期刊
CELLS TISSUES ORGANS
卷 193, 期 1-2, 页码 41-52出版社
KARGER
DOI: 10.1159/000320180
关键词
Transforming growth factor-beta; Receptor Smads; alpha-Smooth muscle actin; Myogenic program; Epithelial-mesenchymal transition; Myocardin-related transcription factor; Intercellular contacts
资金
- Canadian Institutes of Health Research
- Kidney Foundation of Canada
Epithelial-mesenchymal transition (EMT) has emerged as a major mechanism in the pathogenesis of organ fibrosis. The epithelium has been proposed to be a significant source of matrix-producing fibroblasts and of myofibroblasts (MFs), a motile and contractile cell type hallmarked by the expression of alpha-smooth muscle actin (SMA). Importantly, tissue accumulation of MFs shows strong correlation with the severity and progression of fibrotic diseases. The pleiotropic cytokine transforming growth factor-beta(1) has been long known as the chief inducer of fibrosis, EMT and MF generation. Accordingly, receptor Smads (Smad2 and particularly Smad3), the direct targets of the activated transforming growth factor-beta receptor have been implicated as critical mediators in fibrogenesis and EMT. However, evidence is accumulating that the role of Smad3 is complex and apparently controversial; in fact, Smad3 may differentially affect the various components of EMT, including the loss of epithelial markers (de-epithelialization), the production of extracellular matrix (fibrogenesis) and the expression of SMA (myogenic program). In this review, we revisit the role of Smad3 in epithelial-myofibroblast transition (EMyT). We first summarize the evidence supporting the thesis that Smad3 is a key mediator of EMT and MF generation; next, we present evidence supporting the antithesis that Smad3 is in fact a negative regulator of SMA expression and the activation of the myogenic program in the epithelium; finally, we propose a synthesis, which depicts Smad3 as a timekeeper and context-dependent modulator of EMyT. We suggest that EMyT is composed of an early, mesenchymal, Smad3-promoted phase and a late, myogenic, Smad3-inhibitable phase. Copyright (C) 2010 S. Karger AG, Basel
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