Altered Biogenesis and MicroRNA Content of Hippocampal Exosomes Following Experimental Status Epilepticus

Here, we characterised the effects of experimental status epilepticus on the expression of exosome biosynthesis components and analysed microRNA content in exosome-enriched fractions prepared from the mouse hippocampus. Status epilepticus induced by unilateral intra-amygdala kainic acid resulted in acute subfield-specific, bi-directional changes in transcripts associated with exosome biosynthesis including up-regulation of ESCRT–dependent and –independent pathways. Increased expression of exosome components including Alix were detectable in samples obtained two weeks after status epilepticus and changes occurred in both the ipsilateral and contralateral hippocampus. Small RNAseq analysis of exosome-enriched fractions prepared using two different techniques detected a rich diversity of conserved microRNAs and determined status epilepticus selectively alters microRNA contents, including upregulation of the glia-enriched miR-21a-3p. We also characterized editing sites of the exosome-enriched miRNAs and found six exosome-enriched miRNAs that were Adenosine-to-Inosine (ADAR) edited with the majority of the editing events predicted to occur within miRNA seed regions. However, the prevalence of these editing events was not altered by status epilepticus. These studies demonstrate status epilepticus alters the exosome pathway and its microRNA content, but not editing patterns. Exosomes were extracted using two different methods (ultracentrifugation or using commercial extraction kit (ExoQuick) at two different time points (24 hrs and 2 weeks). Small RNA librarires were prepared from the exosomes and sequenced on Illumina Mi-Seq. Each group has 3 biological samples.