Encapsulation of Nano‐Bortezomib in Apoptotic Stem Cell‐Derived Vesicles for the Treatment of Multiple Myeloma

Abstract Extracellular vesicles (EVs) are lipid bilayer nanovesicles released from living or apoptotic cells that can transport DNA, RNA, protein, and lipid cargo. EVs play critical roles in cell–cell communication and tissue homeostasis, and have numerous therapeutic uses including serving as carriers for nanodrug delivery. There are multiple ways to load EVs with nanodrugs, such as electroporation, extrusion, and ultrasound. However, these approaches may have limited drug‐loading rates, poor EV membrane stability, and high cost for large‐scale production. Here, it is shown that apoptotic mesenchymal stem cells (MSCs) can encapsulate exogenously added nanoparticles into apoptotic vesicles (apoVs) with a high loading efficiency. When nano‐bortezomib is incorporated into apoVs in culture‐expanded apoptotic MSCs, nano‐bortezomib‐apoVs show a synergistic combination effect of bortezomib and apoVs to ameliorate multiple myeloma (MM) in a mouse model, along with significantly reduced side effects of nano‐bortezomib. Moreover, it is shown that Rab7 regulates the nanoparticle encapsulation efficiency in apoptotic MSCs and that activation of Rab7 can increase nanoparticle‐apoV production. In this study, a previously unknown mechanism to naturally synthesize nano‐bortezomib‐apoVs to improve MM therapy is revealed.