Isolation of Tumour‐Derived Extracellular Vesicles From the Plasma of Dogs Affected by Intracranial Tumours Showing Heterologous and Cross‐Species Tropism: A Pilot Study

Canine and human brain tumours exhibit similar incidence rates and prognoses. Recent studies have demonstrated that extracellular vesicles derived from human patients (PDEVs) can be loaded with contrast agents and exhibit tumour tropism in murine models. We showed in a previous study that gadolinium-labelled EVs derived from canine gliomas (cPDEVs) can selectively targets murine glioblastoma cells in animal models. As a further step, we investigated the potential heterologous and cross-species tumour tropism of cPDEVs with brain tumours. With the perspective of imminent clinical application as both markers and drug delivery tools, we have successfully established the isolation protocol for cPDEVs and confirmed the aseptic conditions of the procedure and therefore the sterility of the isolated EVs. To assess the functionality of cPDEVs as drug delivery tool, they were loaded with indocyanine green (ICG) and injected into murine models of cancer for in vivo fluorescence biodistribution studies. Biodistribution analysis in mice revealed that ICG-loaded cPDEVs injected into murine models of subcutaneous tumours accumulated exclusively in the neoplastic tissue, even when evaluated 24 h post-injection, thus showing the cross-species and heterologous selective tumour tropism of the nanoparticles. With these tests, we have established a safe protocol for isolating and loading autologous cPDEVs with various markers, thereby paving the way for the clinical testing phase. These significant findings suggest the potential use of cPDEVs as a theranostic tool in the management of canine brain tumours, with promising implications for translational medicine applications in the future.