To identify and confirm the repeatability of biomarker miRNAs in plasma and cerebrospinal fluids (CSF) of patients with sporadic amyotrophic lateral sclerosis (sALS), and analyze their target genes with an overexpression cell model.

Specific biomarkers for ALS could improve early disease detection and diagnosis. MicroRNAs (miRNAs) are small single-stranded non-coding RNA molecules that play important regulatory roles by targeting mRNAs for cleavage or translational inhibition, and they are also essential for nervous system development and survival. There have been some experiments of the quantification of miRNAs for sALS, but an evaluation of repeatability and support by functional analysis has been insufficient.

We compared miRNAs in the plasma and CSF from ALS patients and healthy controls. Two cohorts, a discovery cohort analyzed with microarray and a validation cohort confirmed with quantitative PCR, were used for each analysis. Some of the patients provided their blood two or more times, in six or 12 months intervals. The biomarker miRNAs were synthesized and transfected into SH-SY5Y cells to make overexpression model cells, and the comprehensive gene expression were compared using a microarray system.

hsa-miR-4649-5p was up-regulated and hsa-miR-4299 was down-regulated in patients' plasma . There were no up-regulated miRNAs in patients' CSF, but hsa-miR-663b and hsa-miR-4258 were significantly down-regulated. hsa-miR-663b in patients' plasma also showed an increase over time. To define target genes of the biomarker candidate miRNAs, we identified differentially expressed genes (DEGs). Some DEGs of hsa-miR-663b were found to be related to neuronal networks. hsa-miR-4649-5p and hsa-miR-4299 had 16 genes or long non-coding RNAs, extracted as DEGs, in common.

We have shown the relationship of circulating miRNAs in sALS patients and verified their target genes. miRNAs have the potential to be reliable ALS biomarkers and to be a therapy target.