Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
-Catenin Is a Central Mediator In Systemic Sclerosis.
Beyer1, Christian, Schramm1, Amelie, Akhmetshina1, Alfiya, Kireva1, Trayana, Dees1, Clara, Schindler1, Sonia C., Taketo2, Makoto M.
Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
Kyoto University Yoshida-Konoé-cho, Kyoto, Japan
University Hospital Zurich, Zurich, Switzerland
Department of Internal Medicine 3 and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany
b-catenin is the central integrator of canonical Wnt signaling. Binding of Wnts to their receptors causes stabilization of b-catenin, which translocates into the nucleus and regulates the transcription of target genes. Since recent evidence suggests a central role of Wnt signaling in fibrosis, we examined the Wnt pathway in SSc and focused on the role of b-catenin in fibroblast activation.
We performed qPCR for several Wnt ligands and axin-2 to examine Wnt expression in SSc skin. We further studied protein levels of Wnt-1, -4, -10b and b-catenin by IHC. To establish the effects of Wnt signaling on collagen release, we used fibroblasts with either stabilization of b-catenin (DEx3 b-cateninwt/ex) or fibroblasts carrying a deletion of both b-catenin alleles (Ctnnb1ex/ex). Finally, we created mice with fibroblast-specific stabilization of b-catenin (DEx3 b-cateninwt/fl× Col1a2;Cre-ER) as well as mice carrying fibroblast-specific deletion of b-catenin (Ctnnb1fl/fl x Col1a2;Cre-ER). We studied spontaneous fibrogenesis in DEx3 b-cateninwt/fl× Col1a2;Cre-ER mice 8 weeks after Cre-activation and challenged activated Ctnnb1fl/fl× Col1a2; Cre-ER mice with bleomycin for 4 weeks.
We could demonstrate mRNA overexpression of Wnt-1, -10b, and -16 as well as increased Wnt-1 and Wnt-10b protein levels in SSc skin. The overexpression of several Wnt ligands resulted in a prominent nuclear accumulation of b-catenin in fibroblasts. Finally, increased mRNA levels of the target gene axin-2 confirmed the activation of canonical Wnt signaling.
In DEx3 b-cateninwt/ex fibroblasts, we addressed the consequences of enhanced Wnt signaling and increased accumulation of b-catenin for SSc fibrogenesis: In vitro stabilization of b-catenin resulted in an increase of collagen release by 112 ± 7 % (p < 0.05). By contrast, deletion of b-catenin in Ctnnb1ex/ex fibroblasts reduced collagen production by 55 ± 17 % (p < 0.05). Collagen mRNA levels were altered accordingly.
To confirm the crucial role of b-catenin in dermal fibrosis in vivo, we selectively targeted b-catenin in fibroblasts. Cre-activated DEx3 b-cateninwt/fl× Col1a2;Cre-ER mice showed massive and spontaneous dermal thickening with increases of 3.98 ± 0.1fold (p < 0.05). Hydroxyproline content and myofibroblast counts were also increased prominently. In contrast to the pro-fibrotic effects of b-catenin stabilization, deletion of b-catenin in Ctnnb1fl/fl x Col1a2;Cre-ER mice protected from bleomycin-induced dermal fibrosis (reduction of skin thickness by 54 ± 4 %; p < 0.05).
We demonstrated a prominent activation of canonical Wnt signaling in SSc with nuclear accumulation of b-catenin in fibroblasts and activation of the target gene axin-2. Our results showed that fibroblast-specific stabilization of b-catenin resulted in enhanced collagen release in vitro and in vivo, whereas deletion of b-catenin potently reduced collagen production. Together, our findings highlight a key-role of b-catenin in fibroblast activation and fibrosis. Thus, b-catenin may be promising molecular targets for anti-fibrotic therapies.
To cite this abstract, please use the following information:
Beyer, Christian, Schramm, Amelie, Akhmetshina, Alfiya, Kireva, Trayana, Dees, Clara, Schindler, Sonia C., et al; -Catenin Is a Central Mediator In Systemic Sclerosis. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1588