Transit and integration of extracellular mitochondria in human heart cells

Abstract

Tissue ischemia adversely affects the function of mitochondria, which results in impairment of oxidative phosphorylation and compromised recovery of the affected organ. The impact of ischemia on mitochondrial function has been extensively studied in the heart because of the morbidity and mortality associated with injury to this organ. As conventional methods to preserve cardiac cell viability and contractile function following ischemia are limited in their efficacy, we developed a unique approach to protect the heart by transplanting respiration-competent mitochondria to the injured region. Our previous animal experiments showed that transplantation of isolated mitochondria to ischemic heart tissue leads to decreases in cell death, increases in energy production, and improvements in contractile function. We also discovered that exogenously-derived mitochondria injected or perfused into ischemic hearts were rapidly internalised by cardiac cells. Here, we used three-dimensional super-resolution microscopy and transmission electron microscopy to determine the intracellular fate of endocytosed exogenous mitochondria in human iPS-derived cardiomyocytes and primary cardiac fibroblasts. We found isolated mitochondria are incorporated into cardiac cells within minutes and then transported to endosomes and lysosomes. The majority of exogenous mitochondria escape from these compartments and fuse with the endogenous mitochondrial network, while some of these organelles are degraded through hydrolysis.

Intercellular mitochondria trafficking highlighting the dual role of mesenchymal stem cells as both sensors and rescuers of tissue injury

“…They observed that, by simple co-incubation, chloramphenicol-(CAP s ) and efrapeptin-(EF s ) sensitive mammalian cells were able to incorporate mitochondria, purified beforehand from CAP r and EF r resistant cells [97]. Ever since, many cells have been reported to undergo mitochondrial transformation [55,[98][99][100][101][102]. This process is believed to occur via macropinocytosis.…”

Mitochondrial transplantation: applications for pediatric patients with congenital heart disease

“…Mitochondrial number, viability and purity are assessed in all mitochondrial preparations using an aliquot of the isolated mitochondria. Mitochondrial number and size are determined by particle size analysis and light microscopy using fluorescent mitochondrial specific labels MitoTracker Red CMXRos (Invitrogen, Carlsbad, CA, USA) which labels only viable mitochondria maintaining membrane potential followed by MitoTracker Green FM, which labels all mitochondria independent of membrane potential and then by transmission electron microscopy (15)(16)(17)19). Mitochondrial viability is determined by oxygen consumption rate using a Clark-type electrode and fluorescent probe analysis (15,17,21,22).…”

“…These cytokines are associated with reduced cardiomyocyte apoptosis and enhanced functional cardiac recovery and cardiac remodeling independent of cardiac myocyte regeneration (16). The mitochondria are rapidly internalized (2.5-60 min) into myocardial cells by actin-dependent endocytosis where they up-regulate cellular function and repair damaged mitochondrial DNA (17,19). The transplanted, mitochondria maintain viability and function for at least 28 days and have no pro-arrhythmic inflammatory, immune or auto-immune response (16,18,20).…”

Improvement of cognitive and motor performance with mitotherapy in aged mice

“…The entry mechanism of mitochondria into cells would be associated with actin-mediated endocytosis because actin polymerization inhibitors can prevent the internalization of mitochondria by cells [34,35]. After the mitochondria enter cells, they are transported to lysosomes, then majority of the mitochondria can escape from the lysosomes and play roles in cytosol [36]. Moreover, it has been identified that exogenous mitochondria can promote neurogenesis, and activate the expression of brain-derived neurotrophic factor (BDNF) in the reported articles [7,37,38].…”