Figure 5: In vivo visualization of EVs.

(a) PalmGFP-expressing EL4 tumours were implanted in pre-installed dorsal skinfold chambers (DSFCs) in C57BL/6 mice, and imaged 9 days later by MP-IVM. (b) Intravital micrograph from the central region of an EL4 tumour with regions characterized by the absence (subpanel 1), low (subpanel 2) and intermediate density (subpanel 3) of detectable PalmGFP⁺ vesicles. (c) Intravital micrograph of a peripheral region of a tumour with a high density of extracellular PalmGFP⁺ vesicles. Time-lapse recordings highlighting a tethered vesicle (subpanel 1) and a motile cluster of three vesicles (subpanel 2). Time is shown as min:s. (d) An identical experiment was performed as described for (a–c), but EL4 tumour cells expressing soluble GFP instead of PalmGFP were used instead. Note the absence of small micron- and submicron-sized particles (e) Nanoparticle tracking analysis of vesicles purified from the supernatant of PalmGFP-expressing EL4 tumour cells. (f) Non-fluorescent EL4 tumours were implanted into DSFCs and purified PalmGFP⁺ vesicles directly injected into the tumour on day 9. (g) Intravital micrograph of an EL4 tumour 60 min after injection of GFP⁺ EVs.