Age-associated metabolic and epigenetic barriers during direct reprogramming of mouse fibroblasts into induced cardiomyocytes

Heart disease is the leading cause of mortality in developed countries and novel regenerative procedures are warranted. Direct cardiac conversion (DCC) of adult fibroblasts can create induced cardiomyocytes (iCMs) for gene and cell-based heart therapy and, besides holding great promise, still lack effectiveness as metabolic and age-associated barriers remain elusive. Here, by employing MGT (Mef2c, Gata4, Tbx5)- transduction of mouse embryonic (MEFs) and adult (skin ear-derived and cardiac) fibroblasts from animals at different ages, we provide evidence that direct reprogramming of fibroblasts into iCMs decreases with age. Analysis of histone post-translational modifications and ChIP-qPCR revealed age-dependent alterations in the epigenetic landscape during DCC. Moreover, DCC is accompanied by profound mitochondrial metabolic adaptations, including less abundance of anabolic metabolites, remodeling of the network and reliance in mitochondrial respiration. Metabolic modulation in vitro and dietary manipulations in vivo improves DCC efficiency and is accompanied by significant alterations in the histone marks and mitochondria homeostasis. Importantly, adult-derived iCMs present increase accumulation of oxidative stress in the mitochondria and pharmacological activation of mitophagy or dietary lipids, improves DCC and reverts mitochondrial oxidative damage. Our study provides evidence that metaboloepigenetics has a direct role in cell fate transitions driving DCC, highlighting the potential use of metabolic modulation for improving cardiac regenerative strategies.