Extracellular vesicle in vivo biodistribution is determined by cell source, route of administration and targeting

Abstract

Extracellular vesicles (EVs) have emerged as important mediators of intercellular communication in a diverse range of biological processes. For future therapeutic applications and for EV biology research in general, understanding the in vivo fate of EVs is of utmost importance. Here we studied biodistribution of EVs in mice after systemic delivery. EVs were isolated from 3 different mouse cell sources, including dendritic cells (DCs) derived from bone marrow, and labelled with a near-infrared lipophilic dye. Xenotransplantation of EVs was further carried out for cross-species comparison. The reliability of the labelling technique was confirmed by sucrose gradient fractionation, organ perfusion and further supported by immunohistochemical staining using CD63-EGFP probed vesicles. While vesicles accumulated mainly in liver, spleen, gastrointestinal tract and lungs, differences related to EV cell origin were detected. EVs accumulated in the tumour tissue of tumour-bearing mice and, after introduction of the rabies virus glycoprotein-targeting moiety, they were found more readily in acetylcholine-receptor-rich organs. In addition, the route of administration and the dose of injected EVs influenced the biodistribution pattern. This is the first extensive biodistribution investigation of EVs comparing the impact of several different variables, the results of which have implications for the design and feasibility of therapeutic studies using EVs.

Therapeutic and diagnostic applications of extracellular vesicles

“…As EVs are abundantly present and stable in the blood circulation, it was speculated that EVs could have longer circulation times and mediate drug targeting to extrahepatic and non-lymphoid tissues. However, reports studying the PK of IV injected EVs described short half-lives (~2 minutes [115,116] and ~20 minutes [117]) with predominant uptake by liver, lung, kidney and spleen, thus closely resembling the biodistribution of synthetic liposomes [70,118,119]. The elimination after IV injection occurs via hepatic and renal routes [117] in which MPS-associated macrophages seem to play a key role [118].…”

“…These authors showed that the VSV-G protein stimulated MHC I mediated antigen presentation and elicited an antigen-specific CD8 + T cell response [142]. The previously mentioned RVG targeting ligand [119,144,145] and iRGD [133,146] have also been reported to have membrane-destabilizing properties, possibly contributing to enhanced cytoplasmic delivery of the encapsulated cargo.…”

“…The same targeting ligand was also used to shuttle liposomes over the BBB for the delivery of siRNA [125]. The BBB targeting enhancement was later quantified by Wiklander et al to be around two-fold [119]. Nonetheless, the majority of the vesicles was still present in MPS-associated tissues (i.e.…”

“…Nonetheless, the majority of the vesicles was still present in MPS-associated tissues (i.e. liver, spleen and lung) [119]. The fact that targeting ligands are providing modest benefits is likely the result of the short circulation time.…”

“…This event was reported to be rare, yet occurs more frequently under peripheral inflammatory conditions [129]. The mechanism behind this process remains to be [119]. After footpad injection accumulation of EVs in the lymph nodes was reported [135,136] and intranasal application showed an accumulation in the brain [137,138] in which the delivered anti-inflammatory cargo (i.e.…”