Abstract 16406: Epigenetic Regulation of Myofibroblast Differentiation and Persistence is Mediated by Enhanced Glutaminolysis

Abstract

Cardiac fibrosis is mediated by the activation and differentiation of resident cardiac fibroblasts. While initially reparative, chronic activation leads to progressive cardiac dysfunction. Associated with myofibroblast formation are changes in metabolites directly linked to the activity of epigenetic-modifying enzymes. To define the signaling linking fibroblast activation with changes to the epigenetic landscape, we treated primary adult murine cardiac fibroblasts (CFs) with the pro-fibrotic agonist, TGFβ, and subjected them to next-gen sequencing techniques (RNA-seq, ATAC-seq). Following activation, we observed alterations in chromatin accessibility corresponding to the transcriptional activation and suppression of key fibrotic genes. Intriguingly, increased chromatin accessibility was strongly associated with both transcriptional activation and suppression, while decreased accessibility correlated with neither transcriptional repression or activation. Regions of increased accessibility were enriched for canonical fibrotic TF binding motifs (e.g. SMADs, NFAT). We recently reported that αKG-dependent lysine demethylases may be required for myofibroblast formation, so we made correlative comparisons between chromatin remodeling and the synthesis and utilization of metabolites critical for (de)methylation by applying unbiased, stable isotope metabolomics. These studies indicated enhanced glutaminolysis as the driver of increased αKG abundance. In the presence of TGFβ, pharmacologic inhibition (CB-839) or genetic deletion ( Gls1 -/- ) of glutaminolysis prevented myofibroblast formation as indicated by αSMA positivity, fibrotic gene program activation, and collagen contraction assays. Following myofibroblast formation, inhibition of glutaminolysis was sufficient to revert activated myofibroblasts to a non-fibrotic phenotype, during sustained stress. Remarkably, these results were recapitulated in CFs from human heart failure patients. Collectively, these findings suggest that metabolic remodeling is necessary for the epigenetic modifications that underlie myofibroblast formation and persistence, providing substantial rationale to evaluate several new therapeutic targets to treat fibrosis.