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Small RNA sequencing of human and macaque brain tissue and brain-derived extracellular vesicles separated by size exclusion chromatography

ABSTRACT: Extracellular vesicles (EVs) are involved in a wide range of physiological and pathological processes by shuttling material out of and between cells. Tissue EVs may thus lend insights into disease mechanisms and also betray disease when released into easily accessed biological fluids. Since brain-derived EVs (bdEVs) and their cargo may serve as biomarkers of neurodegenerative diseases, we evaluated modifications to a published, rigorous protocol for separation of EVs from brain tissue and studied effects of processing variables on quantitative and qualitative outcomes. To this end, size exclusion chromatography (SEC) and sucrose density gradient ultracentrifugation were compared as final separation steps in protocols involving stepped ultracentrifugation. bdEVs were separated from brain tissues of human, macaque. Effects of post-mortem interval (PMI) before final bdEV separation were probed. MISEV2018-compliant EV characterization was performed, and both small RNA and protein profiling were done. We conclude that the modified, SEC-employing protocol achieves EV separation efficiency roughly similar to a protocol using gradient density ultracentrifugation, while decreasing operator time and, potentially, variability. The protocol appears to yield bdEVs of higher purity for human tissues compared with macaque, suggesting opportunities for optimization. The interval between death/tissue storage/processing and final bdEV separation can also affect bdEV populations and composition and should thus be recorded for rigorous reporting. Different populations of EVs obtained through the modified method reported herein display characteristic RNA and protein content that hint at biomarker potential. To conclude, this study finds that the automatable and increasingly employed technique of SEC can be applied to tissue EV separation, and also reveals more about the importance of species-specific and technical considerations when working with tissue EVs. These results are expected to enhance the use of bdEVs in revealing and understanding brain disease.

ORGANISM(S): Macaca nemestrina Homo sapiens

PROVIDER: GSE150460 | GEO | 2020/05/14

REPOSITORIES: GEO

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Project description:Extracellular vesicles (EVs) exert important functions in the extracellular space and in cell-to-cell communication. Ultracentrifugation, the most frequently used EV isolation technique, requires specialized equipment and provides relatively low purity and yield. A more recently applied and easily accessible EV isolation technique is size exclusion chromatography (SEC). Here, we hypothesized that EVs isolated from dilute cell culture media by concentration on a 10 kDa filter followed by SEC are suitable for proteomic and functional studies. We also hypothesized that the protein-rich SEC fractions are suitable controls to assess biological effects of the non-EV associated secretome. Cell-depleted medium from BEAS-2B bronchial epithelial cells (60 ml) was 0.22 µm filtered, concentrated to 0.5 ml by 10 kDa UF and run over a sepharose CL-4B column. Fractions were assessed for protein and EV content. EV-rich and protein-rich fractions were concentrated by 10 kDa UF. EV concentrates were characterized by tuneable resistive pulse sensing, cryo transmission electron microscopy and nanoLC-MS/MS. Finally, we assessed the effect of EVs or free secreted protein from unexposed cells or cells exposed to 1% (v/v) cigarette smoke extract (CSE) on IL-8 release by naïve BEAS-2B cells or on adhesion of THP-1 monocytes to endothelial cells. UF concentrated the EVs with approximately 100% recovery. Most of EVs eluted in SEC fractions 6-11, while protein became detectable at fraction 12. The final EV recovery was 40 ± 4%, as compared to 27 ± 8% by ultracentrifugation. Mass Spectrometry of the EV fractions identified 388 different proteins, including various EV markers. Only the protein, but not the EV fractions from media of CSE-exposed cells induced IL-8 release by naïve bronchial epithelial cells, whereas only EVs, but not the protein fractions induced THP-1 adhesion to endothelial cells. Thus, UF followed by SEC provides EV isolates with sufficient yield and purity for proteomic studies and allows directly comparing the functional effects of EVs and the non-EV associated secretome.

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Small RNA sequencing of human and macaque brain tissue and brain-derived extracellular vesicles separated by size exclusion chromatography

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