Corneal Fibroblasts Respond Rapidly to Changes in Local Mechanical Stress

Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
Investigative Ophthalmology &amp Visual Science (Impact Factor: 3.4). 11/2004; 45(10):3466-74. DOI: 10.1167/iovs.04-0361
Source: PubMed


To investigate the response of corneal fibroblasts to local changes in extracellular matrix (ECM) tension.
Rabbit and human corneal fibroblasts were plated inside fibrillar collagen matrices. After 18 to 72 hours, a glass microneedle was inserted into the ECM and either pushed toward a cell to reduce local tension, or pulled away to increase tension. Time-lapse differential interference contrast (DIC) imaging was performed both before and after needle micromanipulation. ECM displacements were quantified, and strain maps were generated by finite element modeling. In some experiments, cells were treated with the Rho-kinase inhibitor Y-27632 either 30 minutes before, or 1 hour after they were pushed with the microneedle. Changes in focal adhesion organization were also evaluated in a subset of cells expressing green fluorescent protein (GFP)-zyxin, by simultaneous fluorescent and DIC imaging.
Pulling on the ECM resulted in initial cell elongation, followed by disengagement and retraction of pseudopodia. In contrast, pushing the ECM toward a cell induced rapid shortening (contraction), presumably since existing cellular forces were no longer counterbalanced by ECM tension. Pseudopodial extension (spreading) was then observed at both ends of the cell. The ECM was pulled inward during this secondary spreading, and rapid turnover of focal adhesions was observed along extending pseudopodia. Preincubation with Y-27632 or cytochalasin D blocked both the initial contractile and secondary spreading responses.
Overall, the data suggest that corneal fibroblasts actively respond to increases or decreases in local matrix stress in an attempt to maintain tensional homeostasis (constant tension), and that this response may be mediated by Rho and/or Rac.

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Available from: Walter Matthew Petroll, Jul 15, 2014
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    • "traction to the extracellular matrix (ECM) depends on cell shape, size and focal adhesions (Rape et al., 2011). Cells monitor their mechanical state and adjust traction forces depending on the environmental conditions to reach 'tensional homeostasis' (Brown et al., 1998; Saez et al., 2005; Ghibaudo et al., 2008; Petroll et al., 2004). Cell traction results in alignment of the collagen network (Stopak and Harris, 1982), which in turn becomes a topological trigger for cells to orient. "
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    • "FEM analysis showed that fibroblasts partially re-establish baseline ECM tension during this secondary spreading, presumably in an attempt to maintain tensional homeostasis [19]. Overall, while durotaxis has been shown to regulate cell alignment and migration within collagen matrices under static conditions, tensional homeostasis may modulate cell behavior in response to more transient changes in ECM tension, at both the local and global level [19] [97] [98]. Interestingly, when a needle is pushed toward the trailing edge of a migrating cell in 3-D, the same initial contraction and secondary spreading response identified at the leading edge is induced. "
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