NDT Advance Access originally published online on December 18, 2008
Nephrology Dialysis Transplantation 2009 24(5):1443-1454; doi:10.1093/ndt/gfn699
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Disruption of the Smad7 gene promotes renal fibrosis and inflammation in unilateral ureteral obstruction (UUO) in mice
1 Departments of Medicine, The University of Hong Kong Li Ka Shing Faculty of Medicine, Hong Kong, China 2 KFC, Center For Clinical Research, Karolinska Hospital Huddinge, Sweden
Correspondence and offprint requests to: Hui Y. Lan, Department of Medicine, The University of Hong Kong, L8-39, Laboratory Block, 21 Sassoon Road, Hong Kong. Tel: +852-28197745; Fax: +852-28162095; E-mail: hylan{at}hku.hk
| Abstract |
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Background. The present study tested the hypothesis that disruption of Smad7 function may accelerate renal fibrosis and inflammation.
Methods. This was investigated in a unilateral ureteral obstruction (UUO) model induced in wild-type (WT) and Smad7
E1 mice in which functional Smad7 is disrupted by deleting exon I in the Smad7 gene. Renal fibrosis and inflammation after UUO were examined by histology, real-time PCR, western blot analyses and immunohistochemistry.
Results. Seven days after UUO, severe tubulointerstitial fibrosis developed in WT mice as evidenced by a marked increase in
-SMA, collagen I and III extracellular matrix. This was associated with a significant upregulation of renal TGF-β1 and CTGF and activation of Smad2/3. Interestingly, compared to WT UUO mice, Smad7
E1 mice with UUO exhibited a further increase in TGF-β/Smad2/3-dependent renal fibrosis. Moreover, compared to WT UUO mice, deletion of the Smad7 gene also sustained NF-
B activation and thus enhanced further renal inflammation such as macrophage infiltration and upregulation of TNF-
, MCP-1, OPN and ICAM-1.
Conclusion. Smad7 is a critical negative regulator of TGF-β/Smad2/3 and NF-
B signalling and plays a negative regulating role in both renal fibrosis and inflammation after UUO. Results from this study further support the notion that Smad7 may be a therapeutic agent for kidney diseases.
Keywords: renal fibrosis; renal inflammation; Smad7; TGF-β signalling; UUO
Received for publication: 14.10.08
Accepted in revised form: 21.11.08