Mechanical stretch induces TGF-beta synthesis in hepatic stellate cells.
BACKGROUND
It is known that mechanical stress induces extracellular matrix via transforming growth factor-beta (TGF-beta) synthesis in vascular smooth muscle cells. Activated hepatic stellate cells (HSCs) are an important source of TGF-beta in the liver. However, it remains unclear whether mechanical stress induces TGF-beta in HSCs. The Rho small GTP-binding protein (Rho) has recently emerged as an important regulator of actin and cytoskeleton. We examined whether TGF-beta is expressed in stretched HSCs and whether Rho is involved in stretch-induced TGF-beta synthesis.


METHODS
A cultured human HSC cell line, LI90, was used for this study. Hepatic stellate cells were cyclically stretched using the Flexercell(R) strain unit. Concentration of TGF-beta in the conditioned medium was estimated by a bioassay using mink lung epithelial cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct. Transforming growth factor-beta mRNA expression of HSCs was estimated by a reverse-transcription polymerase chain reaction. Replication-defective adenoviral vectors expressing a dominant negative type of Rho was utilized to suppress its effect on HSCs.


RESULTS
Transforming growth factor-beta concentration of the conditioned media of stretched HSCs showed time-dependent increases as compared to nonstretched HSCs from 2 h to 24 h. Transforming growth factor-beta mRNA expression in stretched HSCs was increased compared with that in nonstretched HSCs. Transfection of dominant negative Rho inhibited the stretch-induced TGF-beta synthesis.


CONCLUSIONS
Mechanical stretch enhanced TGF-beta expression on mRNA and protein level in HSCs. Rho was closely related to stretch-induced TGF-beta synthesis in HSCs.
Sakata
R
R
Kurume University School of Medicine, Asahi-machi, Kurume, and University of Occupational and Environmental Health, Kitakyushu, Japan.
Ueno
T
T
Nakamura
T
T
Ueno
H
H
Sata
M
M
D000256:Adenoviridae / Q000235:genetics; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics
D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta