ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 2708

The Hedgehog Transcription Factor Gli-2 Is a Novel Downstream Mediator Of The Pro-Fibrotic Effects Of Transforming Growth Factor-Beta

Barbora Sumova1,2, Cinzia Cordazzo3, Katrin Palumbo-Zerr4, Clara Dees4, Pawel Zerr4, Oliver Distler5, Georg Schett6, Ladislav Senolt7 and Joerg H. W. Distler4, 1Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Germany, Erlangen, Germany, 2Department of Rheumatology of the First Faculty of Medicine, Institute of Rheumatology and Connective Tissue Research Laboratory, Prague, Czech Republic, 33Dipartimento Cardiotoracico e Vascolare, Laboratory of Respiratory Cell Biology, University of Pisa, Pisa, Italy, 4Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany, 5Division of Rheumatology, University Hospital Zurich, Zurich, Switzerland, 6Dept of Medicine 3, Rheumatology and Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany, 7Institute of Rheumatology, Department of Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords:

Session Information

Title: Systemic Sclerosis, Fibrosing Syndromes and Raynaud's: Pathogenesis, Animal Models, Genetics: Novel Signaling Pathways Mediating Fibrosis

Session Type: Abstract Submissions (ACR)

Background/Purpose: Systemic sclerosis (SSc) is characterized by aberrant activation of fibroblasts with increased release of extracellular matrix components. TGFβ is a key-mediator of fibroblast activation in SSc. More recently, hedgehog signaling (Hh) has also been shown to induce tissue fibrosis in SSc. Gli-2 is activated by Hh signaling and induces the transcription of hedgehog target genes. Since the TGFβ and Hh signaling are both key drivers of fibroblast activation in SSc, the aim of this study was to investigate potential crosstalk between those two pathways in SSc.

Methods: The expression of Gli2 in the fibroblasts and tissue was analyzed by real- time PCR and IF staining. Collagen synthesis was quantified by real-time PCR and hydroxyproline assay. Selective knockdown strategies were used to evaluate the role of Gli2 in TGFβ signaling in vitro and in vivo. The interaction between Gli-2 and TGFβ signaling was analyzed using mice with inducible, fibroblast-specific knockout of Gli2 (Gli-2; Col1a2 CreER) and fibroblast-specific overexpression of a constitutively active TGFβ receptor I TBR (TBR; Col1a2 CreER). Cre mediated recombination was induced postnatally by injection of tamoxifen.

Results: The expression of Gli-2 was significantly increased in the skin of SSc patients compared to healthy controls. In particular, SSc fibroblasts expressed high levels of Gli-2. A prominent overexpression of Gli-2 in fibroblasts was also observed in mice overexpressing TBR. Consistently, stimulation with TGFβ increased the mRNA and the protein level of Gli2 in a time-dependent manner with maximal effects after 3 hours of stimulation (6-fold increase, p<0.05) and induced nuclear translocation of Gli2. Gli-2 knockout fibroblasts expressed lower levels of TGFβ targeted genes col1a2 (-47 %), CTGF (-30 %), Smad7 (-44 %), PAI-1 (-37 %) upon stimulation with TGFβ compared to control fibroblasts (p<0.05 each). The role of Gli-2 as a downstream mediator of TGFβ in fibroblasts was further analyzed in vivo using mice with fibroblast-specific depletion of Gli-2 and simultaneous overexpression of TBR. Fibroblast-specific overexpression of TBR in TBR; Col1a2 CreER mice induced progressive skin fibrosis. Fibroblast-specific, postnatal depletion of Gli-2 in Gli-2; Col1a2 CreER did not result in a basal skin phenotype. However, fibroblast-specific knockdown of Gli-2 protected from TBR induced fibrosis. Gli-2 x TBR; Col1a2 CreER mice treated with tamoxifen showed reduced dermal thickening (-30 %), decreased myofibroblast counts (-41 %) and lower hydroxyproline levels (-45 %) (p<0.05 each) compared to TBR; Col1a2 CreER mice.

Conclusion:

We present here first evidence for a novel interaction of TGFβ and Hh signaling in fibrosis. TGFβ stimulates Hh signaling in a non-canonical manner by activation of the downstream transcription factor Gli-2. Fibroblast-specific knockdown of Gli-2 reduces the stimulatory effects of TGFβ on fibroblasts and ameliorates TBR-induced skin fibrosis, thereby demonstrating Gli-2 is as a novel downstream mediator of the pro-fibrotic effects of TGFβ.

Disclosure:

B. Sumova,
None;

C. Cordazzo,
None;

K. Palumbo-Zerr,
None;

C. Dees,
None;

P. Zerr,
None;

O. Distler,

Sanofi, Active Biotech, Pfizer, Actelion, and Novartis,

2,

Actelion, Sanofi-Aventis, Roche, Genentech, Active Biotec, medac, Novartis, Sinoxa, 4D Science,

5;

G. Schett,
None;

L. Senolt,
None;

J. H. W. Distler,
None.

« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-hedgehog-transcription-factor-gli-2-is-a-novel-downstream-mediator-of-the-pro-fibrotic-effects-of-transforming-growth-factor-beta/