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T. Meyer–ter–Vehn, B. Katzenberger, S. Sieprath, F. Grehn, G. Schlunck; Cell Contractility Is a Prerequisite for TGFbeta–Induced Myofibroblast Transdifferentiation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):40.
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© ARVO (1962-2015); The Authors (2016-present)
Persistent transdifferentiation of fibroblasts to myofibroblasts is a hallmark of scarring processes. Cell–matrix interactions and matrix rigidity influence myofibroblast transdifferentiation and modulate signal transduction processes. The GTPase Rho and Rho–associated protein kinase (ROCK) regulate actin cytoskeleton reorganization in response to cell–matrix interactions. Here, we focus on the relevance of ROCK–signaling in TGFbeta–induced myofibroblast transdifferentiation and its impact on signaling pathways involved.
Primary human tenon fibroblast (HTF) cultures were pretreated with ROCK inhibitors Y27632, H1152 and HA–1077 or with the myosin light chain kinase (MLCK) inhibitor ML–7 and stimulated with TGFbeta for 48h. To analyze myofibroblast transdifferentiation, de novo synthesis of the marker protein smooth muscle actin (SMA) was measured by Western Blot and SMA–recruitment to stress fibers by immunofluorescence. Signalling pathways were examined using Western Blot and immunofluorescence.
Both ROCK and MLCK inhibition attenuated TGFbeta–induced myofibroblast transdifferentiation in a dose–dependent manner, suggesting a central role of cell contractility in this process. While TGFbeta–induced SMAD2 phosphorylation and nuclear translocation were unaffected by ROCK–inhibition, sustained p38 activation was averted by ROCK inhibitors.
Our results indicate a central role of cell contractility in TGFbeta–induced myofibroblast transdifferentiation. Recently, we showed a critical involvement of p38–signaling in this process. Since ROCK–inhibition affects only TGFbeta–induced p38 activation but not SMAD–signaling, this adds further evidence to the significance of p38 in this process. Moreover, increased rigidity of subconjunctival tissue due to chronic inflammation by topic medications is considered a risk factor for postoperative scarring after fistulating glaucoma surgery. One might speculate that "softening" of subconjunctival fibroblasts using ROCK–inhibitors might provide a new anti–scarring strategy.
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