Differential expression of exosomal microRNAs in prefrontal cortices of schizophrenia and bipolar disorder patients

Exosomes are cellular secretory vesicles containing microRNAs
(miRNAs). Once secreted, exosomes are able to attach to recipient
cells and release miRNAs potentially modulating the function of the
recipient cell. We hypothesized that exosomal miRNA expression in
brains of patients diagnosed with schizophrenia (SZ) and bipolar
disorder (BD) might differ from controls, reflecting either
disease-specific or common aberrations in SZ and BD patients. The
sources of the analyzed samples included McLean 66 Cohort
Collection (Harvard Brain Tissue Resource Center), BrainNet Europe
II (BNE, a consortium of 18 brain banks across Europe) and Boston
Medical Center (BMC). Exosomal miRNAs from frozen postmortem
prefrontal cortices with well-preserved RNA were isolated and
submitted to profiling by Luminex FLEXMAP 3D microfluidic device.
Multiple statistical analyses of microarray data suggested that
certain exosomal miRNAs were differentially expressed in SZ and BD
subjects in comparison to controls. RT-PCR validation confirmed
that two miRNAs, miR-497 in SZ samples and miR-29c in BD samples,
have significantly increased expression when compared to control
samples. These results warrant future studies to evaluate the
potential of exosome-derived miRNAs to serve as biomarkers of SZ
and BD.