Cellular Response to Substrate Rigidity Is Governed by Either Stress or Strain

• Published in: Biophysical journal Vol. 104; no. 1; pp. 19 - 29
• Main Authors: Yip, Ai Kia, Iwasaki, Katsuhiko, Ursekar, Chaitanya, Machiyama, Hiroaki, Saxena, Mayur, Chen, Huiling, Harada, Ichiro, Chiam, Keng-Hwee, Sawada, Yasuhiro
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08-01-2013; Biophysical Society; The Biophysical Society
• Subjects: Aminocaproic Acid - pharmacology; Animals; Azides - pharmacology; Cell Biophysics; Cells; Collagen; Collagen - metabolism; deformation; Deformities; Elastic Modulus - drug effects; Embryo, Mammalian - cytology; extracellular matrix; fibroblasts; Fibroblasts - cytology; Fibroblasts - drug effects; Fluorescent Antibody Technique; Focal Adhesions - drug effects; Focal Adhesions - metabolism; gels; Gels - pharmacology; Measurement; Mice; NIH 3T3 Cells; polyacrylamide; Stress, Mechanical; Substrates; Succinimides - pharmacology
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/j.bpj.2012.11.3805

Cells sense the rigidity of their substrate; however, little is known about the physical variables that determine their response to this rigidity. Here, we report traction stress measurements carried out using fibroblasts on polyacrylamide gels with Young’s moduli ranging from 6 to 110 kPa. We prepared the substrates by employing a modified method that involves N-acryloyl-6-aminocaproic acid (ACA). ACA allows for covalent binding between proteins and elastomers and thus introduces a more stable immobilization of collagen onto the substrate when compared to the conventional method of using sulfo-succinimidyl-6-(4-azido-2-nitrophenyl-amino) hexanoate (sulfo-SANPAH). Cells remove extracellular matrix proteins off the surface of gels coated using sulfo-SANPAH, which corresponds to lower values of traction stress and substrate deformation compared to gels coated using ACA. On soft ACA gels (Young’s modulus <20 kPa), cell-exerted substrate deformation remains constant, independent of the substrate Young’s modulus. In contrast, on stiff substrates (Young’s modulus >20 kPa), traction stress plateaus at a limiting value and the substrate deformation decreases with increasing substrate rigidity. Sustained substrate strain on soft substrates and sustained traction stress on stiff substrates suggest these may be factors governing cellular responses to substrate rigidity.