Alpha-smooth muscle actin expression upregulates fibroblast contractile activity.
To evaluate whether alpha-smooth muscle actin (alpha-SMA) plays a role in fibroblast contractility, we first compared the contractile activity of rat subcutaneous fibroblasts (SCFs), expressing low levels of alpha-SMA, with that of lung fibroblasts (LFs), expressing high levels of alpha-SMA, with the use of silicone substrates of different stiffness degrees. On medium stiffness substrates the percentage of cells producing wrinkles was similar to that of alpha-SMA-positive cells in each fibroblast population. On high stiffness substrates, wrinkle production was limited to a subpopulation of LFs very positive for alpha-SMA. In a second approach, we measured the isotonic contraction of SCF- and LF-populated attached collagen lattices. SCFs exhibited 41% diameter reduction compared with 63% by LFs. TGFbeta1 increased alpha-SMA expression and lattice contraction by SCFs to the levels of LFs; TGFbeta-antagonizing agents reduced alpha-SMA expression and lattice contraction by LFs to the level of SCFs. Finally, 3T3 fibroblasts transiently or permanently transfected with alpha-SMA cDNA exhibited a significantly higher lattice contraction compared with wild-type 3T3 fibroblasts or to fibroblasts transfected with alpha-cardiac and beta- or gamma-cytoplasmic actin. This took place in the absence of any change in smooth muscle or nonmuscle myosin heavy-chain expression. Our results indicate that an increased alpha-SMA expression is sufficient to enhance fibroblast contractile activity.
Hinz
B
B
Department of Pathology, CMU, University of Geneva, 1211 Geneva 4, Switzerland.
Celetta
G
G
Tomasek
J J
JJ
Gabbiani
G
G
Chaponnier
C
C
D016475:3T3 Cells; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D005782:Gels; D051379:Mice; D008856:Microscopy, Fluorescence; D009130:Muscle, Smooth / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012825:Silicon / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D015854:Up-Regulation
D000199:Actins; D005782:Gels; D020033:Protein Isoforms; D016212:Transforming Growth Factor beta; D003094:Collagen; D012825:Silicon