Connective tissue growth factor/CCN2-null mouse embryonic fibroblasts retain intact transforming growth factor-[beta] responsiveness

Background The matricellular protein connective tissue growth factor (CCN2) has been implicated in pathological fibrosis, but its physiologic role remains elusive. In vitro, transforming growth factor-[beta] (TGF-[beta]) induces CCN2 expression in mesenchymal cells. Because CCN2 can enhance profibro...

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Published in:Experimental cell research 2008-03, Vol.314 (5), p.1094
Main Authors: Mori, Yasuji, Hinchcliff, Monique, Wu, Minghua, Warner-Blankenship, Matthew, M Lyons, Karen, Varga, John
Format: Article
Language:English
Subjects:
60 APPLIED LIFE SCIENCES
ACTIN
BLEOMYCIN
Cellular biology
COLLAGEN
CONNECTIVE TISSUE
Developmental biology
FIBROBLASTS
FIBROSIS
Gene expression
GROWTH FACTORS
IN VITRO
MICE
PHOSPHORYLATION
POLYMERASE CHAIN REACTION
Proteins
Rodents
SKIN
STIMULATION
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Summary:Background The matricellular protein connective tissue growth factor (CCN2) has been implicated in pathological fibrosis, but its physiologic role remains elusive. In vitro, transforming growth factor-[beta] (TGF-[beta]) induces CCN2 expression in mesenchymal cells. Because CCN2 can enhance profibrotic responses elicited by TGF-[beta], it has been proposed that CCN2 functions as an essential downstream signaling mediator for TGF-[beta]. To explore this notion, we characterized TGF-[beta]-induced activation of fibroblasts from CCN2-null (CCN2-/-) mouse embryos. Methods The regulation of CCN2 expression was examined in vivo in a model of fibrosis induced by bleomycin. Cellular TGF-[beta] signal transduction and regulation of collagen gene expression were examined in CCN2-/- MEFs by immunohistochemistry, Northern, Western and RT-PCR analysis, immunocytochemistry and transient transfection assays. Results Bleomycin-induced skin fibrosis in the mouse was associated with substantial CCN2 up-regulation in lesional fibroblasts. Whereas in vitro proliferation rate of CCN2-/- MEFs was markedly reduced compared to wild type MEFs, TGF-[beta]-induced activation of the Smad pathways, including Smad2 phosphorylation, Smad2/3 and Smad4 nuclear accumulation and Smad-dependent transcriptional responses, were unaffected by loss of CCN2. The stimulation of COL1A2 and fibronectin mRNA expression and promoter activity, and of corresponding protein levels, showed comparable time and dose-response in wild type and CCN2-/- MEFs, whereas stimulation of alpha smooth muscle actin and myofibroblast transdifferentiation showed subtle impairment in MEFs lacking CCN2. Conclusion Whereas endogenous CCN2 plays a role in regulation of proliferation and TGF-[beta]-induced myofibroblast transdifferentiation, it appears to be dispensable for Smad-dependent stimulation of collagen and extracellular matrix synthesis in murine embryonic fibroblasts. [PUBLICATION ABSTRACT]
ISSN:0014-4827
1090-2422
DOI:10.1016/j.yexcr.2007.12.010