Data on common carotid artery occlusion inducing focalized stroke lesions after Pertussis toxin injection.

This article contains raw and processed data related to research published by Vega et al. (2022). This complementary dataset provides further insight into the experimental validation of a single common carotid artery occlusion (CCAO) model upon pretreatment with pertussis toxin (PTX). We present data showing the extent of different PTX concentrations on neurological severity measured by Bederson score following CCAO. In addition, data indicate a protective effect of isoflurane on cerebral infarction and neurological deficits, as well as the consequences of PTX pretreatment on reperfusion after occlusion using time-of-flight magnetic resonance angiography. With these data, we aim to provide detailed experimental settings of this newly described model.

Multiparametric MRI identifies subtle adaptations for demarcation of disease transition in murine aortic valve stenosis.

Aortic valve stenosis (AS) is the most frequent valve disease with relevant prognostic impact. Experimental model systems for AS are scarce and comprehensive imaging techniques to simultaneously quantify function and morphology in disease progression are lacking. Therefore, we refined an acute murine AS model to closely mimic human disease characteristics and developed a high-resolution magnetic resonance imaging (MRI) approach for simultaneous in-depth analysis of valvular, myocardial as well as aortic morphology/pathophysiology to identify early changes in tissue texture and critical transition points in the adaptive process to AS. AS was induced by wire injury of the aortic valve. Four weeks after surgery, cine loops, velocity, and relaxometry maps were acquired at 9.4 T to monitor structural/functional alterations in valve, aorta, and left ventricle (LV). In vivo MRI data were subsequently validated by histology and compared to echocardiography. AS mice exhibited impaired valve opening accompanied by significant valve thickening due to fibrotic remodelling. While control mice showed bell-shaped flow profiles, AS resulted not only in higher peak flow velocities, but also in fragmented turbulent flow patterns associated with enhanced circumferential strain and an increase in wall thickness of the aortic root. AS mice presented with a mild hypertrophy but unaffected global LV function. Cardiac MR relaxometry revealed reduced values for both T1 and T2 in AS reflecting subtle myocardial tissue remodelling with early alterations in mitochondrial function in response to the enhanced afterload. Concomitantly, incipient impairments of coronary flow reserve and myocardial tissue integrity get apparent accompanied by early troponin release. With this, we identified a premature transition point with still compensated cardiac function but beginning textural changes. This will allow interventional studies to explore early disease pathophysiology and novel therapeutic targets.

Multi-targeted 1H/19F MRI unmasks specific danger patterns for emerging cardiovascular disorders.

Prediction of the transition from stable to acute coronary syndromes driven by vascular inflammation, thrombosis with subsequent microembolization, and vessel occlusion leading to irreversible myocardial damage is still an unsolved problem. Here, we introduce a multi-targeted and multi-color nanotracer platform technology that simultaneously visualizes evolving danger patterns in the development of progressive coronary inflammation and atherothrombosis prior to spontaneous myocardial infarction in mice. Individual ligand-equipped perfluorocarbon nanoemulsions are used as targeting agents and are differentiated by their specific spectral signatures via implementation of multi chemical shift selective 19F MRI. Thereby, we are able to identify areas at high risk of and predictive for consecutive development of myocardial infarction, at a time when no conventional parameter indicates any imminent danger. The principle of this multi-targeted approach can easily be adapted to monitor also a variety of other disease entities and constitutes a technology with disease-predictive potential.

Cardiac magnetic resonance T2 mapping and feature tracking in athlete's heart and HCM.

OBJECTIVES: Distinguishing hypertrophic cardiomyopathy (HCM) from left ventricular hypertrophy (LVH) due to systematic training (athlete's heart, AH) from morphologic assessment remains challenging. The purpose of this study was to examine the role of T2 mapping and deformation imaging obtained by cardiovascular magnetic resonance (CMR) to discriminate AH from HCM with (HOCM) or without outflow tract obstruction (HNCM). METHODS: Thirty-three patients with HOCM, 9 with HNCM, 13 strength-trained athletes as well as individual age- and gender-matched controls received CMR. For T2 mapping, GRASE-derived multi-echo images were obtained and analyzed using dedicated software. Besides T2 mapping analyses, left ventricular (LV) dimensional and functional parameters were obtained including LV mass per body surface area (LVMi), interventricular septum thickness (IVS), and global longitudinal strain (GLS). RESULTS: While LVMi was not significantly different, IVS was thickened in HOCM patients compared to athlete's. Absolute values of GLS were significantly increased in patients with HOCM/HNCM compared to AH. Median T2 values were elevated compared to controls except in athlete's heart. ROC analysis revealed T2 values (AUC 0.78) and GLS (AUC 0.91) as good parameters to discriminate AH from overall HNCM/HOCM. CONCLUSION: Discrimination of pathologic from non-pathologic LVH has implications for risk assessment of competitive sports in athletes. Multiparametric CMR with parametric T2 mapping and deformation imaging may add information to distinguish AH from LVH due to HCM. KEY POINTS: • Structural analyses using T2 mapping cardiovascular magnetic resonance imaging (CMR) may help to further distinguish myocardial diseases. • To differentiate pathologic from non-pathologic left ventricular hypertrophy, CMR including T2 mapping was obtained in patients with hypertrophic obstructive/non-obstructive cardiomyopathy (HOCM/HNCM) as well as in strength-trained athletes. • Elevated median T2 values in HOCM/HNCM compared with athlete's may add information to distinguish athlete's heart from pathologic left ventricular hypertrophy.

Biomedical 19F MRI Using Perfluorocarbons.

Background-free fluorine (19F) MR imaging exhibits an excellent degree of specificity, and facilitates among others the in vivo visualization of inflammatory processes. Merging19F MR images with morphologically matching1H MR images enables the exact anatomic localization of the observed19F signal. Biochemically inert nanoemulsions of perfluorocarbons, which are known to be taken up by the macrophage/monocyte system, are widely used as contrast agents for preclinical applications. Herein, the most common protocols are described to obtain high-resolution and artifact-free19F MR images even for compounds with complex19F MR spectra. In addition, we report on the utilization of perfluorocarbons with individual spectral identities and targeting approaches to specifically visualize thrombi by19F MRI.

Multimodal assessment of orbital immune cell infiltration and tissue remodeling during development of graves disease by 1 H19 F MRI.

PURPOSE: To evaluate key molecular and cellular features of Graves orbitopathy (GO) by simultaneous monitoring of alterations in morphology, inflammatory patterns, and tissue remodeling. METHODS: To this end, we utilized a murine model of GO induced by immunization with a human thyroid-stimulating hormone receptor A-subunit plasmid. Altogether, 52 mice were used: 27 GOs and 25 controls (Ctrl) immunized with ß-galactasidose plasmid. From these, 17 GO and 12 Ctrl mice were subjected to multimodal MRI at 9.4T, whereas 23 mice only underwent histology. Beyond anatomical hydrogen-1 (1 H) MRI, we employed transverse relaxation time (T2 ) mapping for visualization of edema, chemical exchange saturation transfer (CEST) for detection of hyaluronan, and fluorine-19 (19 F) MRI for tracking of in situ-labeled immune cells after intravenous injection of perfluorcarbons (PFCs). RESULTS: 1 H/19 F MRI demonstrated substantial infiltration of PFC-loaded immune cells in peri and retro-orbital regions of GO mice, whereas healthy Ctrls showed only minor 19 F signals. In parallel, T2 mapping indicated onset of edema in periorbital tissue and adjacent ocular glands (P = 0.038/0.017), which were associated with enhanced orbital CEST signals in GO mice (P = 0.031). Concomitantly, a moderate expansion of retrobulbar fat (P = 0.029) was apparent; however, no signs for extraocular myopathy were detectable. 19 F MRI-based visualization of orbital inflammation exhibited the highest significance level to discriminate between GO and Ctrl mice (P = 0.006) and showed the best correlation with the clinical score (P = 0.0007). CONCLUSION: The present approach permits the comprehensive characterization of orbital tissue and holds the potential for accurate GO diagnosis in the clinical setting. Magn Reson Med 80:711-718, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

Cardiovascular Magnetic Resonance Relaxometry Predicts Regional Functional Outcome After Experimental Myocardial Infarction.

BACKGROUND: Cardiovascular magnetic resonance with gadolinium-based contrast agents has established as gold standard for tissue characterization after myocardial infarction (MI). Beyond accurate diagnosis, the value of cardiovascular magnetic resonance to predict the outcome after MI has yet to be substantiated. METHODS AND RESULTS: Recent cardiovascular magnetic resonance approaches were systematically compared for quantification of tissue injury and functional impairment after MI using murine models with permanent left anterior descending coronary artery ligation (n=14) or 50 minutes ischemia/reperfusion (n=13). Cardiovascular magnetic resonance included native/postcontrast T1 maps, T2 maps, and late gadolinium enhancement at days 1 and 21 post-MI. For regional correlation of parametric and functional measures, the left ventricle was analyzed over 200 sectors. For T1 mapping, we used retrospective triggering with variable flip angle analysis. Sectoral analysis of native T1 maps already revealed in the acute phase after MI substantial discrepancies in myocardial tissue texture between the 2 MI models (native T1 day 1: permanent ligation, 1280.0±162.6 ms; ischemia/reperfusion, 1115.0±140.5 ms; P<0.001; n=14/13), which were later associated with differential functional outcome (left ventricular ejection fraction day 21: permanent ligation, 24.5±7.0%; ischemia/reperfusion, 33.7±11.6%; P<0.05; n=14/13). At this early time, any other parameter was indicative for the subsequent worsening of left ventricular ejection fraction in permanent ligation mice. Linear regression of acute individual measures with contractile function in corresponding areas at day 21 demonstrated for early native T1 values the best correlation with the later functional impairment (R2 =0.94). CONCLUSIONS: The present T1 mapping approach permits accurate characterization of local tissue injury and holds the potential for sensitive and graduated prognosis of the functional outcome after MI without gadolinium-based contrast agents.

CD73 on T Cells Orchestrates Cardiac Wound Healing After Myocardial Infarction by Purinergic Metabolic Reprogramming.

BACKGROUND: T cells are required for proper healing after myocardial infarction. The mechanism of their beneficial action, however, is unknown. The proinflammatory danger signal ATP, released from damaged cells, is degraded by the ectonucleotidases CD39 and CD73 to the anti-inflammatory mediator adenosine. Here, we investigate the contribution of CD73-derived adenosine produced by T cells to cardiac remodeling after ischemia/reperfusion and define its mechanism of action. METHODS: Myocardial ischemia (50 minutes followed by reperfusion) was induced in global CD73-/- and CD4-CD73-/- mice. Tissue injury, T-cell purinergic signaling, cytokines, and cardiac function (magnetic resonance tomography at 9.4 T over 4 weeks) were analyzed. RESULTS: Changes in functional parameters of CD4-CD73-/- mice were identical to those in global CD73 knockouts (KOs). T cells infiltrating the injured heart significantly upregulated at the gene (quantitative polymerase chain reaction) and protein (enzymatic activity) levels critical transporters and enzymes (connexin43, connexin37, pannexin-1, equilibrative nucleoside transporter 1, CD39, CD73, ecto-nucleotide pyrophosphatase/phosphodiesterases 1 and 3, CD157, CD38) for the accelerated release and hydrolysis of ATP, cAMP, AMP, and NAD to adenosine. It is surprising that a lack of CD39 on T cells (from CD39-/- mice) did not alter ATP hydrolysis and very likely involves pyrophosphatases (ecto-nucleotide pyrophosphatase/phosphodiesterases 1 and 3). Circulating T cells predominantly expressed A2a receptor (A2aR) transcripts. After myocardial infarction, A2b receptor (A2bR) transcription was induced in both T cells and myeloid cells in the heart. Thus, A2aR and A2bR signaling may contribute to myocardial responses after myocardial infarction. In the case of T cells, this was associated with an accelerated secretion of proinflammatory and profibrotic cytokines (interleukin-2, interferon-γ, and interleukin-17) when CD73 was lacking. Cytokine production by T cells from peripheral lymph nodes was inhibited by A2aR activation (CGS-21680). The A2bR agonist BAY 60-6583 showed off-target effects. The adenosine receptor agonist NECA inhibited interferon-γ and stimulated interleukin-6 production, each of which was antagonized by a specific A2bR antagonist (PSB-603). CONCLUSIONS: This work demonstrates that CD73 on T cells plays a crucial role in the cardiac wound healing process after myocardial infarction. The underlying mechanism involves a profound increase in the hydrolysis of ATP/NAD and AMP, resulting primarily from the upregulation of pyrophosphatases and CD73. We also define A2bR/A2aR-mediated autacoid feedback inhibition of proinflammatory/profibrotic cytokines by T cell-derived CD73.

Abnormal T2 mapping cardiovascular magnetic resonance correlates with adverse clinical outcome in patients with suspected acute myocarditis.

BACKGROUND: While most patients recover from suspected acute myocarditis (sAMC) some develop progressive disease with 5-year mortality up to 20%. Recently, parametric Cardiovascular Magnetic Resonance (CMR) approaches, quantifying native T1 and T2 relaxation time, have demonstrated the ability to increase diagnostic accuracy. However, prognostic implications of T2 values in this cohort are unknown. The purpose of the study was to investigate the prognostic relevance of elevated CMR T2 values in patients with sAMC. METHODS AND RESULTS: We carried out a prospective study in 46 patients with sAMC defined by current ESC recommendations. A combined endpoint was defined by the occurrence of at least one major adverse cardiac event (MACE) and hospitalisation for heart failure. Event rate was 24% (n = 11) for 1-year-MACE and hospitalisation. A follow-up after 11 ± 7 months was performed in 98% of the patients. Global T2 values were significantly increased at acute stage of disease compared to controls and decreased over time. During acute disease, elevated global T2 time (odds ratio 6.3, p < 0.02) as well as myocardial fraction with T2 time >80 ms (odds ratio 4.9, p < 0.04) predicted occurrence of the combined endpoint. Patients with clinical recovery revealed significantly decreased T2 relaxation times at follow-up examinations; however, T2 values were still elevated compared to healthy controls. CONCLUSION: Assessment of myocardial T2 relaxation times at initial presentation facilitates CMR-based risk stratification in patients with acute myocarditis. T2 Mapping may emerge as a new tool to monitor inflammatory myocardial injuries during the course of disease.

Multiparametric cardiac magnetic resonance imaging (CMR) for the diagnosis of Loeffler's endocarditis: a case report.

BACKGROUND: Endocarditis parietalis fibroplastica Löfflein (EPF) is a rare form of primary restrictive cardiomyopathy with poor prognosis. It is generally caused by hypereosinophilic syndrome with eosinophilic penetration of the heart. This leads to congestive heart failure in three different stages. As a frequent manifestation of neoplastic diseases, cardiac involvement means poor prognosis. CASE PRESENTATION: The present report deals with a case of EPF caused by non-specified T-cell lymphoma (T-NOS). Besides an elevated Troponin-T enzyme, the electrocardiogram and the transthoracic echocardiography did not show any characteristic results. Due to risk/benefit assessment and low thrombocyte amounts, endomyocardial biopsy and catheterization were discarded. Using cardiovascular magnetic resonance (CMR) with steady-state free precession sequences, T2-mappping, strain analysis and late gadolinium enhancement, we were able to clearly highlight cardiac involvement at different stages. These findings characterized T-NOS as a palliative situation. CONCLUSION: Multiparametric CMR can not only identify EPF but also characterize the patchy disease state. This provides an individual prognosis assessment. Aside from prognosis estimation, it can also be used for therapy monitoring.

Epicardium-Derived Cells Formed After Myocardial Injury Display Phagocytic Activity Permitting In Vivo Labeling and Tracking.

UNLABELLED: Epicardium-derived cells (EPDCs) cover the heart surface and can function as a source of both progenitor cells and trophic factors for cardiac repair. Currently, EPDCs cannot be conveniently labeled in vivo to permit imaging and cell tracking. EPDCs formed after myocardial infarction (MI) preferentially take up a perfluorocarbon-containing nanoemulsion (PFC-NE; 130 ± 32 nm) injected 3 days after injury, as measured by (19)F-magnetic resonance imaging ((19)F-MRI). Flow cytometry, immune electron microscopy, and green fluorescent protein (GFP)-transgenic rats (only immune cells, but not epicardial cells, are GFP(+)) demonstrated that PFC-containing EPDCs are nonhematopoietic (CD45(-)/CD11b(-)) but stain positive for markers of mesenchymal stem cells such as platelet-derived growth factor receptor α (PDGFR-α) CD73, CD105, and CD90. When rhodamine-coupled PFC-NE was used, we found that ρ(+) vessel-like structures formed within the infarcted myocardium, comprising approximately 10% of all large vessels positive for smooth muscle actin (SM-actin). The epicardial cell layer, positive for Wilms' tumor 1 (WT-1), PDGFR-α, or KI-67, was shown to be well capillarized (293 ± 78 capillaries per mm(2)), including fenestrated endothelium. Freshly isolated EPDCs were positive for WT-1, GATA-4, KI-67, and FLK-1 (75%), PDGFR-α (50%), and SM-actin (28%) and also exhibited a high capacity for nanoparticle and cell debris uptake. This study demonstrates that EPDCs formed after MI display strong endocytic activity to take up i.v.-injected labeled nanoemulsions. This feature permitted in vivo labeling and tracking of EPDCs, demonstrating their role in myo- and vasculogenesis. The newly discovered endocytic activity permits in vivo imaging of EPDCs with (19)F-MRI and may be used for the liposomal delivery of substances to further study their reparative potential. SIGNIFICANCE: The present study reports that epicardium-derived cells (EPDCs) formed after myocardial infarction can specifically endocytose nanoparticles in vivo and in vitro. This novel feature permitted in vivo targeting of EPDCs with either a perfluorocarbon-containing or rhodamine-conjugated nanoemulsion to track migration and fate decision of EPDC with (19)F-magnetic resonance imaging and fluorescence microscopy. The liposomal nanoemulsions used in the present study may be useful in the future as a nanomedical device for the delivery of substances to direct cell fate of EPDCs.

Noninvasive Imaging of Early Venous Thrombosis by 19F Magnetic Resonance Imaging With Targeted Perfluorocarbon Nanoemulsions.

BACKGROUND: Noninvasive detection of deep venous thrombi and subsequent pulmonary thromboembolism is a serious medical challenge, since both incidences are difficult to identify by conventional ultrasound techniques. METHODS AND RESULTS: Here, we report a novel technique for the sensitive and specific identification of developing thrombi using background-free 19F magnetic resonance imaging, together with α2-antiplasmin peptide (α2AP)-targeted perfluorocarbon nanoemulsions (PFCs) as contrast agent, which is cross-linked to fibrin by active factor XIII. Ligand functionality was ensured by mild coupling conditions using the sterol-based postinsertion technique. Developing thrombi with a diameter<0.8 mm could be visualized unequivocally in the murine inferior vena cava as hot spots in vivo by simultaneous acquisition of anatomic matching 1H and 19F magnetic resonance images at 9.4 T with both excellent signal-to-noise and contrast-to-noise ratios (71±22 and 17±5, respectively). Furthermore, α2AP-PFCs could be successfully applied for the diagnosis of experimentally induced pulmonary thromboembolism. In line with the reported half-life of factor XIIIa, application of α2AP-PFCs>60 minutes after thrombus induction no longer resulted in detectable 19F magnetic resonance imaging signals. Corresponding results were obtained in ex vivo generated human clots. Thus, α2AP-PFCs can visualize freshly developed thrombi that might still be susceptible to pharmacological intervention. CONCLUSIONS: Our results demonstrate that 1H/19F magnetic resonance imaging, together with α2AP-PFCs, is a sensitive, noninvasive technique for the diagnosis of acute deep venous thrombi and pulmonary thromboemboli. Furthermore, ligand coupling by the sterol-based postinsertion technique represents a unique platform for the specific targeting of PFCs for in vivo 19F magnetic resonance imaging.

Myocardial T2 mapping reveals age- and sex-related differences in volunteers.

BACKGROUND: T2 mapping indicates to be a sensitive method for detection of tissue oedema hidden beyond the detection limits of T2-weighted Cardiovascular Magnetic Resonance (CMR). However, due to variability of baseline T2 values in volunteers, reference values need to be defined. Therefore, the aim of the study was to investigate the effects of age and sex on quantitative T2 mapping with a turbo gradient-spin-echo (GRASE) sequence at 1.5 T. For that reason, we studied sensitivity issues as well as technical and biological effects on GRASE-derived myocardial T2 maps. Furthermore, intra- and interobserver variability were calculated using data from a large volunteer group. METHODS: GRASE-derived multiecho images were analysed using dedicated software. After sequence optimization, validation and sensitivity measurements were performed in muscle phantoms ex vivo and in vivo. The optimized parameters were used to analyse CMR images of 74 volunteers of mixed sex and a wide range of age with typical prevalence of hypertension and diabetes. Myocardial T2 values were analysed globally and according to the 17 segment model. Strain-encoded (SENC) imaging was additionally performed to investigate possible effects of myocardial strain on global or segmental T2 values. RESULTS: Ex vivo studies in muscle phantoms showed, that GRASE-derived T2 values were comparable to those acquired by a standard multiecho spinecho sequence but faster by a factor of 6. Besides that, T2 values reflected tissue water content. The in vivo measurements in volunteers revealed intra- and interobserver correlations with R2=0.91 and R2=0.94 as well as a coefficients of variation of 2.4% and 2.2%, respectively. While global T2 time significantly decreased towards the heart basis, female volunteers had significant higher T2 time irrespective of myocardial region. We found no correlation of segmental T2 values with maximal systolic, diastolic strain or heart rate. Interestingly, volunteers´ age was significantly correlated to T2 time while that was not the case for other coincident cardiovascular risk factors. CONCLUSION: GRASE-derived T2 maps are highly reproducible. However, female sex and aging with typical prevalence of hypertension and diabetes were accompanied by increased myocardial T2 values. Thus, sex and age must be considered as influence factors when using GRASE in a diagnostic manner.

Growth and metastasis of B16-F10 melanoma cells is not critically dependent on host CD73 expression in mice.

BACKGROUND: Recent studies have suggested that adenosine generated by ecto-5'-nucleotidase (CD73) in the tumor microenvironment plays a major role in promoting tumor growth by suppressing the immune response and stimulating angiogenesis via A2A and A2B receptors. However, adenosine has also been reported to inhibit tumor growth acting via A1 and A3 receptors. Therefore the aim of this study was to clarify the role of host CD73, which catalyzes the extracellular hydrolysis of AMP to adenosine, on tumor growth and metastasis of B16-F10 melanoma cells. METHODS: CD73 and alkaline phosphatase (AP) activity of B16-F10 melanoma cells were measured by HPLC. Tumor cells were injected either subcutaneously or intradermally in WT and CD73-/- mice and tumor growth was monitored by MRI at 9.4 T. Immune cell subpopulations within tumors were assessed by FACS after enzymatic digestion. An endothelium specific CD73-/- was created using Tie2-Cre+ mice and CD73flox/flox (loxP) mice. Chimeric mice lacking CD73-/- on hematopoietic cells was generated by bone marrow transplantation. Lung metastatic spread was measured after intravenous B16-F10 application. RESULTS: B16-F10 cells showed very little CD73 and negligible AP activity. Neither complete loss of host CD73 nor specific knockout of CD73 on endothelial cells or hematopoietic cells affected tumor growth after subcutaneous or intradermal tumor cell application. Only peritumoral edema formation was significantly attenuated in global CD73-/- mice in the intradermal model. Immune cell composition revealed no differences in the different transgenic mice models. Also lung metastasis after intravenous B16-F10 injection was not altered in CD73-/- mice. CONCLUSIONS: CD73 expression on host cells, particularly on endothelial and hematopoietic cells, does not modulate tumor growth and metastatic spread of B16-F10 melanoma cells most likely because of insufficient adenosine formation by the tumor itself.

Multifunctional MR monitoring of the healing process after myocardial infarction.

Healing of the myocardium after infarction comprises a variety of local adaptive processes which contribute to the functional outcome after the insult. Therefore, we aimed to establish a setting for concomitant assessment of regional alterations in contractile function, morphology, and immunological state to gain prognostic information on cardiac recovery after infarction. For this, mice were subjected to myocardial ischemia/reperfusion (I/R) and monitored for 28 days by cine MRI, T2 mapping, late gadolinium enhancement (LGE), and (19)F MRI. T2 values were calculated from gated multi-echo sequences. (19)F-loaded nanoparticles were injected intravenously for labelling circulating monocytes and making them detectable by (19)F MRI. In-house developed software was used for regional analysis of cine loops, T2 maps, LGE, and (19)F images to correlate local wall movement, tissue damage as well as monocyte recruitment over up to 200 sectors covering the left ventricle. This enabled us to evaluate simultaneously zonal cardiac necrosis, oedema, and inflammation patterns together with sectional fractional shortening (FS) and global myocardial function. Oedema, indicated by a rise in T2, showed a slightly better correlation with FS than LGE. Regional T2 values increased from 19 ms to above 30 ms after I/R. In the course of the healing process oedema resolved within 28 days, while myocardial function recovered. Infiltrating monocytes could be quantitatively tracked by (19)F MRI, as validated by flow cytometry. Furthermore, (19)F MRI proved to yield valuable insight on the outcome of myocardial infarction in a transgenic mouse model. In conclusion, our approach permits a comprehensive surveillance of key processes involved in myocardial healing providing independent and complementary information for individual prognosis.

Loss of UCP2 attenuates mitochondrial dysfunction without altering ROS production and uncoupling activity.

Although mitochondrial dysfunction is often accompanied by excessive reactive oxygen species (ROS) production, we previously showed that an increase in random somatic mtDNA mutations does not result in increased oxidative stress. Normal levels of ROS and oxidative stress could also be a result of an active compensatory mechanism such as a mild increase in proton leak. Uncoupling protein 2 (UCP2) was proposed to play such a role in many physiological situations. However, we show that upregulation of UCP2 in mtDNA mutator mice is not associated with altered proton leak kinetics or ROS production, challenging the current view on the role of UCP2 in energy metabolism. Instead, our results argue that high UCP2 levels allow better utilization of fatty acid oxidation resulting in a beneficial effect on mitochondrial function in heart, postponing systemic lactic acidosis and resulting in longer lifespan in these mice. This study proposes a novel mechanism for an adaptive response to mitochondrial cardiomyopathy that links changes in metabolism to amelioration of respiratory chain deficiency and longer lifespan.

RIP3, a kinase promoting necroptotic cell death, mediates adverse remodelling after myocardial infarction.

AIMS: Programmed necrosis (necroptosis) represents a newly identified mechanism of cell death combining features of both apoptosis and necrosis. Like apoptosis, necroptosis is tightly regulated by distinct signalling pathways. A key regulatory role in programmed necrosis has been attributed to interactions of the receptor-interacting protein kinases, RIP1 and RIP3. However, the specific functional role of RIP3-dependent signalling and necroptosis in the heart is unknown. The aims of this study were thus to assess the significance of necroptosis and RIP3 in the context of myocardial ischaemia. METHODS AND RESULTS: Immunoblots revealed strong expression of RIP3 in murine hearts, indicating potential functional significance of this protein in the myocardium. Consistent with a role in promoting necroptosis, adenoviral overexpression of RIP3 in neonatal rat cardiomyocytes and stimulation with TNF-α induced the formation of a complex of RIP1 and RIP3. Moreover, RIP3 overexpression was sufficient to induce necroptosis of cardiomyocytes. In vivo, cardiac expression of RIP3 was up-regulated upon myocardial infarction (MI). Conversely, mice deficient for RIP3 (RIP3(-/-)) showed a significantly better ejection fraction (45 ± 3.6 vs. 32 ± 4.4%, P < 0.05) and less hypertrophy in magnetic resonance imaging studies 30 days after experimental infarction due to left anterior descending coronary artery ligation. This was accompanied by a diminished inflammatory response of infarcted hearts and decreased generation of reactive oxygen species. CONCLUSION: Here, we show that RIP3-dependent necroptosis modulates post-ischaemic adverse remodelling in a mouse model of MI. This novel signalling pathway may thus be an attractive target for future therapies that aim to limit the adverse consequences of myocardial ischaemia.

Probing different perfluorocarbons for in vivo inflammation imaging by 19F MRI: image reconstruction, biological half-lives and sensitivity.

Inflammatory processes can reliably be assessed by (19)F MRI using perfluorocarbons (PFCs), which is primarily based on the efficient uptake of emulsified PFCs by circulating cells of the monocyte-macrophage system and subsequent infiltration of the (19)F-labeled cells into affected tissue. An ideal candidate for the sensitive detection of fluorine-loaded cells is the biochemically inert perfluoro-15-crown-5 ether (PFCE), as it contains 20 magnetically equivalent (19)F atoms. However, the biological half-life of PFCE in the liver and spleen is extremely long, and so this substance is not suitable for future clinical applications. In the present study, we investigated alternative, nontoxic PFCs with predicted short biological half-lives and high fluorine content: perfluorooctyl bromide (PFOB), perfluorodecalin (PFD) and trans-bis-perfluorobutyl ethylene (F-44E). Despite the complex spectra of these compounds, we obtained artifact-free images using sine-squared acquisition-weighted three-dimensional chemical shift imaging and dedicated reconstruction accomplished with in-house-developed software. The signal-to-noise ratio of the images was maximized using a Nutall window with only moderate localization error. Using this approach, the retention times of the different PFCs in murine liver and spleen were determined at 9.4 T. The biological half-lives were estimated to be 9 days (PFD), 12 days (PFOB) and 28 days (F-44E), compared with more than 250 days for PFCE. In vivo sensitivity for inflammation imaging was assessed using an ear clip injury model. The alternative PFCs PFOB and F-44E provided 37% and 43%, respectively, of the PFCE intensities, whereas PFD did not show any signal in the ear model. Thus, for in vivo monitoring of inflammatory processes, PFOB emerges as the most promising candidate for possible future translation of (19)F MR inflammation imaging to human applications.

Technical advance: monitoring the trafficking of neutrophil granulocytes and monocytes during the course of tissue inflammation by noninvasive 19F MRI.

Inflammation results in the recruitment of neutrophils and monocytes, which is crucial for the healing process. In the present study, we used (19)F MRI to monitor in vivo the infiltration of neutrophils and monocytes from the onset of inflammation to the resolution and healing phase. Matrigel, with or without LPS, was s.c.-implanted into C57BL/6 mice. This resulted in a focal inflammation lasting over a period of 20 days, with constantly decreasing LPS levels in doped matrigel plugs. After i.v. administration of (19)F containing contrast agent, (19)F MRI revealed a zonular (19)F signal in the periphery of LPS containing matrigel plugs, which was not observed in control plugs. Analysis of the (19)F signal over the observation period demonstrated the strongest (19)F signal after 24 h, which decreased to nearly zero after 20 days. The (19)F signal was mirrored by the amount of leukocytes in the matrigel, with neutrophils dominating at early time-points and macrophages at later time-points. Both populations were shown to take up the (19)F contrast agent. In conclusion, (19)F MRI, in combination with the matrigel/LPS model, permits the noninvasive analysis of neutrophil and monocyte infiltration over the complete course of inflammation in vivo.