S100A4 amplifies TGF-β-induced fibroblast activation in systemic sclerosis.
OBJECTIVE
S100A4 is a calcium binding protein with regulatory functions in cell homeostasis, proliferation and differentiation that has been shown to promote cancer progression and metastasis. In the present study, we evaluated the role of S100A4 in fibroblast activation in systemic sclerosis (SSc).


METHODS
The expression of S100A4 was analysed in human samples, murine models of SSc and in cultured fibroblasts by real-time PCR, immunohistochemistry and western blot. The functional role of S100A4 was evaluated using siRNA, overexpression, recombinant protein and S100A4 knockout (S100A4(-/-)) mice. Transforming growth factor β (TGF-β) signalling was assessed by reporter assays, staining for phosphorylated Smad2/3 and analyses of target genes.


RESULTS
The expression of S100A4 was increased in SSc skin and in experimental fibrosis in a TGF-β/Smad-dependent manner. Overexpression of S100A4 or stimulation with recombinant S100A4 induced an activated phenotype in resting normal fibroblasts. In contrast, knockdown of S100A4 reduced the pro-fibrotic effects of TGF-β and decreased the release of collagen. S100A4(-/-) mice were protected from bleomycin-induced skin fibrosis with reduced dermal thickening, decreased hydroxyproline content and lower myofibroblast counts. Deficiency of S100A4 also ameliorated fibrosis in the tight-skin-1 (Tsk-1) mouse model.


CONCLUSIONS
We characterised S100A4 as a downstream mediator of the stimulatory effects of TGF-β on fibroblasts in SSc. TGF-β induces the expression of S100A4 to stimulate the release of collagen in SSc fibroblasts and induce fibrosis. Since S100A4 is essentially required for the pro-fibrotic effects of TGF-β and neutralising antibodies against S100A4 are currently evaluated, S100A4 might be a candidate for novel antifibrotic therapies.
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany Department of Rheumatology, 1st Faculty of Medicine, Institute of Rheumatology, Charles University, Prague, Czech Republic.
Michal
M
Tomcik
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Katrin
K
Palumbo-Zerr
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Pawel
P
Zerr
Rheumatology A Department, Paris Descartes University, Cochin Hospital, Paris, France.
Jerome
J
Avouac
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Clara
C
Dees
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany Department of Rheumatology, 1st Faculty of Medicine, Institute of Rheumatology, Charles University, Prague, Czech Republic.
Barbora
B
Sumova
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Alfiya
A
Distler
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Christian
C
Beyer
Department of Rheumatology, 1st Faculty of Medicine, Institute of Rheumatology, Charles University, Prague, Czech Republic.
Lucie Andres
LA
Cerezo
Department of Rheumatology, 1st Faculty of Medicine, Institute of Rheumatology, Charles University, Prague, Czech Republic.
Radim
R
Becvar
Center of Experimental Rheumatology and Zurich Center of Integrative Human Physiology, University Hospital, Zurich, Switzerland.
Oliver
O
Distler
Neuro-Oncology Group, Faculty of Health Sciences, Institute of Neuroscience and Pharmacology, Copenhagen University, Copenhagen, Denmark.
Mariam
M
Grigorian
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Georg
G
Schett
Department of Rheumatology, 1st Faculty of Medicine, Institute of Rheumatology, Charles University, Prague, Czech Republic.
Ladislav
L
Senolt
Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
Jörg H W
JH
Distler
D000328:Adult; D000368:Aged; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000378:metabolism*; D012595:Scleroderma, Systemic / Q000378:metabolism*; D012867:Skin / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D055815:Young Adult
D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C470944:S100a4 protein, mouse; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; C077591:S100A4 protein, human