Abstract W MP86: Microrna-146a Modulates Neurogenesis And Oligodendrogenesis After Stroke

Abstract

Background: Neurogenesis and oligodendrogenesis are associated with functional recovery after stroke. However, the molecules that regulate the generation of new neurons and oligodendrocytes have not been fully investigated. MicroRNAs (miRNAs) post-transcriptionally regulate gene expression. MiR-146a has been reported to regulate the immune response in cells, but the role of miR-146a in neural (NPCs) and oligodendrocyte progenitor cells (OPCs) remains unexplored. Methods and Results: Adult Wistar rats were subjected to right middle cerebral artery occlusion (MCAo). In situ hybridization using locked nucleic acid (LNA)probes against miR-146a showed that stroke considerably increased miR-146a density in the subventricular zone (SVZ, 19 ± 1 vs 6 ± 0.1 area/mm2 in non-MCAo group, p<0.05, n=4/group) and corpus callosum (24 ± 3 vs 8±1 area/mm2 in non-MCAo group) of the ischemic hemisphere. Quantitative RT-PCR also demonstrated a marked upregulation of miR-146a transcript in ischemic NPCs (8.5 fold), suggesting an important role in stroke-induced neurogenesis and oligodendrogenesis. To test its biological function, we over-expressed miR-146a in neural progenitor cells by transfection of miR-146a mimics using nucleofector and found that elevation of miR-146a significantly increased the percentage of Tuj1+ neuroblasts (5 ± 0.3 vs 1 ± 0.2%, p<0.05, n=6/group) and O4+ OPCs (10 ± 1 vs 4 ± 0.4%, p<0.05). Moreover, over-expression of miR-146a in primary cultured OPCs significantly increased several myelin proteins including MBP and PLP, and decreased levels of OPC marker proteins including PDGFRα and NG2, whereas attenuation of miR-146a by siRNA against miR-146a suppressed myelin proteins and augmented OPC marker proteins. Furthermore, miR-146a levels in the OPCs were inversely related to IRAK1 proteins, one of miR-146a target genes. Attenuation of IRAK1 in OPCs substantially increased myelin proteins, indicating that miR-146a mediates oligodendrocyte maturation via targeting IRAK1. Conclusion: Our data provide new insight into molecular mechanisms underlying stroke-induced neurogenesis and oligodendrogenesis by revealing a novel role of miR-146a in NPCs and OPCs, which has potential to be used as a new therapy for neurorecovery after stroke.