Figure 1.

ECM compliance controls development of the myofibroblast phenotype in three-dimensional collagen gels. Differentiated rat lung myofibroblasts were grown in mechanically restrained collagen gels produced very soft with a concentration of 0.5 mg/ml (A, B) and comparably stiff with 3.5 mg/ml (C, D). Cells were immunostained after 36 hours for α-SMA (A, C: red; B, D: blue), β-cytoplasmic actin (A, C: green; B, D: red), focal adhesion protein vinculin (B, D: green), and nuclei (A, C: blue) and observed by confocal microscopy. Note that cells in soft gels attain a dendritic morphology with cortical actin distribution and point-like small adhesion sites; α-SMA is not organized in stress fibers (A, inset). In stiff collagen, myofibroblasts develop α-SMA-positive stress fibers (C, inset) that terminate in supermature FAs. Bars: 25 μm and 10 μm (insets).