MicroRNA expression profiles of multiple system atrophy from formalin-fixed paraffin-embedded samples.

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression. Recently, we have shown that informative miRNA data can be derived from archived formalin-fixed paraffin-embedded (FFPE) samples from postmortem cases of amyotrophic lateral sclerosis and normal controls. miRNA analysis has now been performed on FFPE samples from affected brain regions in patients with multiple system atrophy (MSA) and the same areas in neurologically normal controls. We evaluated 50 samples from patients with MSA (n=13) and controls (n=13). Twenty-six samples were selected for miRNA analysis on the basis of the criteria reported previously: (i) a formalin fixation time of less than 4 weeks, (ii) a total RNA yield per sample of more than 500ng, and (iii) sufficient quality of the RNA electrophoresis pattern. These included 11 cases of MSA and 5 controls. Thus, the success rate for analysis of RNA from FFPE samples was 52% (26 of 50). For MSA, a total of 395 and 383 miRNAs were identified in the pons and cerebellum, respectively; 5 were up-regulated and 33 were down-regulated in the pons and 5 were up-regulated and 18 were down-regulated in the cerebellum. Several miRNAs down-regulated in the pons (miR-129-2-3p and miR-129-5p) and cerebellum (miR-129-2-3p, miR-129-5p and miR-132-3p) had already been identified in frozen cerebellum from MSA patients. These findings suggest that archived FFPE postmortem samples can be a valuable source for miRNA profiling in MSA.