Identification of plasma microRNA expression profile in radiographic axial spondyloarthritis-a pilot study

At present, there are no studies that have established a microRNA (miRNA)-based signature profile in patients with radiographic axial spondyloarthritis (rad-axial SpA), and we hypothesized that these patients may have aberrantly expressed circulating miRNAs reflective of underlying disease and inflammation. This study aims to determine the expression profile of miRNAs in plasma of patients with rad-axial SpA and compare it with healthy, age, and sex-matched controls. Fifteen subjects with rad-axial SpA based on ASAS classification criteria and 5 controls were recruited from our local SpA registry. Demographic data were collected and disease activity was measured using Bath Ankylosing Spondylitis Disease Activity Index (BASDI). Peripheral blood samples (5 ml) were obtained from eligible consenting patients and controls. RNA from the plasma was prepared using miRNeasy kit (Qiagen) by a modified protocol. Expression of 175 miRNAs was screened in the plasma of all 15 patients and 5 controls using serum/plasma miRNA PCR arrays (Exiqon Inc. Woburn, MA) essentially following the manufacturer's instructions. Real-time PCR was carried out on StepOne Plus (Applied Biosystems) and the data was extracted and analyzed using ExiGen Enterprise software (MultiD, Göteborg, Sweden). Potential miRNA targets were identified using bioinformatics. ESR and CRP levels were measured by standard laboratory methods. We identified 7 differentially expressed miRNAs (2 upregulated and 5 downregulated). miR-34a, which was overexpressed in patients with rad-axial SpA, was predicted to target BMP-3 mRNA by TargetscanS and PicTar miRNA target algorithms. miR-150 was downregulated in all of the samples analyzed by us using the TaqMan Gene Expression assay. The most repressed miRNA was miR-16 and is predicted to regulate the expression of activin A receptor (ACVR2B), a receptor for growth, and differentiation factor-5 (GDF-5). Our data indicates that (1) patients with axial SpA, as compared to controls, have dysregulated expression of selected miRNAs in the plasma; and (2) the differentially expressed miRNAs are predicted to target genes that play a role in bone morphogenesis, growth, and immune response.