Potential of Circulating MicroRNA Panels to Discriminate Peripheral Arthritis in the Spondyloarthritis Spectrum: A...

Background and Objectives: The clinical differentiation of peripheral involvement within the spondyloarthritis (SpA) spectrum remains a significant challenge. Identifying patients at the stage of psoriasis without clinical arthritis (PsO), before the onset of overt arthritis, is crucial for early disease management. MicroRNAs (miRNAs) have emerged as potential epigenetic regulators in inflammatory rheumatic diseases. This study aimed to identify circulating miRNA profiles that serve as discriminative biomarkers between PsO and peripheral SpA (p-SpA). Materials and Methods: This exploratory study was conducted in two phases. In the preliminary discovery phase, plasma miRNA expression was analyzed using high-throughput microarrays in patients with p-SpA (modeled by peripheral psoriatic arthritis, n = 6), PsO (psoriasis without clinical arthritis, n = 3), and osteoarthritis (n = 3). In the validation phase, candidate miRNAs were verified using TaqMan-based qPCR in an independent cohort (n = 30) of various SpA phenotypes, categorized into those with peripheral arthritis (SpA-A) and those without (SpA-N). Results: The preliminary discovery phase identified altered levels of hsa-miR-140-5p, hsa-miR-192-5p, and hsa-miR-146a-5p among the groups; however, due to the small sample size, these initial findings required strict downstream verification. Functional enrichment analysis revealed that these candidate miRNAs primarily targeted the NF-κB signaling pathway (hsa04064) and Toll-like receptor (TLR) signaling pathway (hsa04620). The validation cohort confirmed that these three miRNAs could reliably differentiate SpA-A from SpA-N patients. Furthermore, bioinformatic mapping predicted that downstream targets, including TRAF6, IRAK1, and CXCL2, may be associated with these clinical phenotypes, serving as hypothesis-generating observations for future studies. Conclusions: Our findings suggest that specific plasma miRNA profiles are associated with the inflammatory pathways driving peripheral involvement in the SpA spectrum. These miRNAs represent potential biomarkers associated with peripheral arthritis in the SpA spectrum. While they offer new molecular insights into disease pathogenesis, their predictive value for identifying PsO patients at risk of developing overt arthritis requires confirmation in future longitudinal studies.