Jochen Zwerina

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a severe condition encompassing two major syndromes: granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis) and microscopic polyangiitis. Its cause is unknown, and there is debate about whether it is a single disease entity and what role ANCA plays in its pathogenesis. We investigated its genetic basis. METHODS: A genomewide association study was performed in a discovery cohort of 1233 U.K. patients with ANCA-associated vasculitis and 5884 controls and was replicated in 1454 Northern European case patients and 1666 controls. Quality control, population stratification, and statistical analyses were performed according to standard criteria. RESULTS: We found both major-histocompatibility-complex (MHC) and non-MHC associations with ANCA-associated vasculitis and also that granulomatosis with polyangiitis and microscopic polyangiitis were genetically distinct. The strongest genetic associations were with the antigenic specificity of ANCA, not with the clinical syndrome. Anti-proteinase 3 ANCA was associated with HLA-DP and the genes encoding α(1)-antitrypsin (SERPINA1) and proteinase 3 (PRTN3) (P=6.2×10(-89), P=5.6×10(-12,) and P=2.6×10(-7), respectively). Anti-myeloperoxidase ANCA was associated with HLA-DQ (P=2.1×10(-8)). CONCLUSIONS: This study confirms that the pathogenesis of ANCA-associated vasculitis has a genetic component, shows genetic distinctions between granulomatosis with polyangiitis and microscopic polyangiitis that are associated with ANCA specificity, and suggests that the response against the autoantigen proteinase 3 is a central pathogenic feature of proteinase 3 ANCA-associated vasculitis. These data provide preliminary support for the concept that proteinase 3 ANCA-associated vasculitis and myeloperoxidase ANCA-associated vasculitis are distinct autoimmune syndromes. (Funded by the British Heart Foundation and others.).

The transforming growth factor-β (TGF-β) signalling pathway is a key mediator of fibroblast activation that drives the aberrant synthesis of extracellular matrix in fibrotic diseases. Here we demonstrate a novel link between transforming growth factor-β and the canonical Wnt pathway. TGF-β stimulates canonical Wnt signalling in a p38-dependent manner by decreasing the expression of the Wnt antagonist Dickkopf-1. Tissue samples from human fibrotic diseases show enhanced expression of Wnt proteins and decreased expression of Dickkopf-1. Activation of the canonical Wnt pathway stimulates fibroblasts in vitro and induces fibrosis in vivo. Transgenic overexpression of Dickkopf-1 ameliorates skin fibrosis induced by constitutively active TGF-β receptor type I signalling and also prevents fibrosis in other TGF-β-dependent animal models. These findings demonstrate that canonical Wnt signalling is necessary for TGF-β-mediated fibrosis and highlight a key role for the interaction of both pathways in the pathogenesis of fibrotic diseases. Aberrant activation of the TGF-β pathway leads to fibrotic disease. Distler and colleagues show that TGF-β-mediated fibrosis requires the decrease of Dickkopf-1, an antagonist of canonical Wnt signalling, suggesting that the two pathways interact for the manifestation of this disease.

OBJECTIVE: Imatinib mesylate is a clinically well-tolerated small molecule inhibitor that exerts selective, dual inhibition of the transforming growth factor beta (TGFbeta) and platelet-derived growth factor (PDGF) pathways. This study was undertaken to test the potential use of imatinib mesylate as an antifibrotic drug for the treatment of dermal fibrosis in systemic sclerosis (SSc). METHODS: The expression of extracellular matrix (ECM) proteins in SSc and normal dermal fibroblasts was analyzed by real-time polymerase chain reaction, Western blot, and Sircol collagen assay. Proliferation capacity was assessed with the MTT assay. Cell viability was analyzed by mitochondrial membrane potential and by annexin V/propidium iodide staining. Bleomycin-induced experimental dermal fibrosis was used to assess the antifibrotic effects of imatinib mesylate in vivo. RESULTS: Imatinib mesylate efficiently reduced basal synthesis of COL1A1, COL1A2, and fibronectin 1 messenger RNA in SSc and normal dermal fibroblasts, in a dose-dependent manner. The induction of ECM proteins after stimulation with TGFbeta and PDGF was also strongly and dose-dependently inhibited by imatinib mesylate. These results were confirmed at the protein level. Imatinib mesylate did not alter proliferation or induce apoptosis and necrosis in dermal fibroblasts. Consistent with the in vitro findings, imatinib mesylate reduced dermal thickness, the number of myofibroblasts, and synthesis of ECM proteins in experimental dermal fibrosis, without evidence of toxic side effects. CONCLUSION: These data show that imatinib mesylate at biologically relevant concentrations has potent antifibrotic effects in vitro and in vivo, without toxic side effects. Considering its favorable pharmacokinetics and clinical experience with its use in other diseases, imatinib mesylate is a promising candidate for the treatment of fibrotic diseases such as SSc.

OBJECTIVE: To investigate whether Treg cells can suppress osteoclast differentiation, and to define a new potential link between the immune system and the skeleton. METHODS: Regulatory CD4+,CD25+,Foxp3+ T cells were isolated and purified from the spleen and cocultured with CD11b+ osteoclast precursor cells isolated from bone marrow. Osteoclastogenesis and bone erosion were assessed by tartrate-resistant acid phosphatase staining and pit resorption assay, respectively. In addition, Transwell experiments and cytokine-blocking experiments were performed to define the mechanisms of interaction between Treg cells and osteoclasts. RESULTS: CD4+,CD25+,Foxp3+ T cells, but not CD4+,CD25- T cells, dose dependently inhibited macrophage colony-stimulating factor- and RANKL-dependent osteoclast formation. Pit formation was inhibited by up to 80% when Treg cells were added. The blockade of osteoclast formation was not based on the alteration of RANKL/osteoprotegerin balance but was essentially dependent on direct cell-cell contact via CTLA-4. Treg cell-mediated expression of transforming growth factor beta, interleukin-4 (IL-4), and IL-10 contributed but was not essential to the inhibitory effect on osteoclastogenesis. CONCLUSION: These data show that CD4+,CD25+,Foxp3+ Treg cells suppress osteoclast formation, provide a new link between the immune system and bone, and extend our knowledge on regulation of bone homeostasis by the immune system.