Mitochondrial transplantation by intra-arterial injection for acute kidney injury.

Acute kidney injury is a common clinical disorder and one of the major causes of morbidity and mortality in the postoperative period. In this study, the safety and efficacy of autologous mitochondrial transplantation by intra-arterial injection for renal protection in a swine model of bilateral renal ischemia-reperfusion injury were investigated. Female Yorkshire pigs underwent percutaneous bilateral temporary occlusion of the renal arteries with balloon catheters. Following 60 min of ischemia, the balloon catheters were deflated and animals received either autologous mitochondria suspended in vehicle or vehicle alone, delivered as a single bolus to the renal arteries. The injected mitochondria were rapidly taken up by the kidney and were distributed throughout the tubular epithelium of the cortex and medulla. There were no safety-related issues detected with mitochondrial transplantation. Following 24 h of reperfusion, estimated glomerular filtration rate and urine output were significantly increased while serum creatinine and blood urea nitrogen were significantly decreased in swine that received mitochondria compared with those that received vehicle. Gross anatomy, histopathological analysis, acute tubular necrosis scoring, and transmission electron microscopy showed that the renal cortex of the vehicle-treated group had extensive coagulative necrosis of primarily proximal tubules, while the mitochondrial transplanted kidney showed only patchy mild acute tubular injury. Renal cortex IL-6 expression was significantly increased in vehicle-treated kidneys compared with the kidneys that received mitochondrial transplantation. These results demonstrate that mitochondrial transplantation by intra-arterial injection provides renal protection from ischemia-reperfusion injury, significantly enhancing renal function and reducing renal damage.

Mitochondrial transplantation enhances murine lung viability and recovery after ischemia-reperfusion injury.

The most common cause of acute lung injury is ischemia-reperfusion injury (IRI), during which mitochondrial damage occurs. We have previously demonstrated that mitochondrial transplantation is an efficacious therapy to replace or augment mitochondria damaged by IRI, allowing for enhanced muscle viability and function in cardiac tissue. Here, we investigate the efficacy of mitochondrial transplantation in a murine lung IRI model using male C57BL/6J mice. Transient ischemia was induced by applying a microvascular clamp on the left hilum for 2 h. Upon reperfusion mice received either vehicle or vehicle-containing mitochondria either by vascular delivery (Mito V) through the pulmonary artery or by aerosol delivery (Mito Neb) via the trachea (nebulization). Sham control mice underwent thoracotomy without hilar clamping and were ventilated for 2 h before returning to the cage. After 24 h recovery, lung mechanics were assessed and lungs were collected for analysis. Our results demonstrated that at 24 h of reperfusion, dynamic compliance and inspiratory capacity were significantly increased and resistance, tissue damping, elastance, and peak inspiratory pressure (Mito V only) were significantly decreased (P < 0.05) in Mito groups as compared with their respective vehicle groups. Neutrophil infiltration, interstitial edema, and apoptosis were significantly decreased (P < 0.05) in Mito groups as compared with vehicles. No significant differences in cytokines and chemokines between groups were shown. All lung mechanics results in Mito groups except peak inspiratory pressure in Mito Neb showed no significant differences (P > 0.05) as compared with Sham. These results conclude that mitochondrial transplantation by vascular delivery or nebulization improves lung mechanics and decreases lung tissue injury.

Mitochondrial transplantation prolongs cold ischemia time in murine heart transplantation.

BACKGROUND: Cold ischemia time (CIT) causes ischemia‒reperfusion injury to the mitochondria and detrimentally effects myocardial function and tissue viability. Mitochondrial transplantation replaces damaged mitochondria and enhances myocardial function and tissue viability. Herein we investigated the efficacy of mitochondrial transplantation in enhancing graft function and viability after prolonged CIT. METHODS: Heterotopic heart transplantation was performed in C57BL/6J mice. Upon heart harvesting from C57BL/6J donors, 0.5 ml of either mitochondria (1 × 108 in respiration buffer; mitochondria group) or respiration buffer (vehicle group) was delivered antegrade to the coronary arteries via injection to the coronary ostium. The hearts were excised and preserved for 29 ± 0.3 hours in cold saline (4°C). The hearts were then heterotopically transplanted. A second injection of either mitochondria (1 × 108) or respiration buffer (vehicle) was delivered antegrade to the coronary arteries 5 minutes after transplantation. Grafts were analyzed for 24 hours. Beating score, graft function, and tissue injury were measured. RESULTS: Beating score, calculated ejection fraction, and shortening fraction were significantly enhanced (p < 0.05), whereas necrosis and neutrophil infiltration were significantly decreased (p < 0.05) in the mitochondria group as compared with the vehicle group at 24 hours of reperfusion. Transmission electron microscopy showed the presence of contraction bands in vehicle but not in mitochondria grafts. CONCLUSIONS: Mitochondrial transplantation prolongs CIT to 29 hours in the murine heart transplantation model, significantly enhances graft function, and decreases graft tissue injury. Mitochondrial transplantation may provide a means to reduce graft failure and improve transplantation outcomes after prolonged CIT.

A Novel Biological Strategy for Myocardial Protection by Intracoronary Delivery of Mitochondria: Safety and Efficacy.

Mitochondrial dysfunction is the determinant insult of ischemia-reperfusion injury. Autologous mitochondrial transplantation involves supplying one's healthy mitochondria to the ischemic region harboring damaged mitochondria. The authors used in vivo swine to show that mitochondrial transplantation in the heart by intracoronary delivery is safe, with specific distribution to the heart, and results in significant increase in coronary blood flow, which requires intact mitochondrial viability, adenosine triphosphate production, and, in part, the activation of vascular KIR channels. Intracoronary mitochondrial delivery after temporary regional ischemia significantly improved myocardial function, perfusion, and infarct size. The authors concluded that intracoronary delivery of mitochondria is safe and efficacious therapy for myocardial ischemia-reperfusion injury.

Intracoronary Delivery of Mitochondria to the Ischemic Heart for Cardioprotection.

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.

Improved quality of pediatric 123I-MIBG images with medium-energy collimators.

UNLABELLED: Our objective was to optimize the quality of (123)I-metaiodobenzylguanidine (MIBG) scans by using a medium-energy collimator to reduce high-energy-photon septal penetration. METHODS: In addition to the 159-keV γ-ray, (123)I has a small abundance of energies above 400 keV that can compromise the image quality of MIBG studies because of septal penetration. Using a low-energy ultrahigh-resolution collimator (LEUHR), a low-energy high-resolution collimator (LEHR), and a medium-energy collimator, we obtained and compared SPECT and planar images of a SPECT phantom filled with (123)I. These studies were acquired at a count level comparable to clinical MIBG images, 24,000 counts per view for SPECT and 300,000 counts for planar imaging. Also, we evaluated the sensitivity of the 3 collimators at 0 and 10 cm using the National Electrical Manufacturers Association protocol. RESULTS: The image quality for both SPECT and planar (123)I images using the medium-energy collimator was determined to be substantially better than that using the LEUHR or LEHR collimator. The septa of the medium-energy collimator are thicker than those of the low-energy collimators (1.14 vs. 0.13-0.16 mm), leading to a significant reduction in septal penetration of the high-energy γ-rays and a marked improvement in image quality. The sensitivity for the medium-energy collimator did not change with distance (8.00 cpm/kBq), as opposed to the LEUHR collimator (6.59 and 5.51 cpm/kBq for 0 and 10 cm, respectively) and the LEHR collimator (14.32 and 12.30 cpm/kBq for 0 and 10 cm, respectively). This variation in sensitivity for the LEUHR collimator is again due to the presence of high-energy photons. CONCLUSION: Use of a medium-energy collimator substantially improves the quality of both planar and SPECT (123)I images. We recommend that a medium-energy collimator routinely be used for (123)I-MIBG imaging.