Abstract
We previously identified transforming growth factor (TGF)-β signaling as a fibronectin-independent mechanism of type I collagen fibrillogenesis following adult liver injury. To address the contribution of TGF-β signaling during the development of liver fibrosis, we generated adult mice lacking TGF-β type II receptor (TGF-βIIR) from the liver. TGF-βIIR knockout livers indeed showed a dominant effect in reducing fibrosis, but fibrosis still remained approximately 45% compared with control and fibronectin knockout livers. Unexpectedly, this was accompanied by significant up-regulation of connective tissue growth factor mRNA levels. Organized type I collagen networks in TGF-βIIR knockout livers colocalized well with fibronectin. We provide evidence that elimination of TGF-βIIR is not sufficient to completely prevent liver fibrosis. Our results indicate a TGF-β-independent mechanism of type I collagen production and suggest connective tissue growth factor as its potent mediator. We advocate combined elimination of TGF-β signaling and connective tissue growth factor as a potential therapeutic target by which to attenuate liver fibrosis.
Copyright © 2014 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Carbon Tetrachloride / toxicity
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Chronic Disease
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Collagen Type I / genetics
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Collagen Type I / metabolism
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Connective Tissue Growth Factor / genetics
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Connective Tissue Growth Factor / metabolism*
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Disease Models, Animal
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Fibronectins / genetics
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Fibronectins / metabolism
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Gene Expression Regulation*
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Humans
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Liver / drug effects
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Liver / metabolism
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Liver / pathology
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Liver Cirrhosis / chemically induced
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Liver Cirrhosis / metabolism*
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Liver Cirrhosis / pathology
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Mice
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Mice, Knockout
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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RNA, Messenger / genetics
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Receptor, Transforming Growth Factor-beta Type II
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Receptors, Transforming Growth Factor beta / genetics
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Receptors, Transforming Growth Factor beta / metabolism*
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Signal Transduction*
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Transforming Growth Factor beta / genetics
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Transforming Growth Factor beta / metabolism*
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Up-Regulation
Substances
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CCN2 protein, mouse
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Collagen Type I
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Fibronectins
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RNA, Messenger
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Receptors, Transforming Growth Factor beta
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Transforming Growth Factor beta
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Connective Tissue Growth Factor
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Carbon Tetrachloride
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Protein Serine-Threonine Kinases
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Receptor, Transforming Growth Factor-beta Type II