Our previous study demonstrated increased expression of Heat shock protein (Hsp) 90 in the skin of patients with systemic sclerosis (SSc). We aimed to evaluate plasma Hsp90 in SSc and characterize its association with SSc-related features. Ninety-two SSc patients and 92 age-/sex-matched healthy controls were recruited for the cross-sectional analysis. The longitudinal analysis comprised 30 patients with SSc associated interstitial lung disease (ILD) routinely treated with cyclophosphamide. Hsp90 was increased in SSc compared to healthy controls. Hsp90 correlated positively with C-reactive protein and negatively with pulmonary function tests: forced vital capacity and diffusing capacity for carbon monoxide (DLCO). In patients with diffuse cutaneous (dc) SSc, Hsp90 positively correlated with the modified Rodnan skin score. In SSc-ILD patients treated with cyclophosphamide, no differences in Hsp90 were found between baseline and after 1, 6, or 12 months of therapy. However, baseline Hsp90 predicts the 12-month change in DLCO. This study shows that Hsp90 plasma levels are increased in SSc patients compared to age-/sex-matched healthy controls. Elevated Hsp90 in SSc is associated with increased inflammatory activity, worse lung functions, and in dcSSc, with the extent of skin involvement. Baseline plasma Hsp90 predicts the 12-month change in DLCO in SSc-ILD patients treated with cyclophosphamide.

Mesenchymal responses are an essential aspect of tissue repair. Failure to terminate this repair process correctly, however, results in fibrosis and organ dysfunction. Therapies that block fibrosis and restore tissue homeostasis are not yet available for clinical use. Here we characterize the nuclear receptor NR4A1 as an endogenous inhibitor of transforming growth factor-β (TGF-β) signaling and as a potential target for anti-fibrotic therapies. NR4A1 recruits a repressor complex comprising SP1, SIN3A, CoREST, LSD1, and HDAC1 to TGF-β target genes, thereby limiting pro-fibrotic TGF-β effects. Even though temporary upregulation of TGF-β in physiologic wound healing induces NR4A1 expression and thereby creates a negative feedback loop, the persistent activation of TGF-β signaling in fibrotic diseases uses AKT- and HDAC-dependent mechanisms to inhibit NR4A1 expression and activation. Small-molecule NR4A1 agonists can overcome this lack of active NR4A1 and inhibit experimentally-induced skin, lung, liver, and kidney fibrosis in mice. Our data demonstrate a regulatory role of NR4A1 in TGF-β signaling and fibrosis, providing the first proof of concept for targeting NR4A1 in fibrotic diseases.

No abstract

Objective. Hedgehog signaling not only plays crucial roles during human development but also has been implicated in the pathogenesis of several diseases in adults. The aim of the present study was to investigate the role of the hedgehog pathway in fibroblast activation in systemic sclerosis (SSc).Methods. Activation of the hedgehog pathway was analyzed by immunohistochemistry and real-time polymerase chain reaction (PCR). The effects of sonic hedgehog (SHH) on collagen synthesis were analyzed by reporter assays, real-time PCR, and Sircol assays. Myofibroblast differentiation was assessed by quantification of ␣-smooth muscle actin and stress fiber staining. The role of hedgehog signaling in vivo was analyzed by adenoviral overexpression of SHH and using mice lacking 1 allele of the gene for inhibitory receptor Patched homolog 1 (Ptch ؉/؊ mice).Results. SHH was overexpressed and resulted in activation of hedgehog signaling in patients with SSc, with accumulation of the transcription factors Gli-1 and Gli-2 and increased transcription of hedgehog target genes. Activation of hedgehog signaling induced an activated phenotype in cultured fibroblasts, with differentiation of resting fibroblasts into myofibroblasts and increased release of collagen. Adenoviral overexpression of SHH in the skin of mice was sufficient to induce skin fibrosis. Moreover, Ptch ؉/؊ mice with increased hedgehog signaling were more sensitive to bleomycin-induced dermal fibrosis.Conclusion. We demonstrated that the hedgehog pathway is activated in patients with SSc. Hedgehog signaling potently stimulates the release of collagen and myofibroblast differentiation in vitro and is sufficient to induce fibrosis in vivo. These findings identify the hedgehog cascade as a profibrotic pathway in SSc.

