Bioenergetic and Metabolic Impairments in Induced Pluripotent Stem Cell-Derived Cardiomyocytes Generated from Duchenne Muscular Dystrophy Patients

Abstract

Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene and dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality in DMD patients. We tested the hypothesis that DCM is caused by metabolic impairments by employing induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from four DMD patients; an adult male, an adult female, a 7-year-old (7y) male and a 13-year-old (13y) male, all compared to two healthy volunteers. To test the hypothesis, we measured the bioenergetics, metabolomics, electrophysiology, mitochondrial morphology and mitochondrial activity of CMs, using respirometry, LC–MS, patch clamp, electron microscopy (EM) and confocal microscopy methods. We found that: (1) adult DMD CMs exhibited impaired energy metabolism and abnormal mitochondrial structure and function. (2) The 7y CMs demonstrated arrhythmia-free spontaneous firing along with “healthy-like” metabolic status, normal mitochondrial morphology and activity. In contrast, the 13y CMs were mildly arrhythmogenic and showed adult DMD-like bioenergetics deficiencies. (3) In DMD adult CMs, mitochondrial activities were attenuated by 45–48%, whereas the 7y CM activity was similar to that of healthy CMs. (4) In DMD CMs, but not in 7y CMs, there was a 75% decrease in the mitochondrial ATP production rate compared to healthy iPSC-CMs. In summary, DMD iPSC-CMs exhibit bioenergetic and metabolic impairments that are associated with rhythm disturbances corresponding to the patient’s phenotype, thereby constituting novel targets for alleviating cardiomyopathy in DMD patients.

IPSC derived cardiac fibroblasts of DMD patients show compromised actin microfilaments, metabolic shift and pro-fibrotic phenotype

“…The reshaped distribution and the reduced number of mitochondria in DMD hiPSC-derived cardiac fibroblasts blunted mitochondrial respiration, which was further confirmed by the lower expression of ETC complexes. A recent study reported impaired energy metabolism as well as abnormal mitochondrial structure and function in iPSC-derived cardiomyocytes generated from adult DMD patients, but not from a young DMD patient [ 28 ]. Similarly, mitochondrial function and biogenesis were found compromised in cardiomyocytes from the Duchenne mouse model mdx with “humanized” telomeres [ 29 ] suggesting that mitochondrial dysfunction accompanies dystrophin loss and may account for the etiology of dystrophic heart failure.…”

Ion Channels of the Sarcolemma and Intracellular Organelles in Duchenne Muscular Dystrophy: A Role in the Dysregulation of Ion Homeostasis and a Possible Target for Therapy

“…This is also accompanied by an increase in the respiratory activity of organelles, which is noted in mdx mice [171,175]. In the case of young DMD patients, a healthy-like metabolic status and mitochondrial respiratory activity was also found [176]. However, in later stages, model animals and DMD patients show a significant decrease in mitochondrial function, which is also accompanied by abnormal organelle morphology [179].…”

“…Indeed, skeletal muscle mitochondria of mdx mice show a decrease in the efficiency of oxidative phosphorylation and ATP synthesis [167,168,177,178,181,205], which is accompanied by a change in the level of electron transport chain (ETC) complexes and the efficiency of their functioning, as well as a decrease in the membrane potential of organelles (Figure 2) [168,177,178,181,205]. A decrease in the efficiency of ATP synthesis is also shown on biopsy specimens of DMD patients [176,183]. Dystrophin-deficient animals also show a reduction in some important mitochondrial inner membrane exchangers and, in particular, ANT1, which is responsible for the release of ATP from mitochondria in exchange for ADP [159,167].…”

“…Activation of calcium transport in the heart mitochondria of young mdx mice is also accompanied by an increase in the intensity of oxidative phosphorylation [171,175], which, as we suggest, may determine the adaptation of the heart to an increase in the level of calcium in cardiomyocytes and delay cardiac pathology. It is possible that similar reprogramming is also observed in cardiomyocytes of DMD patients showing signs of metabolic adaptation [176], but this issue needs to be studied. It is also not known what happens to MCUC structure and function in the setting of advanced cardiomyopathy in mdx mice or mdx:utr −/− mice, which exhibit a much earlier onset of heart failure.…”

Mitochondria in Duchenne Muscular Dystrophy-induced Cardiomyopathy: A Prospective Therapeutic Target to Improve Treatment Response

“…While no study has performed functional assessments of cardiac mitochondrial oxidative phosphorylation in people with DMD, one study found iPSC-derived cardiomyocytes from adults with DMD had significant reductions oxygen consumption coupled to ATP synthesis (Willi et al, 2022). Attenuations in the phosphocreatine (PCr) energy system indicated by lower PCr concentrations were also observed in these cells (Willi et al, 2022).…”