Background The underlying pathogenesis of systemic sclerosis (SSc) remains poorly understood contributing to limited efficacy of therapeutic options.
MicroRNAs (miRNAs) are small non-coding RNAs that play an important role in post-transcriptional gene regulation.1,2 Two families of dysregulated miRNAs, miR-21 and miR-29, have been implicated in the pathogenesis of fibrotic diseases and replicated in SSc. 3–6,7,9 These studies focused on a miRNA of interest and global skin miRNA profiling in SSc has not been reported.
Recent advances in quantitative polymerase chain reaction (qPCR) allow simultaneous measurement of hundreds of miRNAs. The objective of this study was to use this technology to identify the unbiased, global miRNA profiling of SSc skin and evaluate their potential role in its pathogenesis.
Methods We investigated the miRNA profile in SSc skin compared to unaffected controls using multiplex qPCR platform. We obtained forearm skin samples (3 mm punch biopsy) from 10 patients with early SSc (<5 yrs, on no immunosuppression) and 10 age-, gender- and ethnicity matched controls. Total RNA was isolated using Qiagen miRNAeasy mini kit and examined by Exiqon LNA-enhanced (locked nucleic acid) miRNA qPCR. Levels of 752 miRNAs were determined. Unsupervised hierarchical clustering analysis was performed. Patient and control sample miRNA levels were compared and differences with a p<0.01, false discovery rate (FDR) <10% and fold change >2 were considered statistically significant.
Results The unsupervised hierarchical clustering analysis showed that the miRNA skin profile almost perfectly separated SSc patients and controls. Only one patient clustered along with controls (Figure 1). Comparison of patient to control samples revealed 26 miRNAs that were differentially expressed. Eighteen of these (69%) were part of the largest known human miRNA cluster (miR-379/miR-656) located on chromosome 14q32.3.10 Three miRNAs were encoded in a cluster on chromosome X (Xq26.3). We confirmed the previously reported up-regulation of miR21-5p in SSc.7,9
Conclusions To our knowledge, this is the first global, unbiased examination of miRNAs in SSc skin. The miRNA profile almost perfectly separated SSc patients and controls. We observed 26 dysregulated miRNAs, most of them coming from two clusters, one of them located in chromosome X. This finding might have important biological implications considering the female predilection of SSc. Dysregulation of these miRNA clusters have not been reported in SSc and other autoimmune diseases. The results of our study link miRNA to the pathogenesis of SSc and could have important ramifications for future drug and biomarker development.
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