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M. Fini, A. J. LaGier, S. Yoo, E. C. Alfonso, S. A. Meiners, V. Lemmon; Inhibition of Corneal Epithelial Cell Production of Fibrotic Mediator TGF-beta2 by Basement Membrane-Like Extracellular Matrix. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3499.
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Transforming Growth Factor-beta2 (TGF-beta2) is a major epithelial mediator of fibrotic marker expression. Production of TGF-beta2 protein is reduced by plating on matrigel, a basement membrane-like extracellular matrix extract. The goal of the current study was to further understand the mechanism of matrigel regulation.
We used a human epithelial cell culture model for these studies. Chemical panel screening was done in multi-well plate format using cells transfected with a beta-lactamase reporter gene construct driven by the TGF-beta2 promoter.
TGF-beta2 production is inhibited by matrigel at the level of mRNA accumulation and activity of the TGF-beta2 gene transcriptional promoter. The effects of matrigel cannot be explained by growth factor contaminants, reduction in heparin sulfate proteoglycans has no effect, and pure forms of the major ECM components laminin and collagen IV can not alone reproduce the effect. Experiments also failed to implicate inhibition of a constitutive TGF-beta2 autocrine feedback loop. Thus we went on to consider hypotheses that incorporated a requirement for complexity. Matrigel caused a reduction of ezrin, a member of the ezrin/ radixin/ moesin (ERM) family, which plays a role in establishing polarity of epithelial cells in tissues through the Rho signaling pathway and the actin cytoskelton. A set of know chemical compounds was screened for the capacity to inhibit TGF-beta2 promoter activity, yielding two hits - one an inhibiter of actin polymerization and another an inhibitor of the PDGF receptor tyrosine kinase.
These findings indicate that matrigel inhibits TGF-beta2 gene expression and point to a mechanism requiring the complexity of matrigel composition and structure. Ezrin and the actin cytoskelton, Rho kinase, and the PDGF receptor tyrosine kinase are implicated in this mechanism. Chemical compounds that affect this pathway might be used as pharmacologic modulators to improve the quality of wound healing and refractive surgical outcomes in the cornea.
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