Alpha-smooth muscle actin expression upregulates fibroblast contractile activity

• Published in: Molecular biology of the cell Vol. 12; no. 9; pp. 2730 - 2741
• Main Authors: Hinz, B, Celetta, G, Tomasek, J J, Gabbiani, G, Chaponnier, C
• Format: Journal Article
• Language: English
• Published: United States The American Society for Cell Biology 01.09.2001
• Subjects: 3T3 Cells; Actins - genetics; Actins - metabolism; Animals; Blotting, Western; Cell Size - drug effects; Cells, Cultured; Collagen - metabolism; Fibroblasts - cytology; Fibroblasts - drug effects; Fibroblasts - metabolism; Gels; Mice; Microscopy, Fluorescence; Muscle, Smooth - metabolism; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Silicon - metabolism; Transfection; Transforming Growth Factor beta - pharmacology; Up-Regulation
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.12.9.2730

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.