation of p38 MAPK and its downstream target CREB was also inhibited by the ASO. Our results strongly suggest that blocking CTGF using a chimeric ASO holds substantial promise for the treatment of DN.