Background/Purpose: MicroRNAs (miRNAs) have evolved as a novel class of biomarkers We proposed to test the hypothesis that patients with ankylosing spondylitis (AS) have an altered miRNA expression profile compared to control subjects and selected miRNAs identified in the study correlate with disease activity as measured by BASDAI and ASDAS and markers of inflammation ( ESR and CRP) .

Methods: 51 patients ≥18 years of age with AS based on modified New York classification criteria (grade 3 and 4 sacroiliitis) and 23 (age and sex matched) controls were prospectively recruited. Subjects with active malignancy in last 5 years, rheumatoid arthritis or systemic lupus erythematosus and evidence of HIV or chronic hepatitis B or C infection were excluded. Patients and controls were screened, consented and peripheral blood samples (5 ml) were obtained. The samples were centrifuged at 400 g for seven minutes; plasma transferred to nuclease free tubes and stored at -20°C until analyses. ESR and CRP were measured using routine laboratory methods. Various validated Questionnaires to assess disease, functional activity and patient reported outcomes in AS were administered to the patients. 62 circulating miRNAs in the plasma of all the study subjects were profiled by Firefly Multiplex Circulating miRNA Assay (Abcam) using the Immunology Panel. Forty microliters of plasma samples were first digested using the supplied enzyme mix and then the assay was performed following the instructions provided by the manufactures. The assay beads were scanned on BD Accuri C6 flow cytometer (BD Biosciences). Data were analyzed using Firefly Analyis Workbench (Abcam). Descriptive analyses included continuous variables (the mean ± SD) and the categorical variables (percentage). Linear regression analysis was performed to assess the association between BASDAI, BASMI, ASDAS, Rapid 3, ESR, CRP and differentially dysregulated candidate miRNAs in plasma of patients with AS.

Results: 34 males and 17 females with demographics and clinical characteristics in table 1. Mean (±SD) values of the disease parameters are shown in table 2. miR-181b-5p was differentially expressed in AS patients compared to healthy controls (p <0.05). miR-181b-5p also showed a significant linear relationship with BASDAI score (p=0.008) and ASDAS( p=0.054).  

Conclusion: miR-181b-5p correlated with validated tools of disease activity in AS and may be proposed as a potential biomarker for disease activity in AS.

Table 1- Demographics and Clinical Characteristics of the Patients

Table 2- Disease Activity Measures