Ojective To investigate the effect of overexpression of Smad7 on proteinuria and renal pathology in the Adriamycin-induced nephropathy (ADN) rat model. Methods ADN model was established by single tail intravenous injection of Adriamycin (ADR). Smad7 gene was transferred by means of infusing a recombinant adenovirus into the left renal artery. Recombinant adenovirus-Smad7 (Ad-Smad7) was detected under fluorescence microscope. HE staining was used to examine renal pathological changes of each group. Pyrogallol red colorimetry was used to detect 24-h urinary protein. Results SD rats received a single intravenous injection of ADR (6.5 mg/kg), which constructed the ADN model. The pathology was similar to minimal change nephropathy at the fourth weekend. Unilateral renal artery infusion was efficient to transfer Ad-Smad7 to the target kidney. Urinary protein of the Ad-Smad7 group (38.4 ±
6.0) decreased compared to the ADR group (69.58 ± 10.63) at the fourth weekend (P < 0.05). Smad7 was mainly expressed in renal tubular epithelia in the Ad-Smad7 group, scarcely seen in glomeruli. The pathological changes of the Ad-Smad7 group were mild, while the changes of the Ad-GFP and ADR groups were similar to focal segmental glomerulosclerosis. Conclusions Ad-Smad7 can be transferred to the target kidney through unilateral renal artery infusion, and overexpression of Smad7 can ameliorate proteinuria and pathological changes of Adriamycin-induced nephropathy.