Abstract 219: Translational Profiling Of Embryonic And Adult-derived Macrophages Exposed To Hypoxia

Abstract

Cardiac-resident macrophages are largely of embryonic (fetal liver) origin and long-lived, while bone marrow-derived macrophages (BMDM) are recruited following an acute perturbation, such as hypoxia in the setting of myocardial ischemia. Prior transcriptome analyses identified BMDM and fetal liver-derived macrophage (FLDM) differences at the RNA expression level. Post-transcriptional regulation at the levels of mRNA stability and translation may override transcriptional signals in response to hypoxia. We hypothesized that profiling of actively translated mRNAs in BMDM and FLDM after exposure to hypoxia would uncover functional differences in gene expression between these macrophage subsets. We used a translating ribosome affinity purification (TRAP) assay coupled with RNA-seq and validation by qRT-PCR, flow cytometry and immunoblotting to identify translated transcripts in macrophages exposed to hypoxia. We identified non-overlapping transcripts with increased translation in BMDM (Ly6e, vimentin, PF4) and FLDM (Ccl7, Ccl2). Induction of most transcripts, including those encoding enzymes associated with glycolysis, was accompanied by increased translation. However, induction of the mRNA encoding complement receptor C5ar1 was accompanied by reduced translation efficiency. Furthermore, we determined the effects of deletion of the RNA-binding protein HuR on induction and translation of transcripts in response to hypoxia. Overall, these findings define translational differences in macrophage subset gene expression programs, highlighting potential macrophage-directed therapeutic targets in ischemic myocardium.