Allogenic mitochondria transfer improves cardiac function in iPS-cell-differentiated cardiomyocytes of a patient with Barth syndrome

Barth syndrome (BTHS) is an ultrarare, infantile-onset, X-linked recessive mitochondrial disorder that primarily affects males, owing to mutations in TAFAZZIN, which catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mitochondrial transplantation is a novel technique to treat mitochondrial dysfunction by delivering healthy mitochondria to diseased cells or tissues. Here we explored the possibility of using stem-cell-derived cardiomyocytes as a source of mitochondrial transplantation to treat BTHS. We established induced pluripotent stem (iPS) cells from healthy individuals and from patients with BTHS and differentiated them into cardiomyocytes. The iPS-cell-differentiated cardiomyocytes (CMs) derived from patients with BTHS exhibited less expression of cardiomyocytes markers, such as α-SA, cTnT and cTnI, and smaller cell size than normal iPS-cell-derived CMs. Multielectrode array analysis revealed that BTHS CMs exhibited shorter beat period and longer field potential duration than normal CMs. In addition, mitochondrial morphology and function were impaired and mitophagy was decreased in BTHS CMs compared with normal CMs. Transplantation of mitochondria isolated from normal CMs induced mitophagy in BTHS CMs, mitigated mitochondrial dysfunction and promoted mitochondrial biogenesis. Furthermore, mitochondrial transplantation stimulated cardiac maturation and alleviated cardiac arrhythmia of BTHS CMs. These results suggest that normal CMs are useful for allogeneic transplantation in the treatment of mitochondrial diseases, including BTHS.