Multi-omic Evaluations Nominate an ER-Mitochondrial Axis and Inflammatory Macrophage as Drivers of Right Atrial Dysfunction

BackgroundRight atrial (RA) dysfunction is an emerging risk factor for poor outcomes in pulmonary arterial hypertension, however the mechanisms underlying compromised RA function are understudied. ObjectivesMulti-omic analyses defined the cellular and molecular mediators associated with RA dysfunction in pulmonary artery banded (PAB) swine. Methods4-week-old castrated male Yorkshire pigs were subjected to PAB and aged six weeks to induce right heart failure. Cardiac MRI evaluated RA size and function. snRNAseq defined the cell-specific alterations in RA tissue. Mitochondrial proteomics and metabolomics analyses examined the metabolic alterations in RA samples. Inducible pluripotent stem cell-derived atrial cardiomyocytes (iPSC-ACM) were treated with tunicamycin to induce endoplasmic reticulum (ER) stress and mitochondrial structure and function were probed. ResultsPAB induced RA dilation/dysfunction and atrial cardiomyocyte hypertrophy. snRNAseq demonstrated PAB altered the cellular composition of the RA defined by increased inflammatory macrophages and an alteration of cardiomyocyte subpopulations. RA cardiomyocytes exhibited ER stress and mitochondrial metabolic enzyme dysregulation. PAB RAs, but not PAB right ventricles, had downregulation of branched chain amino acid degrading enzymes. Metabolomics profiling revealed BCAA and fatty acid metabolism were impaired in the dysfunctional RA. Tunicamycin-induced ER stress disrupted mitochondrial structure/function in iPSC-ACMs. ConclusionsMulti-omic evaluations demonstrate RA dysfunction is characterized by cardiomyocyte metabolic derangements due to ER dysregulation and an accumulation of pro-inflammatory macrophages.