Smaddening complexity: the role of Smad3 in epithelial-myofibroblast transition.
Cells Tissues Organs
; 193(1-2): 41-52, 2011.
Article
in En
| MEDLINE
| ID: mdl-21051861
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 α-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-ß(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-ß 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.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Epithelial Cells
/
Smad3 Protein
/
Myofibroblasts
Type of study:
Prognostic_studies
Limits:
Animals
/
Humans
Language:
En
Journal:
Cells Tissues Organs
Journal subject:
ANATOMIA
Year:
2011
Document type:
Article
Affiliation country:
Country of publication: