Intracoronary Delivery of Mitochondria to the Ischemic Heart for Cardioprotection

Abstract

We have previously shown that transplantation of autologously derived, respiration-competent mitochondria by direct injection into the heart following transient ischemia and reperfusion enhances cell viability and contractile function. To increase the therapeutic potential of this approach, we investigated whether exogenous mitochondria can be effectively delivered through the coronary vasculature to protect the ischemic myocardium and studied the fate of these transplanted organelles in the heart. Langendorff-perfused rabbit hearts were subjected to 30 minutes of ischemia and then reperfused for 10 minutes. Mitochondria were labeled with 18F-rhodamine 6G and iron oxide nanoparticles. The labeled mitochondria were either directly injected into the ischemic region or delivered by vascular perfusion through the coronary arteries at the onset of reperfusion. These hearts were used for positron emission tomography, microcomputed tomography, and magnetic resonance imaging with subsequent microscopic analyses of tissue sections to confirm the uptake and distribution of exogenous mitochondria. Injected mitochondria were localized near the site of delivery; while, vascular perfusion of mitochondria resulted in rapid and extensive dispersal throughout the heart. Both injected and perfused mitochondria were observed in interstitial spaces and were associated with blood vessels and cardiomyocytes. To determine the efficacy of vascular perfusion of mitochondria, an additional group of rabbit hearts were subjected to 30 minutes of regional ischemia and reperfused for 120 minutes. Immediately following regional ischemia, the hearts received unlabeled, autologous mitochondria delivered through the coronary arteries. Autologous mitochondria perfused through the coronary vasculature significantly decreased infarct size and significantly enhanced post-ischemic myocardial function. In conclusion, the delivery of mitochondria through the coronary arteries resulted in their rapid integration and widespread distribution throughout the heart and provided cardioprotection from ischemia-reperfusion injury.

Transit and integration of extracellular mitochondria in human heart cells

“…Our previous studies demonstrated that transplanting isolated mitochondria to the ischemic heart leads to reductions in infarct size, increases in adenosine triphosphate (ATP) production, and improvements in contractility 6,7 . We also observed that mitochondria injected or perfused into the heart were rapidly internalised by a variety of cardiac cells including cardiomyocytes and fibroblasts 7,8 . Additional experiments using cell cultures proved that the uptake of mitochondria occurs through actin-dependent endocytosis and results in rescue of cellular function by increasing energy production and replenishing mitochondrial DNA (mtDNA) 9 .…”

“…1c), whereas transmission electron microscopy revealed these organelles were structurally intact (Fig. 1d) 7,8,21 .…”

Alternative Methods for Mitochondrial Transplantation: Efficiency of Unpackaged and Lipid-Packaged Preparations

“…There are benefits to be gained by exploring and comparing techniques that could be applied to enhance mitochondrial activity in large numbers of cells, as might be used in tissue repair to address mitochondrial deficits that underlie many common disorders, such as disease or aging related dysfunctions of brain and muscle. Several groups have begun experiments with such techniques, in culture, as here, and by injection of mitochondrial preparations into tissue (15,18). The results presented here suggest that for those purposes, exposure of cells to substantially pure mitochondrial preparations packaged in lipids that match cell membranes may produce greater uptake of mitochondria by recipient cells than the use of unpackaged mitochondria.…”

New and revisited approaches to preserving the reperfused myocardium

“…The development of strategies targeting hexokinase (a regulator of PTP opening) to mitochondria 120–122 , as well as more specific PTP blockers that target mitochondria 123 might lead to new therapies for the treatment of ischaemia–reperfusion injury. Several other mitochondrial approaches to protect the heart in this setting are also under development, including methods to deliver autologously derived mitochondria 124–126 , new mitochondria-targeting peptides 43,127–130 , strategies that target calcium-activated mitochondrial potassium channels 131 or block ATP-sensitive potassium channels 132–134 , and approaches that block the inflammation caused by mitochondrial DNA after MI 135,136 .…”