Tracking Radiolabeled Endothelial Microvesicles Predicts Their Therapeutic Efficacy: A Proof-of-Concept Study in Peripheral Ischemia Mouse Model Using SPECT/CT Imaging

Abstract

Microvesicles, so-called endothelial large extracellular vesicles (LEVs), are of great interest as biological markers and cell-free biotherapies in cardiovascular and oncologic diseases. However, their therapeutic perspectives remain limited due to the lack of reliable data regarding their systemic biodistribution after intravenous administration. Methods: Applied to a mouse model of peripheral ischemia, radiolabeled endothelial LEVs were tracked and their in vivo whole-body distribution was quantified by microSPECT/CT imaging. Hindlimb perfusion was followed by LASER Doppler and motility impairment function was evaluated up to day 28 post-ischemia. Results: Early and specific homing of LEVs to ischemic hind limbs was quantified on the day of ischemia and positively correlated with reperfusion intensity at a later stage on day 28 after ischemia, associated with an improved motility function. Conclusions: This concept is a major asset for investigating the biodistribution of LEVs issued from other cell types, including cancer, thus partly contributing to better knowledge and understanding of their fate after injection.

Theranostic extracellular vesicles: a concise review of current imaging technologies and labeling strategies

“…In a week, EVs promoted a significantly earlier and higher vascular recovery and a positive correlation with the concentration of EVs addressed to the site was observed after 28 days. Despite being the most widely used radionuclide, the short half-life of 99 mTc only allows imaging for up to 24 h post administration, which is not suitable for long-term in vivo tracking of EVs [ 83 ] . 131 I is another convenient ligand that can be used to conveniently radiolabel EVs derived from various cell lines with a half-life of 8 days [ 84 ] .…”

“…Alternatively, the radiolabel can be entrapped in the intra-vesicular space. It relies on the presence of glutathione, which can modify complexes from lipophilic to hydrophilic states to get trapped in the aqueous core, or on an ionophore-chelator binding method that exploits ionophore ligands, such as 8-hydroxyquinoline(oxine) and tropolone, which form a neutral, metastable amalgam with the radioligands, allowing them to transport across the phospholipid layer and bind to internal proteins [82] .…”

Design and preclinical evaluation of a novel apelin-based PET radiotracer targeting APJ receptor for molecular imaging of angiogenesis

“…Unilateral hindlimb ischemia (HLI) was induced on 9-week-old female Swiss mice (Janvier Labs, n = 8) after femoral artery excision under 2% isoflurane anesthesia as previously described [ 40 ]. LASER Doppler perfusion imaging (Perimed, Craponne, France) was used to assess revascularization from day 0 to day 21 after surgery.…”

Extracellular Vesicles and Intercellular Communication: Challenges for In Vivo Molecular Imaging and Tracking

“…Technetium-99m was also used as a complex in the form of both [ 99m Tc(CO) 3 (H 2 O) 3 ] + , able to bind several amino acids of the surface proteins [ 76 ], and [ 99m Tc]Tc-Annexin-V-128, able to bind the phosphatidylserine molecules present in the membrane of EVs. The latter was used for the study of the in vivo biodistribution of EC–EVs after systemic injection in a preclinical model of hind limb ischemia, demonstrating an early and specific homing of radiolabeled EC–EVs to the ischemic hind limb with therapeutic angiogenic effects [ 99 ].…”