Multitargeted Immunomodulatory Therapy for Viral Myocarditis by Engineered Extracellular Vesicles.

Immune regulation therapies are considered promising for treating classically activated macrophage (M1)-driven viral myocarditis (VM). Alternatively, activated macrophage (M2)-derived extracellular vesicles (M2 EVs) have great immunomodulatory potential owing to their ability to reprogram macrophages, but their therapeutic efficacy is hampered by insufficient targeting capacity in vivo. Therefore, we developed cardiac-targeting peptide (CTP) and platelet membrane (PM)-engineered M2 EVs enriched with viral macrophage inflammatory protein-II (vMIP-II), termed CTP/PM-M2 EVs ^{vMIP-II-Lamp2b} , to improve the delivery of EVs "cargo" to the heart tissues. In a mouse model of VM, the intravenously injected CTP/PM-M2 EVs ^{vMIP-II-Lamp2b} could be carried into the myocardium via CTP, PM, and vMIP-II. In the inflammatory microenvironment, macrophages differentiated from circulating monocytes and macrophages residing in the heart showed enhanced endocytosis rates for CTP/PM-M2 EVs ^{vMIP-II-Lamp2b} . Subsequently, CTP/PM-M2 EVs ^{vMIP-II-Lamp2b} successfully released functional M2 EVs ^{vMIP-II-Lamp2b} into the cytosol, which facilitated the reprogramming of inflammatory M1 macrophages to reparative M2 macrophages. vMIP-II not only helps to increase the targeting ability of M2 EVs but also collaborates with M2 EVs to regulate M1 macrophages in the inflammatory microenvironment and downregulate the levels of multiple chemokine receptors. Finally, the cardiac immune microenvironment was protectively regulated to achieve cardiac repair. Taken together, our findings suggest that CTP-and-PM-engineered M2 EVs ^{vMIP-II-Lamp2b} represent an effective means for treating VM and show promise for clinical applications.