Legumain In Situ Engineering Promotes Efferocytosis of CAR Macrophage to Treat Cardiac Fibrosis

Abstract Uncontrolled and excessive cardiac fibrosis after myocardial infarction (MI) is a primary contributor to mortality by heart failure. Chimeric antigen receptor macrophage (CAR‐MΦ) therapy shows great promise in cardiac fibrosis, however, the overwhelming apoptotic cells after MI results in an overburdened efferocytosis in CAR‐MΦ, which compromises their antifibrotic potency. This work here reports an in situ engineered legumain (Lgmn) to elevate the cargo degradation of phagolysosome for promoting the efferocytosis of CAR‐MΦs, restoring their antifibrotic capability. Specifically, with the in‐house customized macrophages‐targeting lipid nanoparticles, this work first creates an efferocytosis‐boosted fibrosis‐specific CAR‐MΦs by introducing dual mRNAs that encode Lgmn, an endolysosomal cysteine protease, along with an anti‐fibroblast activation protein (FAP) CAR, respectively. This data demonstrate these CAR‐MΦs displayed a significantly increased phagocytic capacity as well as improved efferocytosis and enhanced antifibrotic capability. Treatment with the in situ reprogrammed CAR‐MΦs in MI mice obviously reduced the infarct size and mitigated cardiac fibrosis, leading to significant restoration of cardiac function. In sum, these findings establish that promoting efferocytosis through Lgmn engineering effectively relieved the overburdened efferocytosis of CAR‐MΦs, and enhanced their treatment efficacy of cardiac fibrosis with broad application in other fibrotic diseases.