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Title: 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 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{sup -/-}) 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{sup -/-} 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{sup -/-} 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 typemore » and CCN2{sup -/-} 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.« less
Authors:
; ; ;  [1] ;  [2] ;  [3]
  1. Division of Rheumatology, Northwestern University Feinberg School of Medicine, 240 E Huron Street, Chicago, IL 60611 (United States)
  2. OH/UCLA Department of Orthopedic Surgery, David Geffen School of Medicine, UCLA, Los Angeles, CA (United States)
  3. Division of Rheumatology, Northwestern University Feinberg School of Medicine, 240 E Huron Street, Chicago, IL 60611 (United States), E-mail: j-varga@northwestern.edu
Publication Date:
OSTI Identifier:
21045950
Resource Type:
Journal Article
Resource Relation:
Journal Name: Experimental Cell Research; Journal Volume: 314; Journal Issue: 5; Other Information: DOI: 10.1016/j.yexcr.2007.12.010; PII: S0014-4827(07)00584-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACTIN; BLEOMYCIN; COLLAGEN; CONNECTIVE TISSUE; FIBROBLASTS; FIBROSIS; GROWTH FACTORS; IN VITRO; MICE; PHOSPHORYLATION; POLYMERASE CHAIN REACTION; SKIN; STIMULATION