Extracellular miR-145, miR-223 and miR-326 expression signature allow for differential diagnosis of immune-mediated neuroinflammatory diseases.

Background: Although misdiagnosis of neuromyelitis optica spectrum disorder (NMOSD) with neuropsychiatric systemic lupus erythematosus (NPSLE) or multiple sclerosis (MS) is not infrequent, reliable biomarkers remains an unmet need. Extracellular microRNAs (miRNAs) represent a worthy avenue to identify biomarkers for differential diagnosis. We aimed to explore the potential role of some selected circulating miRNAs as biomarkers for the differential diagnosis in immune-mediated neuroinflammatory diseases.

Methods: A total of 80 subjects were enrolled in the present study, including 37 patients with MS (relapsing-remitting MS [RRMS; n=18] and secondary progressive MS [SPMS; n=19]), 10 patients with NMOSD and 10 patients with NPSLE as well as 23 healthy subjects. Serum expression levels of three selected miRNAs (miR-145, miR-223 and miR-326) were measured using quantitative real-time polymerase chain reaction (qRT-PCR). Whole blood expression levels of cellular immune response-relevant target genes, including signaling mother against decapentaplegic peptide 3 (SMAD3) and specificity protein 1 (SP1), were also measured using qRT-PCR.

Results: In comparison to healthy subjects, only miR-145 and miR-223 were significantly up-regulated in MS patients, whereas, all the analyzed miRNAs revealed insignificant upregulation in NMOSD patients. All the examined miRNAs were significantly down-regulated in NPSLE patients compared to healthy subjects. miR-145, miR-223 and miR-326 expression profile is a promising diagnostic biomarker for MS and NPSLE, but not for NMOSD. This expression profile is capable of differentiating not only among MS, NMOSD and NPSLE, but also between RRMS and SPMS.

Conclusion: Specific circulating miRNAs expression signature may have the potential to differentially diagnose immune-mediated neuroinflammatory diseases.