Brain-Dead Donor-Derived Plasma Extracellular Vesicles May Induce Systemic Inflammation and Microvascular Dysfunction

Abstract

Purpose Brain death (BD) may affect the function of grafts and the outcome of transplantation. However, the mechanisms of BD on grafts remain unclear. Considering extracellular vesicles (EVs) are promising mediators in cell-to-cell communication by delivering functional genetic molecules, we analyzed BDD EVs to elucidate the roles of donor-derived EVs. Methods Brain-dead donor (BDD) EVs were isolated from 29 BDDs and 9 healthy individuals. Isolated EVs were examined on electron microscopy and nanoparticle tracking analysis. Extracted EV RNA samples were analyzed with next-generation RNA sequencing. The sequencing data were used for differentially expressed gene (DEG) analysis, gene ontology (GO) enrichment analysis and KEGG pathway analysis. Furthermore, human umbilical endothelial cells and human cardiac microvascular endothelial cells were treated with BDD EVs for further functional assays to investigate the roles of donor EVs. Results When compared to healthy individuals, 2120 protein coding genes were differentially expressed. Among these, 1821 were upregulated while 299 were downregulated in BDDs. In BDDs, mRNA expression of inflammatory mediators as well as transcripts involved in acute phase responses were significantly upregulated. Furthermore, GO enrichment analysis and pathway analysis revealed the DEGs were related to innate immune responses, angiogenesis, metabolism, complement and coagulation cascades. Conclusion BDD EVs showed distinct transcriptomic profiles compared to healthy controls. Significantly upregulated transcripts in BDDs were related to acute phase responses, and activation of innate immune responses. Therefore, BDD EVs may contribute to systemic inflammation and microvascular dysfunction by delivering the transcripts and modulating gene expression in BDDs. Additional functional assay results will be presented during ISHLT 2021.