Long non-coding RNAs (lncRNAs) are thought to have various functions other than RNA silencing. We tried to evaluate the expression of lncRNAs in patients with systemic sclerosis (SSc) and determined whether lncRNAs controls collagen expression in dermal fibroblasts. lncRNA expression was determined by real-time PCR and in situ hybridization. Protein and mRNA levels of collagen were analysed using immunoblotting and real-time PCR. We found TSIX, one of the lncRNAs, was overexpressed in SSc dermal fibroblasts both in vivo and in vitro, which was inhibited by the transfection of transforming growth factor (TGF)-β1 siRNA. TSIX siRNA reduced the mRNA expression of type I collagen in normal and SSc dermal fibroblasts, but not the levels of major disease-related cytokines. In addition, TSIX siRNA significantly reduced type I collagen mRNA stability, but not protein half-lives. Furthermore, we first investigated serum lncRNA levels in patients with SSc, and serum TSIX levels were significantly increased in SSc patients. TSIX is a new regulator of collagen expression which stabilizes the collagen mRNA. The upregulation of TSIX seen in SSc fibroblasts may result from activated endogenous TGF-β signalling and may play a role in the constitutive upregulation of collagen in these cells. Further studies on the regulatory mechanism of tissue fibrosis by lncRNAs in SSc skin lead to a better understanding of the pathogenesis, new diagnostic methods by their serum levels and new therapeutic approaches using siRNAs.

Localized scleroderma (LSc), a connective tissue disorder restricted to the skin and subcutaneous tissue, is characterized by skin fibrosis due to an excessive deposition of types I collagen. The mechanism of such fibrosis is still unknown, but epigenetics may play some roles in the excessive collagen expression. In the present study, we investigated the mechanism of fibrosis seen in LSc, focusing on microRNA (miRNA). miRNA expression was determined by PCR array, real-time PCR, and in situ hybridization. The function of miRNA was evaluated using specific inhibitor. Immunoblotting was performed to detect α2(I) collagen protein. PCR array analysis using tissue miRNA demonstrated miR-7 level was significantly decreased in LSc skin as well as keloid tissue compared to normal skin in vivo. In situ hybridization also showed miR-7 expression in dermal fibroblasts was decreased in LSc dermis. The transfection of specific inhibitor for miR-7 into cultured normal dermal fibroblasts resulted in the up-regulation of α2(I) collagen protein in vitro. Also, the serum levels of miR-7 were significantly decreased in LSc patients compared with healthy controls, but serum miR-29a levels not. Systemic or local down-regulation of miR-7 may contribute to the pathogenesis of LSc via the overexpression of α2(I) collagen, and serum miR-7 may be useful as a disease marker. Investigation of the regulatory mechanisms of LSc by miRNA may lead to new treatments by the transfection into the lesional skin of this disease.

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Macrophages may play a role in the pathogenesis of systemic sclerosis (SSc), and CD163-positive M2 macrophages are potentially important source for fibrosis-inducing cytokines. However, no link between M2 macrophages and SSc has been established. The aim is to evaluate the possibility that serum levels of soluble CD163 (sCD163) can be a useful marker for SSc, reflecting M2 activation of macrophages in this disease. Serum sCD163 levels of 43 patients with SSc, 10 patients with scleroderma spectrum disorder (SSD), and 12 healthy controls were measured with specific enzyme-linked immunosorbent assays. SSc patients had significantly higher serum sCD163 levels than healthy controls. The sCD163 levels in SSD patients were higher than healthy controls and lower than SSc patients. Significantly higher right ventricular systolic pressure and lower % DLco levels, and shorter duration of disease were seen in SSc patients with elevated serum sCD163 levels than those with normal levels. These results suggest that sCD163 levels may be increased in proportion to the progression of this disease, indicating the involvement of CD163 in the pathogenesis of SSc. Furthermore, serum sCD163 levels may be a marker of pulmonary hypertension at the early stage in patients with SSc.

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