Dynamic Biodistribution of Extracellular Vesicles in Vivo Using a Multimodal Imaging Reporter

Abstract

Extracellular vesicles (EVs) are nano-sized vesicles released by normal and diseased cells as a novel form of intercellular communication, and can serve as an effective therapeutic vehicle for genes and drugs. Yet, much remains unknown about the in vivo properties of EVs such as tissue distribution, and blood levels and urine clearance - important parameters that will define their therapeutic effectiveness and potential toxicity. Here we combined Gaussia luciferase and metabolic biotinylation to create a sensitive EV reporter (EV-GlucB) for multimodal imaging in vivo, as well as monitoring of EV levels in the organs and biofluids ex vivo after administration of EVs. Bioluminescence and fluorescence-mediated tomography imaging on mice displayed a predominant localization of intravenously administered EVs in the spleen followed by the liver. Monitoring EV signal in the organs, blood and urine further revealed that the EVs first undergo a rapid distribution phase followed by a longer elimination phase via hepatic and renal routes within six hours, which are both faster than previously reported using dye-labeled EVs. Moreover, we demonstrate systemically injected EVs can be delivered to tumor sites within an hour following injection. Altogether, we show the EVs are dynamically processed in vivo with accurate spatiotemporal resolution, and target a number of normal organs as well as tumors with implications for disease pathology and therapeutic design.

Modularized Extracellular Vesicles: The Dawn of Prospective Personalized and Precision Medicine

“…In tracing the target cells of EVs, transmembrane proteins fused to luciferase or fluorescent proteins in EVs can be used as tracers, and the luciferase or fluorescent activity of distant cells can be measured to trace the effects of EVs 42, 111…”

Post Isolation Modification of Exosomes for Nanomedicine Applications

“…One example of this approach, relying on modification of engineered exosomal components ( Figure 1A), was recently described by Lai et al [16]. Researchers' engineered human embryonic kidney 293T exosomes expressing a membrane-bound Gaussian luciferase fused to a biotin receptor domain.…”

“…Alternatively, rather than using molecular cell biology approaches to enable downstream modifications of exosome surface macromolecules, 'click chemistry' can be used to directly attach molecules to the sur-future science group Post isolation modification of exosomes for nanomedicine applications Perspective [16] Mouse 4T1 breast cancer Natural structure modification…”

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].…”

“…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]. It is conceivable that this recognition is in part mediated by the exposure of PS at the external side of EV (subtypes) [120,121].…”