SAT0026 Combined inhibition of notch, hedgehog and wnt signaling exerts additive anti-fibrotic effects and reduces toxicity
Authors: V.R. Lang, C. Dees, C. Beyer, O. Distler, G. Schett, J.H.W. Distler
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Recent studies demonstrated that the morphogenic pathways Notch, hedgehog (Hh) and Wnt are activated in systemic sclerosis and that inhibition of these morphogen pathways exerted potent anti-fibrotic effects in different pre-clinical models. As Notch and Wnt signaling are crucial for the proliferation especially of intestinal stem cells and Hh-ligands drive stem cell differentiation, interfering with morphogen pathways might be complicated by inhibitory effects on stem cell regeneration. Thus, high-dose therapies completely abrogating Notch, Hh and canonical Wnt signaling might be limited by adverse effects on stem cells <h3>Objectives</h3> (I) To assess the anti-fibrotic effects of combined inhibition of Notch/Hh or Wnt/Hh-signaling and (II) to show the improved tolerability of the combination therapy with low doses of inhibitors in particular with respect to intestinal stem cells. <h3>Methods</h3> Bleomycin was applied as described by [1]. Mice were feed by gavages with the Notch-inhibitor DAPT (1.5 mg/kg/d), the Hh-inhibitor cyclopamine (5mg/kg/d)or injected i.p. with the Wnt-inhibitor ICG-001 (2 mg/kg/d). The applied dosages represent low-dose treatment. The combined treatment was administered accordingly. Skin thickness, myofibroblast counts and hydroxyproline contents of the skin were assessed as described by [1]. Lgr5+ intestinal stem cells in sections of the colon- and the small intestine were detected by immunohistochemistry and counted in a blinded manner. <h3>Results</h3> Low-dose single inhibition of all the three morphogen pathways, Notch, Hh and Wnt, efficiently reduced bleomycin-induced dermal fibrosis with reduced dermal thickness, decreased myofibroblast counts and reduced hydroxyproline content. Combined inhibition of the Notch and Hh-signaling or Notch and Wnt-signaling were superior to single low-dose therapy. In the mice treated with the combination of DAPT/cyclopamine or DAPT/ICG-001, dermal thickness was reduced up to 75% or 60%, numbers of myofibroblasts were decreased by 80% or 70% and the hydroxyproline content by 80% or 65% of control mice (bleomycin/vehicle), respectively.Of note, combination therapies were well tolerated and did not cause weight loss. Consistently, combined inhibition of either Notch/Hh- or of Wnt/Hh-signaling did not significantly reduce numbers of Lgr5+ positive stem cells in the colon and the small intestine compared to sham treated mice. <h3>Conclusions</h3> Combined partial inhibition of morphogen-signaling with low doses of inhibition more potently prevents the development of bleomycin-induced skin fibrosis than single therapies. Combination therapies were well tolerated and did not deplete Lgr5+ intestinal stem cells. Combined targeting of different morphogenic pathways with low doses of inhibitors may not only reduce side-effects, but also increase the anti-fibrotic effects. <h3>References</h3> Dees C, Zerr P, Tomcik M, et al. Inhibition of Notch signaling prevents experimental fibrosis and induces regression of established fibrosis. Arthritis Rheum 2011;63:1396-1404. <h3>Disclosure of Interest</h3> None Declared