In vivo single-cell CRISPR screening reveals that Slc7a8 is a key molecule in post-myocardial infarction repair

Background Although interventional therapies have markedly improved acute survival after myocardial infarction (MI), long-term cardiac remodeling and heart failure remain prevalent. Cardiac resident macrophages are critical regulators of immune homeostasis. Following MI, these cells are rapidly depleted and replaced by infiltrating monocyte-derived macrophages, which, under local microenvironmental cues, differentiate into resident-like macrophages (RLMs) that support tissue repair and homeostasis. However, this phenotypic transition is temporally constrained. Insufficient early microenvironmental signaling delays the acquisition of reparative and pro-angiogenic functions, preventing RLMs from effectively governing the critical window of inflammation resolution and immune restoration. Consequently, the limited early protective capacity of RLMs contributes to adverse ventricular remodeling. Methods The major methodological highlight of this study is the application of an in vivo single-cell CRISPR screening platform. This approach was integrated with metabolomic sequencing, flow cytometry, macrophage fate mapping, and functional assays to identify key molecular regulators governing macrophage fate and to evaluate the impact of macrophage phagocytic capacity on tissue recovery.Furthermore, by analyzing the association between circulating serum amino acids in the UK Biobank and post-MI prognosis, we explored amino acid supplementation as a potential novel dietary therapeutic strategy to enhance cardiac repair following MI. Results We identified Slc7a8 as a critical regulator of cardiac resident-like macrophage fate and characterized its dynamic expression during cardiac repair. Genetic deletion of Slc7a8 significantly impaired the differentiation of monocytes into cardiac RLMs and reduced the expression of the canonical resident macrophage marker Folr2. Consequently, RLMs exhibited diminished capacity to clear apoptotic cardiomyocytes and regulate inflammatory responses, leading to impaired cardiac repair. Immunometabolic analyses further revealed that specific amino acid metabolic pathways drive macrophage functional reprogramming. Clinical serum data suggested that Slc7a8-mediated neutral amino acid transport is closely associated with clinical prognosis, identifying a potential therapeutic target to enhance cardiac repair. Conclusions Our findings highlight the therapeutic potential of targeting the transition of monocytes into cardiac resident-like macrophages to improve immune regulation and tissue repair following MI. This study provides a foundation for the development of precision therapeutic strategies aimed at enhancing cardiac repair and preventing adverse remodeling through functional reprogramming of cardiac macrophages. Moreover, our work offers new insights into immunonutritional interventions for cardiovascular diseases, with the potential to substantially improve clinical outcomes in patients with heart disease.CRISPR Screenaverall figure