Interleukin-31 promotes pathogenic mechanisms underlying skin and lung fibrosis in scleroderma.

OBJECTIVES: Cytokines released by infiltrating T cells may promote mechanisms leading to fibrosis in scleroderma. The aim of this study was to investigate the role of the Th2 cytokine IL-31, and its receptor IL-31RA, in scleroderma skin and lung fibrosis. METHODS: IL-31 was measured by ELISA of plasma, and by immunochemistry of fibrotic skin and lung tissue of scleroderma patients. The receptor, IL-31RA, was assayed by qPCR of tissue resident cells. Next-generation sequencing was used to profile the responses of normal skin fibroblasts to IL-31. In wild-type Balb/c mice, IL-31 was administered by subcutaneous mini pump, with or without additional TGFß, and the fibrotic reaction measured by histology and ELISA of plasma. RESULTS: IL-31 was present at high levels in plasma and fibrotic skin and lung lesions in a subset of scleroderma patients, and the receptor overexpressed by downstream cells relevant to the disease process, including skin and lung fibroblasts, through loss of epigenetic regulation by miR326. In skin fibroblasts, IL-31 induced next generation sequencing profiles associated with cellular growth and proliferation, anaerobic metabolism and mineralization, and negatively associated with angiogenesis and vascular repair, as well as promoting phenotype changes including migration and collagen protein release via pSTAT3, resembling the activation state in the disease. In mice, IL-31 induced skin and lung fibrosis. No synergy was seen with TGFß, which supressed IL-31RA. CONCLUSION: IL-31/IL-31RA is confirmed as a candidate pro-fibrotic pathway, which may contribute to skin and lung fibrosis in a subset of scleroderma patients.

Pathogenic Activation of Mesenchymal Stem Cells Is Induced by the Disease Microenvironment in Systemic Sclerosis.

OBJECTIVE: In systemic sclerosis (SSc), a persistent tissue repair process leads to progressive fibrosis of the skin and internal organs. The role of mesenchymal stem cells (MSCs), which characteristically initiate and regulate tissue repair, has not been fully evaluated. We undertook this study to investigate whether dividing metakaryotic MSCs are present in SSc skin and to examine whether exposure to the disease microenvironment activates MSCs and leads to transdifferentiation. METHODS: Skin biopsy material from patients with recent-onset diffuse SSc was examined by collagenase spread of 1-mm-thick surface-parallel sections, in order to identify dividing metakaryotic stem cells in each tissue plane. Adipose-derived MSCs from healthy controls were treated with dermal blister fluid (BF) from patients with diffuse SSc and profiled by next-generation sequencing, or they were evaluated for phenotypic changes relevant to SSc. Differential responses of dermal fibroblasts were studied in parallel. RESULTS: MSC-like cells undergoing active metakaryotic division were identified in SSc sections (but not control sections) most prominently in the deep dermis and adjacent to damaged microvessels, in both clinically involved and uninvolved skin. Furthermore, exposure to SSc BF caused selective MSC activation, inducing a myofibroblast signature, while reducing signatures of vascular repair and adipogenesis and enhancing migration and contractility. Microenvironmental factors implicated in inducing transdifferentiation included the profibrotic transforming growth factor ß, the presence of lactate, and mechanosensing, while the microenvironment Th2 cytokine, interleukin-31, enhanced osteogenic commitment (calcinosis). CONCLUSION: Dividing MSC-like cells are present in the SSc disease microenvironment where multiple factors, likely acting in concert, promote transdifferentiation and lead to a complex and resistant disease state.