Background Fibrosis is a major socioeconomic burden, but effective anti-fibrotic therapies are not available in clinical routine. Fibrosis emerges from excessive release of extracellular matrix components by pathologically activated fibroblasts, which results in disruption of the physiological tissue architecture and causes organ failure. Growing evidence demonstrates a crucial role of canonical Wnt signaling in this pathologic fibroblast activation in fibrotic diseases such as systemic sclerosis (SSc). In SSc, overexpression of Wnt1 and Wnt10b leads to stabilization of β-catenin and increased transcription of target genes, resulting in tissue fibrosis. Of note, TGF-β signaling stimulates canonical Wnt signaling by decreasing the levels of the endogenous Wnt inhibitor Dickkopf-1.
Objectives To evaluate the translational potential of these recent findings, we tested pharmacological Wnt inhibitors in different experimental models of dermal fibrosis.
Methods We evaluated the anti-fibrotic effects of PKF118-310 and ICG-001, two novel inhibitors of downstream canonical Wnt signaling, in the model of bleomycin-induced dermal fibrosis and in experimental fibrosis induced by adenoviral overexpression of a constitutively active TGF-β receptor I (adTBRIact). Antifibrotic effects were assessed by measuring dermal thickness, hydroxyproline content and α-smooth muscle actin counts. Body weight, activity and texture of the fur were used to assess tolerability.
Results PKF118-310 and ICG-001 were well-tolerated throughout all experiments with animals showing constant body weight, normal activity and normal texture of the fur. PKF118-310 showed strong anti-fibrotic effects in both the bleomycin and the adTBRIact mouse model. In the bleomycin challenged mice, skin thickness was reduced by 43.5% (p =0.002), and by 63.1% (p = 0.0020) in the adTBRIact model. Hydroxyproline content and α-smooth muscle actin-positive fibroblasts were significantly reduced in a similar extent in both models. Similar to PKF118-310, ICG-001 was effective in inhibiting bleomycin-induced dermal fibrosis and TGF-β receptor I-driven fibrosis. When treated with ICG-001, skin thickening decreased by 49.1% (p <0.0001) in bleomycin-challenged mice. In addition, ICG-001 reduced dermal thickening by 47.7% (p=0.0025) in the adTBRIact model. Similar to the reduction of dermal thickening, hydroxyproline content and α-smooth muscle actin-positive fibroblasts were significantly reduced in both models.
Conclusions Blockade of canonical Wnt signaling by PKF118-310 and ICG-001 showed anti-fibrotic effects in the inflammation-dependent model of bleomycin-induced dermal fibrosis and the TGF-β-driven adTBRIact model, reflecting different stages of fibrotic disease. Efficacy of Wnt inhibitors in the adTBRIact model provided further evidence for a close link between TGF-β- and canonical Wnt signaling. Of note, both Wnt inhibitors showed good tolerability in our models. Although further experimental evidence for efficacy and tolerability is necessary, inhibition of canonical Wnt signaling is a potential molecular targeted treatment approach for fibrosis in SSc.
Disclosure of Interest None Declared