“Attractive” Treatment for Abdominal Aortic Aneurysm Repair: Magnetic Localization of Silk-Iron Packaged Extracellular Vesicles

Abdominal aortic aneurysm (AAA) is a dilatation of the distal aorta to a diameter of 50% or more of its normal size of about 2 cm. Risk of aortic rupture can be nearly eliminated with either open surgery or endovascular repair. Procedural risks limit the value of these interventions unless the diameter of the aneurysm has reached a critical threshold (established as 5.5 cm in men or 5.0 cm in women). Thus, patients are monitored until this threshold is reached. Approximately 80% of small AAA will grow and exceed the threshold, providing a therapeutic window for altering this natural history and reducing the risk of rupture. Previous work in our lab has utilized adipose-derived mesenchymal stem cells (ASCs) to treat AAA in vivo, preserving elastic fibers and slowing aneurysm expansion. This work sought to create a delivery system for therapeutic extracellular vesicles (ASC-EVs) secreted by ASCs. Our delivery system incorporated the biocompatibility of regenerated silk fibroin (RSF), the magnetic moveability of iron oxide nanoparticles (IONPs), and the regenerative nature of ASC-EVs to create silk-iron packaged extracellular vesicles (SIPEs). Using this system, we tested the ability to magnetically localize the SIPEs and release their encapsulated ASC-EVs to exert their regenerative effects in vitro. We were successful in magnetically localizing the SIPEs in vitro and silk-iron microparticles (SIMPs) in vivo and in detecting their releasates via flow cytometry and cellular uptake assays. However, while their releasates were detected, their biological effects were diminished compared to unencapsulated controls. Thus, additional optimization related to loading efficiency is needed.