Background: Macrophages play a crucial role in the immune response during allograft rejection in organ transplantation. Therefore, our study aimed to explore the genomic features of macrophages in mouse heart transplants and use single-cell RNA sequencing to investigate Galectin-9 (Gal-9, Lgals9), a lectin that can mediate the activation and differentiation of immune cells through ligand-receptor interactions, with the effects of their regulations in the transplantation.
Methods: We used single-cell RNA sequencing (scRNA-Seq) to reveal the heterogeneity of macrophages in mouse heart transplants before and after the transplantation. Furthermore, we validated our findings using RT-qPCR and Western blotting and also investigated the impact of Lgals9 on macrophage function through flow cytometry and ELISA.
Results: In vivo, we discovered a new subset of macrophages called "Myoz2+ macrophages" which is a specifically expressed genes related to myocardial contraction. We identified a distinct differentiation trajectory and process for the Saa3+ macrophage population, representing anti-inflammatory functionality. Also, we observed a significant downregulation of Lgals9 expression in the macrophages after mouse heart transplantation. Furthermore, in vitro, we found those rLgals9 (Recombinant Mouse Galectin-9 Protein) treated macrophages polarized towards the M2b phenotype at appropriate concentrations.
Conclusion: In heart transplants, certain macrophages may be involved in specific physiological processes related to myocardial repair and inflammation. Our findings suggested that rLgals9 induced macrophage polarization towards the M2b subtype and enhanced their immunomodulatory function. This provided valuable insights into the role and mechanisms of macrophages in heart transplantation and myocardial repair.