Plasma Extracellular Vesicles May Regulate Inflammation and Hemodynamic Changes in Brain-Dead Donors

Abstract

Brain death causes hemodynamic instability and systemic inflammatory responses. However, the consequences of brain death on donor organs, and in particular on the microvascular endothelium, remains unknown. Extracellular vesicles (EV) are involved in cell-to-cell communication by delivering their functional cargo to target cells. EVs are able to cross the blood-brain barrier and may affect the function of the cells of donor organs and immune cells. To get insight into the molecular mechanisms of brain death, we sequenced and analyzed plasma EV RNA from brain-dead solid organ donors and healthy controls. We analyzed circulating EV RNA samples of 30 brain-dead (BD) donors and 9 healthy controls. The identity of the isolated plasma EVs was confirmed on electron microscopy and nanoparticle tracking analysis. The quality of the purified RNA was analyzed on a bioanalyzer, followed by analysis with next-generation RNA sequencing. The sequencing data were used for differentially expressed gene analysis, gene ontology enrichment analysis, and pathway analysis. Transcripts with p-values less than 0.05 and a log2 fold change larger than 1.5 were considered to be significant. Preliminary results of sequencing data analyses from 17 BD donors revealed that brain death clearly affects the transcriptomic profiles of plasma EV. In BD donors, 2165 genes were differentially expressed, of which 1873 were upregulated and 292 transcripts were downregulated compared to the controls. Based on the gene annotation terms, the identified differentially expressed transcripts were related to inflammatory responses and coagulation. Moreover, pathway analysis indicated that the genes are related to cell survival, cytokine production, and regulation of gene expression, and are involved in PI3K-Akt-, NF-kB-, and PPAR- signaling pathways. Our results demonstrate that brain death significantly affects the plasma EV transcriptome profiles. Thus, plasma EVs released after brain death may accelerate inflammation and hemodynamic changes. Further studies are required to elucidate the origin of EVs and their effects on microvascular dysfunction in potential donor organs to develop targeted therapy for donor treatment to prevent ischemia-reperfusion injury.