LAUSR

Cardiac fibrosis occurs in ischemic heart failure, genetic cardiomyopathies, diabetes, and aging. While initially considered reparative, resident cardiac fibroblasts (CFs) activation/differentiation to myofibroblasts provide contractile and integral support; however, persistent activation leads to progressive cardiac dysfunction and maladaptive remodeling. Recent reports implicate acute and/or chronic changes in metabolism as a central driver for many cellular differentiation programs. Indeed, metabolite bioavailability is directly linked to the activity of epigenetic-modifying enzymes implicated in lineage commitment and differentiation. We recently identified αKG-dependent lysine demethylases as key contributors to myofibroblast formation. Here, TGFβ stimulated fibroblasts isolated from adult mouse hearts were subjected to next-gen sequencing methodologies (RNA-seq, ATAC-seq, and RRBS-seq) to identify dynamic modifications in chromatin architecture and DNA accessibility at gene loci critical to the myofibroblast gene program. Utilizing unbiased and stable-isotope metabolomics, we correlated chromatin remodeling with a significant decrease in abundance/utilization of s-adenosylmethionine, the methyl donor for cytosine and histone methylation. In addition, a significant increase in αKG abundance driven by enhanced glutaminolysis was observed. To investigate the significance of glutaminolysis and enhanced αKG biosynthesis, we treated CFs with a glutaminase inhibitor (CB-839) and evaluated differentiation. Treatment with CB-839 in the presence of TGFβ prevented activation of the fibrotic gene program (RT-qPCR) and myofibroblast formation. Furthermore, following TGFβ-induced differentiation, inhibition of glutaminolysis was sufficient to revert activated myofibroblasts to a quiescent non-fibrotic phenotype, even during sustained stress. Importantly, this phenomenon is reproducible in CFs derived from human HF patients. Collectively, these results suggest a primary role for metabolism in not only initiating differentiation, but also the persistence of myofibroblasts, potentially through epigenetic-dependent gene transcription, providing new therapeutic targets to treat fibrosis.