Effect of TGF-?/Smad signaling pathway on lung myofibroblast differentiation

Abstract

Aim: Myofibroblasts play important roles in the pathogenesis of lung fibrosis. Transforming growth factor (TGF)‐β1 has been widely recognized as a key fibrogenic cytokine. The major signaling pathway of TGF‐β1 is through cytoplasmic Smad proteins. Our study investigated the role of individual TGF‐β1/Smad signal proteins in mediating α‐smooth muscle actin (α‐SMA) gene expression, which is a well‐known key marker of myofibroblast differentiation. Methods: We transiently cotransfected α‐SMA promoter‐luciferase fusion plasmid (p895‐Luc) and Smad expression plasmids and measured Luc activity in TGF‐β1‐treated human fetal lung fibroblasts. We induced Smad3 knockout mice lung fibrosis by bleomycin. α‐SMA protein expression was assessed by Western blotting. Collagen protein was analyzed by measuring hydroxyprolin. Myofibroblast morphology was assessed by immunohistochemistry. Results: We found that the overexpression of Smad3, not Smad2 markedly increased TGF‐β1‐induced α‐SMA promoter activity and α‐SMA protein expression in vitro, whereas the over‐expression of dominant negative mutant Smad3 and Smad7 repressed TGF‐β1 induced α‐SMA gene expression. Compared to wild‐type mice, Smad3 knockout mice showed attenuated lung fibrosis after bleomycin treatment, manifested by lower collagen production and myofibroblast differentiation. Conclusion: Our study suggested TGF‐β1/Smad3 is a major pathway which regulated the myofibroblast differentiation. This result indicates a potential significance for future attempts of attenuating the progression of human lung fibrosis by the inhibition of the Smad3 cascade.

Periostin modulates myofibroblast differentiation during full-thickness cutaneous wound repair

“…Canonical TGFb signaling is not altered in Postn 2/2 fibroblasts TGFb is known to cause an increase in a-SMA expression through phosphorylation of Smad3 (Gu et al, 2007), and plays a major role in myofibroblast differentiation (Desmouliere et al, 1993). Therefore, to determine whether the reduction in a-SMA expression and immunoreactivity in Postn 2/2 granulation tissue was due to defective TGFb-Smad3 signaling, we assessed the number of nuclei positive for phosphorylated Smad2 and Smad3 (Smad2/3-P) within the granulation tissue.…”

FTY720 Ameliorates Murine Sclerodermatous Chronic Graft‐Versus‐Host Disease by Promoting Expansion of Splenic Regulatory Cells and Inhibiting Immune Cell Infiltration Into Skin

“…PTEN deficiency has been reported to be associated with fibrosis (30). Furthermore, TGF␤1 was shown to simultaneously activate phosphorylation of the Smad3 signaling pathway in fibroblasts (31). Immunohistochemical analysis suggested that treatment with FTY720 markedly decreased the infiltration of CD3ϩ cells, CD4ϩ T cells, and CD11bϩ monocyte/macrophages into the skin 42 days after BMT.…”

Regulation of epithelial to mesenchymal transition by bone morphogenetic proteins

“…The switch of epithelial cells towards a mesenchymal phenotype is unfavourable and leads to the disruption of epithelial layers and functions [4]. TGF-β1 expression is elevated during fibrosis in several animal and human models [59]. However, despite being members of the TGF-β superfamily, few studies have addressed the role of BMPs in fibrosis.…”