[The mechanism of transforming growth factor beta1 in myofibroblast differentiation].
OBJECTIVE
To investigate the mechanism underlying myofibroblast differentiation induced by transforming growth factor (TGF) beta1 in obliterative bronchiolitis following lung transplantation.


METHODS
Heterotopic tracheal transplantation was performed in Smad3 wild-type and knock-out mice to simulate the lung transplantation in human. Murine tracheal fibroblasts cultivated in primary culture were used for in vitro study. Immunohistochemistry, immunocytochemistry, Western Blotting, RT-PCR and DNA electrophoresis mobility gel shift assay were conducted to detect the expression of alpha-smooth muscle actin (alphaSMA), the marker of fibroblast-myofibroblast differentiation, and the activation of Smad3, p38 and ERK1/2.


RESULTS
In affected airways of experimental obliterative bronchiolitis, abundant expression of alphaSMA were found. In vitro study for tracheal fibroblasts, the activation of Smad3 by TGF-beta1 presents as three major forms, phosphorylation, nuclear translocation and DNA binding. In Smad3 wild-type fibroblasts, TGF-beta1 induces the increase of the myofibroblasts transformation, characterized by the elevation of alphaSMA, both at transcription and protein level. While in Smad3 knock-out fibroblasts, the transformation of myofibroblasts induced by TGF-beta1 is significantly decreased (t = 2.080, P = 0.027; t = 1.982, P = 0.032), but not completely abolished. Further study in Smad3-deficient fibroblasts demonstrates that p38 and ERK1/2 could be activated by TGF-beta1 and result in fibroblast differentiation.


CONCLUSIONS
TGF-beta1 could promote the transformation of fibroblasts into myofibroblasts in Smad3 dependent and independent signal pathways, especially the Smad3 dependent path, and result in the development of obliterative bronchiolitis.
Liu
Hong-xu
HX
Department of Thoracic Surgery, First Hospital, China Medical University, Shenyang 110001, China. hongxuliu@yahoo.com
Wang
Si-wen
SW
Zhao
Cheng-hai
CH
Liu
Yang
Y
Li
Yu
Y
Zhang
Qi-gang
QG
Cong
Wei
W
Lan
Xin-gang
XG
Xu
Shun
S
Han
Li-bo
LB
Zhang
Lin
L
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001989:Bronchiolitis Obliterans / Q000235:genetics / Q000473:pathology* / Q000601:surgery; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D014132:Trachea / Q000166:cytology / Q000637:transplantation; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000199:Actins; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases