A new bioluminescent reporter system to study the biodistribution of systematically injected tumor-derived bioluminescent extracellular vesicles in mice.

biodistribution and fate of extracellular vesicles (EVs) are still largely unknown and require reliable tracking techniques. In this study, bioluminescence imaging (BLI) using Renilla luciferase (Rluc) was developed and applied to monitoring of EVs derived from thyroid cancer (CAL-62 cells) and breast cancer (MDA-MB-231) in nude mice after intravenous administration and was compared with a dye-based labeling method for EV derived from CAL-62 cells. The EVs were successfully labeled with Rluc and visualized by BLI in mice. distribution of the EVs, as measured by BLI, was consistent with the results of organ analysis. EV-CAL-62/Rluc showed strong signals at lung followed by liver, spleen & kidney ( < 0.05). EV-MDA-MB-231/Rluc showed strong signals at liver followed by lung, spleen & kidney ( < 0.05). EV-CAL-62/Rluc and EV-MDA-MB-231/Rluc stayed in animal till day 9 and 3, respectively; showed a differential distribution. Spontaneous EV-CAL-62/Rluc shown distributed mostly to lung followed by liver, spleen & kidney. The new BLI system used to show spontaneous distribution of EV-CAL-62/Rluc in subcutaneous CAL-62/Rluc bearing mice. Dye (DiR)-labeled EV-CAL-62/Rluc showed a different distribution & compared to EV-CAL-62/Rluc. Fluorescent signals were predominately detected in the liver ( < 0.05) and spleen ( < 0.05) regions. The bioluminescent EVs developed in this study may be used for monitoring of EVs . This novel reporter-imaging approach to visualization of EVs in real time is expected to pave the way for monitoring of EVs in EV-based treatments.