Related Experiment Videos
Deficient Smad7 expression: a putative molecular defect in scleroderma
Chunming Dong1, Shoukang Zhu, Tao Wang
1Division of Cardiology, Duke University Medical Center, 7504 Duke Hospital North, Box 3845, Durham, NC 27710, USA.
Abstract:
Scleroderma is a chronic systemic disease that leads to fibrosis of affected organs. Transforming growth factor (TGF) beta has been implicated in the pathogenesis of scleroderma. Smad proteins are signaling transducers downstream from TGF-beta receptors. Three families of Smads have been identified: (i) receptor-regulated Smad2 and -3 (R-Smads); (ii) common partner Smad4 (Co-Smad); and (iii) inhibitory Smad6 and -7 (I-Smads, part of a negative feedback loop). We have investigated the signaling components for the TGF-beta pathway and TGF-beta activity in scleroderma lesions in vivo and in scleroderma fibroblasts in vitro. Basal level and TGF-beta-inducible expression of Smad7 are selectively decreased, whereas Smad3 expression is increased both in scleroderma skin and in explanted scleroderma fibroblasts in culture. TGF-beta signaling events, including phosphorylation of Smad2 and -3, and transcription of the PAI-1 gene are increased in scleroderma fibroblasts, relative to normal fibroblasts. In vitro adenoviral gene transfer with Smad7 restores normal TGF-beta signaling in scleroderma fibroblasts. These results suggest that alterations in the Smad pathway, including marked Smad7 deficiency and Smad3 up-regulation, may be responsible for TGF-beta hyperresponsiveness observed in scleroderma.
Insights
Scleroderma involves fibrosis linked to transforming growth factor-beta (TGF-β) signaling. Reduced Smad7 and increased Smad3 in scleroderma fibroblasts cause TGF-β hyperresponsiveness, which Smad7 gene therapy can correct.
Area of Science:
- Connective tissue diseases
- Molecular biology
- Cell signaling
Background:
- Scleroderma is a chronic systemic disease characterized by organ fibrosis.
- Transforming growth factor-beta (TGF-β) signaling is implicated in scleroderma pathogenesis.
- Smad proteins are key intracellular mediators of TGF-β signaling.
Purpose of the Study:
- To investigate TGF-β pathway signaling components and activity in scleroderma.
- To examine Smad protein expression and function in scleroderma fibroblasts.
- To determine if Smad7 deficiency contributes to TGF-β hyperresponsiveness in scleroderma.
Main Methods:
- Analysis of Smad protein expression in scleroderma skin and cultured fibroblasts.
- Assessment of TGF-β-induced signaling events (Smad phosphorylation, PAI-1 transcription) in scleroderma fibroblasts.
- In vitro adenoviral gene transfer of Smad7 into scleroderma fibroblasts.
Main Results:
- Scleroderma fibroblasts exhibit decreased Smad7 and increased Smad3 expression compared to normal fibroblasts.
- TGF-β signaling, including Smad2/3 phosphorylation and PAI-1 gene transcription, is enhanced in scleroderma fibroblasts.
- Adenoviral delivery of Smad7 normalized TGF-β signaling in scleroderma fibroblasts.
Conclusions:
- Alterations in the Smad pathway, specifically Smad7 deficiency and Smad3 upregulation, contribute to TGF-β hyperresponsiveness in scleroderma.
- Smad7 replacement therapy shows potential for restoring normal TGF-β signaling in scleroderma.
- These findings elucidate a molecular mechanism underlying scleroderma pathogenesis.