Decreased circulating miRNA levels in patients with primary progressive multiple sclerosis.

Emerging evidence underlines the importance of micro(mi)RNAs in the pathogenesis of multiple sclerosis (MS). Free-circulating miRNAs were investigated in serum from MS patients compared to controls. Statistically significant decreased levels of miR-15b, miR-23a and miR-223 were observed in MS patients (p < 0.05). Results were validated and replicated in two further independent MS populations. A direct correlation between miRNA levels and the EDSS score was determined in PPMS (p < 0.007). The generalized trend toward miRNA down-regulation could result in over-expression of target genes involved in disease pathogenesis. Circulating miRNA profiling could thus represent a new avenue to identify easily detectable disease biomarkers.