High degree of correlation between whole blood and PBMC expression levels of miR-155 and miR-146a in healthy controls and rheumatoid arthritis patients

Elevated expression of specific microRNAs (miRNA) in peripheral blood-derived mononuclear cells (PBMC), particularly miR-146a and miR-155, is associated with rheumatoid arthritis (RA). Whole blood has not been explored as a potential clinical material for monitoring the expression of miRNAs in RA. We sought to determine whether miRNA levels detected in whole blood samples correlated with those detected in simultaneously isolated peripheral blood-derived mononuclear cells (PBMC) from the same individuals, thus establishing the feasibility of using whole blood as a viable clinical material for monitoring miRNA expression in RA and other disorders. We demonstrated a highly significant linear correlation between miR-146a and miR-155 expression in PBMC and whole blood, from both healthy individuals and RA patients. Whole blood samples accurately reflect miRNA levels in PBMC and would be useful in monitoring the expression of miRNAs as biomarkers. The detection of miRNA levels in samples that are readily obtained in routine clinical practice, such as whole blood, enhances their potential utility in detecting changes in the immunological mechanisms underlying autoimmune diseases such as RA.