Wnt/β-catenin signaling is hyperactivated in systemic sclerosis and induces Smad-dependent fibrotic responses in mesenchymal cells.
OBJECTIVE
Fibrosis in human diseases and animal models is associated with aberrant Wnt/β-catenin pathway activation. The aim of this study was to characterize the regulation, activity, mechanism of action, and significance of Wnt/β-catenin signaling in the context of systemic sclerosis (SSc).


METHODS
The expression of Wnt signaling pathway components in SSc skin biopsy specimens was analyzed. The regulation of profibrotic responses by canonical Wnt/β-catenin was examined in explanted human mesenchymal cells. Fibrotic responses were studied using proliferation, migration, and gel contraction assays. The cell fate specification of subcutaneous preadipocytes by canonical Wnt signaling was evaluated.


RESULTS
Analysis of published genome-wide expression data revealed elevated expression of the Wnt receptor FZD2 and the Wnt target LEF1 and decreased expression of Wnt antagonists DKK2 and WIF1 in skin biopsy specimens from subsets of patients with diffuse cutaneous SSc compared to the other distinct subsets. Immunohistochemical analysis showed increased nuclear β-catenin expression in these biopsy specimens. In vitro, Wnt-3a induced β-catenin activation, stimulated fibroblast proliferation and migration, collagen gel contraction, and myofibroblast differentiation, and enhanced profibrotic gene expression. Genetic and pharmacologic approaches were used to demonstrate that these profibrotic responses involved autocrine transforming growth factor β signaling via Smads. In contrast, in explanted subcutaneous preadipocytes, Wnt-3a repressed adipogenesis and promoted myofibroblast differentiation.


CONCLUSIONS
Canonical Wnt signaling was hyperactivated in SSc skin biopsy specimens. In explanted mesenchymal cells, Wnt-3a stimulated fibrogenic responses while suppressing adipogenesis. Taken together, these results indicate that Wnts have potent profibrotic effects, and that canonical Wnt signaling plays an important role in the pathogenesis of fibrosis and lipoatrophy in SSc.
Northwestern University, Feinberg School of Medicine, Chicago, Illinois 60611, USA.
Jun
J
Wei
Feng
F
Fang
Anna P
AP
Lam
Jennifer L
JL
Sargent
Emily
E
Hamburg
Monique E
ME
Hinchcliff
Cara J
CJ
Gottardi
Radhika
R
Atit
Michael L
ML
Whitfield
John
J
Varga
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000328:Adult; D001706:Biopsy; D016022:Case-Control Studies; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D051157:Frizzled Receptors / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000378:metabolism; D008648:Mesoderm / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D012097:Repressor Proteins / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin / Q000378:metabolism / Q000473:pathology; D051785:Smad Proteins / Q000378:metabolism*; D051153:Wnt Proteins / Q000378:metabolism*; D060509:Wnt3A Protein / Q000494:pharmacology; D051176:beta Catenin / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C498622:DKK2 protein, human; C489742:FZD2 protein, human; D051157:Frizzled Receptors; D036341:Intercellular Signaling Peptides and Proteins; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; D012097:Repressor Proteins; D051785:Smad Proteins; C485569:WIF1 protein, human; D051153:Wnt Proteins; D060509:Wnt3A Protein; D051176:beta Catenin