Smad3 deficiency attenuates renal fibrosis, inflammation,and apoptosis after unilateral ureteral obstruction.
BACKGROUND
Transforming growth factor-beta (TGF-beta) has been implicated in the development of renal fibrosis induced by unilateral ureteral obstruction (UUO). However, there is little information on signaling pathways mediating TGF-beta activity involved in molecular and cellular events leading to renal fibrosis induced by UUO. In this study, we sought to determine whether Smad3, a major signaling component of TGF-beta, mediated renal fibrosis induced by UUO.


METHODS
Renal fibrosis, inflammation, and apoptosis induced by UUO were macroscopically and histologically compared between wild-type mice and Smad3 null mice.


RESULTS
Gross appearance of the kidney after UUO showed relatively intact kidney in Smad3 null mice [Smad3(-/-) mice] when compared with that of wild-type mice [Smad3(+/+) mice]. Renal interstitial fibrosis based on the interstitial area stained with Aniline-blue or Sirius red solution was significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Deposition of type I and type III collagens were also significantly reduced in the obstructed kidney of Smad3(-/-) mice. In addition, the numbers of myofibroblasts, macrophages, and CD4/CD8 T cells infiltrated into the kidney after UUO were significantly attenuated in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Furthermore, terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining after UUO showed significantly reduced number of tubular apoptotic cells in the obstructed kidney of Smad3(-/-) mice when compared with that of Smad3(+/+) mice. Endogenous Smad pathway was activated in the obstructed kidney after UUO in wild-type mice as judged by the increase of phosphorylated Smad2 or phosphorylated Smad2/3-positive cells in renal interstitial area.


CONCLUSIONS
Smad3 deficiency attenuated renal fibrosis, inflammation, and apoptosis after UUO, suggesting that Smad3 was a key molecule mediating TGF-beta activity leading to real fibrosis after UUO.
Inazaki
Kumi
K
Atopy (Allergy) Research Center, Juntendo University School of Medicine, Tokyo, Japan.
Kanamaru
Yutaka
Y
Kojima
Yuko
Y
Sueyoshi
Noriyoshi
N
Okumura
Ko
K
Kaneko
Kazunari
K
Yamashiro
Yuichiro
Y
Ogawa
Hideoki
H
Nakao
Atsuhito
A
D000818:Animals; D017209:Apoptosis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005355:Fibrosis; D007668:Kidney / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009393:Nephritis / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D010641:Phenotype; D010766:Phosphorylation; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014517:Ureteral Obstruction / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology*
D004268:DNA-Binding Proteins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D015534:Trans-Activators