Myocardial fibrosis is an irreversible pathological consequence that occurs as various heart diseases progress to their end stages. Currently, no effective therapeutic strategies have been established in clinical practice for its management. The development of T-cell therapy offers promising and innovative opportunities for the treatment of myocardial fibrosis. In this study, we employed CD3-targeted lipid nanoparticles (LNPs) to efficiently deliver the designed chimeric antigen receptor (CAR) structure and the molecular switch HuEGFRt mRNA into T cells, thereby successfully constructing CAR-T cells targeting fibroblast activation protein (FAP). The experimental results demonstrated that FAP-CAR-T cells could specifically eliminate target cells with high FAP expression while exhibiting minimal cytotoxicity on normal cells. Furthermore, the in vivo-generated FAP-CAR-T cells significantly alleviated myocardial fibrosis and effectively improved cardiac function. Regarding safety evaluation, the introduced molecular switch HuEGFRt could selectively induce apoptosis of CAR-T cells via complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) in the presence of cetuximab. Blood routine and biochemistry test results confirmed that the in vivo-generated FAP-CAR-T cells did not elicit any adverse reactions in the mouse model. Therefore, the in vivo generation of FAP-CAR-T cells via LNPs targeting CD3 represents an effective and safe therapeutic strategy for treating myocardial fibrosis. This innovative method not only exhibits substantial therapeutic potential but also expands the clinical application prospects for patients with myocardial fibrosis.
