Background/Purpose: JDM, the most common of the idiopathic inflammatory myopathies, is a systemic vasculopathy, associated with premature development of cardiovascular disease. Studies by others had implicated miRNA -10a in atherosclerosis.  MicroRNAs (miRNAs) are short, non-coding RNAs and inhibit mRNAs by binding to complementary sequences on target mRNAs, resulting in translational repression or target degradation and gene silencing. Hypothesis:  miRNA-10a may play a role in the vasculopathy of untreated JDM.

Methods: After informed consent (IRB# 2008-13457) and under MRI guidance a diagnostic muscle biopsy was obtained from the involved area in untreated children with definite/probable JDM. The patient population consisted of 10 girls and 7 boys, the mean age was 6.0±2.9 years old, and their race was: White 77.8%, Hispanic 16.7%, White/Indian 5.6%; for the controls, the 3 girls, 3 boys were white and their mean age was 12.1±3.8 years old. Total RNA was extracted from muscle biopsy samples and used for Exiqon miRNA DNA microarray analysis. Validation of differentially expressed miRNAs and their putative target mRNAs was conducted by TaqMan qPCR.

Results: Of 1435 mature human miRNAs on the Exiqon miRNA DNA microarray, ~335 miRNAs were expressed in JDM and control samples. The expression analysis identified 20 miRNAs that were significantly differentially expressed (p<0.05). Several of these miRNAs, e.g. miR-10a [Fold Change (FC)= -1.96], miR-10b (FC= -1.62) and miR-142-5p (FC= 2.17), regulate inflammatory pathways. To validate those differentially expressed miRNAs, we performed qPCR for miR-10a, miR-10b and miR-142-5p. Our results showed that miR-10a and miR-10b levels were decreased by 3.58 and 2.41 fold respectively; and miR-142p level was increased by 2.90 fold. Those altered microRNA expression levels were consistent with the results from miRNA DNA microarray data. Homeobox A1 (HOXA1) gene is a well-known target of miR-10a and it is negatively regulated by miR-10a. To confirm whether HOXA1 gene was up-regulated because miR-10a expression was decreased significantly in JDM, we conducted qPCR for the HOXA1 gene. The results documented that the HOXA1 gene was significantly increased by 2.12±1.14 fold (p<0.01) in JDM compared to controls. miR-10a plays an important role in regulation of NFkB pathway: decreased miR-10a lowers NFkB degradation and promotes inflammatory biomarker gene expression. Further investigation showed that inflammatory biomarker genes, IL-6 and VCAM-1, were significantly elevated in JDM compared with controls: IL-6 and VCAM-1 gene expression levels were increased by 2.81±2.16 and 2.93±1.45 fold respectively (p<0.01).

Conclusion: Profiling identified 20 differentially expressed miRNAs in JDM compared to controls. Decreased miR-10a expression and increased HOXA1, IL-6 and VCAM-1 gene expression demonstrated that specific miRNAs, miR-10a and 10b may play a role in the regulation of the inflammatory pathway in JDM.  We speculate that miRNA-10a may be associated with the vasculopathy characteristic of JDM and that their mimics may be of value in therapy.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/microarray-analysis-for-mirna-expression-in-juvenile-dermatomyositis-jdm/