Multiplexed mRNA analysis of brain-derived extracellular vesicles upon experimental stroke in mice reveals increased mRNA content related to inflammation and recovery processes

Abstract

Extracellular vesicles (EVs) are lipid bilayer enclosed structures that not only represent a newly discovered means for cell-to-cell communication but may also serve as promising disease biomarkers and therapeutic tools. Apart from proteins, lipids, and metabolites, EVs can deliver genetic information such as mRNA eliciting a response in the recipient cells. In the present study, we have analyzed the mRNA content of brain-derived EVs (BDEVs) isolated 72 hours after experimental stroke in mice and compared them to controls (shams) using the nCounter® Nanostring panels, with or without prior RNA isolation from BDEVs. We found that both panels show similar results when comparing upregulated mRNA in stroke. Notably, the higher upregulated mRNAs were related to processes of stress and immune system responses, but also to anatomical structure development, cell differentiation, and extracellular matrix organization, indicating that regenerative mechanisms are already taking place at this time-point. The five top overexpressed mRNAs in stroke mice compared to shams were confirmed by RT-qPCR and, interestingly, were found to be present as full-length open-reading frame in BDEVs. We could reveal that the majority of the mRNA cargo in BDEVs was of microglial origin and probably predominantly present in small BDEVs (≤200 nm in diameter). However, the EV population with the highest increase in the total BDEVs pool at 72 h after stroke was of oligodendrocytic origin. Our study shows that nCounter® panels are a good tool to study mRNA content in tissue-derived EVs as they can be carried out even without previous mRNA isolation and that the mRNA cargo of BDEVs indicates their participation in inflammatory but also recovery processes after stroke.