Background/Purpose: The pathology of juvenile dermatomyositis (JDM) is characterized by prominent vessel wall and perivascular inflammation. This feature of the disease has remained unexplained and under-investigated. We have hypothesized that plasma exosomes, which play an important role in inter-cellular communication, may play a role in the vascular injury associated with JDM.

Methods: We purified exosomes from plasma samples of children with active, untreated JDM (n= 10) and healthy controls (n= 10) using the ExoQuick Precipitation method. We characterized the small RNA cargoes in JDM and control exosomes by RNA sequencing using the Illumina HiSeq 2500 platform. We incubated isolated exosomes from healthy controls and JDM patients with cultured human aortic endothelial cells (HAEC) for 24 hours. Fluorescence microscopy was used to confirm that both control and JDM exosomes were taken up by HAEC. RNA was then purified from HAEC that had been incubated with either control or JDM exosomes and sequenced on the Illumina platform. Differential expression of mRNAs from HAEC incubated with control or JDM exosomes was ascertained using standard computational methods. Finally, we assessed the degree to which differential gene expression in HAEC could be attributed to the different small RNA cargoes in JDM vs control exosomes using conventional and novel analytic methods.

Results: We identified 10 small RNA molecules that showed differential abundance when we compared JDM and healthy control exosomes. Fluorescence microscopy of labeled exosomes confirmed that both JDM and control exosomes were taken up by HAEC. Differential gene expression analysis revealed 193 genes that showed differential expression between HAEC incubated with JDM exosomes vs HAEC incubated with exosmes from controls. Gene ontology analysis revealed that many of these differentially expressed genes (e.g., CXCL8/IL8) are associated with leukocyte migration and adherence. Analysis of the differentially expressed genes, however, failed to provide a strong link between the miRNA cargoes in the exosomes and patterns of gene expression

Conclusion: Plasma exosomes from children with active, untreated JDM are taken up by HAEC and are associated with alterations in gene expression in those cells. However, we were unable to establish a strong link between transcriptional changes and the small RNA cargoes of JDM exosomes. This suggests that other exosome components are more likely to be involved.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/plasma-exosomes-from-children-with-juvenile-dermatomyositis-are-taken-up-by-human-aortic-endothelial-cells-and-are-associated-with-altered-gene-expression-in-those-cells/