Purpose Tissue fibrosis caused by pathological activation of fibroblasts with increased synthesis of extracellular matrix components is a major hallmark of systemic sclerosis (SSc). Notch signalling regulates tissue differentiation and pathologic activation of Notch signaling has been implicated in the pathogenesis of various malignancies. The aim of the present study was to investigate the role of Notch signaling in SSc and to evaluate the therapeutic potential of Notch inhibition for the treatment of fibrosis. Methods Activation of the Notch pathways was analyzed by staining for the Notch intracellular domain (NICD) and quantification of the mRNA levels hes-1. Notch signaling was inhibited in the mouse model of bleomycin induced dermal fibrosis and in tight-skin-1 mice by the γ-secretase inhibitor DAPT and by overexpression of a Notch-1 antisense construct. Results Notch signaling is activated in SSc in vivo with accumulation of the NICD and increased transcription of the target gene hes-1. Overexpression of a Notch antisense construct prevented bleomycin-induced fibrosis and hypodermal thickening in tight-skin 1 mice. Potent anti-fibrotic effects were also obtained by treatment with DAPT. In addition to prevention of fibrosis, targeting Notch signaling resulted in almost complete regression of pre-established experimental fibrosis. Conclusion We demonstrate that pharmacologic as well as genetic inhibition of Notch signaling exerts potent anti-fibrotic effects in different murine models of SSc. These findings might have direct translational implications because different inhibitors of the γ-secretase complex are available and yielded promising results in cancer trials.

Objective. To investigate whether JAK-2 contributes to the pathologic activation of fibroblasts in patients with systemic sclerosis (SSc) and to evaluate the antifibrotic potential of JAK-2 inhibition for the treatment of SSc.Methods. Activation of JAK-2 in human skin and in experimental fibrosis was determined by immunohistochemical analysis. JAK-2 signaling was inhibited by the selective JAK-2 inhibitor TG101209 or by small interfering RNA. Bleomycin-induced dermal fibrosis in mice and TSK-1 mice were used to evaluate the antifibrotic potential of specific JAK-2 inhibition in vivo.Results. Increased activation of JAK-2 was detected in the skin of patients with SSc, particularly in fibroblasts. The activation of JAK-2 was dependent on transforming growth factor ␤ (TGF␤) and persisted in cultured SSc fibroblasts. Inhibition of JAK-2 reduced basal collagen synthesis selectively in SSc fibroblasts but not in resting healthy dermal fibroblasts. Moreover, inhibition of JAK-2 prevented the stimulatory effects of TGF␤ on fibroblasts. Treatment with TG101209 not only prevented bleomycin-induced fibrosis but also effectively reduced skin fibrosis in TSK-1 mice.Conclusion. We demonstrated that JAK-2 is activated in a TGF␤-dependent manner in SSc. Considering the potent antifibrotic effects of JAK-2 inhibition, our study might have direct translational implications, because inhibitors of JAK-2 are currently being evaluated in clinical trials for myeloproliferative disorders and would also be available for evaluation in patients with SSc.

BACKGROUND: Dermal fibroblasts from patients with systemic sclerosis (SSc) release excessive amounts of collagen resulting in tissue fibrosis. The molecular mechanisms underlying this pathological activation are incompletely understood. OBJECTIVE: To investigate whether Notch signalling contributes to the uncontrolled activation of fibroblasts in SSc. METHODS: Activation of the Notch pathway was assessed by immunohistochemistry or Western blot for the Notch intracellular domain and the Notch ligand Jagged-1 (Jag-1) and real-time PCR for the target gene hes-1. Differentiation of resting dermal fibroblasts into myofibroblasts was assessed by staining for -smooth muscle actin. The synthesis of collagen was quantified by real-time PCR and Sircol assays. RESULTS: Notch signalling was activated in lesional skin of patients with SSc. The activation persisted in cultured dermal SSc fibroblasts. Stimulation of healthy dermal fibroblasts with recombinant human Jag-1-Fc chimera resulted in an SSc-like phenotype with increased release of collagen and differentiation of resting fibroblasts into myofibroblasts. Consistent with the selective activation of the Notch pathway in dermal SSc fibroblasts, DAPT or siRNA against Notch strongly reduced the basal collagen expression in SSc fibroblasts, but not in fibroblasts from healthy volunteers. CONCLUSION: It was shown that Notch signalling is activated in SSc and plays an important role in fibroblast activation and collagen release. Inhibition of Notch signalling might be an effective strategy to selectively prevent the aberrant activation of SSc fibroblasts. Conclusion:We demonstrated that Notch signaling is activated in SSc and plays an important role in fibroblast activation and collagen release. Inhibition of Notch signaling might be an effective strategy to selectively prevent the aberrant activation of SSc fibroblasts.

No abstract