Dynamic Biodistribution of Extracellular Vesicles <i>in Vivo</i> Using a Multimodal Imaging Reporter

TLDR

Extracellular vesicles are nanosized vesicles released by cells that can act as therapeutic vehicles, yet their in vivo tissue distribution, blood levels, and urine clearance remain largely unknown. The study aimed to develop a sensitive EV reporter, EV‑GlucB, by combining Gaussia luciferase and metabolic biotinylation for multimodal imaging and ex vivo monitoring of EV levels. Using bioluminescence and fluorescence‑mediated tomography in mice, the authors tracked EV distribution and quantified signals in organs, blood, and urine. The reporter revealed that intravenously injected EVs mainly accumulate in spleen and liver, undergo rapid distribution followed by a six‑hour elimination phase via hepatic and renal routes—faster than dye‑labeled EVs—and reach tumor sites within an hour, demonstrating dynamic in vivo processing with high spatiotemporal resolution.

Abstract

Extracellular vesicles (EVs) are nanosized 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, 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.