Plasma let-7i, miR-16, and miR-221 levels as candidate biomarkers for the assessment of ankylosing spondylitis in Mexican patients naive to anti-TNF therapy

Novel biomarkers are needed for the diagnosis and clinical assessment of ankylosing spondylitis (AS). Our objective was to investigate plasma microRNAs differentially expressed between AS patients and controls and to evaluate their potential as biomarkers in Mexican subjects. A cross-sectional study including 15 AS patients naive to anti-TNF therapy and 13 controls was performed. Disease activity, physical function, and global well-being were evaluated by the AS Disease Activity Score (ASDAS-CRP), the Bath AS Disease Activity Index (BASDAI), the Bath AS Functional Index (BASFI), and the AS Quality of Life Questionnaire (ASQoL), respectively. Total RNA was isolated from plasma of participants and relative expression of let-7i, miR-16, and miR-221 was evaluated. Serum levels of C-reactive protein (CRP), matrix metalloproteinase-1 (MMP-1), MMP-9, and intercellular adhesion molecule-1 (ICAM-1) were also measured. Expression of let-7i was higher in patients than in controls (1.8, 0.9 to 3.4 versus 0.6, 0.4 to 1.2; P=0.033) with an AUC/ROC of 0.74 (0.54 to 0.93; P=0.032). Levels of miR-16 and miR-221 were unable to discriminate between patients and controls. Notably, plasma miR-16 levels were inversely correlated with the ASDAS-CRP score (rho -64, -0.87 to -0.18; P=0.011), the BASFI score (rho -0.78, -0.93 to -0.43; P=0.001), and serum MMP-1 levels (rho -0.59, -0.85 to -0.09; P=0.022). No other associations were found. Plasma let-7i levels may serve as a biomarker for the diagnosis of AS in Mexican individuals. Additionally, plasma miR-16 levels are associated with disease activity and physical functionality in patients naive to anti-TNF therapy.