Gene transfer of Smad7 using electroporation of adenovirus prevents renal fibrosis in post-obstructed kidney

Abstract

Unilateral ureteral obstruction (UUO) leads to interstitial fibrosis of the obstructed kidney, and TGF-beta is considered to play an important role in this fibrotic process. Smad7 has been recently identified as an antagonist of TGF-beta signaling. To investigate whether this novel molecule can be exploited for therapy of renal fibrosis, we determined the effect of exogenous Smad7, introduced by a recombinant adenovirus vector combined with in vivo electroporation (EP), on UUO-induced renal fibrosis in rats. A model of UUO was made in SD rats by ligating their left ureters. The next day, the rats were divided into four groups and adenovirus was injected into the extended pelvic space (two groups received AdCMV-LacZ and two groups received AdCMV-Smad7). Then, EP was performed in one group of AdCMV-LacZ-injected rats and one group of AdCMV-Smad7-injected rats. The renal tissues were obtained 3, 5, 10, and 14 days after the UUO operation. We detected the efficiency of transgene by immunoblots of renal cortical and medullary tissues and immunohistochemical studies for Smad7 and FLAG (the FLAG gene was introduced in the AdCMV-Smad7 as a marker). The renal fibrosis was monitored by histological scoring of Masson stainings. In immunoblotting, both Smad7 and FLAG were clearly detected in the renal medullary tissue of the rats given AdCMV-Smad7 with EP. In contrast, immunoblots of renal cortical tissue did not demonstrate positive bands. In immunohistological study, Smad7 was stained in the renal medulla in the rats given AdCMV-Smad7 with EP. In the rats given AdCMV-Smad7 without EP, only a weak signal was detected in renal medullary tissue. The rats given AdCMV-Smad7 with EP demonstrated significantly more suppression of renal fibrosis than rats treated with AdCMV-LacZ. The rats treated with AdCMV-Smad7 without EP did not demonstrate significant suppression of renal fibrosis. These data indicate that gene transfer of Smad7 prevents UUO-induced renal fibrosis, suggesting that Smad7 may be applicable for the treatment of renal fibrosis. In vivo electroporation of adenovirus may be a powerful tool for gene delivery in renal tissue.