Primary progressive multiple sclerosis (PPMS) is a clinical subtype of MS characterized by the progressive accumulation of disability from onset. It is diagnosed in approximately 15% of people with multiple sclerosis (MS).
microRNAs (miRNAs) are small non-coding RNA molecules that participate in the regulation of gene expression. Their role in different diseases, including MS, is being studied.
Current disease-modifying therapies for MS as well as miRNA studies mainly focus on relapsing-remitting MS (RRMS), the most common subtype.
The aim of this study was to identify and validate a differential profile of circulating miRNAs in PPMS patients compared to RRMS and controls with other neurological disease (OND) subjects in order to increase our knowledge of the biological processes involved in the different forms of the disease.
miRNAs were extracted from serum and cerebrospinal fluid (CSF) from a cohort of 111 patients (49 PPMS, 35 RRMS and 27 OND). In the identification phase, samples were analyzed using TaqMan OpenArray Human Advanced MicroRNA panels and in the validation phase, the quantification of the miRNAs was performed by qPCR. Differential expression was analyzed using the Kruskal-Wallis test with the normalized value of miRNAs.
In the identification phase, 10 miRNAs showed differential expression in serum between some of the groups; while in CSF, miR-143-3p presented differential expression in PPMS group (p= 0.009), and let-7b-5p and miR-451a showed a tendency to be deregulated.
In serum samples, the validation phase showed miR-20a-5p overexpression in PPMS compared to controls, and miR-26a-5p among the forms of MS (p= 0.002 and p= 0.036, respectively). On the other hand, miR-142-5p was differentially expressed in RRMS compared to OND (p= 0.036).
In CSF, let-7b-5p and miR-143-3p presented significantly reduced levels in PPMS forms compared to OND (p= 0.029 and p= 0.039, respectively).
miR-20a-5p, miR-26a-5p, let-7b-5p and miR-143-3p present deregulation in PPMS versus RRMS and OND, indicating that they are involved in the pathophysiological mechanisms of PPMS forms. Further studies will be necessary to determine the role of these miRNAs in the development of the different forms of the disease.