Background: Scleroderma (SSc) is a rare autoimmune disease characterized by vascular impairment and progressive fibrosis of the skin and other organs. Oncostatin M, a member of the IL-6 family, is elevated in SSc serum and was recognized as a significant player in various stages of fibrosis. The goal of this study was to assess the contribution of the OSM/OSMRβ pathway to endothelial cell (EC) injury and activation in SSc. Methods: IHC and IF were used to assess the distribution of OSM and

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... in SSc (n=14) and healthy control (n=7) skin biopsies. Cell culture experiments were performed in human dermal microvascular endothelial cells (HDMECs) and included mRNA and protein analysis, and cell migration and proliferation assays. Ex vivo skin organoid culture was used to evaluate the effect of OSM on perivascular fibrosis.Results: OSMRβ protein was elevated in dermal ECs and in fibroblasts of SSc patients. Treatments of HDMECs with OSM or IL-6 +sIL-6R have demonstrated that both cytokines similarly stimulated proinflammatory genes and genes related to endothelial-to mesenchymal transition ((EndMT). OSM was more effective than IL-6+sIL-6R in inducing cell migration, while both treatments similarly induced cell proliferation. The effects of OSM were mediated via OSMRβ and STAT3, while the LIFR did not contribute to these responses. Both, OSM and IL-6+sIL-6R induced profibrotic gene expression in HDMECs, as well as expansion of the perivascular PDGFRβ+ cells in the ex vivo human skin culture system. Additional studies in HDMECs showed that siRNA-mediated downregulation of FLI1 and its close homolog ERG resulted in increased expression of OSMRβ in HDMECs.Conclusions: This work provides new insights into the role of the OSM/OSMRβ axis in activation/injury of dermal ECs and supports the involvement of this pathway in SSc vascular disease.