Collective cell durotaxis emerges from long-range intercellular force transmission

Raimon Sunyer, Vito Conte, Jorge Escribano, Alberto Elosegui-Artola, Anna Labernadie, Léo Valon, Daniel Navajas, José
Manuel García-Aznar, José J. Muñoz, Pere Roca-Cusachs and
Xavier Trepat (September 8, 2016) Science 353 (6304), 1157-1161. [doi: 10.1126/science.aaf7119]

 

Summary & Highlights

  • Ability of cell to follow ECM stiffness = durotaxis
  • “Here, we found multicellular clusters that exhibited durotaxis even if isolated constituent cells did not.”
  • Applied to several epithelial cell types, required myosin motors, originated from supracellular transmission of contractile physical forces
  • Method
    • Using PDMS stencil, micropattern rectangular clusters of human mammary epithelial cells on fibronectin-coated polyacrylamide gels with uniform gradient or stiffness gradient > more migration to the stiff edge… MCF10A, MDCK, human epidermoid carcinoma spheroids
  • Single cells did not durotax, but faster random velocity on stiffer gels
    • “this feature could explain collective durotaxis because volume exclusion would force cells to move persistently away from the cluster at a higher speed on the stiffer edge.”
    • To test this, knock down cell-cell junction
    • Cell-cell adhesions are required for collective cell durotaxis
      • Not based on local stiffness sensing, point to a long-range mechanism involving cell-cell adhesion
    • Does long-range mechanism involve transmission of physical forces across the cluster?
      • Use TFM
      • Highest tractions localized @ edges and pointed toward the midline of the cluster; lower tractions in bulk showed no particular orientation
      • Use monolayer stress microscopy
        • interecellular tension (normal component of stress tensor in direction of expansion) increased up to a plateau within the first few cells at the monolayer edges
        • monolayer expands by generating contractile traction forces of equal magnitude at both edges, forces transmitted across the cluster
    • Uniform Stiffness: symmetric expansion, actin polymerization exceeds acto-myosin contraction to same extent at both edges
    • Gradient Stiffness: substrate deforms and opposes polymerization more on the soft edge, tilting monolayer expansion toward stiff edge
    • Reduced stiffness gradient = less durotaxis
    • Impair long-range force transmission by knocking down alpha-catenin and laser-ablating clusters in the direction parallel to the midline

Future Questions

  • What if instead of a gradient stiffness, it’s multiple changes from soft > stiff > soft?
  • Does the extracellular matrix the cell is adhered on affect the force transmission, long-range sensing?
  • Are the cells at the leading edge vs. the lagging edge exhibit different phenotypes after apply gradient edge if removed from rest of the population? Are there genetic changes?

Personal Thoughts

  • Must think about long-range sensing! Forces from the core (proliferation?), from the environment?
  • How can this be translated to 3-D; does the cell acknowledge its own polarity differently in 3D vs. 2D?
  • Cool quantitative analysis! Can be used as basis for 3D, though will necessarily need to be pretty different.
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