RNA Sequencing Analysis of cultured macrophages harvested from the infarcted heart of WT mice and il21 receptor deficient mice (il21r-/-)

Ly6Clow macrophages promote scar formation and prevent early infarct expansion after myocardial infarction (MI). Although CD4+ T cells influence the regulation of Ly6Clow macrophages after MI, the mechanism remains largely unknown. Here, we focused on IL-21 and uncovered its physiological relevance in post-MI hearts. CD4+ T cells harvested from the infarcted heart produce IL-21 upon stimulation, and IL-21 receptor was expressed on Ly6Clo macrophages in the infarcted heart. The survival rate after MI was significantly improved in IL-21-deficient mice compared with WT mice. Moreover, transcriptome analysis of infarcted heart tissue demonstrated that inflammation was persistent in WT mice compared with IL-21-deficient mice. The number of neutrophils was significantly decreased, whereas the number of Ly6Clow macrophages was significantly increased in IL-21-deficient mice. Consistently, IL-21 enhanced the apoptosis of Ly6Clow macrophages. Furthermore, RNA-seq analysis of Ly6Chi and Ly6Clo macrophages stimulated with or without IL-21 for 24 hours revealed that IL-21 induces inflammatory responses in both Ly6Chi and Ly6Clo macrophages. Finally, the treatment with IL-21 receptor Fc protein significantly increased the survival after MI. Thus, the deletion of IL-21 improves survival after MI by preventing Ly6Clo macrophage apoptosis. We collected Ly6Chi macrophages and Ly6Clo macrophages from the infarcted hearts of WT mice and il21 receptor deficient mice (il21r-/-) at 3 days after MI. mRNA profiles from cultured macrophages stimulated with or without IL-21 for 24 hours.